Project acronym 20SComplexity
Project An integrative approach to uncover the multilevel regulation of 20S proteasome degradation
Researcher (PI) Michal Sharon
Host Institution (HI) WEIZMANN INSTITUTE OF SCIENCE
Call Details Starting Grant (StG), LS1, ERC-2014-STG
Summary For many years, the ubiquitin-26S proteasome degradation pathway was considered the primary route for proteasomal degradation. However, it is now becoming clear that proteins can also be targeted for degradation by a ubiquitin-independent mechanism mediated by the core 20S proteasome itself. Although initially believed to be limited to rare exceptions, degradation by the 20S proteasome is now understood to have a wide range of substrates, many of which are key regulatory proteins. Despite its importance, little is known about the mechanisms that control 20S proteasomal degradation, unlike the extensive knowledge acquired over the years concerning degradation by the 26S proteasome. Our overall aim is to reveal the multiple regulatory levels that coordinate the 20S proteasome degradation route.
To achieve this goal we will carry out a comprehensive research program characterizing three distinct levels of 20S proteasome regulation:
Intra-molecular regulation- Revealing the intrinsic molecular switch that activates the latent 20S proteasome.
Inter-molecular regulation- Identifying novel proteins that bind the 20S proteasome to regulate its activity and characterizing their mechanism of function.
Cellular regulatory networks- Unraveling the cellular cues and multiple pathways that influence 20S proteasome activity using a novel systematic and unbiased screening approach.
Our experimental strategy involves the combination of biochemical approaches with native mass spectrometry, cross-linking and fluorescence measurements, complemented by cell biology analyses and high-throughput screening. Such a multidisciplinary approach, integrating in vitro and in vivo findings, will likely provide the much needed knowledge on the 20S proteasome degradation route. When completed, we anticipate that this work will be part of a new paradigm – no longer perceiving the 20S proteasome mediated degradation as a simple and passive event but rather a tightly regulated and coordinated process.
Summary
For many years, the ubiquitin-26S proteasome degradation pathway was considered the primary route for proteasomal degradation. However, it is now becoming clear that proteins can also be targeted for degradation by a ubiquitin-independent mechanism mediated by the core 20S proteasome itself. Although initially believed to be limited to rare exceptions, degradation by the 20S proteasome is now understood to have a wide range of substrates, many of which are key regulatory proteins. Despite its importance, little is known about the mechanisms that control 20S proteasomal degradation, unlike the extensive knowledge acquired over the years concerning degradation by the 26S proteasome. Our overall aim is to reveal the multiple regulatory levels that coordinate the 20S proteasome degradation route.
To achieve this goal we will carry out a comprehensive research program characterizing three distinct levels of 20S proteasome regulation:
Intra-molecular regulation- Revealing the intrinsic molecular switch that activates the latent 20S proteasome.
Inter-molecular regulation- Identifying novel proteins that bind the 20S proteasome to regulate its activity and characterizing their mechanism of function.
Cellular regulatory networks- Unraveling the cellular cues and multiple pathways that influence 20S proteasome activity using a novel systematic and unbiased screening approach.
Our experimental strategy involves the combination of biochemical approaches with native mass spectrometry, cross-linking and fluorescence measurements, complemented by cell biology analyses and high-throughput screening. Such a multidisciplinary approach, integrating in vitro and in vivo findings, will likely provide the much needed knowledge on the 20S proteasome degradation route. When completed, we anticipate that this work will be part of a new paradigm – no longer perceiving the 20S proteasome mediated degradation as a simple and passive event but rather a tightly regulated and coordinated process.
Max ERC Funding
1 500 000 €
Duration
Start date: 2015-04-01, End date: 2020-03-31
Project acronym 3DCellPhase-
Project In situ Structural Analysis of Molecular Crowding and Phase Separation
Researcher (PI) Julia MAHAMID
Host Institution (HI) EUROPEAN MOLECULAR BIOLOGY LABORATORY
Call Details Starting Grant (StG), LS1, ERC-2017-STG
Summary This proposal brings together two fields in biology, namely the emerging field of phase-separated assemblies in cell biology and state-of-the-art cellular cryo-electron tomography, to advance our understanding on a fundamental, yet illusive, question: the molecular organization of the cytoplasm.
Eukaryotes organize their biochemical reactions into functionally distinct compartments. Intriguingly, many, if not most, cellular compartments are not membrane enclosed. Rather, they assemble dynamically by phase separation, typically triggered upon a specific event. Despite significant progress on reconstituting such liquid-like assemblies in vitro, we lack information as to whether these compartments in vivo are indeed amorphous liquids, or whether they exhibit structural features such as gels or fibers. My recent work on sample preparation of cells for cryo-electron tomography, including cryo-focused ion beam thinning, guided by 3D correlative fluorescence microscopy, shows that we can now prepare site-specific ‘electron-transparent windows’ in suitable eukaryotic systems, which allow direct examination of structural features of cellular compartments in their cellular context. Here, we will use these techniques to elucidate the structural principles and cytoplasmic environment driving the dynamic assembly of two phase-separated compartments: Stress granules, which are RNA bodies that form rapidly in the cytoplasm upon cellular stress, and centrosomes, which are sites of microtubule nucleation. We will combine these studies with a quantitative description of the crowded nature of cytoplasm and of its local variations, to provide a direct readout of the impact of excluded volume on molecular assembly in living cells. Taken together, these studies will provide fundamental insights into the structural basis by which cells form biochemical compartments.
Summary
This proposal brings together two fields in biology, namely the emerging field of phase-separated assemblies in cell biology and state-of-the-art cellular cryo-electron tomography, to advance our understanding on a fundamental, yet illusive, question: the molecular organization of the cytoplasm.
Eukaryotes organize their biochemical reactions into functionally distinct compartments. Intriguingly, many, if not most, cellular compartments are not membrane enclosed. Rather, they assemble dynamically by phase separation, typically triggered upon a specific event. Despite significant progress on reconstituting such liquid-like assemblies in vitro, we lack information as to whether these compartments in vivo are indeed amorphous liquids, or whether they exhibit structural features such as gels or fibers. My recent work on sample preparation of cells for cryo-electron tomography, including cryo-focused ion beam thinning, guided by 3D correlative fluorescence microscopy, shows that we can now prepare site-specific ‘electron-transparent windows’ in suitable eukaryotic systems, which allow direct examination of structural features of cellular compartments in their cellular context. Here, we will use these techniques to elucidate the structural principles and cytoplasmic environment driving the dynamic assembly of two phase-separated compartments: Stress granules, which are RNA bodies that form rapidly in the cytoplasm upon cellular stress, and centrosomes, which are sites of microtubule nucleation. We will combine these studies with a quantitative description of the crowded nature of cytoplasm and of its local variations, to provide a direct readout of the impact of excluded volume on molecular assembly in living cells. Taken together, these studies will provide fundamental insights into the structural basis by which cells form biochemical compartments.
Max ERC Funding
1 228 125 €
Duration
Start date: 2018-02-01, End date: 2023-01-31
Project acronym AAMDDR
Project DNA damage response and genome stability: The role of ATM, ATR and the Mre11 complex
Researcher (PI) Vincenzo Costanzo
Host Institution (HI) CANCER RESEARCH UK LBG
Call Details Starting Grant (StG), LS1, ERC-2007-StG
Summary Chromosomal DNA is continuously subjected to exogenous and endogenous damaging insults. In the presence of DNA damage cells activate a multi-faceted checkpoint response that delays cell cycle progression and promotes DNA repair. Failures in this response lead to genomic instability, the main feature of cancer cells. Several cancer-prone human syndromes including the Ataxia teleangiectasia (A-T), the A-T Like Disorder (ATLD) and the Seckel Syndrome reflect defects in the specific genes of the DNA damage response such as ATM, MRE11 and ATR. DNA damage response pathways are poorly understood at biochemical level in vertebrate organisms. We have established a cell-free system based on Xenopus laevis egg extract to study molecular events underlying DNA damage response. This is the first in vitro system that recapitulates different aspects of the DNA damage response in vertebrates. Using this system we propose to study the biochemistry of the ATM, ATR and the Mre11 complex dependent DNA damage response. In particular we will: 1) Dissect the signal transduction pathway that senses DNA damage and promotes cell cycle arrest and DNA damage repair; 2) Analyze at molecular level the role of ATM, ATR, Mre11 in chromosomal DNA replication and mitosis during normal and stressful conditions; 3) Identify substrates of the ATM and ATR dependent DNA damage response using an innovative screening procedure.
Summary
Chromosomal DNA is continuously subjected to exogenous and endogenous damaging insults. In the presence of DNA damage cells activate a multi-faceted checkpoint response that delays cell cycle progression and promotes DNA repair. Failures in this response lead to genomic instability, the main feature of cancer cells. Several cancer-prone human syndromes including the Ataxia teleangiectasia (A-T), the A-T Like Disorder (ATLD) and the Seckel Syndrome reflect defects in the specific genes of the DNA damage response such as ATM, MRE11 and ATR. DNA damage response pathways are poorly understood at biochemical level in vertebrate organisms. We have established a cell-free system based on Xenopus laevis egg extract to study molecular events underlying DNA damage response. This is the first in vitro system that recapitulates different aspects of the DNA damage response in vertebrates. Using this system we propose to study the biochemistry of the ATM, ATR and the Mre11 complex dependent DNA damage response. In particular we will: 1) Dissect the signal transduction pathway that senses DNA damage and promotes cell cycle arrest and DNA damage repair; 2) Analyze at molecular level the role of ATM, ATR, Mre11 in chromosomal DNA replication and mitosis during normal and stressful conditions; 3) Identify substrates of the ATM and ATR dependent DNA damage response using an innovative screening procedure.
Max ERC Funding
1 000 000 €
Duration
Start date: 2008-07-01, End date: 2013-06-30
Project acronym ABCTRANSPORT
Project Minimalist multipurpose ATP-binding cassette transporters
Researcher (PI) Dirk Jan Slotboom
Host Institution (HI) RIJKSUNIVERSITEIT GRONINGEN
Call Details Starting Grant (StG), LS1, ERC-2011-StG_20101109
Summary Many Gram-positive (pathogenic) bacteria are dependent on the uptake of vitamins from the environment or from the infected host. We have recently discovered the long-elusive family of membrane protein complexes catalyzing such transport. The vitamin transporters have an unprecedented modular architecture consisting of a single multipurpose energizing module (the Energy Coupling Factor, ECF) and multiple exchangeable membrane proteins responsible for substrate recognition (S-components). The S-components have characteristics of ion-gradient driven transporters (secondary active transporters), whereas the energizing modules are related to ATP-binding cassette (ABC) transporters (primary active transporters).
The aim of the proposal is threefold: First, we will address the question how properties of primary and secondary transporters are combined in ECF transporters to obtain a novel transport mechanism. Second, we will study the fundamental and unresolved question how protein-protein recognition takes place in the hydrophobic environment of the lipid bilayer. The modular nature of the ECF proteins offers a natural system to study the driving forces used for membrane protein interaction. Third, we will assess whether the ECF transport systems could become targets for antibacterial drugs. ECF transporters are found exclusively in prokaryotes, and their activity is often essential for viability of Gram-positive pathogens. Thus they could turn out to be an Achilles’ heel for the organisms.
Structural and mechanistic studies (X-ray crystallography, microscopy, spectroscopy and biochemistry) will reveal how the different transport modes are combined in a single protein complex, how transport is energized and catalyzed, and how protein-protein recognition takes place. Microbiological screens will be developed to search for compounds that inhibit prokaryote-specific steps of the mechanism of ECF transporters.
Summary
Many Gram-positive (pathogenic) bacteria are dependent on the uptake of vitamins from the environment or from the infected host. We have recently discovered the long-elusive family of membrane protein complexes catalyzing such transport. The vitamin transporters have an unprecedented modular architecture consisting of a single multipurpose energizing module (the Energy Coupling Factor, ECF) and multiple exchangeable membrane proteins responsible for substrate recognition (S-components). The S-components have characteristics of ion-gradient driven transporters (secondary active transporters), whereas the energizing modules are related to ATP-binding cassette (ABC) transporters (primary active transporters).
The aim of the proposal is threefold: First, we will address the question how properties of primary and secondary transporters are combined in ECF transporters to obtain a novel transport mechanism. Second, we will study the fundamental and unresolved question how protein-protein recognition takes place in the hydrophobic environment of the lipid bilayer. The modular nature of the ECF proteins offers a natural system to study the driving forces used for membrane protein interaction. Third, we will assess whether the ECF transport systems could become targets for antibacterial drugs. ECF transporters are found exclusively in prokaryotes, and their activity is often essential for viability of Gram-positive pathogens. Thus they could turn out to be an Achilles’ heel for the organisms.
Structural and mechanistic studies (X-ray crystallography, microscopy, spectroscopy and biochemistry) will reveal how the different transport modes are combined in a single protein complex, how transport is energized and catalyzed, and how protein-protein recognition takes place. Microbiological screens will be developed to search for compounds that inhibit prokaryote-specific steps of the mechanism of ECF transporters.
Max ERC Funding
1 500 000 €
Duration
Start date: 2012-01-01, End date: 2017-12-31
Project acronym ABCvolume
Project The ABC of Cell Volume Regulation
Researcher (PI) Berend Poolman
Host Institution (HI) RIJKSUNIVERSITEIT GRONINGEN
Call Details Advanced Grant (AdG), LS1, ERC-2014-ADG
Summary Cell volume regulation is crucial for any living cell because changes in volume determine the metabolic activity through e.g. changes in ionic strength, pH, macromolecular crowding and membrane tension. These physical chemical parameters influence interaction rates and affinities of biomolecules, folding rates, and fold stabilities in vivo. Understanding of the underlying volume regulatory mechanisms has immediate application in biotechnology and health, yet these factors are generally ignored in systems analyses of cellular functions.
My team has uncovered a number of mechanisms and insights of cell volume regulation. The next step forward is to elucidate how the components of a cell volume regulatory circuit work together and control the physicochemical conditions of the cell.
I propose construction of a synthetic cell in which an osmoregulatory transporter and mechanosensitive channel form a minimal volume regulatory network. My group has developed the technology to reconstitute membrane proteins into lipid vesicles (synthetic cells). One of the challenges is to incorporate into the vesicles an efficient pathway for ATP production and maintain energy homeostasis while the load on the system varies. We aim to control the transmembrane flux of osmolytes, which requires elucidation of the molecular mechanism of gating of the osmoregulatory transporter. We will focus on the glycine betaine ABC importer, which is one of the most complex transporters known to date with ten distinct protein domains, transiently interacting with each other.
The proposed synthetic metabolic circuit constitutes a fascinating out-of-equilibrium system, allowing us to understand cell volume regulatory mechanisms in a context and at a level of complexity minimally needed for life. Analysis of this circuit will address many outstanding questions and eventually allow us to design more sophisticated vesicular systems with applications, for example as compartmentalized reaction networks.
Summary
Cell volume regulation is crucial for any living cell because changes in volume determine the metabolic activity through e.g. changes in ionic strength, pH, macromolecular crowding and membrane tension. These physical chemical parameters influence interaction rates and affinities of biomolecules, folding rates, and fold stabilities in vivo. Understanding of the underlying volume regulatory mechanisms has immediate application in biotechnology and health, yet these factors are generally ignored in systems analyses of cellular functions.
My team has uncovered a number of mechanisms and insights of cell volume regulation. The next step forward is to elucidate how the components of a cell volume regulatory circuit work together and control the physicochemical conditions of the cell.
I propose construction of a synthetic cell in which an osmoregulatory transporter and mechanosensitive channel form a minimal volume regulatory network. My group has developed the technology to reconstitute membrane proteins into lipid vesicles (synthetic cells). One of the challenges is to incorporate into the vesicles an efficient pathway for ATP production and maintain energy homeostasis while the load on the system varies. We aim to control the transmembrane flux of osmolytes, which requires elucidation of the molecular mechanism of gating of the osmoregulatory transporter. We will focus on the glycine betaine ABC importer, which is one of the most complex transporters known to date with ten distinct protein domains, transiently interacting with each other.
The proposed synthetic metabolic circuit constitutes a fascinating out-of-equilibrium system, allowing us to understand cell volume regulatory mechanisms in a context and at a level of complexity minimally needed for life. Analysis of this circuit will address many outstanding questions and eventually allow us to design more sophisticated vesicular systems with applications, for example as compartmentalized reaction networks.
Max ERC Funding
2 247 231 €
Duration
Start date: 2015-07-01, End date: 2020-06-30
Project acronym ABDESIGN
Project Computational design of novel protein function in antibodies
Researcher (PI) Sarel-Jacob Fleishman
Host Institution (HI) WEIZMANN INSTITUTE OF SCIENCE
Call Details Starting Grant (StG), LS1, ERC-2013-StG
Summary We propose to elucidate the structural design principles of naturally occurring antibody complementarity-determining regions (CDRs) and to computationally design novel antibody functions. Antibodies represent the most versatile known system for molecular recognition. Research has yielded many insights into antibody design principles and promising biotechnological and pharmaceutical applications. Still, our understanding of how CDRs encode specific loop conformations lags far behind our understanding of structure-function relationships in non-immunological scaffolds. Thus, design of antibodies from first principles has not been demonstrated. We propose a computational-experimental strategy to address this challenge. We will: (a) characterize the design principles and sequence elements that rigidify antibody CDRs. Natural antibody loops will be subjected to computational modeling, crystallography, and a combined in vitro evolution and deep-sequencing approach to isolate sequence features that rigidify loop backbones; (b) develop a novel computational-design strategy, which uses the >1000 solved structures of antibodies deposited in structure databases to realistically model CDRs and design them to recognize proteins that have not been co-crystallized with antibodies. For example, we will design novel antibodies targeting insulin, for which clinically useful diagnostics are needed. By accessing much larger sequence/structure spaces than are available to natural immune-system repertoires and experimental methods, computational antibody design could produce higher-specificity and higher-affinity binders, even to challenging targets; and (c) develop new strategies to program conformational change in CDRs, generating, e.g., the first allosteric antibodies. These will allow targeting, in principle, of any molecule, potentially revolutionizing how antibodies are generated for research and medicine, providing new insights on the design principles of protein functional sites.
Summary
We propose to elucidate the structural design principles of naturally occurring antibody complementarity-determining regions (CDRs) and to computationally design novel antibody functions. Antibodies represent the most versatile known system for molecular recognition. Research has yielded many insights into antibody design principles and promising biotechnological and pharmaceutical applications. Still, our understanding of how CDRs encode specific loop conformations lags far behind our understanding of structure-function relationships in non-immunological scaffolds. Thus, design of antibodies from first principles has not been demonstrated. We propose a computational-experimental strategy to address this challenge. We will: (a) characterize the design principles and sequence elements that rigidify antibody CDRs. Natural antibody loops will be subjected to computational modeling, crystallography, and a combined in vitro evolution and deep-sequencing approach to isolate sequence features that rigidify loop backbones; (b) develop a novel computational-design strategy, which uses the >1000 solved structures of antibodies deposited in structure databases to realistically model CDRs and design them to recognize proteins that have not been co-crystallized with antibodies. For example, we will design novel antibodies targeting insulin, for which clinically useful diagnostics are needed. By accessing much larger sequence/structure spaces than are available to natural immune-system repertoires and experimental methods, computational antibody design could produce higher-specificity and higher-affinity binders, even to challenging targets; and (c) develop new strategies to program conformational change in CDRs, generating, e.g., the first allosteric antibodies. These will allow targeting, in principle, of any molecule, potentially revolutionizing how antibodies are generated for research and medicine, providing new insights on the design principles of protein functional sites.
Max ERC Funding
1 499 930 €
Duration
Start date: 2013-09-01, End date: 2018-08-31
Project acronym ACCENT
Project Unravelling the architecture and the cartography of the human centriole
Researcher (PI) Paul, Philippe, Desiré GUICHARD
Host Institution (HI) UNIVERSITE DE GENEVE
Call Details Starting Grant (StG), LS1, ERC-2016-STG
Summary The centriole is the largest evolutionary conserved macromolecular structure responsible for building centrosomes and cilia or flagella in many eukaryotes. Centrioles are critical for the proper execution of important biological processes ranging from cell division to cell signaling. Moreover, centriolar defects have been associated to several human pathologies including ciliopathies and cancer. This state of facts emphasizes the importance of understanding centriole biogenesis. The study of centriole formation is a deep-rooted question, however our current knowledge on its molecular organization at high resolution remains fragmented and limited. In particular, exquisite details of the overall molecular architecture of the human centriole and in particular of its central core region are lacking to understand the basis of centriole organization and function. Resolving this important question represents a challenge that needs to be undertaken and will undoubtedly lead to groundbreaking advances. Another important question to tackle next is to develop innovative methods to enable the nanometric molecular mapping of centriolar proteins within distinct architectural elements of the centriole. This missing information will be key to unravel the molecular mechanisms behind centriolar organization.
This research proposal aims at building a cartography of the human centriole by elucidating its molecular composition and architecture. To this end, we will combine the use of innovative and multidisciplinary techniques encompassing spatial proteomics, cryo-electron tomography, state-of-the-art microscopy and in vitro assays and to achieve a comprehensive molecular and structural view of the human centriole. All together, we expect that these advances will help understand basic principles underlying centriole and cilia formation as well as might have further relevance for human health.
Summary
The centriole is the largest evolutionary conserved macromolecular structure responsible for building centrosomes and cilia or flagella in many eukaryotes. Centrioles are critical for the proper execution of important biological processes ranging from cell division to cell signaling. Moreover, centriolar defects have been associated to several human pathologies including ciliopathies and cancer. This state of facts emphasizes the importance of understanding centriole biogenesis. The study of centriole formation is a deep-rooted question, however our current knowledge on its molecular organization at high resolution remains fragmented and limited. In particular, exquisite details of the overall molecular architecture of the human centriole and in particular of its central core region are lacking to understand the basis of centriole organization and function. Resolving this important question represents a challenge that needs to be undertaken and will undoubtedly lead to groundbreaking advances. Another important question to tackle next is to develop innovative methods to enable the nanometric molecular mapping of centriolar proteins within distinct architectural elements of the centriole. This missing information will be key to unravel the molecular mechanisms behind centriolar organization.
This research proposal aims at building a cartography of the human centriole by elucidating its molecular composition and architecture. To this end, we will combine the use of innovative and multidisciplinary techniques encompassing spatial proteomics, cryo-electron tomography, state-of-the-art microscopy and in vitro assays and to achieve a comprehensive molecular and structural view of the human centriole. All together, we expect that these advances will help understand basic principles underlying centriole and cilia formation as well as might have further relevance for human health.
Max ERC Funding
1 498 965 €
Duration
Start date: 2017-01-01, End date: 2021-12-31
Project acronym ACTINONSRF
Project MAL: an actin-regulated SRF transcriptional coactivator
Researcher (PI) Richard Treisman
Host Institution (HI) THE FRANCIS CRICK INSTITUTE LIMITED
Call Details Advanced Grant (AdG), LS1, ERC-2010-AdG_20100317
Summary MAL: an actin-regulated SRF transcriptional coactivator
Recent years have seen a revitalised interest in the role of actin in nuclear processes, but the molecular mechanisms involved remain largely unexplored. We will elucidate the molecular basis for the actin-based control of the SRF transcriptional coactivator, MAL. SRF controls transcription through two families of coactivators, the actin-binding MRTFs (MAL, Mkl2), which couple its activity to cytoskeletal dynamics, and the ERK-regulated TCFs (Elk-1, SAP-1, Net). MAL subcellular localisation and transcriptional activity responds to signal-induced changes in G-actin concentration, which are sensed by its actin-binding N-terminal RPEL domain. Members of a second family of RPEL proteins, the Phactrs, also exhibit actin-regulated nucleocytoplasmic shuttling. The proposal addresses the following novel features of actin biology:
¿ Actin as a transcriptional regulator
¿ Actin as a signalling molecule
¿ Actin-binding proteins as targets for regulation by actin, rather than regulators of actin function
We will analyse the sequences and proteins involved in actin-regulated nucleocytoplasmic shuttling, using structural biology and biochemistry to analyse its control by changes in actin-RPEL domain interactions. We will characterise the dynamics of shuttling, and develop reporters for changes in actin-MAL interaction for analysis of pathway activation in vivo. We will identify genes controlling MAL itself, and the balance between the nuclear and cytoplasmic actin pools. The mechanism by which actin represses transcriptional activation by MAL in the nucleus, and its relation to MAL phosphorylation, will be elucidated. Finally, we will map MRTF and TCF cofactor recruitment to SRF targets on a genome-wide scale, and identify the steps in transcription controlled by actin-MAL interaction.
Summary
MAL: an actin-regulated SRF transcriptional coactivator
Recent years have seen a revitalised interest in the role of actin in nuclear processes, but the molecular mechanisms involved remain largely unexplored. We will elucidate the molecular basis for the actin-based control of the SRF transcriptional coactivator, MAL. SRF controls transcription through two families of coactivators, the actin-binding MRTFs (MAL, Mkl2), which couple its activity to cytoskeletal dynamics, and the ERK-regulated TCFs (Elk-1, SAP-1, Net). MAL subcellular localisation and transcriptional activity responds to signal-induced changes in G-actin concentration, which are sensed by its actin-binding N-terminal RPEL domain. Members of a second family of RPEL proteins, the Phactrs, also exhibit actin-regulated nucleocytoplasmic shuttling. The proposal addresses the following novel features of actin biology:
¿ Actin as a transcriptional regulator
¿ Actin as a signalling molecule
¿ Actin-binding proteins as targets for regulation by actin, rather than regulators of actin function
We will analyse the sequences and proteins involved in actin-regulated nucleocytoplasmic shuttling, using structural biology and biochemistry to analyse its control by changes in actin-RPEL domain interactions. We will characterise the dynamics of shuttling, and develop reporters for changes in actin-MAL interaction for analysis of pathway activation in vivo. We will identify genes controlling MAL itself, and the balance between the nuclear and cytoplasmic actin pools. The mechanism by which actin represses transcriptional activation by MAL in the nucleus, and its relation to MAL phosphorylation, will be elucidated. Finally, we will map MRTF and TCF cofactor recruitment to SRF targets on a genome-wide scale, and identify the steps in transcription controlled by actin-MAL interaction.
Max ERC Funding
1 889 995 €
Duration
Start date: 2011-10-01, End date: 2017-09-30
Project acronym altEJrepair
Project Characterisation of DNA Double-Strand Break Repair by Alternative End-Joining: Potential Targets for Cancer Therapy
Researcher (PI) Raphael CECCALDI
Host Institution (HI) INSTITUT CURIE
Call Details Starting Grant (StG), LS1, ERC-2016-STG
Summary DNA repair pathways evolved as an intricate network that senses DNA damage and resolves it in order to minimise genetic lesions and thus preventing tumour formation. Gaining in recognition the last few years, the alternative end-joining (alt-EJ) DNA repair pathway was recently shown to be up-regulated and required for cancer cell viability in the absence of homologous recombination-mediated repair (HR). Despite this integral role, the alt-EJ repair pathway remains poorly characterised in humans. As such, its molecular composition, regulation and crosstalk with HR and other repair pathways remain elusive. Additionally, the contribution of the alt-EJ pathway to tumour progression as well as the identification of a mutational signature associated with the use of alt-EJ has not yet been investigated. Moreover, the clinical relevance of developing small-molecule inhibitors targeting players in the alt-EJ pathway, such as the polymerase Pol Theta (Polθ), is of importance as current anticancer drug treatments have shown limited effectiveness in achieving cancer remission in patients with HR-deficient (HRD) tumours.
Here, we propose a novel, multidisciplinary approach that aims to characterise the players and mechanisms of action involved in the utilisation of alt-EJ in cancer. This understanding will better elucidate the changing interplay between different DNA repair pathways, thus shedding light on whether and how the use of alt-EJ contributes to the pathogenic history and survival of HRD tumours, eventually paving the way for the development of novel anticancer therapeutics.
For all the abovementioned reasons, we are convinced this project will have important implications in: 1) elucidating critical interconnections between DNA repair pathways, 2) improving the basic understanding of the composition, regulation and function of the alt-EJ pathway, and 3) facilitating the development of new synthetic lethality-based chemotherapeutics for the treatment of HRD tumours.
Summary
DNA repair pathways evolved as an intricate network that senses DNA damage and resolves it in order to minimise genetic lesions and thus preventing tumour formation. Gaining in recognition the last few years, the alternative end-joining (alt-EJ) DNA repair pathway was recently shown to be up-regulated and required for cancer cell viability in the absence of homologous recombination-mediated repair (HR). Despite this integral role, the alt-EJ repair pathway remains poorly characterised in humans. As such, its molecular composition, regulation and crosstalk with HR and other repair pathways remain elusive. Additionally, the contribution of the alt-EJ pathway to tumour progression as well as the identification of a mutational signature associated with the use of alt-EJ has not yet been investigated. Moreover, the clinical relevance of developing small-molecule inhibitors targeting players in the alt-EJ pathway, such as the polymerase Pol Theta (Polθ), is of importance as current anticancer drug treatments have shown limited effectiveness in achieving cancer remission in patients with HR-deficient (HRD) tumours.
Here, we propose a novel, multidisciplinary approach that aims to characterise the players and mechanisms of action involved in the utilisation of alt-EJ in cancer. This understanding will better elucidate the changing interplay between different DNA repair pathways, thus shedding light on whether and how the use of alt-EJ contributes to the pathogenic history and survival of HRD tumours, eventually paving the way for the development of novel anticancer therapeutics.
For all the abovementioned reasons, we are convinced this project will have important implications in: 1) elucidating critical interconnections between DNA repair pathways, 2) improving the basic understanding of the composition, regulation and function of the alt-EJ pathway, and 3) facilitating the development of new synthetic lethality-based chemotherapeutics for the treatment of HRD tumours.
Max ERC Funding
1 498 750 €
Duration
Start date: 2017-07-01, End date: 2022-06-30
Project acronym AMYTOX
Project Amyloid fibril cytotoxicity: new insights from novel approaches
Researcher (PI) Sheena Radford
Host Institution (HI) UNIVERSITY OF LEEDS
Call Details Advanced Grant (AdG), LS1, ERC-2012-ADG_20120314
Summary Despite the discovery of amyloidosis more than a century ago, the molecular and cellular mechanisms of these devastating human disorders remain obscure. In addition to their involvement in disease, amyloid fibrils perform physiological functions, whilst others have potentials as biomaterials. To realise their use in nanotechnology and to enable the development of amyloid therapies, there is an urgent need to understand the molecular pathways of amyloid assembly and to determine how amyloid fibrils interact with cells and cellular components. The challenges lie in the transient nature and low population of aggregating species and the panoply of amyloid fibril structures. This molecular complexity renders identification of the culprits of amyloid disease impossible to achieve using traditional methods.
Here I propose a series of exciting experiments that aim to cast new light on the molecular and cellular mechanisms of amyloidosis by exploiting approaches capable of imaging individual protein molecules or single protein fibrils in vitro and in living cells. The proposal builds on new data from our laboratory that have shown that amyloid fibrils (disease-associated, functional and created from de novo designed sequences) kill cells by a mechanism that depends on fibril length and on cellular uptake. Specifically, I will (i) use single molecule fluorescence and non-covalent mass spectrometry and to determine why short fibril samples disrupt biological membranes more than their longer counterparts and electron tomography to determine, for the first time, the structural properties of cytotoxic fibril ends; (ii) develop single molecule force spectroscopy to probe the interactions between amyloid precursors, fibrils and cellular membranes; and (iii) develop cell biological assays to discover the biological mechanism(s) of amyloid-induced cell death and high resolution imaging and electron tomography to visualise amyloid fibrils in the act of killing living cells.
Summary
Despite the discovery of amyloidosis more than a century ago, the molecular and cellular mechanisms of these devastating human disorders remain obscure. In addition to their involvement in disease, amyloid fibrils perform physiological functions, whilst others have potentials as biomaterials. To realise their use in nanotechnology and to enable the development of amyloid therapies, there is an urgent need to understand the molecular pathways of amyloid assembly and to determine how amyloid fibrils interact with cells and cellular components. The challenges lie in the transient nature and low population of aggregating species and the panoply of amyloid fibril structures. This molecular complexity renders identification of the culprits of amyloid disease impossible to achieve using traditional methods.
Here I propose a series of exciting experiments that aim to cast new light on the molecular and cellular mechanisms of amyloidosis by exploiting approaches capable of imaging individual protein molecules or single protein fibrils in vitro and in living cells. The proposal builds on new data from our laboratory that have shown that amyloid fibrils (disease-associated, functional and created from de novo designed sequences) kill cells by a mechanism that depends on fibril length and on cellular uptake. Specifically, I will (i) use single molecule fluorescence and non-covalent mass spectrometry and to determine why short fibril samples disrupt biological membranes more than their longer counterparts and electron tomography to determine, for the first time, the structural properties of cytotoxic fibril ends; (ii) develop single molecule force spectroscopy to probe the interactions between amyloid precursors, fibrils and cellular membranes; and (iii) develop cell biological assays to discover the biological mechanism(s) of amyloid-induced cell death and high resolution imaging and electron tomography to visualise amyloid fibrils in the act of killing living cells.
Max ERC Funding
2 498 465 €
Duration
Start date: 2013-05-01, End date: 2019-04-30
Project acronym ANOBEST
Project Structure function and pharmacology of calcium-activated chloride channels: Anoctamins and Bestrophins
Researcher (PI) Raimund Dutzler
Host Institution (HI) UNIVERSITAT ZURICH
Call Details Advanced Grant (AdG), LS1, ERC-2013-ADG
Summary Calcium-activated chloride channels (CaCCs) play key roles in a range of physiological processes such as the control of membrane excitability, photoreception and epithelial secretion. Although the importance of these channels has been recognized for more than 30 years their molecular identity remained obscure. The recent discovery of two protein families encoding for CaCCs, Anoctamins and Bestrophins, was a scientific breakthrough that has provided first insight into two novel ion channel architectures. Within this proposal we aim to determine the first high resolution structures of members of both families and study their functional behavior by an interdisciplinary approach combining biochemistry, X-ray crystallography and electrophysiology. The structural investigation of eukaryotic membrane proteins is extremely challenging and will require us to investigate large numbers of candidates to single out family members with superior biochemical properties. During the last year we have made large progress in this direction. By screening numerous eukaryotic Anoctamins and prokaryotic Bestrophins we have identified well-behaved proteins for both families, which were successfully scaled-up and purified. Additional family members will be identified within the course of the project. For these stable proteins we plan to grow crystals diffracting to high resolution and to proceed with structure determination. With first structural information in hand we will perform detailed functional studies using electrophysiology and complementary biophysical techniques to gain mechanistic insight into ion permeation and gating. As the pharmacology of both families is still in its infancy we will in later stages also engage in the identification and characterization of inhibitors and activators of Anoctamins and Bestrophins to open up a field that may ultimately lead to the discovery of novel therapeutic strategies targeting calcium-activated chloride channels.
Summary
Calcium-activated chloride channels (CaCCs) play key roles in a range of physiological processes such as the control of membrane excitability, photoreception and epithelial secretion. Although the importance of these channels has been recognized for more than 30 years their molecular identity remained obscure. The recent discovery of two protein families encoding for CaCCs, Anoctamins and Bestrophins, was a scientific breakthrough that has provided first insight into two novel ion channel architectures. Within this proposal we aim to determine the first high resolution structures of members of both families and study their functional behavior by an interdisciplinary approach combining biochemistry, X-ray crystallography and electrophysiology. The structural investigation of eukaryotic membrane proteins is extremely challenging and will require us to investigate large numbers of candidates to single out family members with superior biochemical properties. During the last year we have made large progress in this direction. By screening numerous eukaryotic Anoctamins and prokaryotic Bestrophins we have identified well-behaved proteins for both families, which were successfully scaled-up and purified. Additional family members will be identified within the course of the project. For these stable proteins we plan to grow crystals diffracting to high resolution and to proceed with structure determination. With first structural information in hand we will perform detailed functional studies using electrophysiology and complementary biophysical techniques to gain mechanistic insight into ion permeation and gating. As the pharmacology of both families is still in its infancy we will in later stages also engage in the identification and characterization of inhibitors and activators of Anoctamins and Bestrophins to open up a field that may ultimately lead to the discovery of novel therapeutic strategies targeting calcium-activated chloride channels.
Max ERC Funding
2 176 000 €
Duration
Start date: 2014-02-01, End date: 2020-01-31
Project acronym ANTIVIRNA
Project Structural and mechanistic studies of RNA-guided and RNA-targeting antiviral defense pathways
Researcher (PI) Martin Jinek
Host Institution (HI) UNIVERSITAT ZURICH
Call Details Starting Grant (StG), LS1, ERC-2013-StG
Summary The evolutionary pressures exerted by viruses on their host cells constitute a major force that drives the evolution of cellular antiviral mechanisms. The proposed research is motivated by our interest in the roles of protein-RNA interactions in both prokaryotic and eukaryotic antiviral pathways and will proceed in two directions. The first project stems from our current work on the CRISPR pathway, a recently discovered RNA-guided adaptive defense mechanism in bacteria and archaea that silences mobile genetic elements such as viruses (bacteriophages) and plasmids. CRISPR systems rely on short RNAs (crRNAs) that associate with CRISPR-associated (Cas) proteins and function as sequence-specific guides in the detection and destruction of invading nucleic acids. To obtain molecular insights into the mechanisms of crRNA-guided interference, we will pursue structural and functional studies of DNA-targeting ribonuceoprotein complexes from type II and III CRISPR systems. Our work will shed light on the function of these systems in microbial pathogenesis and provide a framework for the informed engineering of RNA-guided gene targeting technologies. The second proposed research direction centres on RNA-targeting antiviral strategies employed by the human innate immune system. Here, our work will focus on structural studies of major interferon-induced effector proteins, initially examining the allosteric activation mechanism of RNase L and subsequently focusing on other antiviral nucleases and RNA helicases, as well as mechanisms by which RNA viruses evade the innate immune response of the host. In our investigations, we plan to approach these questions using an integrated strategy combining structural biology, biochemistry and biophysics with cell-based functional studies. Together, our studies will provide fundamental molecular insights into RNA-centred antiviral mechanisms and their impact on human health and disease.
Summary
The evolutionary pressures exerted by viruses on their host cells constitute a major force that drives the evolution of cellular antiviral mechanisms. The proposed research is motivated by our interest in the roles of protein-RNA interactions in both prokaryotic and eukaryotic antiviral pathways and will proceed in two directions. The first project stems from our current work on the CRISPR pathway, a recently discovered RNA-guided adaptive defense mechanism in bacteria and archaea that silences mobile genetic elements such as viruses (bacteriophages) and plasmids. CRISPR systems rely on short RNAs (crRNAs) that associate with CRISPR-associated (Cas) proteins and function as sequence-specific guides in the detection and destruction of invading nucleic acids. To obtain molecular insights into the mechanisms of crRNA-guided interference, we will pursue structural and functional studies of DNA-targeting ribonuceoprotein complexes from type II and III CRISPR systems. Our work will shed light on the function of these systems in microbial pathogenesis and provide a framework for the informed engineering of RNA-guided gene targeting technologies. The second proposed research direction centres on RNA-targeting antiviral strategies employed by the human innate immune system. Here, our work will focus on structural studies of major interferon-induced effector proteins, initially examining the allosteric activation mechanism of RNase L and subsequently focusing on other antiviral nucleases and RNA helicases, as well as mechanisms by which RNA viruses evade the innate immune response of the host. In our investigations, we plan to approach these questions using an integrated strategy combining structural biology, biochemistry and biophysics with cell-based functional studies. Together, our studies will provide fundamental molecular insights into RNA-centred antiviral mechanisms and their impact on human health and disease.
Max ERC Funding
1 467 180 €
Duration
Start date: 2013-11-01, End date: 2018-10-31
Project acronym ARCID
Project The Role of Arl Proteins in Retinal and other Ciliary Diseases
Researcher (PI) Alfred Wittinghofer
Host Institution (HI) MAX-PLANCK-GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN EV
Call Details Advanced Grant (AdG), LS1, ERC-2010-AdG_20100317
Summary Arl (Arf-like) proteins, GTP-binding proteins of the Ras superfamily, are molecular switches that cycle between a GDP-bound inactive and GTP-bound active state. There are 16 members of the Arl subfamily in the human genome whose basic mechanistic function is unknown. The interactome of Arl2/3 includes proteins involved in retinopathies and other ciliary diseases such as Leber¿s Congenital Amaurosis (LCA) and kidney diseases such as nephronophthisis. Arl6 has been found mutated in Bardet Biedl Syndrome, another pleiotropic ciliary disease. In the proposed interdisciplinary project I want to explore the function of the protein network of Arl2/3 and Arl6 by a combination of biochemical, biophysical and structural methods and use the knowledge obtained to probe their function in live cells. As with other subfamily proteins of the Ras superfamily which have been found to mediate similar biological functions I want to derive a basic understanding of the function of Arl proteins and how it relates to the development and function of the ciliary organelle and how they contribute to ciliary diseases. The molecules in the focus of the project are: the GTP-binding proteins Arl2, 3, 6; RP2, an Arl3GAP mutated in Retinitis pigmentosa; Regulators of Arl2 and 3; PDE¿ and HRG4, effectors of Arl2/3, which bind lipidated proteins; RPGR, mutated in Retinitis pigmentosa, an interactor of PDE¿; RPGRIP and RPGRIPL, interactors of RPGR mutated in LCA and other ciliopathies; Nephrocystin, mutated in nephronophthisis, an interactor of RPGRIP and Arl6, mutated in Bardet Biedl Syndrome, and the BBS complex. The working hypothesis is that Arl protein network(s) mediate ciliary transport processes and that the GTP switch cycle of Arl proteins is an important element of regulation of these processes.
Summary
Arl (Arf-like) proteins, GTP-binding proteins of the Ras superfamily, are molecular switches that cycle between a GDP-bound inactive and GTP-bound active state. There are 16 members of the Arl subfamily in the human genome whose basic mechanistic function is unknown. The interactome of Arl2/3 includes proteins involved in retinopathies and other ciliary diseases such as Leber¿s Congenital Amaurosis (LCA) and kidney diseases such as nephronophthisis. Arl6 has been found mutated in Bardet Biedl Syndrome, another pleiotropic ciliary disease. In the proposed interdisciplinary project I want to explore the function of the protein network of Arl2/3 and Arl6 by a combination of biochemical, biophysical and structural methods and use the knowledge obtained to probe their function in live cells. As with other subfamily proteins of the Ras superfamily which have been found to mediate similar biological functions I want to derive a basic understanding of the function of Arl proteins and how it relates to the development and function of the ciliary organelle and how they contribute to ciliary diseases. The molecules in the focus of the project are: the GTP-binding proteins Arl2, 3, 6; RP2, an Arl3GAP mutated in Retinitis pigmentosa; Regulators of Arl2 and 3; PDE¿ and HRG4, effectors of Arl2/3, which bind lipidated proteins; RPGR, mutated in Retinitis pigmentosa, an interactor of PDE¿; RPGRIP and RPGRIPL, interactors of RPGR mutated in LCA and other ciliopathies; Nephrocystin, mutated in nephronophthisis, an interactor of RPGRIP and Arl6, mutated in Bardet Biedl Syndrome, and the BBS complex. The working hypothesis is that Arl protein network(s) mediate ciliary transport processes and that the GTP switch cycle of Arl proteins is an important element of regulation of these processes.
Max ERC Funding
2 434 400 €
Duration
Start date: 2011-04-01, End date: 2016-03-31
Project acronym ARGO
Project The Quest of the Argonautes - from Myth to Reality
Researcher (PI) JOHN VAN DER OOST
Host Institution (HI) WAGENINGEN UNIVERSITY
Call Details Advanced Grant (AdG), LS1, ERC-2018-ADG
Summary Argonaute nucleases are key players of the eukaryotic RNA interference (RNAi) system. Using small RNA guides, these Argonaute (Ago) proteins specifically target complementary RNA molecules, resulting in regulation of a wide range of crucial processes, including chromosome organization, gene expression and anti-virus defence. Since 2010, my research team has studied closely-related prokaryotic Argonaute (pAgo) variants. This has revealed spectacular mechanistic variations: several thermophilic pAgos catalyse DNA-guided cleavage of double stranded DNA, but only at elevated temperatures. Interestingly, a recently discovered mesophilic Argonaute (CbAgo) can generate double strand DNA breaks at moderate temperatures, providing an excellent basis for this ARGO project. In addition, genome analysis has revealed many distantly-related Argonaute variants, often with unique domain architectures. Hence, the currently known Argonaute homologs are just the tip of the iceberg, and the stage is set for making a big leap in the exploration of the Argonaute family. Initially we will dissect the molecular basis of functional and mechanistic features of uncharacterized natural Argonaute variants, both in eukaryotes (the presence of an Ago-like subunit in the Mediator complex, strongly suggests a regulatory role of an elusive non-coding RNA ligand) and in prokaryotes (selected Ago variants possess distinct domains indicating novel functionalities). After their thorough biochemical characterization, I aim at engineering the functionality of the aforementioned CbAgo through an integrated rational & random approach, i.e. by tinkering of domains, and by an unprecedented in vitro laboratory evolution approach. Eventually, natural & synthetic Argonautes will be selected for their exploitation, and used for developing original genome editing applications (from silencing to base editing). Embarking on this ambitious ARGO expedition will lead us to many exciting discoveries.
Summary
Argonaute nucleases are key players of the eukaryotic RNA interference (RNAi) system. Using small RNA guides, these Argonaute (Ago) proteins specifically target complementary RNA molecules, resulting in regulation of a wide range of crucial processes, including chromosome organization, gene expression and anti-virus defence. Since 2010, my research team has studied closely-related prokaryotic Argonaute (pAgo) variants. This has revealed spectacular mechanistic variations: several thermophilic pAgos catalyse DNA-guided cleavage of double stranded DNA, but only at elevated temperatures. Interestingly, a recently discovered mesophilic Argonaute (CbAgo) can generate double strand DNA breaks at moderate temperatures, providing an excellent basis for this ARGO project. In addition, genome analysis has revealed many distantly-related Argonaute variants, often with unique domain architectures. Hence, the currently known Argonaute homologs are just the tip of the iceberg, and the stage is set for making a big leap in the exploration of the Argonaute family. Initially we will dissect the molecular basis of functional and mechanistic features of uncharacterized natural Argonaute variants, both in eukaryotes (the presence of an Ago-like subunit in the Mediator complex, strongly suggests a regulatory role of an elusive non-coding RNA ligand) and in prokaryotes (selected Ago variants possess distinct domains indicating novel functionalities). After their thorough biochemical characterization, I aim at engineering the functionality of the aforementioned CbAgo through an integrated rational & random approach, i.e. by tinkering of domains, and by an unprecedented in vitro laboratory evolution approach. Eventually, natural & synthetic Argonautes will be selected for their exploitation, and used for developing original genome editing applications (from silencing to base editing). Embarking on this ambitious ARGO expedition will lead us to many exciting discoveries.
Max ERC Funding
2 177 158 €
Duration
Start date: 2019-07-01, End date: 2024-06-30
Project acronym ASAP
Project Thylakoid membrane in action: acclimation strategies in algae and plants
Researcher (PI) Roberta Croce
Host Institution (HI) STICHTING VU
Call Details Starting Grant (StG), LS1, ERC-2011-StG_20101109
Summary Life on earth is sustained by the process that converts sunlight energy into chemical energy: photosynthesis. This process is operating near the boundary between life and death: if the absorbed energy exceeds the capacity of the metabolic reactions, it can result in photo-oxidation events that can cause the death of the organism. Over-excitation is happening quite often: oxygenic organisms are exposed to (drastic) changes in environmental conditions (light intensity, light quality and temperature), which influence the physical (light-harvesting) and chemical (enzymatic reactions) parts of the photosynthetic process to a different extent, leading to severe imbalances. However, daily experience tells us that plants are able to deal with most of these situations, surviving and happily growing. How do they manage? The photosynthetic membrane is highly flexible and it is able to change its supramolecular organization and composition and even the function of some of its components on a time scale as fast as a few seconds, thereby regulating the light-harvesting capacity. However, the structural/functional changes in the membrane are far from being fully characterized and the molecular mechanisms of their regulation are far from being understood. This is due to the fact that all these mechanisms require the simultaneous presence of various factors and thus the system should be analyzed at a high level of complexity; however, to obtain molecular details of a very complex system as the thylakoid membrane in action has not been possible so far. Over the last years we have developed and optimized a range of methods that now allow us to take up this challenge. This involves a high level of integration of biological and physical approaches, ranging from plant transformation and in vivo knock out of individual pigments to ultrafast-spectroscopy in a mix that is rather unique for my laboratory and will allow us to unravel the photoprotective mechanisms in algae and plants.
Summary
Life on earth is sustained by the process that converts sunlight energy into chemical energy: photosynthesis. This process is operating near the boundary between life and death: if the absorbed energy exceeds the capacity of the metabolic reactions, it can result in photo-oxidation events that can cause the death of the organism. Over-excitation is happening quite often: oxygenic organisms are exposed to (drastic) changes in environmental conditions (light intensity, light quality and temperature), which influence the physical (light-harvesting) and chemical (enzymatic reactions) parts of the photosynthetic process to a different extent, leading to severe imbalances. However, daily experience tells us that plants are able to deal with most of these situations, surviving and happily growing. How do they manage? The photosynthetic membrane is highly flexible and it is able to change its supramolecular organization and composition and even the function of some of its components on a time scale as fast as a few seconds, thereby regulating the light-harvesting capacity. However, the structural/functional changes in the membrane are far from being fully characterized and the molecular mechanisms of their regulation are far from being understood. This is due to the fact that all these mechanisms require the simultaneous presence of various factors and thus the system should be analyzed at a high level of complexity; however, to obtain molecular details of a very complex system as the thylakoid membrane in action has not been possible so far. Over the last years we have developed and optimized a range of methods that now allow us to take up this challenge. This involves a high level of integration of biological and physical approaches, ranging from plant transformation and in vivo knock out of individual pigments to ultrafast-spectroscopy in a mix that is rather unique for my laboratory and will allow us to unravel the photoprotective mechanisms in algae and plants.
Max ERC Funding
1 696 961 €
Duration
Start date: 2011-12-01, End date: 2017-11-30
Project acronym assemblyNMR
Project 3D structures of bacterial supramolecular assemblies by solid-state NMR
Researcher (PI) Adam Lange
Host Institution (HI) FORSCHUNGSVERBUND BERLIN EV
Call Details Starting Grant (StG), LS1, ERC-2013-StG
Summary Supramolecular assemblies – formed by the self-assembly of hundreds of protein subunits – are part of bacterial nanomachines involved in key cellular processes. Important examples in pathogenic bacteria are pili and type 3 secretion systems (T3SS) that mediate adhesion to host cells and injection of virulence proteins. Structure determination at atomic resolution of such assemblies by standard techniques such as X-ray crystallography or solution NMR is severely limited: Intact T3SSs or pili cannot be crystallized and are also inherently insoluble. Cryo-electron microscopy techniques have recently made it possible to obtain low- and medium-resolution models, but atomic details have not been accessible at the resolution obtained in these studies, leading sometimes to inaccurate models.
I propose to use solid-state NMR (ssNMR) to fill this knowledge-gap. I could recently show that ssNMR on in vitro preparations of Salmonella T3SS needles constitutes a powerful approach to study the structure of this virulence factor. Our integrated approach also included results from electron microscopy and modeling as well as in vivo assays (Loquet et al., Nature 2012). This is the foundation of this application. I propose to extend ssNMR methodology to tackle the structures of even larger or more complex homo-oligomeric assemblies with up to 200 residues per monomeric subunit. We will apply such techniques to address the currently unknown 3D structures of type I pili and cytoskeletal bactofilin filaments. Furthermore, I want to develop strategies to directly study assemblies in a native-like setting. As a first application, I will study the 3D structure of T3SS needles when they are complemented with intact T3SSs purified from Salmonella or Shigella. The ultimate goal of this proposal is to establish ssNMR as a generally applicable method that allows solving the currently unknown structures of bacterial supramolecular assemblies at atomic resolution.
Summary
Supramolecular assemblies – formed by the self-assembly of hundreds of protein subunits – are part of bacterial nanomachines involved in key cellular processes. Important examples in pathogenic bacteria are pili and type 3 secretion systems (T3SS) that mediate adhesion to host cells and injection of virulence proteins. Structure determination at atomic resolution of such assemblies by standard techniques such as X-ray crystallography or solution NMR is severely limited: Intact T3SSs or pili cannot be crystallized and are also inherently insoluble. Cryo-electron microscopy techniques have recently made it possible to obtain low- and medium-resolution models, but atomic details have not been accessible at the resolution obtained in these studies, leading sometimes to inaccurate models.
I propose to use solid-state NMR (ssNMR) to fill this knowledge-gap. I could recently show that ssNMR on in vitro preparations of Salmonella T3SS needles constitutes a powerful approach to study the structure of this virulence factor. Our integrated approach also included results from electron microscopy and modeling as well as in vivo assays (Loquet et al., Nature 2012). This is the foundation of this application. I propose to extend ssNMR methodology to tackle the structures of even larger or more complex homo-oligomeric assemblies with up to 200 residues per monomeric subunit. We will apply such techniques to address the currently unknown 3D structures of type I pili and cytoskeletal bactofilin filaments. Furthermore, I want to develop strategies to directly study assemblies in a native-like setting. As a first application, I will study the 3D structure of T3SS needles when they are complemented with intact T3SSs purified from Salmonella or Shigella. The ultimate goal of this proposal is to establish ssNMR as a generally applicable method that allows solving the currently unknown structures of bacterial supramolecular assemblies at atomic resolution.
Max ERC Funding
1 456 000 €
Duration
Start date: 2014-05-01, End date: 2019-04-30
Project acronym ATG9_SOLVES_IT
Project In vitro high resolution reconstitution of autophagosome nucleation and expansion catalyzed byATG9
Researcher (PI) Sharon TOOZE
Host Institution (HI) THE FRANCIS CRICK INSTITUTE LIMITED
Call Details Advanced Grant (AdG), LS1, ERC-2017-ADG
Summary Autophagy is a conserved, lysosomal-mediated pathway required for cell homeostasis and survival. It is controlled by the master regulators of energy (AMPK) and growth (TORC1) and mediated by the ATG (autophagy) proteins. Deregulation of autophagy is implicated in cancer, immunity, infection, aging and neurodegeneration. Autophagosomes form and expand using membranes from the secretory and endocytic pathways but how this occurs is not understood. ATG9, the only transmembrane ATG protein traffics through the cell in vesicles, and is essential for rapid initiation and expansion of the membranes which form the autophagosome. Crucially, how ATG9 functions is unknown. I will determine how ATG9 initiates the formation and expansion of the autophagosome by amino acid starvation through a molecular dissection of proteins resident in ATG9 vesicles which modulate the composition and property of the initiating membrane. I will employ high resolution light and electron microscopy to characterize the nucleation of the autophagosome, proximity-specific biotinylation and quantitative Mass Spectrometry to uncover the proteome required for the function of the ATG9, and optogenetic tools to acutely regulate signaling lipids. Lastly, with our tools and knowledge I will develop an in vitro reconstitution system to define at a molecular level how ATG9 vesicle proteins, membranes that interact with ATG9 vesicles, and other accessory ATG components nucleate and form an autophagosome. In vitro reconstitution of autophagosomes will be assayed biochemically, and by correlative light and cryo-EM and cryo-EM tomography, while functional reconstitution of autophagy will be tested by selective cargo recruitment. The development of a reconstituted system and identification proteins and lipids which are key components for autophagosome formation will provide a means to identify a new generation of targets for translational work leading to manipulation of autophagy for disease related therapies.
Summary
Autophagy is a conserved, lysosomal-mediated pathway required for cell homeostasis and survival. It is controlled by the master regulators of energy (AMPK) and growth (TORC1) and mediated by the ATG (autophagy) proteins. Deregulation of autophagy is implicated in cancer, immunity, infection, aging and neurodegeneration. Autophagosomes form and expand using membranes from the secretory and endocytic pathways but how this occurs is not understood. ATG9, the only transmembrane ATG protein traffics through the cell in vesicles, and is essential for rapid initiation and expansion of the membranes which form the autophagosome. Crucially, how ATG9 functions is unknown. I will determine how ATG9 initiates the formation and expansion of the autophagosome by amino acid starvation through a molecular dissection of proteins resident in ATG9 vesicles which modulate the composition and property of the initiating membrane. I will employ high resolution light and electron microscopy to characterize the nucleation of the autophagosome, proximity-specific biotinylation and quantitative Mass Spectrometry to uncover the proteome required for the function of the ATG9, and optogenetic tools to acutely regulate signaling lipids. Lastly, with our tools and knowledge I will develop an in vitro reconstitution system to define at a molecular level how ATG9 vesicle proteins, membranes that interact with ATG9 vesicles, and other accessory ATG components nucleate and form an autophagosome. In vitro reconstitution of autophagosomes will be assayed biochemically, and by correlative light and cryo-EM and cryo-EM tomography, while functional reconstitution of autophagy will be tested by selective cargo recruitment. The development of a reconstituted system and identification proteins and lipids which are key components for autophagosome formation will provide a means to identify a new generation of targets for translational work leading to manipulation of autophagy for disease related therapies.
Max ERC Funding
2 121 055 €
Duration
Start date: 2018-07-01, End date: 2023-06-30
Project acronym ATMINDDR
Project ATMINistrating ATM signalling: exploring the significance of ATM regulation by ATMIN
Researcher (PI) Axel Behrens
Host Institution (HI) THE FRANCIS CRICK INSTITUTE LIMITED
Call Details Starting Grant (StG), LS1, ERC-2011-StG_20101109
Summary ATM is the protein kinase that is mutated in the hereditary autosomal recessive disease ataxia telangiectasia (A-T). A-T patients display immune deficiencies, cancer predisposition and radiosensitivity. The molecular role of ATM is to respond to DNA damage by phosphorylating its substrates, thereby promoting repair of damage or arresting the cell cycle. Following the induction of double-strand breaks (DSBs), the NBS1 protein is required for activation of ATM. But ATM can also be activated in the absence of DNA damage. Treatment of cultured cells with hypotonic stress leads to the activation of ATM, presumably due to changes in chromatin structure. We have recently described a second ATM cofactor, ATMIN (ATM INteractor). ATMIN is dispensable for DSBs-induced ATM signalling, but ATM activation following hypotonic stress is mediated by ATMIN. While the biological role of ATM activation by DSBs and NBS1 is well established, the significance, if any, of ATM activation by ATMIN and changes in chromatin was up to now completely enigmatic.
ATM is required for class switch recombination (CSR) and the suppression of translocations in B cells. In order to determine whether ATMIN is required for any of the physiological functions of ATM, we generated a conditional knock-out mouse model for ATMIN. ATM signaling was dramatically reduced following osmotic stress in ATMIN-mutant B cells. ATMIN deficiency led to impaired CSR, and consequently ATMIN-mutant mice developed B cell lymphomas. Thus ablation of ATMIN resulted in a severe defect in ATM function. Our data strongly argue for the existence of a second NBS1-independent mode of ATM activation that is physiologically relevant. While a large amount of scientific effort has gone into characterising ATM signaling triggered by DSBs, essentially nothing is known about NBS1-independent ATM signaling. The experiments outlined in this proposal have the aim to identify and understand the molecular pathway of ATMIN-dependent ATM signaling.
Summary
ATM is the protein kinase that is mutated in the hereditary autosomal recessive disease ataxia telangiectasia (A-T). A-T patients display immune deficiencies, cancer predisposition and radiosensitivity. The molecular role of ATM is to respond to DNA damage by phosphorylating its substrates, thereby promoting repair of damage or arresting the cell cycle. Following the induction of double-strand breaks (DSBs), the NBS1 protein is required for activation of ATM. But ATM can also be activated in the absence of DNA damage. Treatment of cultured cells with hypotonic stress leads to the activation of ATM, presumably due to changes in chromatin structure. We have recently described a second ATM cofactor, ATMIN (ATM INteractor). ATMIN is dispensable for DSBs-induced ATM signalling, but ATM activation following hypotonic stress is mediated by ATMIN. While the biological role of ATM activation by DSBs and NBS1 is well established, the significance, if any, of ATM activation by ATMIN and changes in chromatin was up to now completely enigmatic.
ATM is required for class switch recombination (CSR) and the suppression of translocations in B cells. In order to determine whether ATMIN is required for any of the physiological functions of ATM, we generated a conditional knock-out mouse model for ATMIN. ATM signaling was dramatically reduced following osmotic stress in ATMIN-mutant B cells. ATMIN deficiency led to impaired CSR, and consequently ATMIN-mutant mice developed B cell lymphomas. Thus ablation of ATMIN resulted in a severe defect in ATM function. Our data strongly argue for the existence of a second NBS1-independent mode of ATM activation that is physiologically relevant. While a large amount of scientific effort has gone into characterising ATM signaling triggered by DSBs, essentially nothing is known about NBS1-independent ATM signaling. The experiments outlined in this proposal have the aim to identify and understand the molecular pathway of ATMIN-dependent ATM signaling.
Max ERC Funding
1 499 881 €
Duration
Start date: 2012-02-01, End date: 2018-01-31
Project acronym ATMMACHINE
Project Structural mechanism of recognition, signaling and resection of DNA double-strand breaks
Researcher (PI) Karl-Peter Hopfner
Host Institution (HI) LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN
Call Details Advanced Grant (AdG), LS1, ERC-2012-ADG_20120314
Summary DNA double-strand breaks are perhaps the most harmful DNA damages and result in carcinogenic chromosome aberrations. Cells protect their genome by activating a complex signaling and repair network, collectively denoted DNA damage response (DDR). A key initial step of the DDR is the activation of the 360 kDa checkpoint kinase ATM (ataxia telangiectasia mutated) by the multifunctional DSB repair factor Mre11-Rad50-Nbs1 (MRN). MRN senses and tethers DSBs, processes DSBs for further resection, and recruits and activates ATM to trigger the DDR. A mechanistic basis for the activities of the core DDR sensor MRN has not been established, despite intense research over the past decade. Our recent breakthroughs on structures of core Mre11-Rad50 and Mre11-Nbs1 complexes enable us now address three central questions to finally clarify the mechanism of MRN in the DDR:
- How does MRN interact with DNA or DNA ends in an ATP dependent manner?
- How do MRN and associated factors such as CtIP process blocked DNA ends?
- How do MRN and DNA activate ATM?
We will employ an innovative structural biology hybrid methods approach by combining X-ray crystallography, electron microscopy and small angle scattering with crosslink mass spectrometry and combine the structure-oriented techniques with validating in vitro and in vivo functional studies. The anticipated outcome will clarify the structural mechanism of one of the most important but enigmatic molecular machineries in maintaining genome stability and also help understand the molecular defects associated with several prominent cancer predisposition and neurodegenerative disorders.
Summary
DNA double-strand breaks are perhaps the most harmful DNA damages and result in carcinogenic chromosome aberrations. Cells protect their genome by activating a complex signaling and repair network, collectively denoted DNA damage response (DDR). A key initial step of the DDR is the activation of the 360 kDa checkpoint kinase ATM (ataxia telangiectasia mutated) by the multifunctional DSB repair factor Mre11-Rad50-Nbs1 (MRN). MRN senses and tethers DSBs, processes DSBs for further resection, and recruits and activates ATM to trigger the DDR. A mechanistic basis for the activities of the core DDR sensor MRN has not been established, despite intense research over the past decade. Our recent breakthroughs on structures of core Mre11-Rad50 and Mre11-Nbs1 complexes enable us now address three central questions to finally clarify the mechanism of MRN in the DDR:
- How does MRN interact with DNA or DNA ends in an ATP dependent manner?
- How do MRN and associated factors such as CtIP process blocked DNA ends?
- How do MRN and DNA activate ATM?
We will employ an innovative structural biology hybrid methods approach by combining X-ray crystallography, electron microscopy and small angle scattering with crosslink mass spectrometry and combine the structure-oriented techniques with validating in vitro and in vivo functional studies. The anticipated outcome will clarify the structural mechanism of one of the most important but enigmatic molecular machineries in maintaining genome stability and also help understand the molecular defects associated with several prominent cancer predisposition and neurodegenerative disorders.
Max ERC Funding
2 498 019 €
Duration
Start date: 2013-05-01, End date: 2018-04-30
Project acronym AutoClean
Project Cell-free reconstitution of autophagy to dissect molecular mechanisms
Researcher (PI) Claudine Simone Kraft
Host Institution (HI) UNIVERSITAETSKLINIKUM FREIBURG
Call Details Consolidator Grant (CoG), LS1, ERC-2017-COG
Summary Autophagy, a lysosomal degradation pathway in which the cell digests its own components, is an essential biological pathway that promotes organismal health and longevity and helps combat cancer and neurodegenerative diseases. Accordingly, the 2016 Nobel Prize in Physiology or Medicine was awarded for research in autophagy. Although autophagy has been extensively studied from yeast to mammals, the molecular events that underlie its induction and progression remain elusive. A highly conserved protein kinase, Atg1, plays a unique and essential role in initiating autophagy, yet despite this pivotal importance it has taken over twenty years for its first downstream target to be discovered. However, whilst our identification of the autophagy related membrane protein Atg9 as the first Atg1 substrate is an important advance, the molecular mechanisms that enable the extensive remodelling of cellular membranes that occurs during autophagy is still completely undefined. A detailed knowledge of the inputs and outputs of the Atg1 kinase will enable us to provide a definitive mechanistic understanding of autophagy. We have devised a novel permeabilized cell assay that reconstitutes the pathway in vitro, allowing us to recapitulate key steps in the autophagic process and thereby determine how the individual steps that lead up to autophagy are controlled. We will use this system to dissect the functional role of Atg1 kinase in autophagosome-vacuole fusion (Objective 1), and to determine the origin of the autophagic membrane and the role of Atg1 in expanding these (Objective 2). To reveal how Atg1/ULK1 kinase is activated in mammalian cells, we will apply the unique and carefully tailored synthetic in vivo approaches that we have recently developed (Objective 3). By focusing on the activation of the Atg1 kinase and the molecular events that it executes, we will be able to explain its central role in regulating the autophagic process and define the mechanistic steps in the pathway.
Summary
Autophagy, a lysosomal degradation pathway in which the cell digests its own components, is an essential biological pathway that promotes organismal health and longevity and helps combat cancer and neurodegenerative diseases. Accordingly, the 2016 Nobel Prize in Physiology or Medicine was awarded for research in autophagy. Although autophagy has been extensively studied from yeast to mammals, the molecular events that underlie its induction and progression remain elusive. A highly conserved protein kinase, Atg1, plays a unique and essential role in initiating autophagy, yet despite this pivotal importance it has taken over twenty years for its first downstream target to be discovered. However, whilst our identification of the autophagy related membrane protein Atg9 as the first Atg1 substrate is an important advance, the molecular mechanisms that enable the extensive remodelling of cellular membranes that occurs during autophagy is still completely undefined. A detailed knowledge of the inputs and outputs of the Atg1 kinase will enable us to provide a definitive mechanistic understanding of autophagy. We have devised a novel permeabilized cell assay that reconstitutes the pathway in vitro, allowing us to recapitulate key steps in the autophagic process and thereby determine how the individual steps that lead up to autophagy are controlled. We will use this system to dissect the functional role of Atg1 kinase in autophagosome-vacuole fusion (Objective 1), and to determine the origin of the autophagic membrane and the role of Atg1 in expanding these (Objective 2). To reveal how Atg1/ULK1 kinase is activated in mammalian cells, we will apply the unique and carefully tailored synthetic in vivo approaches that we have recently developed (Objective 3). By focusing on the activation of the Atg1 kinase and the molecular events that it executes, we will be able to explain its central role in regulating the autophagic process and define the mechanistic steps in the pathway.
Max ERC Funding
1 955 666 €
Duration
Start date: 2018-06-01, End date: 2023-05-31
Project acronym Autophagy in vitro
Project Reconstituting Autophagosome Biogenesis in vitro
Researcher (PI) Thomas Wollert
Host Institution (HI) INSTITUT PASTEUR
Call Details Starting Grant (StG), LS1, ERC-2014-STG
Summary Autophagy is a catabolic pathway that delivers cytoplasmic material to lysosomes for degradation. Under vegetative conditions, the pathway serves as quality control system, specifically targeting damaged or superfluous organelles and protein-aggregates. Cytotoxic stresses and starvation, however, induces the formation of larger autophagosomes that capture cargo unselectively. Autophagosomes are being generated from a cup-shaped precursor membrane, the isolation membrane, which expands to engulf cytoplasmic components. Sealing of this structure gives rise to the double-membrane surrounded autophagosomes. Two interconnected ubiquitin (Ub)-like conjugation systems coordinate the expansion of autophagosomes by conjugating the autophagy related (Atg)-protein Atg8 to the isolation membrane. In an effort to unravel the function of Atg8, we reconstituted the system on model membranes in vitro and found that Atg8 forms together with the Atg12–Atg5-Atg16 complex a membrane scaffold which is required for productive autophagy in yeast. Humans possess seven Atg8-homologs and two mutually exclusive Atg16-variants. Here, we propose to investigate the function of the human Ub-like conjugation system using a fully reconstituted in vitro system. The spatiotemporal organization of recombinant fluorescent-labeled proteins with synthetic model membranes will be investigated using confocal and TIRF-microscopy. Structural information will be obtained by atomic force and electron microscopy. Mechanistic insights, obtained from the in vitro work, will be tested in vivo in cultured human cells. We belief that revealing 1) the function of the human Ub-like conjugation system in autophagy, 2) the functional differences of Atg8-homologs and the two Atg16-variants Atg16L1 and TECPR1 and 3) how Atg16L1 coordinates non-canonical autophagy will provide essential insights into the pathophysiology of cancer, neurodegenerative, and autoimmune diseases.
Summary
Autophagy is a catabolic pathway that delivers cytoplasmic material to lysosomes for degradation. Under vegetative conditions, the pathway serves as quality control system, specifically targeting damaged or superfluous organelles and protein-aggregates. Cytotoxic stresses and starvation, however, induces the formation of larger autophagosomes that capture cargo unselectively. Autophagosomes are being generated from a cup-shaped precursor membrane, the isolation membrane, which expands to engulf cytoplasmic components. Sealing of this structure gives rise to the double-membrane surrounded autophagosomes. Two interconnected ubiquitin (Ub)-like conjugation systems coordinate the expansion of autophagosomes by conjugating the autophagy related (Atg)-protein Atg8 to the isolation membrane. In an effort to unravel the function of Atg8, we reconstituted the system on model membranes in vitro and found that Atg8 forms together with the Atg12–Atg5-Atg16 complex a membrane scaffold which is required for productive autophagy in yeast. Humans possess seven Atg8-homologs and two mutually exclusive Atg16-variants. Here, we propose to investigate the function of the human Ub-like conjugation system using a fully reconstituted in vitro system. The spatiotemporal organization of recombinant fluorescent-labeled proteins with synthetic model membranes will be investigated using confocal and TIRF-microscopy. Structural information will be obtained by atomic force and electron microscopy. Mechanistic insights, obtained from the in vitro work, will be tested in vivo in cultured human cells. We belief that revealing 1) the function of the human Ub-like conjugation system in autophagy, 2) the functional differences of Atg8-homologs and the two Atg16-variants Atg16L1 and TECPR1 and 3) how Atg16L1 coordinates non-canonical autophagy will provide essential insights into the pathophysiology of cancer, neurodegenerative, and autoimmune diseases.
Max ERC Funding
1 499 726 €
Duration
Start date: 2015-04-01, End date: 2020-09-30
Project acronym BacNanoMachine
Project Reconstructing the coordinated self-assembly of a bacterial nanomachine
Researcher (PI) Marc Erhardt
Host Institution (HI) HUMBOLDT-UNIVERSITAET ZU BERLIN
Call Details Consolidator Grant (CoG), LS1, ERC-2019-COG
Summary Life has evolved diverse protein machines and bacteria provide many fascinating examples. Despite being unicellular organisms of relatively small size, bacteria produce sophisticated nanomachines with a high degree of self-organization. The motility organelle of bacteria, the flagellum, is a prime example of complex bacterial nanomachines. Flagella are by far the most prominent extracellular structures known in bacteria and made through self-assembly of several dozen different kinds of proteins and thus represents an ideal model system to study sub-cellular compartmentalization and self-organization. The flagellum can function as a macromolecular motility machine only if its many building blocks assemble in a coordinated manner. However, previous studies have focused on phenotypic and genetic analyses, or the characterization of isolated sub-components. Crucially, how bacteria orchestrate the many different cellular processes in time and space in order to construct a functional motility organelle remains enigmatic. The present proposal constitutes a comprehensive research program with the aim to obtain a holistic understanding of the underlying principles that allow bacteria to control and coordinate the simultaneous self-assembly processes of several multi-component nanomachines within a single cell. Towards this goal, we will combine for the first time the visualization of the dynamic self-assembly of individual flagella with quantitative single-cell gene expression analyses, re-engineering of the genetic network and biophysical modeling in order to develop a biophysical model of flagella self-assembly. This novel, integrative approach will allow us to move beyond the classical, descriptive characterization of protein complexes towards an engineering-type understanding of the extraordinarily robust and coordinated assembly of a multi-component molecular machine.
Summary
Life has evolved diverse protein machines and bacteria provide many fascinating examples. Despite being unicellular organisms of relatively small size, bacteria produce sophisticated nanomachines with a high degree of self-organization. The motility organelle of bacteria, the flagellum, is a prime example of complex bacterial nanomachines. Flagella are by far the most prominent extracellular structures known in bacteria and made through self-assembly of several dozen different kinds of proteins and thus represents an ideal model system to study sub-cellular compartmentalization and self-organization. The flagellum can function as a macromolecular motility machine only if its many building blocks assemble in a coordinated manner. However, previous studies have focused on phenotypic and genetic analyses, or the characterization of isolated sub-components. Crucially, how bacteria orchestrate the many different cellular processes in time and space in order to construct a functional motility organelle remains enigmatic. The present proposal constitutes a comprehensive research program with the aim to obtain a holistic understanding of the underlying principles that allow bacteria to control and coordinate the simultaneous self-assembly processes of several multi-component nanomachines within a single cell. Towards this goal, we will combine for the first time the visualization of the dynamic self-assembly of individual flagella with quantitative single-cell gene expression analyses, re-engineering of the genetic network and biophysical modeling in order to develop a biophysical model of flagella self-assembly. This novel, integrative approach will allow us to move beyond the classical, descriptive characterization of protein complexes towards an engineering-type understanding of the extraordinarily robust and coordinated assembly of a multi-component molecular machine.
Max ERC Funding
1 934 950 €
Duration
Start date: 2020-10-01, End date: 2025-09-30
Project acronym BACTERIAL SYRINGES
Project Protein Translocation Through Bacterial Syringes
Researcher (PI) Stefan Raunser
Host Institution (HI) MAX-PLANCK-GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN EV
Call Details Consolidator Grant (CoG), LS1, ERC-2013-CoG
Summary "The main objective of this application is to study the molecular basis of cellular infection by bacterial ABC-type toxins (Tc). Tc complexes are important virulence factors of a range of bacteria, including Photorhabdus luminescens and Yersinia pseudotuberculosis that infect insects and humans. Belonging to the class of pore-forming toxins, tripartite Tc complexes perforate the host membrane by forming channels that translocate toxic enzymes into the host.
In our previous cryo-EM work on the P. luminescens Tc complex we discovered that Tcs use a special syringe-like device for cell entry. Building on these results, we now intend to unravel the molecular mechanism through which this unusual and complicated injection system allows membrane permeation and protein translocation. We will use a hybrid approach, including biochemical reconstitution, structural analysis by cryo-EM and X-ray crystallography, fluorescence-based assays and site-directed mutagenesis to provide a comprehensive description of the molecular mechanism of infection at an unprecedented level of molecular detail.
Our results will be paradigmatic for understanding the mechanism of action of ABC-type toxins and will shed new light on the interactions of bacterial pathogens with their hosts."
Summary
"The main objective of this application is to study the molecular basis of cellular infection by bacterial ABC-type toxins (Tc). Tc complexes are important virulence factors of a range of bacteria, including Photorhabdus luminescens and Yersinia pseudotuberculosis that infect insects and humans. Belonging to the class of pore-forming toxins, tripartite Tc complexes perforate the host membrane by forming channels that translocate toxic enzymes into the host.
In our previous cryo-EM work on the P. luminescens Tc complex we discovered that Tcs use a special syringe-like device for cell entry. Building on these results, we now intend to unravel the molecular mechanism through which this unusual and complicated injection system allows membrane permeation and protein translocation. We will use a hybrid approach, including biochemical reconstitution, structural analysis by cryo-EM and X-ray crystallography, fluorescence-based assays and site-directed mutagenesis to provide a comprehensive description of the molecular mechanism of infection at an unprecedented level of molecular detail.
Our results will be paradigmatic for understanding the mechanism of action of ABC-type toxins and will shed new light on the interactions of bacterial pathogens with their hosts."
Max ERC Funding
1 999 992 €
Duration
Start date: 2014-07-01, End date: 2019-06-30
Project acronym BAS-SBBT
Project Bacterial Amyloid Secretion: Structural Biology and Biotechnology.
Researcher (PI) Han Karel Remaut
Host Institution (HI) VIB VZW
Call Details Consolidator Grant (CoG), LS1, ERC-2014-CoG
Summary Curli are functional amyloid fibers that constitute the major protein component of the extracellular matrix in pellicle biofilms formed by Bacteroidetes and Proteobacteria. Unlike the protein misfolding and aggregation events seen in pathological amyloid diseases such as Alzheimer’s and Parkinson’s disease, curli are the product of a dedicated protein secretion machinery. Curli formation requires a specialised and mechanistically unique transporter in the bacterial outer membrane, as well as two soluble accessory proteins thought to facilitate the safe guidance of the curli subunits across the periplasm and to coordinate their self-assembly at cell surface.
In this interdisciplinary research program we will study the structural and molecular biology of E. coli curli biosynthesis and address the fundamental questions concerning the molecular processes that allow the spatially and temporally controlled transport and deposition of these pro-amyloidogenic polypeptides. We will structurally unravel the secretion machinery, trap and analyse critical secretion intermediates and through in vitro reconstitution, assemble a minimal, self-sufficient peptide transport and fiber assembly system.
The new insights gained will set the stage for targeted interventions in curli -mediated biofilm formation and this research project will develop a new framework to harness the unique properties found in curli structure and biosynthesis for biotechnological applications as in patterned functionalized nanowires and directed, selective peptide carriers.
Summary
Curli are functional amyloid fibers that constitute the major protein component of the extracellular matrix in pellicle biofilms formed by Bacteroidetes and Proteobacteria. Unlike the protein misfolding and aggregation events seen in pathological amyloid diseases such as Alzheimer’s and Parkinson’s disease, curli are the product of a dedicated protein secretion machinery. Curli formation requires a specialised and mechanistically unique transporter in the bacterial outer membrane, as well as two soluble accessory proteins thought to facilitate the safe guidance of the curli subunits across the periplasm and to coordinate their self-assembly at cell surface.
In this interdisciplinary research program we will study the structural and molecular biology of E. coli curli biosynthesis and address the fundamental questions concerning the molecular processes that allow the spatially and temporally controlled transport and deposition of these pro-amyloidogenic polypeptides. We will structurally unravel the secretion machinery, trap and analyse critical secretion intermediates and through in vitro reconstitution, assemble a minimal, self-sufficient peptide transport and fiber assembly system.
The new insights gained will set the stage for targeted interventions in curli -mediated biofilm formation and this research project will develop a new framework to harness the unique properties found in curli structure and biosynthesis for biotechnological applications as in patterned functionalized nanowires and directed, selective peptide carriers.
Max ERC Funding
1 989 489 €
Duration
Start date: 2015-06-01, End date: 2020-05-31
Project acronym BayCellS
Project A Bayesian Framework for Cellular Structural Biology
Researcher (PI) Michael Nilges
Host Institution (HI) INSTITUT PASTEUR
Call Details Advanced Grant (AdG), LS1, ERC-2011-ADG_20110310
Summary The functioning of a single cell or organism is governed by the laws of chemistry and physics. The bridge from biology to chemistry and physics is provided by structural biology: to understand the functioning of a cell, it is necessary to know the atomic structure of macromolecular assemblies, which may contain hundreds of components. To characterise the structures of the increasingly large and often flexible complexes, high resolution structure determination (as was possible for example for the ribosome) will likely stay the exception, and multiple sources of structural data at multiple resolutions are employed. Integrating these data into one consistent picture poses particular difficulties, since data are much more sparse than in high resolution methods, and the data sets from heterogeneous sources are of highly different and unknown quality and may be mutually inconsistent, and that data are in general averaged over large ensembles and long times. Molecular modelling, a crucial element of any structure determination, plays an even more important role in these multi-scale and multi-technique approaches, not only to obtain structures from the data, but also to evaluate their reliability. This proposal is to develop a consistent framework for this highly complex data integration problem, principally based on Bayesian probability theory. Appropriate models for the major types data types used in hybrid approaches will be developed, as well as representations to include structural knowledge for the components of the complexes, at multiple scales. The new methods will be applied to a series of problems with increasing complexity, going from the determination of protein complexes with high resolution information, over low resolution structures based on protein-protein interaction data such as the nuclear pore, to the genome organisation in the nucleus.
Summary
The functioning of a single cell or organism is governed by the laws of chemistry and physics. The bridge from biology to chemistry and physics is provided by structural biology: to understand the functioning of a cell, it is necessary to know the atomic structure of macromolecular assemblies, which may contain hundreds of components. To characterise the structures of the increasingly large and often flexible complexes, high resolution structure determination (as was possible for example for the ribosome) will likely stay the exception, and multiple sources of structural data at multiple resolutions are employed. Integrating these data into one consistent picture poses particular difficulties, since data are much more sparse than in high resolution methods, and the data sets from heterogeneous sources are of highly different and unknown quality and may be mutually inconsistent, and that data are in general averaged over large ensembles and long times. Molecular modelling, a crucial element of any structure determination, plays an even more important role in these multi-scale and multi-technique approaches, not only to obtain structures from the data, but also to evaluate their reliability. This proposal is to develop a consistent framework for this highly complex data integration problem, principally based on Bayesian probability theory. Appropriate models for the major types data types used in hybrid approaches will be developed, as well as representations to include structural knowledge for the components of the complexes, at multiple scales. The new methods will be applied to a series of problems with increasing complexity, going from the determination of protein complexes with high resolution information, over low resolution structures based on protein-protein interaction data such as the nuclear pore, to the genome organisation in the nucleus.
Max ERC Funding
2 130 212 €
Duration
Start date: 2012-05-01, End date: 2017-04-30
Project acronym BENDER
Project BiogENesis and Degradation of Endoplasmic Reticulum proteins
Researcher (PI) Friedrich Förster
Host Institution (HI) UNIVERSITEIT UTRECHT
Call Details Consolidator Grant (CoG), LS1, ERC-2016-COG
Summary The Endoplasmic Reticulum (ER) membrane in all eukaryotic cells has an intricate protein network that facilitates protein biogene-sis and homeostasis. The molecular complexity and sophisticated regulation of this machinery favours study-ing it in its native microenvironment by novel approaches. Cryo-electron tomography (CET) allows 3D im-aging of membrane-associated complexes in their native surrounding. Computational analysis of many sub-tomograms depicting the same type of macromolecule, a technology I pioneered, provides subnanometer resolution insights into different conformations of native complexes.
I propose to leverage CET of cellular and cell-free systems to reveal the molecular details of ER protein bio-genesis and homeostasis. In detail, I will study: (a) The structure of the ER translocon, the dynamic gateway for import of nascent proteins into the ER and their maturation. The largest component is the oligosaccharyl transferase complex. (b) Cotranslational ER import, N-glycosylation, chaperone-mediated stabilization and folding as well as oligomerization of established model substrate such a major histocompatibility complex (MHC) class I and II complexes. (c) The degradation of misfolded ER-residing proteins by the cytosolic 26S proteasome using cytomegalovirus-induced depletion of MHC class I as a model system. (d) The structural changes of the ER-bound translation machinery upon ER stress through IRE1-mediated degradation of mRNA that is specific for ER-targeted proteins. (e) The improved ‘in silico purification’ of different states of native macromolecules by maximum likelihood subtomogram classification and its application to a-d.
This project will be the blueprint for a new approach to structural biology of membrane-associated processes. It will contribute to our mechanistic understanding of viral immune evasion and glycosylation disorders as well as numerous diseases involving chronic ER stress including diabetes and neurodegenerative diseases.
Summary
The Endoplasmic Reticulum (ER) membrane in all eukaryotic cells has an intricate protein network that facilitates protein biogene-sis and homeostasis. The molecular complexity and sophisticated regulation of this machinery favours study-ing it in its native microenvironment by novel approaches. Cryo-electron tomography (CET) allows 3D im-aging of membrane-associated complexes in their native surrounding. Computational analysis of many sub-tomograms depicting the same type of macromolecule, a technology I pioneered, provides subnanometer resolution insights into different conformations of native complexes.
I propose to leverage CET of cellular and cell-free systems to reveal the molecular details of ER protein bio-genesis and homeostasis. In detail, I will study: (a) The structure of the ER translocon, the dynamic gateway for import of nascent proteins into the ER and their maturation. The largest component is the oligosaccharyl transferase complex. (b) Cotranslational ER import, N-glycosylation, chaperone-mediated stabilization and folding as well as oligomerization of established model substrate such a major histocompatibility complex (MHC) class I and II complexes. (c) The degradation of misfolded ER-residing proteins by the cytosolic 26S proteasome using cytomegalovirus-induced depletion of MHC class I as a model system. (d) The structural changes of the ER-bound translation machinery upon ER stress through IRE1-mediated degradation of mRNA that is specific for ER-targeted proteins. (e) The improved ‘in silico purification’ of different states of native macromolecules by maximum likelihood subtomogram classification and its application to a-d.
This project will be the blueprint for a new approach to structural biology of membrane-associated processes. It will contribute to our mechanistic understanding of viral immune evasion and glycosylation disorders as well as numerous diseases involving chronic ER stress including diabetes and neurodegenerative diseases.
Max ERC Funding
2 496 611 €
Duration
Start date: 2017-04-01, End date: 2022-03-31
Project acronym BFTERRA
Project Biogenesis and Functions of Telomeric Repeat-containing RNA
Researcher (PI) Claus Maria Azzalin
Host Institution (HI) EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZUERICH
Call Details Starting Grant (StG), LS1, ERC-2009-StG
Summary Telomeres are heterochromatic nucleoprotein complexes located at the end of linear eukaryotic chromosomes. Contrarily to a longstanding dogma, we have recently demonstrated that mammalian telomeres are transcribed into TElomeric Repeat containing RNA (TERRA) molecules. TERRA transcripts contain telomeric RNA repeats and are produced at least in part by DNA-dependent RNA polymerase II-mediated transcription of telomeric DNA. TERRA molecules form discrete nuclear foci that co-localize with telomeric heterochromatin in both interphase and transcriptionally inactive metaphase cells. This indicates that TERRA is an integral component of telomeres and suggests that TERRA might participate in maintaining proper telomere heterochromatin. We will use a variety of biochemistry, cell biology, molecular biology and microscopy based approaches applied to cultured mammalian cells and to the yeast Schizosaccharomyces pombe, to achieve four distinct major goals: i) We will over-express or deplete TERRA in mammalian cells in order to characterize the molecular details of putative TERRA-associated functions in maintaining normal telomere structure and function; ii) We will locate TERRA promoter regions on different human chromosome ends; iii) We will generate mammalian cellular systems in which to study artificially seeded telomeres that can be transcribed in an inducible fashion; iv) We will identify physiological regulators of TERRA by analyzing it in mammalian cultured cells where the functions of candidate factors are compromised. In parallel, taking advantage of the recent discovery of TERRA also in fission yeast, we will systematically analyze TERRA levels in fission yeast mutants derived from a complete gene knockout collection. The study of TERRA regulation and function at chromosome ends will strongly contribute to our understanding of how telomeres are maintained and will help to clarify the general functions of mammalian non-coding RNAs.
Summary
Telomeres are heterochromatic nucleoprotein complexes located at the end of linear eukaryotic chromosomes. Contrarily to a longstanding dogma, we have recently demonstrated that mammalian telomeres are transcribed into TElomeric Repeat containing RNA (TERRA) molecules. TERRA transcripts contain telomeric RNA repeats and are produced at least in part by DNA-dependent RNA polymerase II-mediated transcription of telomeric DNA. TERRA molecules form discrete nuclear foci that co-localize with telomeric heterochromatin in both interphase and transcriptionally inactive metaphase cells. This indicates that TERRA is an integral component of telomeres and suggests that TERRA might participate in maintaining proper telomere heterochromatin. We will use a variety of biochemistry, cell biology, molecular biology and microscopy based approaches applied to cultured mammalian cells and to the yeast Schizosaccharomyces pombe, to achieve four distinct major goals: i) We will over-express or deplete TERRA in mammalian cells in order to characterize the molecular details of putative TERRA-associated functions in maintaining normal telomere structure and function; ii) We will locate TERRA promoter regions on different human chromosome ends; iii) We will generate mammalian cellular systems in which to study artificially seeded telomeres that can be transcribed in an inducible fashion; iv) We will identify physiological regulators of TERRA by analyzing it in mammalian cultured cells where the functions of candidate factors are compromised. In parallel, taking advantage of the recent discovery of TERRA also in fission yeast, we will systematically analyze TERRA levels in fission yeast mutants derived from a complete gene knockout collection. The study of TERRA regulation and function at chromosome ends will strongly contribute to our understanding of how telomeres are maintained and will help to clarify the general functions of mammalian non-coding RNAs.
Max ERC Funding
1 602 600 €
Duration
Start date: 2009-10-01, End date: 2014-09-30
Project acronym BioMatrix
Project Structural Biology of Exopolysaccharide Secretion in Bacterial Biofilms
Researcher (PI) Petya Violinova KRASTEVA
Host Institution (HI) CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
Call Details Starting Grant (StG), LS1, ERC-2017-STG
Summary Bacterial biofilm formation is a paramount developmental process in both Gram-positive and Gram-negative species and in many pathogens has been associated with processes of horizontal gene transfer, antibiotic resistance development and pathogen persistence. Bacterial biofilms are collaborative sessile macrocolonies embedded in complex extracellular matrix that secures both mechanical resistance and a medium for intercellular exchange.
Biogenesis platforms for the secretion of biofilm matrix components - many of which controlled directly or indirectly by the intracellular second messenger c-di-GMP - are important determinants for biofilm formation and bacterial disease, and therefore present compelling targets for the development of novel therapeutics. During my Ph.D. and post-doctoral work I studied the structure and function of c-di-GMP-sensing protein factors controling extracellular matrix production by DNA-binding at the transcription initiation level or by inside-out signalling mechanisms at the cell envelope, as well as membrane exporters involved directly in downstream matrix component secretion.
Here, I propose to apply my expertise in microbiology, protein science and structural biology to study the structure and function of exopolysaccharide secretion systems in Gram-negative species. Using Pseudomonas aeruginosa, Vibrio spp. and Escherichia coli as model organisms, my team will aim to reveal the global architecture and individual building components of several expolysaccharide-producing protein megacomplexes. We will combine X-ray crystallography, biophysical and biochemical assays, electron microscopy and in cellulo functional studies to provide a comprehensive view of extracellular matrix production that spans the different resolution levels and presents molecular blueprints for the development of novel anti-infectives. Over the last year I have laid the foundation of these studies and have demonstrated the overall feasibility of the project.
Summary
Bacterial biofilm formation is a paramount developmental process in both Gram-positive and Gram-negative species and in many pathogens has been associated with processes of horizontal gene transfer, antibiotic resistance development and pathogen persistence. Bacterial biofilms are collaborative sessile macrocolonies embedded in complex extracellular matrix that secures both mechanical resistance and a medium for intercellular exchange.
Biogenesis platforms for the secretion of biofilm matrix components - many of which controlled directly or indirectly by the intracellular second messenger c-di-GMP - are important determinants for biofilm formation and bacterial disease, and therefore present compelling targets for the development of novel therapeutics. During my Ph.D. and post-doctoral work I studied the structure and function of c-di-GMP-sensing protein factors controling extracellular matrix production by DNA-binding at the transcription initiation level or by inside-out signalling mechanisms at the cell envelope, as well as membrane exporters involved directly in downstream matrix component secretion.
Here, I propose to apply my expertise in microbiology, protein science and structural biology to study the structure and function of exopolysaccharide secretion systems in Gram-negative species. Using Pseudomonas aeruginosa, Vibrio spp. and Escherichia coli as model organisms, my team will aim to reveal the global architecture and individual building components of several expolysaccharide-producing protein megacomplexes. We will combine X-ray crystallography, biophysical and biochemical assays, electron microscopy and in cellulo functional studies to provide a comprehensive view of extracellular matrix production that spans the different resolution levels and presents molecular blueprints for the development of novel anti-infectives. Over the last year I have laid the foundation of these studies and have demonstrated the overall feasibility of the project.
Max ERC Funding
1 499 901 €
Duration
Start date: 2018-08-01, End date: 2023-07-31
Project acronym BIOMEMOS
Project Higher order structure and function of biomembranes
Researcher (PI) Poul Nissen
Host Institution (HI) AARHUS UNIVERSITET
Call Details Advanced Grant (AdG), LS1, ERC-2009-AdG
Summary The biomembrane is a prerequisite of life. It enables the cell to maintain a controlled environment and to establish electrochemical gradients as rapidly accessible energy stores. Biomembranes also provide scaffold for organisation and spatial definition of signal transmission in the cell. Crystal structures of membrane proteins are determined with an increasing pace. Along with functional studies integral studies of individual membrane proteins are now widely implemented. The BIOMEMOS proposal goes a step further and approaches the function of the biomembrane at the higher level of membrane protein complexes. Through a combination of X-ray crystallography, electrophysiology, general biochemistry, biophysics and bioinformatics and including also the application of single-particle cryo-EM and small-angle X-ray scattering, the structure and function of membrane protein complexes of key importance in life will be investigated. The specific targets for investigation in this proposal include: 1) higher-order complexes of P-type ATPase pumps such as signalling complexes of Na+,K+-ATPase, and 2) development of methods for structural studies of membrane protein complexes Based on my unique track record in structural studies of large, difficult structures (ribosomes and membrane proteins) in the setting of a thriving research community in structural biology and biomembrane research in Aarhus provides a critical momentum for a long-term activity. The activity will take advantage of the new possibilities offered by synchrotron sources in Europe. Furthermore, a single-particle cryo-EM research group formed on my initiative in Aarhus, and a well-established small-angle X-ray scattering community provides for an optimal setting through multiple cues in structural biology and functional studies
Summary
The biomembrane is a prerequisite of life. It enables the cell to maintain a controlled environment and to establish electrochemical gradients as rapidly accessible energy stores. Biomembranes also provide scaffold for organisation and spatial definition of signal transmission in the cell. Crystal structures of membrane proteins are determined with an increasing pace. Along with functional studies integral studies of individual membrane proteins are now widely implemented. The BIOMEMOS proposal goes a step further and approaches the function of the biomembrane at the higher level of membrane protein complexes. Through a combination of X-ray crystallography, electrophysiology, general biochemistry, biophysics and bioinformatics and including also the application of single-particle cryo-EM and small-angle X-ray scattering, the structure and function of membrane protein complexes of key importance in life will be investigated. The specific targets for investigation in this proposal include: 1) higher-order complexes of P-type ATPase pumps such as signalling complexes of Na+,K+-ATPase, and 2) development of methods for structural studies of membrane protein complexes Based on my unique track record in structural studies of large, difficult structures (ribosomes and membrane proteins) in the setting of a thriving research community in structural biology and biomembrane research in Aarhus provides a critical momentum for a long-term activity. The activity will take advantage of the new possibilities offered by synchrotron sources in Europe. Furthermore, a single-particle cryo-EM research group formed on my initiative in Aarhus, and a well-established small-angle X-ray scattering community provides for an optimal setting through multiple cues in structural biology and functional studies
Max ERC Funding
2 444 180 €
Duration
Start date: 2010-04-01, End date: 2015-03-31
Project acronym BIRTOACTION
Project From birth to action: regulation of gene expression through transcription complex biogenesis
Researcher (PI) Laszlo Tora
Host Institution (HI) CENTRE EUROPEEN DE RECHERCHE EN BIOLOGIE ET MEDECINE
Call Details Advanced Grant (AdG), LS1, ERC-2013-ADG
Summary "Transcriptional regulation of protein coding genes in eukaryotic cells requires a complex interplay of sequence-specific DNA-binding factors, co-activators, general transcription factors (GTFs), RNA polymerase II and the epigenetic status of target sequences. Nuclear transcription complexes function as large multiprotein assemblies and are often composed of functional modules. The regulated decision-making that exists in cells governing the assembly and the allocation of factors to different transcription complexes to regulate distinct gene expression pathways is not yet understood. To tackle this fundamental question, we will systematically analyse the regulated biogenesis of transcription complexes from their sites of translation in the cytoplasm, through their assembly intermediates and nuclear import, to their site of action in the nucleus. The project will have four main Aims to decipher the biogenesis of transcription complexes:
I) Investigate their co-translation-driven assembly
II) Determine their cytoplasmic intermediates and factors required for their assembly pathways
III) Uncover their nuclear import
IV) Understand at the single molecule level their nuclear assembly, dynamics and action at target genes
To carry out these aims we propose a combination of multidisciplinary and cutting edge approaches, out of which some of them will be high-risk taking, while others will utilize methods routinely run by the group. The project builds on several complementary expertise and knowledge either already existing in the group or that will be implemented during the project. At the end of the proposed project we will obtain novel results extensively describing the different steps of the regulatory mechanisms that control the assembly and the consequent gene regulatory function of transcription complexes. Thus, we anticipate that the results of our research will have a major impact on the field and will lead to a new paradigm for contemporary metazoan transcription."
Summary
"Transcriptional regulation of protein coding genes in eukaryotic cells requires a complex interplay of sequence-specific DNA-binding factors, co-activators, general transcription factors (GTFs), RNA polymerase II and the epigenetic status of target sequences. Nuclear transcription complexes function as large multiprotein assemblies and are often composed of functional modules. The regulated decision-making that exists in cells governing the assembly and the allocation of factors to different transcription complexes to regulate distinct gene expression pathways is not yet understood. To tackle this fundamental question, we will systematically analyse the regulated biogenesis of transcription complexes from their sites of translation in the cytoplasm, through their assembly intermediates and nuclear import, to their site of action in the nucleus. The project will have four main Aims to decipher the biogenesis of transcription complexes:
I) Investigate their co-translation-driven assembly
II) Determine their cytoplasmic intermediates and factors required for their assembly pathways
III) Uncover their nuclear import
IV) Understand at the single molecule level their nuclear assembly, dynamics and action at target genes
To carry out these aims we propose a combination of multidisciplinary and cutting edge approaches, out of which some of them will be high-risk taking, while others will utilize methods routinely run by the group. The project builds on several complementary expertise and knowledge either already existing in the group or that will be implemented during the project. At the end of the proposed project we will obtain novel results extensively describing the different steps of the regulatory mechanisms that control the assembly and the consequent gene regulatory function of transcription complexes. Thus, we anticipate that the results of our research will have a major impact on the field and will lead to a new paradigm for contemporary metazoan transcription."
Max ERC Funding
2 500 000 €
Duration
Start date: 2014-01-01, End date: 2018-12-31
Project acronym BIZEB
Project Bio-Imaging of Zoonotic and Emerging Bunyaviruses
Researcher (PI) Juha Huiskonen
Host Institution (HI) HELSINGIN YLIOPISTO
Call Details Consolidator Grant (CoG), LS1, ERC-2014-CoG
Summary We aim to understand host cell entry of enveloped viruses at molecular level. A crucial step in this process is when the viral membrane fuses with the cell membrane. Similarly to cell–cell fusion, this step is mediated by fusion proteins (classes I–III). Several medically important viruses, notably dengue and many bunyaviruses, harbour a class II fusion protein. Class II fusion protein structures have been solved in pre- and post-fusion conformation and in some cases different factors promoting fusion have been determined. However, questions about the most important steps of this key process remain unanswered. I will focus on the entry mechanism of bunyaviruses by using cutting-edge, high spatial and temporal resolution bio-imaging techniques. These viruses have been chosen as a model system to maximise the significance of the project: they form an emerging viral threat to humans and animals, no approved vaccines or antivirals exist for human use and they are less studied than other class II fusion protein systems. Cryo-electron microscopy and tomography will be used to solve high-resolution structures (up to ~3 Å) of viruses, in addition to virus–receptor and virus–membrane complexes. Advanced fluorescence microscopy techniques will be used to probe the dynamics of virus entry and fusion in vivo and in vitro. Deciphering key steps in virus entry is expected to contribute to rational vaccine and drug design. During this project I aim to establish a world-class laboratory in structural and cellular biology of emerging viruses. The project greatly benefits from our unique biosafety level 3 laboratory offering advanced bio-imaging techniques. Furthermore it will also pave way for similar projects on other infectious viruses. Finally the novel computational image processing methods developed in this project will be broadly applicable for the analysis of flexible biological structures, which often pose the most challenging yet interesting questions in structural biology.
Summary
We aim to understand host cell entry of enveloped viruses at molecular level. A crucial step in this process is when the viral membrane fuses with the cell membrane. Similarly to cell–cell fusion, this step is mediated by fusion proteins (classes I–III). Several medically important viruses, notably dengue and many bunyaviruses, harbour a class II fusion protein. Class II fusion protein structures have been solved in pre- and post-fusion conformation and in some cases different factors promoting fusion have been determined. However, questions about the most important steps of this key process remain unanswered. I will focus on the entry mechanism of bunyaviruses by using cutting-edge, high spatial and temporal resolution bio-imaging techniques. These viruses have been chosen as a model system to maximise the significance of the project: they form an emerging viral threat to humans and animals, no approved vaccines or antivirals exist for human use and they are less studied than other class II fusion protein systems. Cryo-electron microscopy and tomography will be used to solve high-resolution structures (up to ~3 Å) of viruses, in addition to virus–receptor and virus–membrane complexes. Advanced fluorescence microscopy techniques will be used to probe the dynamics of virus entry and fusion in vivo and in vitro. Deciphering key steps in virus entry is expected to contribute to rational vaccine and drug design. During this project I aim to establish a world-class laboratory in structural and cellular biology of emerging viruses. The project greatly benefits from our unique biosafety level 3 laboratory offering advanced bio-imaging techniques. Furthermore it will also pave way for similar projects on other infectious viruses. Finally the novel computational image processing methods developed in this project will be broadly applicable for the analysis of flexible biological structures, which often pose the most challenging yet interesting questions in structural biology.
Max ERC Funding
1 998 375 €
Duration
Start date: 2015-04-01, End date: 2020-03-31
Project acronym BrokenGenome
Project Breaking and rebuilding the genome: mechanistic rules for the dangerous game of sex.
Researcher (PI) Corentin CLAEYS BOUUAERT
Host Institution (HI) UNIVERSITE CATHOLIQUE DE LOUVAIN
Call Details Starting Grant (StG), LS1, ERC-2018-STG
Summary Sexual reproduction depends on the programmed induction of DNA double-strand breaks (DSBs) and their ensuing repair by homologous recombination. This complex process is essential for sexual reproduction because it ultimately allows the pairing and separation of homologous chromosomes during formation of haploid gametes. Although meiotic recombination has been investigated for decades, many of the underlying molecular processes remain unclear, largely due to the lack of biochemical studies. I have recently made important progress by, for the first time, successfully purifying proteins involved in two aspects of meiotic recombination: DSB formation and the final stage of formation of the crossovers that are a central raison-d’être of meiotic recombination. This has opened new avenues for future research that I intend to pursue in my own laboratory. Here, I propose a set of biochemical approaches, complemented by molecular genetics methods, to gain insights into four central problems: (i) How meiotic proteins collaborate to induce DSBs; (ii) How DSB proteins interact with components that form the axes of meiotic chromosomes; (iii) How proteins involved at later stages of recombination form crossovers; and (iv) How crossover proteins interact with components of synapsed chromosomes. For each problem, I will set up in vitro systems to probe the activities of the players involved, their interactions with DNA, and their assembly into macromolecular complexes. In addition, I propose to develop new methodology for identifying proteins that are associated with DNA that has undergone recombination-related DNA synthesis. My goal is to gain insights into the mechanisms that govern meiotic recombination. Importantly, these mechanisms are intimately linked not only to gamete formation, but also to the general recombination pathways that all cells use to maintain genome stability. In both contexts, our findings will be relevant to the development and avoidance of disease states.
Summary
Sexual reproduction depends on the programmed induction of DNA double-strand breaks (DSBs) and their ensuing repair by homologous recombination. This complex process is essential for sexual reproduction because it ultimately allows the pairing and separation of homologous chromosomes during formation of haploid gametes. Although meiotic recombination has been investigated for decades, many of the underlying molecular processes remain unclear, largely due to the lack of biochemical studies. I have recently made important progress by, for the first time, successfully purifying proteins involved in two aspects of meiotic recombination: DSB formation and the final stage of formation of the crossovers that are a central raison-d’être of meiotic recombination. This has opened new avenues for future research that I intend to pursue in my own laboratory. Here, I propose a set of biochemical approaches, complemented by molecular genetics methods, to gain insights into four central problems: (i) How meiotic proteins collaborate to induce DSBs; (ii) How DSB proteins interact with components that form the axes of meiotic chromosomes; (iii) How proteins involved at later stages of recombination form crossovers; and (iv) How crossover proteins interact with components of synapsed chromosomes. For each problem, I will set up in vitro systems to probe the activities of the players involved, their interactions with DNA, and their assembly into macromolecular complexes. In addition, I propose to develop new methodology for identifying proteins that are associated with DNA that has undergone recombination-related DNA synthesis. My goal is to gain insights into the mechanisms that govern meiotic recombination. Importantly, these mechanisms are intimately linked not only to gamete formation, but also to the general recombination pathways that all cells use to maintain genome stability. In both contexts, our findings will be relevant to the development and avoidance of disease states.
Max ERC Funding
1 499 075 €
Duration
Start date: 2019-07-01, End date: 2024-06-30
Project acronym BUNDLEFORCE
Project Unravelling the Mechanosensitivity of Actin Bundles in Filopodia
Researcher (PI) Antoine Guillaume Jegou
Host Institution (HI) CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
Call Details Starting Grant (StG), LS1, ERC-2015-STG
Summary Eukaryotic cells constantly convert signals between biochemical energy and mechanical work to timely accomplish many key functions such as migration, division or development. Filopodia are essential finger-like structures that emerge at the cell front to orient the cell in response to its chemical and mechanical environment. Yet, the molecular interactions that make the filopodia mechanosensitive are not known. To tackle this challenge we propose unique biophysical in vitro and in vivo experiments of increasing complexity. Here we will focus on how the underlying actin filament bundle regulates filopodium growth and retraction cycles at the micrometer and seconds scales. These parallel actin filaments are mainly elongated at their barbed-end by formins and cross-linked by bundling proteins such as fascins.
We aim to:
1) Elucidate how formin and fascin functions are regulated by mechanics at the single filament level. We will investigate how formin partners and competitors present in filopodia affect formin processivity; how fascin affinity for the side of filaments is modified by filament tension and formin presence at the barbed-end.
2) Reconstitute filopodium-like actin bundles in vitro to understand how actin bundle size and fate are regulated down to the molecular scale. Using a unique experimental setup that combines microfluidics and optical tweezers, we will uncover for the first time actin bundles mechanosensitive capabilities, both in tension and compression.
3) Decipher in vivo the mechanics of actin bundles in filopodia, using fascins and formins with integrated fluorescent tension sensors.
This framework spanning from in vitro single filament to in vivo meso-scale actin networks will bring unprecedented insights into the role of actin bundles in filopodia mechanosensitivity.
Summary
Eukaryotic cells constantly convert signals between biochemical energy and mechanical work to timely accomplish many key functions such as migration, division or development. Filopodia are essential finger-like structures that emerge at the cell front to orient the cell in response to its chemical and mechanical environment. Yet, the molecular interactions that make the filopodia mechanosensitive are not known. To tackle this challenge we propose unique biophysical in vitro and in vivo experiments of increasing complexity. Here we will focus on how the underlying actin filament bundle regulates filopodium growth and retraction cycles at the micrometer and seconds scales. These parallel actin filaments are mainly elongated at their barbed-end by formins and cross-linked by bundling proteins such as fascins.
We aim to:
1) Elucidate how formin and fascin functions are regulated by mechanics at the single filament level. We will investigate how formin partners and competitors present in filopodia affect formin processivity; how fascin affinity for the side of filaments is modified by filament tension and formin presence at the barbed-end.
2) Reconstitute filopodium-like actin bundles in vitro to understand how actin bundle size and fate are regulated down to the molecular scale. Using a unique experimental setup that combines microfluidics and optical tweezers, we will uncover for the first time actin bundles mechanosensitive capabilities, both in tension and compression.
3) Decipher in vivo the mechanics of actin bundles in filopodia, using fascins and formins with integrated fluorescent tension sensors.
This framework spanning from in vitro single filament to in vivo meso-scale actin networks will bring unprecedented insights into the role of actin bundles in filopodia mechanosensitivity.
Max ERC Funding
1 499 190 €
Duration
Start date: 2016-03-01, End date: 2021-02-28
Project acronym BURSTREG
Project Single-molecule visualization of transcription dynamics to understand regulatory mechanisms of transcriptional bursting and its effects on cellular fitness
Researcher (PI) Tineke LENSTRA
Host Institution (HI) STICHTING HET NEDERLANDS KANKER INSTITUUT-ANTONI VAN LEEUWENHOEK ZIEKENHUIS
Call Details Starting Grant (StG), LS1, ERC-2017-STG
Summary Transcription in single cells is a stochastic process that arises from the random collision of molecules, resulting in heterogeneity in gene expression in cell populations. This heterogeneity in gene expression influences cell fate decisions and disease progression. Interestingly, gene expression variability is not the same for every gene: noise can vary by several orders of magnitude across transcriptomes. The reason for this transcript-specific behavior is that genes are not transcribed in a continuous fashion, but can show transcriptional bursting, with periods of gene activity followed by periods of inactivity. The noisiness of a gene can be tuned by changing the duration and the rate of switching between periods of activity and inactivity. Even though transcriptional bursting is conserved from bacteria to yeast to human cells, the origin and regulators of bursting remain largely unknown. Here, I will use cutting-edge single-molecule RNA imaging techniques to directly observe and measure transcriptional bursting in living yeast cells. First, bursting properties will be quantified at different endogenous and mutated genes to evaluate the contribution of cis-regulatory promoter elements on bursting. Second, the role of trans-regulatory complexes will be characterized by dynamic depletion or gene-specific targeting of transcription regulatory proteins and observing changes in RNA synthesis in real-time. Third, I will develop a new technology to visualize the binding dynamics of single transcription factor molecules at the transcription site, so that the stability of upstream regulatory factors and the RNA output can directly be compared in the same cell. Finally, I will examine the phenotypic effect of different bursting patterns on organismal fitness. Overall, these approaches will reveal how bursting is regulated at the molecular level and how different bursting patterns affect the heterogeneity and fitness of the organism.
Summary
Transcription in single cells is a stochastic process that arises from the random collision of molecules, resulting in heterogeneity in gene expression in cell populations. This heterogeneity in gene expression influences cell fate decisions and disease progression. Interestingly, gene expression variability is not the same for every gene: noise can vary by several orders of magnitude across transcriptomes. The reason for this transcript-specific behavior is that genes are not transcribed in a continuous fashion, but can show transcriptional bursting, with periods of gene activity followed by periods of inactivity. The noisiness of a gene can be tuned by changing the duration and the rate of switching between periods of activity and inactivity. Even though transcriptional bursting is conserved from bacteria to yeast to human cells, the origin and regulators of bursting remain largely unknown. Here, I will use cutting-edge single-molecule RNA imaging techniques to directly observe and measure transcriptional bursting in living yeast cells. First, bursting properties will be quantified at different endogenous and mutated genes to evaluate the contribution of cis-regulatory promoter elements on bursting. Second, the role of trans-regulatory complexes will be characterized by dynamic depletion or gene-specific targeting of transcription regulatory proteins and observing changes in RNA synthesis in real-time. Third, I will develop a new technology to visualize the binding dynamics of single transcription factor molecules at the transcription site, so that the stability of upstream regulatory factors and the RNA output can directly be compared in the same cell. Finally, I will examine the phenotypic effect of different bursting patterns on organismal fitness. Overall, these approaches will reveal how bursting is regulated at the molecular level and how different bursting patterns affect the heterogeneity and fitness of the organism.
Max ERC Funding
1 950 775 €
Duration
Start date: 2018-01-01, End date: 2022-12-31
Project acronym C-CLEAR
Project Complement: to clear or not to clear
Researcher (PI) Piet Gros
Host Institution (HI) UNIVERSITEIT UTRECHT
Call Details Advanced Grant (AdG), LS1, ERC-2017-ADG
Summary Mammalian complement recognizes a variety of cell-surface danger and damage signals to clear invading microbes and injured host cells, while protecting healthy host cells. Improper complement responses contribute to diverse pathologies, ranging from bacterial infections up to paralyzing Guillain-Barré syndrome and schizophrenia. What determines the balance between complement attack reactions and host-cell defense measures and, thus, what drives cell fate is unclear.
My lab has a long-standing track record in elucidating molecular mechanisms underlying key complement reactions. We have revealed, for example, how the interplay between assembly and proteolysis of these large multi-domain protein complexes achieves elementary regulatory functions, such as localization, amplification and inhibition, in the central (so-called alternative) pathway of complement. Results from my lab underpin research programs for the development of novel therapeutic approaches in academia and industry.
Here the goal is to understand how the molecular mechanisms of complement attack and defense on cell membranes determine clearance of a cell. Enabled by new mechanistic insights and preliminary data we can now address both long-standing and novel questions. In particular, we will address the role of membrane organization and dynamics in complement attack and defense. Facilitated by recent technological developments, we will combine crystallography, cryo-EM, cryo-ET and high-resolution microscopy to resolve complement complex formations and reactions on membranes.
Thus, this project aims to provide an integrative understanding of the molecular complement mechanisms that determine cell fate. Results will likely be of immediate importance for novel therapeutic approaches for a range of complement-related diseases. Furthermore, it will provide clarity into the general, and possibly fundamental, role of complement in tissue maintenance in mammals.
Summary
Mammalian complement recognizes a variety of cell-surface danger and damage signals to clear invading microbes and injured host cells, while protecting healthy host cells. Improper complement responses contribute to diverse pathologies, ranging from bacterial infections up to paralyzing Guillain-Barré syndrome and schizophrenia. What determines the balance between complement attack reactions and host-cell defense measures and, thus, what drives cell fate is unclear.
My lab has a long-standing track record in elucidating molecular mechanisms underlying key complement reactions. We have revealed, for example, how the interplay between assembly and proteolysis of these large multi-domain protein complexes achieves elementary regulatory functions, such as localization, amplification and inhibition, in the central (so-called alternative) pathway of complement. Results from my lab underpin research programs for the development of novel therapeutic approaches in academia and industry.
Here the goal is to understand how the molecular mechanisms of complement attack and defense on cell membranes determine clearance of a cell. Enabled by new mechanistic insights and preliminary data we can now address both long-standing and novel questions. In particular, we will address the role of membrane organization and dynamics in complement attack and defense. Facilitated by recent technological developments, we will combine crystallography, cryo-EM, cryo-ET and high-resolution microscopy to resolve complement complex formations and reactions on membranes.
Thus, this project aims to provide an integrative understanding of the molecular complement mechanisms that determine cell fate. Results will likely be of immediate importance for novel therapeutic approaches for a range of complement-related diseases. Furthermore, it will provide clarity into the general, and possibly fundamental, role of complement in tissue maintenance in mammals.
Max ERC Funding
2 332 500 €
Duration
Start date: 2018-07-01, End date: 2023-06-30
Project acronym CaBiS
Project Chemistry and Biology in Synergy - Studies of hydrogenases using a combination of synthetic chemistry and biological tools
Researcher (PI) Gustav Oskar BERGGREN
Host Institution (HI) UPPSALA UNIVERSITET
Call Details Starting Grant (StG), LS1, ERC-2016-STG
Summary My proposal aims to take advantage of my ground-breaking finding that it is possible to mature, or activate, the [FeFe] hydrogenase enzyme (HydA) using synthetic mimics of its catalytic [2Fe] cofactor. (Berggren et al, Nature, 2013) We will now explore the chemistry and (bio-)technological potential of the enzyme using an interdisciplinary approach ranging from in vivo biochemical studies all the way to synthetic model chemistry. Hydrogenases catalyse the interconversion between protons and H2 with remarkable efficiency. Consequently, they are intensively studied as alternatives to Pt-catalysts for these reactions, and are arguably of high (bio-) technological importance in the light of a future “hydrogen society”.
The project involves the preparation of novel “artificial” hydrogenases with the primary aim of designing spectroscopic model systems via modification(s) of the organometallic [2Fe] subsite. In parallel we will prepare in vitro loaded forms of the maturase HydF and study its interaction with apo-HydA in order to further elucidate the maturation process of HydA. Moreover we will develop the techniques necessary for in vivo application of the artificial activation concept, thereby paving the way for a multitude of studies including the reactivity of artificial hydrogenases inside a living cell, but also e.g. gain-of-function studies in combination with metabolomics and proteomics. Inspired by our work on the artificial maturation system we will also draw from our knowledge of Nature’s [FeS] cluster proteins in order to prepare a novel class of “miniaturized hydrogenases” combining synthetic [4Fe4S] binding oligopeptides with [2Fe] cofactor model compounds.
Our interdisciplinary approach is particularly appealing as it not only provides further insight into hydrogenase chemistry and the maturation of metalloproteins, but also involves the development of novel tools and concepts applicable to the wider field of bioinorganic chemistry.
Summary
My proposal aims to take advantage of my ground-breaking finding that it is possible to mature, or activate, the [FeFe] hydrogenase enzyme (HydA) using synthetic mimics of its catalytic [2Fe] cofactor. (Berggren et al, Nature, 2013) We will now explore the chemistry and (bio-)technological potential of the enzyme using an interdisciplinary approach ranging from in vivo biochemical studies all the way to synthetic model chemistry. Hydrogenases catalyse the interconversion between protons and H2 with remarkable efficiency. Consequently, they are intensively studied as alternatives to Pt-catalysts for these reactions, and are arguably of high (bio-) technological importance in the light of a future “hydrogen society”.
The project involves the preparation of novel “artificial” hydrogenases with the primary aim of designing spectroscopic model systems via modification(s) of the organometallic [2Fe] subsite. In parallel we will prepare in vitro loaded forms of the maturase HydF and study its interaction with apo-HydA in order to further elucidate the maturation process of HydA. Moreover we will develop the techniques necessary for in vivo application of the artificial activation concept, thereby paving the way for a multitude of studies including the reactivity of artificial hydrogenases inside a living cell, but also e.g. gain-of-function studies in combination with metabolomics and proteomics. Inspired by our work on the artificial maturation system we will also draw from our knowledge of Nature’s [FeS] cluster proteins in order to prepare a novel class of “miniaturized hydrogenases” combining synthetic [4Fe4S] binding oligopeptides with [2Fe] cofactor model compounds.
Our interdisciplinary approach is particularly appealing as it not only provides further insight into hydrogenase chemistry and the maturation of metalloproteins, but also involves the development of novel tools and concepts applicable to the wider field of bioinorganic chemistry.
Max ERC Funding
1 494 880 €
Duration
Start date: 2017-02-01, End date: 2022-01-31
Project acronym CANCER SIGNALOSOMES
Project Spatially and temporally regulated membrane complexes in cancer cell invasion and cytokinesis
Researcher (PI) Johanna Ivaska
Host Institution (HI) TEKNOLOGIAN TUTKIMUSKESKUS VTT
Call Details Starting Grant (StG), LS1, ERC-2007-StG
Summary Cancer progression, characterized by uncontrolled proliferation and motility of cells, is a complex and deadly process. Integrins, a major cell surface adhesion receptor family, are transmembrane proteins known to regulate cell behaviour by transducing extracellular signals to cytoplasmic protein complexes. We and others have shown that recruitment of specific protein complexes by the cytoplasmic domains of integrins is important in tumorigenesis. Here our aim is to study three interrelated processes in cancer progression which involve integrin signalling, but which have not been elucidated earlier at all. 1) Integrins in cell division (cytokinesis). Since coordinated action of the cytoskeleton and membranes is needed both for cell division and motility, shared integrin functions can regulate both events. 2) Dynamic integrin signalosomes at the leading edge of invading cells. Spatially and temporally regulated, integrin-protein complexes at the front of infiltrating cells are likely to dictate the movement of cancer cells in tissues. 3) Transmembrane segments of integrins as scaffolds for integrin signalling. In addition to cytosolic proteins, integrins most likely interact with proteins within the membrane resulting into new signalling modalities. In this proposal we will use innovative, modern and even unconventional techniques (such as RNAi and live-cell arrays detecting integrin traffic, cell motility and multiplication, laser-microdissection, proteomics and bacterial-two-hybrid screens) to unravel these new integrin functions, for which we have preliminary evidence. Each project will give fundamentally novel mechanistic insight into the role of integrins in cancer. Moreover, these interdisciplinary new openings will increase our understanding in cancer progression in general and will open new possibilities for therapeutic intervention targeting both cancer proliferation and dissemination in the body.
Summary
Cancer progression, characterized by uncontrolled proliferation and motility of cells, is a complex and deadly process. Integrins, a major cell surface adhesion receptor family, are transmembrane proteins known to regulate cell behaviour by transducing extracellular signals to cytoplasmic protein complexes. We and others have shown that recruitment of specific protein complexes by the cytoplasmic domains of integrins is important in tumorigenesis. Here our aim is to study three interrelated processes in cancer progression which involve integrin signalling, but which have not been elucidated earlier at all. 1) Integrins in cell division (cytokinesis). Since coordinated action of the cytoskeleton and membranes is needed both for cell division and motility, shared integrin functions can regulate both events. 2) Dynamic integrin signalosomes at the leading edge of invading cells. Spatially and temporally regulated, integrin-protein complexes at the front of infiltrating cells are likely to dictate the movement of cancer cells in tissues. 3) Transmembrane segments of integrins as scaffolds for integrin signalling. In addition to cytosolic proteins, integrins most likely interact with proteins within the membrane resulting into new signalling modalities. In this proposal we will use innovative, modern and even unconventional techniques (such as RNAi and live-cell arrays detecting integrin traffic, cell motility and multiplication, laser-microdissection, proteomics and bacterial-two-hybrid screens) to unravel these new integrin functions, for which we have preliminary evidence. Each project will give fundamentally novel mechanistic insight into the role of integrins in cancer. Moreover, these interdisciplinary new openings will increase our understanding in cancer progression in general and will open new possibilities for therapeutic intervention targeting both cancer proliferation and dissemination in the body.
Max ERC Funding
1 529 369 €
Duration
Start date: 2008-08-01, End date: 2013-07-31
Project acronym CANCER&AGEING
Project COMMOM MECHANISMS UNDERLYING CANCER AND AGEING
Researcher (PI) Manuel Serrano
Host Institution (HI) FUNDACION CENTRO NACIONAL DE INVESTIGACIONES ONCOLOGICAS CARLOS III
Call Details Advanced Grant (AdG), LS1, ERC-2008-AdG
Summary "In recent years, we have made significant contributions to the understanding of the tumour suppressors p53, p16INK4a, and ARF, particularly in relation with cellular senescence and aging. The current project is motivated by two hypothesis: 1) that the INK4/ARF locus is a sensor of epigenetic damage and this is at the basis of its activation by oncogenes and aging; and, 2) that the accumulation of cellular damage and stress is at the basis of both cancer and aging, and consequently ""anti-damage genes"", such as tumour suppressors, simultaneously counteract both cancer and aging. With regard to the INK4/ARF locus, the project includes: 1.1) the generation of null mice for the Regulatory Domain (RD) thought to be essential for the proper regulation of the locus; 1.2) the study of the INK4/ARF anti-sense transcription and its importance for the assembly of Polycomb repressive complexes; 1.3) the generation of mice carrying the human INK4/ARF locus to analyze, among other aspects, whether the known differences between the human and murine loci are ""locus autonomous""; and, 1.4) to analyze the INK4/ARF locus in the process of epigenetic reprogramming both from ES cells to differentiated cells and, conversely, from differentiated cells to induced-pluripotent stem (iPS) cells. With regard to the impact of ""anti-damage genes"" on cancer and aging, the project includes: 2.1) the analysis of the aging of super-INK4/ARF mice and super-p53 mice; 2.2) we have generated super-PTEN mice and we will examine whether PTEN not only confers cancer resistance but also anti-aging activity; and, finally, 2.3) we have generated super-SIRT1 mice, which is among the best-characterized anti-aging genes in non-mammalian model systems (where it is named Sir2) involved in protection from metabolic damage, and we will study the cancer and aging of these mice. Together, this project will significantly advance our understanding of the molecular mechanisms underlying cancer and aging."
Summary
"In recent years, we have made significant contributions to the understanding of the tumour suppressors p53, p16INK4a, and ARF, particularly in relation with cellular senescence and aging. The current project is motivated by two hypothesis: 1) that the INK4/ARF locus is a sensor of epigenetic damage and this is at the basis of its activation by oncogenes and aging; and, 2) that the accumulation of cellular damage and stress is at the basis of both cancer and aging, and consequently ""anti-damage genes"", such as tumour suppressors, simultaneously counteract both cancer and aging. With regard to the INK4/ARF locus, the project includes: 1.1) the generation of null mice for the Regulatory Domain (RD) thought to be essential for the proper regulation of the locus; 1.2) the study of the INK4/ARF anti-sense transcription and its importance for the assembly of Polycomb repressive complexes; 1.3) the generation of mice carrying the human INK4/ARF locus to analyze, among other aspects, whether the known differences between the human and murine loci are ""locus autonomous""; and, 1.4) to analyze the INK4/ARF locus in the process of epigenetic reprogramming both from ES cells to differentiated cells and, conversely, from differentiated cells to induced-pluripotent stem (iPS) cells. With regard to the impact of ""anti-damage genes"" on cancer and aging, the project includes: 2.1) the analysis of the aging of super-INK4/ARF mice and super-p53 mice; 2.2) we have generated super-PTEN mice and we will examine whether PTEN not only confers cancer resistance but also anti-aging activity; and, finally, 2.3) we have generated super-SIRT1 mice, which is among the best-characterized anti-aging genes in non-mammalian model systems (where it is named Sir2) involved in protection from metabolic damage, and we will study the cancer and aging of these mice. Together, this project will significantly advance our understanding of the molecular mechanisms underlying cancer and aging."
Max ERC Funding
2 000 000 €
Duration
Start date: 2009-04-01, End date: 2015-03-31
Project acronym CANCERLINC
Project Functional and Mecahnistic Roles of Large Intergenic Non-coding RNAs in Cancer
Researcher (PI) Maite Huarte Martinez
Host Institution (HI) FUNDACION PARA LA INVESTIGACION MEDICA APLICADA FIMA
Call Details Starting Grant (StG), LS1, ERC-2011-StG_20101109
Summary Mammalian cells express thousands of RNA molecules structurally similar to protein coding genes –they are large, spliced, poly-adenylated, transcribed by RNA Pol II, with conserved promoters and exonic structures –however lack coding capacity. Although thousands exist, only few of these large intergenic non-coding RNAs (lincRNAs) have been characterized. The few that have, show powerful biological roles as regulators of gene expression by diverse epigenetic and non-epigenetic mechanisms. Significantly, their expression patterns suggest that some lincRNAs are involved in cellular pathways critical in cancer, like the p53 pathway. I explored this association demonstrating that p53 induces the expression of many lincRNAs. One them, named lincRNA-p21, is directly induced by p53 to play a critical role in the p53 response, being required for the global repression of genes that interfere with p53 induction of apoptosis. My results, together with the emerging evidence in the field, suggest that lincRNAs may play key roles in numerous tumor-suppressor and oncogenic pathways, representing an unknown paradigm in cellular transformation. However, their mechanisms of function and biological roles remain largely unexplored.
The goal of this project is to decipher the functional and biological roles of lincRNAs in the context of oncogenic pathways to better understand the cellular mechanisms of gene regulation at the epigenetic and non-epigenetic levels, and be able to implement lincRNA use for diagnostics and therapies. In order to accomplish these goals we will integrate molecular and cell biology techniques with functional genomics approaches and in vivo studies. Importantly, the profiling of patient samples will reveal the relevance of our findings in human disease. Together, the functional study of lincRNAs will not only be crucial for developing improved diagnostics and therapies, but also will help a better understanding of the mechanisms that govern cellular network.
Summary
Mammalian cells express thousands of RNA molecules structurally similar to protein coding genes –they are large, spliced, poly-adenylated, transcribed by RNA Pol II, with conserved promoters and exonic structures –however lack coding capacity. Although thousands exist, only few of these large intergenic non-coding RNAs (lincRNAs) have been characterized. The few that have, show powerful biological roles as regulators of gene expression by diverse epigenetic and non-epigenetic mechanisms. Significantly, their expression patterns suggest that some lincRNAs are involved in cellular pathways critical in cancer, like the p53 pathway. I explored this association demonstrating that p53 induces the expression of many lincRNAs. One them, named lincRNA-p21, is directly induced by p53 to play a critical role in the p53 response, being required for the global repression of genes that interfere with p53 induction of apoptosis. My results, together with the emerging evidence in the field, suggest that lincRNAs may play key roles in numerous tumor-suppressor and oncogenic pathways, representing an unknown paradigm in cellular transformation. However, their mechanisms of function and biological roles remain largely unexplored.
The goal of this project is to decipher the functional and biological roles of lincRNAs in the context of oncogenic pathways to better understand the cellular mechanisms of gene regulation at the epigenetic and non-epigenetic levels, and be able to implement lincRNA use for diagnostics and therapies. In order to accomplish these goals we will integrate molecular and cell biology techniques with functional genomics approaches and in vivo studies. Importantly, the profiling of patient samples will reveal the relevance of our findings in human disease. Together, the functional study of lincRNAs will not only be crucial for developing improved diagnostics and therapies, but also will help a better understanding of the mechanisms that govern cellular network.
Max ERC Funding
1 500 000 €
Duration
Start date: 2012-01-01, End date: 2017-12-31
Project acronym Celcelfus
Project Cell-Cell fusion in fertilization and developmental biology: a structural biology approach
Researcher (PI) Félix A. Rey
Host Institution (HI) INSTITUT PASTEUR
Call Details Advanced Grant (AdG), LS1, ERC-2013-ADG
Summary My group has made seminal contributions in the past toward understanding the mechanism of membrane fusion used by enveloped viruses to infect a cell. This aim of this ERC grant proposal is to achieve similar breakthroughs in understanding fusion between cells, both during fertilization and organogenesis. This proposal is based in recent important results not yet published.
We have determined the crystal structure of the C. elegans protein EFF-1, a member of the “fusion family” (FF). EFF-1 is responsible for a cell-cell fusion event during skin formation in the nematode. Strikingly, the crystal structure shows that EFF-1 is homologous to the “Class II” viral protein fusogens, thus indicating that they have diverged from a common ancestor. The observed homology could not be identified by other means because the proteins have diverged to the point where no remnants of sequence similarity are left, yet the tertiary and quaternary organization is the same. However, the homotypic fusion mechanism of EFF-1 is clearly different to that of viral fusion proteins.
This proposal intends to build on the momentum generated by this exciting discovery, in an attempt to cast light into the fusion mechanism of FF proteins. We will reconstitute them in artificial liposomes and will also follow them within cells with the use of light microscopy. We will also focus in determining the crystal structure of the monomeric pre-fusion form of EFF-1,and of the intact trans-membrane post fusion trimer. In parallel, we want to make use the experience accumulated over the years in crystallizing viral glycoproteins, to apply it to the conserved family of HAP2/GSC1 proteins involved in fusion of gametes during fertilization. These proteins exhibit a similar pattern of secondary structure elements in the ectodomain as class II proteins, but only a crystallographic analysis can identify a possible structural homology and provide the basis to understand the molecular mechanisms of cell-cell fusion.
Summary
My group has made seminal contributions in the past toward understanding the mechanism of membrane fusion used by enveloped viruses to infect a cell. This aim of this ERC grant proposal is to achieve similar breakthroughs in understanding fusion between cells, both during fertilization and organogenesis. This proposal is based in recent important results not yet published.
We have determined the crystal structure of the C. elegans protein EFF-1, a member of the “fusion family” (FF). EFF-1 is responsible for a cell-cell fusion event during skin formation in the nematode. Strikingly, the crystal structure shows that EFF-1 is homologous to the “Class II” viral protein fusogens, thus indicating that they have diverged from a common ancestor. The observed homology could not be identified by other means because the proteins have diverged to the point where no remnants of sequence similarity are left, yet the tertiary and quaternary organization is the same. However, the homotypic fusion mechanism of EFF-1 is clearly different to that of viral fusion proteins.
This proposal intends to build on the momentum generated by this exciting discovery, in an attempt to cast light into the fusion mechanism of FF proteins. We will reconstitute them in artificial liposomes and will also follow them within cells with the use of light microscopy. We will also focus in determining the crystal structure of the monomeric pre-fusion form of EFF-1,and of the intact trans-membrane post fusion trimer. In parallel, we want to make use the experience accumulated over the years in crystallizing viral glycoproteins, to apply it to the conserved family of HAP2/GSC1 proteins involved in fusion of gametes during fertilization. These proteins exhibit a similar pattern of secondary structure elements in the ectodomain as class II proteins, but only a crystallographic analysis can identify a possible structural homology and provide the basis to understand the molecular mechanisms of cell-cell fusion.
Max ERC Funding
2 478 800 €
Duration
Start date: 2014-03-01, End date: 2019-02-28
Project acronym CelluFuel
Project Designer Cellulosomes by Single Molecule Cut & Paste
Researcher (PI) Hermann Eduard Gaub
Host Institution (HI) LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN
Call Details Advanced Grant (AdG), LS1, ERC-2011-ADG_20110310
Summary Biofuel from wood and waste will be a substantial share of our future energy mix. The conversion of lignocellulose to fermentable polysaccharides is the current bottleneck. We propose to use single molecule cut and paste technology to assemble designer cellulosoms and combine enzymes from different species with nanocatalysts.
Summary
Biofuel from wood and waste will be a substantial share of our future energy mix. The conversion of lignocellulose to fermentable polysaccharides is the current bottleneck. We propose to use single molecule cut and paste technology to assemble designer cellulosoms and combine enzymes from different species with nanocatalysts.
Max ERC Funding
2 351 450 €
Duration
Start date: 2012-03-01, End date: 2018-02-28
Project acronym cenRNA
Project The role of RNA in centromere biology and genome integrity
Researcher (PI) Sylvia Erhardt
Host Institution (HI) RUPRECHT-KARLS-UNIVERSITAET HEIDELBERG
Call Details Consolidator Grant (CoG), LS1, ERC-2015-CoG
Summary One of the most astonishing processes in the life of a cell is the division into two daughter cells. Such a highly organized process would presumably be regulated tightly by the underlying centromeric DNA sequence; however, the sites of chromosome attachment to the microtubule spindle are regulated by epigenetic mechanisms. The best-characterized epigenetic mark for centromeres is the histone H3-variant CENP-A, which replaces H3 in some of the nucleosomes within centromeric chromatin. Centromeres are embedded in pericentromeric heterochromatin and it has become apparent in recent years that heterochromatin is transcribed into non-coding RNAs. We have recently shown that a long non-coding RNA from pericentromeric heterochromatin of the X chromosome (SATIII) in Drosophila melanogaster localizes in trans to centromeres of all other chromosomes and is an essential component for correct loading and maintenance of CENP-A and, therefore, genome stability. Additional RNAs in Drosophila and RNAs from other species have been linked to centromeric chromatin, but their function is not understood. We propose that a complex, RNA-based epigenetic mechanism regulates centromere establishment and function.
This proposal is designed to the precise function of SATIII RNA by identifying the associated protein complexes as well as structural and post-transcriptional features of SATIII. We will evaluate the mechanisms by which SATIII functions as a heritable mark of centromeres through generations, during the developing germ line, and species separation. In parallel, we will systematically identify and characterize centromere-associated RNAs (cenRNAs) in Drosophila and human cells. We will elucidate their function in centromere biology and chromosome segregation, essentially as we have done and propose to do for SATIII. These experiments are designed to provide a detailed understanding of the essential, RNA-based epigenetic regulation of centromeres.
Summary
One of the most astonishing processes in the life of a cell is the division into two daughter cells. Such a highly organized process would presumably be regulated tightly by the underlying centromeric DNA sequence; however, the sites of chromosome attachment to the microtubule spindle are regulated by epigenetic mechanisms. The best-characterized epigenetic mark for centromeres is the histone H3-variant CENP-A, which replaces H3 in some of the nucleosomes within centromeric chromatin. Centromeres are embedded in pericentromeric heterochromatin and it has become apparent in recent years that heterochromatin is transcribed into non-coding RNAs. We have recently shown that a long non-coding RNA from pericentromeric heterochromatin of the X chromosome (SATIII) in Drosophila melanogaster localizes in trans to centromeres of all other chromosomes and is an essential component for correct loading and maintenance of CENP-A and, therefore, genome stability. Additional RNAs in Drosophila and RNAs from other species have been linked to centromeric chromatin, but their function is not understood. We propose that a complex, RNA-based epigenetic mechanism regulates centromere establishment and function.
This proposal is designed to the precise function of SATIII RNA by identifying the associated protein complexes as well as structural and post-transcriptional features of SATIII. We will evaluate the mechanisms by which SATIII functions as a heritable mark of centromeres through generations, during the developing germ line, and species separation. In parallel, we will systematically identify and characterize centromere-associated RNAs (cenRNAs) in Drosophila and human cells. We will elucidate their function in centromere biology and chromosome segregation, essentially as we have done and propose to do for SATIII. These experiments are designed to provide a detailed understanding of the essential, RNA-based epigenetic regulation of centromeres.
Max ERC Funding
1 896 250 €
Duration
Start date: 2016-07-01, End date: 2021-06-30
Project acronym CEPODRO
Project Cell polarization in Drosophila
Researcher (PI) Yohanns Bellaiche
Host Institution (HI) INSTITUT CURIE
Call Details Starting Grant (StG), LS1, ERC-2007-StG
Summary Cell polarity is fundamental to many aspects of cell and developmental biology and it is implicated in differentiation, proliferation and morphogenesis in both unicellular and multi-cellular organisms. We study the mechanisms that regulate cell polarity during both asymmetric cell division and epithelial cell polarization in Drosophila. To understand these fundamental processes, we are currently using two complementary approaches. Firstly, we are coupling genetic tools to state of the art time-lapse microscopy to genetically dissect the mechanisms of cortical cell polarization and mitotic spindle orientation. Secondly, we are introducing two innovative inter-disciplinary methodologies into the fields of cell and developmental biology: 1) single molecule imaging during asymmetric cell division, to unravel the mechanism of polarized protein distribution within the cell; 2) multi-scale tensor analysis of epithelial tissues to describe and understand how epithelial tissues grow, acquire and maintain their shape and organization during development. Using both conventional and innovative methodologies, our goals over the next four years are to better understand how molecules and protein complexes move and are activated at different locations within the cell and how cell polarization impacts on cell identities and on epithelial tissue growth and morphogenesis. Since the mechanisms underlying cell polarization are conserved throughout evolution, the proposed experiments will improve our understanding of these processes not only in Drosophila, but in all animals.
Summary
Cell polarity is fundamental to many aspects of cell and developmental biology and it is implicated in differentiation, proliferation and morphogenesis in both unicellular and multi-cellular organisms. We study the mechanisms that regulate cell polarity during both asymmetric cell division and epithelial cell polarization in Drosophila. To understand these fundamental processes, we are currently using two complementary approaches. Firstly, we are coupling genetic tools to state of the art time-lapse microscopy to genetically dissect the mechanisms of cortical cell polarization and mitotic spindle orientation. Secondly, we are introducing two innovative inter-disciplinary methodologies into the fields of cell and developmental biology: 1) single molecule imaging during asymmetric cell division, to unravel the mechanism of polarized protein distribution within the cell; 2) multi-scale tensor analysis of epithelial tissues to describe and understand how epithelial tissues grow, acquire and maintain their shape and organization during development. Using both conventional and innovative methodologies, our goals over the next four years are to better understand how molecules and protein complexes move and are activated at different locations within the cell and how cell polarization impacts on cell identities and on epithelial tissue growth and morphogenesis. Since the mechanisms underlying cell polarization are conserved throughout evolution, the proposed experiments will improve our understanding of these processes not only in Drosophila, but in all animals.
Max ERC Funding
1 159 000 €
Duration
Start date: 2008-09-01, End date: 2013-08-31
Project acronym CFRFSS
Project Chromatin Fiber and Remodeling Factor Structural Studies
Researcher (PI) Timothy John Richmond
Host Institution (HI) EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZUERICH
Call Details Advanced Grant (AdG), LS1, ERC-2012-ADG_20120314
Summary "DNA in higher organisms is organized in a nucleoprotein complex called chromatin. The structure of chromatin is responsible for compacting DNA to fit within the nucleus and for governing its access in nuclear processes. Epigenetic information is encoded chiefly via chromatin modifications. Readout of the genetic code depends on chromatin remodeling, a process actively altering chromatin structure. An understanding of the hierarchical structure of chromatin and of structurally based, remodeling mechanisms will have enormous impact for developments in medicine.
Following our high resolution structure of the nucleosome core particle, the fundamental repeating unit of chromatin, we have endeavored to determine the structure of the chromatin fiber. We showed with our X-ray structure of a tetranucleosome how nucleosomes could be organized in the fiber. Further progress has been limited by structural polymorphism and crystal disorder, but new evidence on the in vivo spacing of nucleosomes in chromatin should stimulate more advances. Part A of this application describes how we would apply these new findings to our cryo-electron microscopy study of the chromatin fiber and to our crystallographic study of a tetranucleosome containing linker histone.
Recently, my laboratory succeeded in providing the first structurally based mechanism for nucleosome spacing by a chromatin remodeling factor. We combined the X-ray structure of ISW1a(ATPase) bound to DNA with cryo-EM structures of the factor bound to two different nucleosomes to build a model showing how this remodeler uses a dinucleosome, not a mononucleosome, as its substrate. Our results from a functional assay using ISW1a further justified this model. Part B of this application describes how we would proceed to the relevant cryo-EM and X-ray structures incorporating dinucleosomes. Our recombinant ISW1a allows us to study in addition the interaction of the ATPase domain with nucleosome substrates."
Summary
"DNA in higher organisms is organized in a nucleoprotein complex called chromatin. The structure of chromatin is responsible for compacting DNA to fit within the nucleus and for governing its access in nuclear processes. Epigenetic information is encoded chiefly via chromatin modifications. Readout of the genetic code depends on chromatin remodeling, a process actively altering chromatin structure. An understanding of the hierarchical structure of chromatin and of structurally based, remodeling mechanisms will have enormous impact for developments in medicine.
Following our high resolution structure of the nucleosome core particle, the fundamental repeating unit of chromatin, we have endeavored to determine the structure of the chromatin fiber. We showed with our X-ray structure of a tetranucleosome how nucleosomes could be organized in the fiber. Further progress has been limited by structural polymorphism and crystal disorder, but new evidence on the in vivo spacing of nucleosomes in chromatin should stimulate more advances. Part A of this application describes how we would apply these new findings to our cryo-electron microscopy study of the chromatin fiber and to our crystallographic study of a tetranucleosome containing linker histone.
Recently, my laboratory succeeded in providing the first structurally based mechanism for nucleosome spacing by a chromatin remodeling factor. We combined the X-ray structure of ISW1a(ATPase) bound to DNA with cryo-EM structures of the factor bound to two different nucleosomes to build a model showing how this remodeler uses a dinucleosome, not a mononucleosome, as its substrate. Our results from a functional assay using ISW1a further justified this model. Part B of this application describes how we would proceed to the relevant cryo-EM and X-ray structures incorporating dinucleosomes. Our recombinant ISW1a allows us to study in addition the interaction of the ATPase domain with nucleosome substrates."
Max ERC Funding
2 500 000 €
Duration
Start date: 2013-01-01, End date: 2017-12-31
Project acronym Chap4Resp
Project Catching in action a novel bacterial chaperone for respiratory complexes
Researcher (PI) Irina Gutsche
Host Institution (HI) CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
Call Details Consolidator Grant (CoG), LS1, ERC-2014-CoG
Summary Cellular respiration provides energy to power essential processes of life. Respiratory complexes are macromolecular batteries coupling electron flow through a wire of metal clusters and cofactors with proton transfer across the inner membrane of mitochondria and bacteria. Waste products of these cellular factories are reactive oxygen species causing ageing and diseases. Assembly and maturation mechanisms of respiratory complexes remain enigmatic because of their membrane location, multisubunit composition and cofactor insertion. E. coli Complex I, one of the largest membrane proteins, composed of 14 conserved subunits with 9 Fe/S clusters and a flavin, is a minimal model for its 45-subunit human homologue. When proton pumping by respiratory complexes is affected, bacteria become resistant to antibiotics requiring proton gradient for uptake. Based on the latest genetic data, we realize that the huge E. coli macromolecular cage, the structure of which we recently solved by cryo-electron microscopy (cryoEM), in conjunction with a novel protein cofactor, is a specific chaperone for Fe/S cluster biogenesis and assembly of respiratory complexes. This integrated multidisciplinary project combines cryoEM and other structural, biophysical and spectroscopic techniques, to uncover the functional mechanism of this emerging chaperone. The structural plasticity of the chaperone fuelled by ATP hydrolysis, and its interaction with Fe/S cluster biogenesis systems and the main respiratory complexes as a function of stresses, will be scrutinized to gain quasiatomic insights into the way the chaperone operates on its substrates. A novel technology for synergetic in situ investigation of protein complexes in the bacterial cytoplasm by optical imaging, state-of-the-art cryogenic correlative light and electron microscopy, and subtomogram analysis, will be developed and used to obtain snapshots of the chaperone-substrate interactions in the cellular context.
Summary
Cellular respiration provides energy to power essential processes of life. Respiratory complexes are macromolecular batteries coupling electron flow through a wire of metal clusters and cofactors with proton transfer across the inner membrane of mitochondria and bacteria. Waste products of these cellular factories are reactive oxygen species causing ageing and diseases. Assembly and maturation mechanisms of respiratory complexes remain enigmatic because of their membrane location, multisubunit composition and cofactor insertion. E. coli Complex I, one of the largest membrane proteins, composed of 14 conserved subunits with 9 Fe/S clusters and a flavin, is a minimal model for its 45-subunit human homologue. When proton pumping by respiratory complexes is affected, bacteria become resistant to antibiotics requiring proton gradient for uptake. Based on the latest genetic data, we realize that the huge E. coli macromolecular cage, the structure of which we recently solved by cryo-electron microscopy (cryoEM), in conjunction with a novel protein cofactor, is a specific chaperone for Fe/S cluster biogenesis and assembly of respiratory complexes. This integrated multidisciplinary project combines cryoEM and other structural, biophysical and spectroscopic techniques, to uncover the functional mechanism of this emerging chaperone. The structural plasticity of the chaperone fuelled by ATP hydrolysis, and its interaction with Fe/S cluster biogenesis systems and the main respiratory complexes as a function of stresses, will be scrutinized to gain quasiatomic insights into the way the chaperone operates on its substrates. A novel technology for synergetic in situ investigation of protein complexes in the bacterial cytoplasm by optical imaging, state-of-the-art cryogenic correlative light and electron microscopy, and subtomogram analysis, will be developed and used to obtain snapshots of the chaperone-substrate interactions in the cellular context.
Max ERC Funding
1 999 956 €
Duration
Start date: 2015-10-01, End date: 2021-09-30
Project acronym ChemBioAP
Project Elucidation of autophagy using novel chemical probes
Researcher (PI) Yaowen Wu
Host Institution (HI) UMEA UNIVERSITET
Call Details Starting Grant (StG), LS1, ERC-2015-STG
Summary The interest on autophagy, an evolutionarily conserved process in eukaryotes, has enormously increased in the last years, since autophagy is involved in many diseases such as cancer and neurodegenerative disorders. Autophagosome formation is the key process in autophagy. Despite extensive work, the model of autophagosome formation is not yet well established. Some important questions on autophagosome biogenesis remain to be elusive, such as where the bona fide marker protein of autophagosome, LC3, is lipidated, how lipidated LC3 functions in autophagosome formation, and how the proteins for LC3 lipidation and delipidation are involved in autophagosome formation. Although genetic approaches have been useful to identify genes involved in autophagy, they are chronic and thereby the dynamics of phenotypic change cannot be followed, making them not suited for study highly dynamic process such as autophagosome formation. Herein, I propose to develop and use novel chemical probes to address these issues. First, I plan to prepare semi-synthetic caged LC3 proteins and apply them to monitor dynamics of autophagosome formation in the cell in order to address those questions on autophagosome formation. The semi-synthetic LC3 proteins are expected to confer a temporal control and to realize manipulation of protein structure, which renders such studies possible. Second, I intend to develop a versatile approach targeting specific endogenous proteins using a reversible chemically induced dimerization (CID) system, termed as “knock on and off” strategy. I plan to use this approach to elucidate the function of two distinct PI3K complexes in autophagosome formation. On one hand, the establishment of novel approaches will open up a new avenue for studying biological processes. On the other hand, the use of the tool will reveal the mechanism of autophagy.
Summary
The interest on autophagy, an evolutionarily conserved process in eukaryotes, has enormously increased in the last years, since autophagy is involved in many diseases such as cancer and neurodegenerative disorders. Autophagosome formation is the key process in autophagy. Despite extensive work, the model of autophagosome formation is not yet well established. Some important questions on autophagosome biogenesis remain to be elusive, such as where the bona fide marker protein of autophagosome, LC3, is lipidated, how lipidated LC3 functions in autophagosome formation, and how the proteins for LC3 lipidation and delipidation are involved in autophagosome formation. Although genetic approaches have been useful to identify genes involved in autophagy, they are chronic and thereby the dynamics of phenotypic change cannot be followed, making them not suited for study highly dynamic process such as autophagosome formation. Herein, I propose to develop and use novel chemical probes to address these issues. First, I plan to prepare semi-synthetic caged LC3 proteins and apply them to monitor dynamics of autophagosome formation in the cell in order to address those questions on autophagosome formation. The semi-synthetic LC3 proteins are expected to confer a temporal control and to realize manipulation of protein structure, which renders such studies possible. Second, I intend to develop a versatile approach targeting specific endogenous proteins using a reversible chemically induced dimerization (CID) system, termed as “knock on and off” strategy. I plan to use this approach to elucidate the function of two distinct PI3K complexes in autophagosome formation. On one hand, the establishment of novel approaches will open up a new avenue for studying biological processes. On the other hand, the use of the tool will reveal the mechanism of autophagy.
Max ERC Funding
1 500 000 €
Duration
Start date: 2016-09-01, End date: 2021-08-31
Project acronym CHROCODYLE
Project Chromosomal Condensin Dynamics: From Local Loading to Global Architecture
Researcher (PI) Stephan GRUBER
Host Institution (HI) UNIVERSITE DE LAUSANNE
Call Details Consolidator Grant (CoG), LS1, ERC-2016-COG
Summary Striking morphological transformations are a hallmark of any cell division cycle. During nuclear division chromatin is compacted into distinctive rod-shaped chromatids in preparation of chromosome segregation by the spindle apparatus. Multi-subunit SMC protein complexes and a large number of regulatory factors are at the heart of this elementary process. SMC complexes also play key roles during other aspects of genome function such as the control of gene expression and the repair of damaged DNA. They are thought to act as chromatin linkers with exquisite specificity for certain pairs of DNA fibres. However, the underlying molecular mechanisms are not understood. Active extrusion of DNA loops by the SMC complex has been proposed to be the mechanistic basis for the establishment of long-range, intra-chromatid DNA bridges.
Here, I put forward a multi-pronged research programme that aims to elucidate fundamentally conserved features of SMC protein function and action using the prokaryotic SMC condensin complex in Bacillus subtilis as a tractable model system. We will conduct a combined structural, biochemical and cell biology approach (including crystallography, electron paramagnetic resonance, ChIP-Seq and ‘native’ HiC) to uncover how the SMC complex acts at the higher levels of organization of the bacterial chromosome to promote the efficient individualization of sister DNA molecules. We will reveal the molecular and structural bases for the association between the SMC complex and the bacterial chromosome at different stages of the loading reaction – each representing a crucial intermediate in a sophisticated chromosome organization process. For the first time, we will be able to map the paths of chromosomal DNA through an SMC complex.
Our in-depth mechanistic insights will likely have implications for the understanding of various pathological conditions and have the potential to contribute to the development of novel antibacterial compounds.
Summary
Striking morphological transformations are a hallmark of any cell division cycle. During nuclear division chromatin is compacted into distinctive rod-shaped chromatids in preparation of chromosome segregation by the spindle apparatus. Multi-subunit SMC protein complexes and a large number of regulatory factors are at the heart of this elementary process. SMC complexes also play key roles during other aspects of genome function such as the control of gene expression and the repair of damaged DNA. They are thought to act as chromatin linkers with exquisite specificity for certain pairs of DNA fibres. However, the underlying molecular mechanisms are not understood. Active extrusion of DNA loops by the SMC complex has been proposed to be the mechanistic basis for the establishment of long-range, intra-chromatid DNA bridges.
Here, I put forward a multi-pronged research programme that aims to elucidate fundamentally conserved features of SMC protein function and action using the prokaryotic SMC condensin complex in Bacillus subtilis as a tractable model system. We will conduct a combined structural, biochemical and cell biology approach (including crystallography, electron paramagnetic resonance, ChIP-Seq and ‘native’ HiC) to uncover how the SMC complex acts at the higher levels of organization of the bacterial chromosome to promote the efficient individualization of sister DNA molecules. We will reveal the molecular and structural bases for the association between the SMC complex and the bacterial chromosome at different stages of the loading reaction – each representing a crucial intermediate in a sophisticated chromosome organization process. For the first time, we will be able to map the paths of chromosomal DNA through an SMC complex.
Our in-depth mechanistic insights will likely have implications for the understanding of various pathological conditions and have the potential to contribute to the development of novel antibacterial compounds.
Max ERC Funding
1 999 599 €
Duration
Start date: 2017-06-01, End date: 2022-05-31
Project acronym ChromADICT
Project Chromatin Adaptations through Interactions of Chaperones in Time
Researcher (PI) Genevieve ALMOUZNI
Host Institution (HI) INSTITUT CURIE
Call Details Advanced Grant (AdG), LS1, ERC-2015-AdG
Summary A central question in chromatin biology is how to organize the genome and mark specific regions with histone variants. Understanding how to establish and maintain, but also change chromatin states is a fundamental challenge. Histone chaperones, escort factors that regulate the supply, loading, and degradation of histone variants, are key in their placement at specific chromatin landmarks and bridge organization from nucleosomes to higher order structures. A series of studies have underlined chaperone-variant partner selectivity in multicellular organisms, yet recently, dosage imbalances in natural and pathological contexts highlight plasticity in these interactions. Considering known changes in histone dosage during development, one should evaluate chaperone function not as fixed modules, but as a dynamic circuitry that adapts to cellular needs during the cell cycle, replication and repair, differentiation, development and pathology.
Here we propose to decipher the mechanisms enabling adaptability to natural and experimentally induced changes in the dosage of histone chaperones and variants over time. To follow new and old proteins, and control dosage, we will engineer cellular and animal models and exploit quantitative readout methods using mass spectrometry, imaging, and single-cell approaches. We will evaluate with an unprecedented level of detail the impact on i) soluble histone complexes and ii) specific chromatin landmarks (centromere, telomeres, heterochromatin and regulatory elements) and their crosstalk. We will apply this to determine the impact of these parameters during distinct developmental transitions, such as ES cell differentiation and T cell commitment in mice.
We aim to define general principles for variants in nuclear organization and dynamic changes during the cell cycle/repair and in differentiation and unravel locus specific-roles of chaperones as architects and bricklayers of the genome, in designing and building specific nuclear domains.
Summary
A central question in chromatin biology is how to organize the genome and mark specific regions with histone variants. Understanding how to establish and maintain, but also change chromatin states is a fundamental challenge. Histone chaperones, escort factors that regulate the supply, loading, and degradation of histone variants, are key in their placement at specific chromatin landmarks and bridge organization from nucleosomes to higher order structures. A series of studies have underlined chaperone-variant partner selectivity in multicellular organisms, yet recently, dosage imbalances in natural and pathological contexts highlight plasticity in these interactions. Considering known changes in histone dosage during development, one should evaluate chaperone function not as fixed modules, but as a dynamic circuitry that adapts to cellular needs during the cell cycle, replication and repair, differentiation, development and pathology.
Here we propose to decipher the mechanisms enabling adaptability to natural and experimentally induced changes in the dosage of histone chaperones and variants over time. To follow new and old proteins, and control dosage, we will engineer cellular and animal models and exploit quantitative readout methods using mass spectrometry, imaging, and single-cell approaches. We will evaluate with an unprecedented level of detail the impact on i) soluble histone complexes and ii) specific chromatin landmarks (centromere, telomeres, heterochromatin and regulatory elements) and their crosstalk. We will apply this to determine the impact of these parameters during distinct developmental transitions, such as ES cell differentiation and T cell commitment in mice.
We aim to define general principles for variants in nuclear organization and dynamic changes during the cell cycle/repair and in differentiation and unravel locus specific-roles of chaperones as architects and bricklayers of the genome, in designing and building specific nuclear domains.
Max ERC Funding
2 499 697 €
Duration
Start date: 2016-07-01, End date: 2022-06-30
Project acronym ChromArch
Project Single Molecule Mechanisms of Spatio-Temporal Chromatin Architecture
Researcher (PI) Johann Christof Manuel Gebhardt
Host Institution (HI) UNIVERSITAET ULM
Call Details Starting Grant (StG), LS1, ERC-2014-STG
Summary Chromatin packaging into the nucleus of eukaryotic cells is highly sophisticated. It not only serves to condense the genomic content into restricted space, but mainly to encode epigenetic traits ensuring temporally controlled and balanced transcription of genes and coordinated DNA replication and repair. The non-random three-dimensional chromatin architecture including looped structures between genomic control elements relies on the action of architectural proteins. However, despite increasing interest in spatio-temporal chromatin organization, mechanistic details of their contributions are not well understood.
With this proposal I aim at unveiling molecular mechanisms of protein–mediated chromatin organization by in vivo single molecule tracking and quantitative super-resolution imaging of architectural proteins using reflected light sheet microscopy (RLSM). I will measure the interaction dynamics, the spatial distribution and the stoichiometry of architectural proteins throughout the nucleus and at specific chromatin loci within single cells. In complement single molecule force spectroscopy experiments using magnetic tweezers (MT), I will study mechanisms of DNA loop formation in vitro by structure-mediating proteins.
Integrating these spatio-temporal and mechanical single molecule information, I will in the third sup-project measure the dynamics of relative end-to-end movements and the forces acting within a looped chromatin structure in living cells.
Taken together, my experiments will greatly enhance our mechanistic understanding of three-dimensional chromatin architecture and inspire future experiments on its regulatory effects on nuclear functions and potential therapeutic utility upon controlled modification.
Summary
Chromatin packaging into the nucleus of eukaryotic cells is highly sophisticated. It not only serves to condense the genomic content into restricted space, but mainly to encode epigenetic traits ensuring temporally controlled and balanced transcription of genes and coordinated DNA replication and repair. The non-random three-dimensional chromatin architecture including looped structures between genomic control elements relies on the action of architectural proteins. However, despite increasing interest in spatio-temporal chromatin organization, mechanistic details of their contributions are not well understood.
With this proposal I aim at unveiling molecular mechanisms of protein–mediated chromatin organization by in vivo single molecule tracking and quantitative super-resolution imaging of architectural proteins using reflected light sheet microscopy (RLSM). I will measure the interaction dynamics, the spatial distribution and the stoichiometry of architectural proteins throughout the nucleus and at specific chromatin loci within single cells. In complement single molecule force spectroscopy experiments using magnetic tweezers (MT), I will study mechanisms of DNA loop formation in vitro by structure-mediating proteins.
Integrating these spatio-temporal and mechanical single molecule information, I will in the third sup-project measure the dynamics of relative end-to-end movements and the forces acting within a looped chromatin structure in living cells.
Taken together, my experiments will greatly enhance our mechanistic understanding of three-dimensional chromatin architecture and inspire future experiments on its regulatory effects on nuclear functions and potential therapeutic utility upon controlled modification.
Max ERC Funding
1 486 578 €
Duration
Start date: 2015-05-01, End date: 2021-04-30
Project acronym ChromatidCohesion
Project Establishment of Sister Chromatid Cohesion
Researcher (PI) Frank Uhlmann
Host Institution (HI) THE FRANCIS CRICK INSTITUTE LIMITED
Call Details Advanced Grant (AdG), LS1, ERC-2014-ADG
Summary Following their synthesis during DNA replication, sister chromatids remain paired by the cohesin complex, which forms the basis for their faithful segregation during cell division. Cohesin is a large ring-shaped protein complex, incorporating an ABC-type ATPase module. Despite its importance for genome stability, the molecular mechanism of cohesin action remains as intriguing as it remains poorly understood. How is cohesin topologically loaded onto chromatin? How is it unloaded again? What happens to cohesin during DNA replication in S-phase, so that it establishes cohesion between newly synthesized sister chromatids? We propose to capitalise on our recent success in the biochemical reconstitution of topological cohesin loading onto DNA. This lays the foundation for a work programme encompassing a combination of biochemical, single molecule, structural and genetic approaches to address the above questions. Five work packages will investigate cohesin’s molecular behaviour during its life-cycle on chromosomes, including the ATP binding and hydrolysis-dependent conformational changes that make this molecular machine work. It will be complemented by mechanistic analyses of the cofactors that help cohesin to load onto chromosomes and establish sister chromatid cohesion. The insight gained will not only advance our molecular knowledge of sister chromatid cohesion. It will more generally advance our understanding of the ubiquitous family of chromosomal SMC ATPases, of which cohesin is a member, and their activity of shaping and segregating genomes.
Summary
Following their synthesis during DNA replication, sister chromatids remain paired by the cohesin complex, which forms the basis for their faithful segregation during cell division. Cohesin is a large ring-shaped protein complex, incorporating an ABC-type ATPase module. Despite its importance for genome stability, the molecular mechanism of cohesin action remains as intriguing as it remains poorly understood. How is cohesin topologically loaded onto chromatin? How is it unloaded again? What happens to cohesin during DNA replication in S-phase, so that it establishes cohesion between newly synthesized sister chromatids? We propose to capitalise on our recent success in the biochemical reconstitution of topological cohesin loading onto DNA. This lays the foundation for a work programme encompassing a combination of biochemical, single molecule, structural and genetic approaches to address the above questions. Five work packages will investigate cohesin’s molecular behaviour during its life-cycle on chromosomes, including the ATP binding and hydrolysis-dependent conformational changes that make this molecular machine work. It will be complemented by mechanistic analyses of the cofactors that help cohesin to load onto chromosomes and establish sister chromatid cohesion. The insight gained will not only advance our molecular knowledge of sister chromatid cohesion. It will more generally advance our understanding of the ubiquitous family of chromosomal SMC ATPases, of which cohesin is a member, and their activity of shaping and segregating genomes.
Max ERC Funding
2 120 100 €
Duration
Start date: 2015-10-01, End date: 2021-09-30
