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Arbona JM, Herbert S, Fabre E, Zimmer C. Inferring the physical properties of yeast chromatin through Bayesian analysis of whole nucleus simulations. Genome Biol 2017; 18:81. [PMID: 28468672 PMCID: PMC5414205 DOI: 10.1186/s13059-017-1199-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 03/23/2017] [Indexed: 01/06/2023] Open
Abstract
Background The structure and mechanical properties of chromatin impact DNA functions and nuclear architecture but remain poorly understood. In budding yeast, a simple polymer model with minimal sequence-specific constraints and a small number of structural parameters can explain diverse experimental data on nuclear architecture. However, how assumed chromatin properties affect model predictions was not previously systematically investigated. Results We used hundreds of dynamic chromosome simulations and Bayesian inference to determine chromatin properties consistent with an extensive dataset that includes hundreds of measurements from imaging in fixed and live cells and two Hi-C studies. We place new constraints on average chromatin fiber properties, narrowing down the chromatin compaction to ~53–65 bp/nm and persistence length to ~52–85 nm. These constraints argue against a 20–30 nm fiber as the exclusive chromatin structure in the genome. Our best model provides a much better match to experimental measurements of nuclear architecture and also recapitulates chromatin dynamics measured on multiple loci over long timescales. Conclusion This work substantially improves our understanding of yeast chromatin mechanics and chromosome architecture and provides a new analytic framework to infer chromosome properties in other organisms. Electronic supplementary material The online version of this article (doi:10.1186/s13059-017-1199-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jean-Michel Arbona
- Unité Imagerie et Modélisation, Institut Pasteur, 25 rue du Docteur Roux, 75015, Paris, France.,UMR 3691, CNRS; C3BI, USR 3756, IP CNRS, Paris, France
| | - Sébastien Herbert
- Unité Imagerie et Modélisation, Institut Pasteur, 25 rue du Docteur Roux, 75015, Paris, France.,UMR 3691, CNRS; C3BI, USR 3756, IP CNRS, Paris, France.,Université Paris Diderot, Sorbonne Paris Cité, Cellule Pasteur, 75015, Paris, France
| | - Emmanuelle Fabre
- Chromosome Biology and Dynamics, Hôpital Saint Louis, Paris, France
| | - Christophe Zimmer
- Unité Imagerie et Modélisation, Institut Pasteur, 25 rue du Docteur Roux, 75015, Paris, France. .,UMR 3691, CNRS; C3BI, USR 3756, IP CNRS, Paris, France.
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52
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Lawrimore J, Barry TM, Barry RM, York AC, Friedman B, Cook DM, Akialis K, Tyler J, Vasquez P, Yeh E, Bloom K. Microtubule dynamics drive enhanced chromatin motion and mobilize telomeres in response to DNA damage. Mol Biol Cell 2017; 28:1701-1711. [PMID: 28450453 PMCID: PMC5469612 DOI: 10.1091/mbc.e16-12-0846] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 03/28/2017] [Accepted: 04/18/2017] [Indexed: 12/13/2022] Open
Abstract
Mechanisms that drive DNA damage-induced chromosome mobility include relaxation of external tethers to the nuclear envelope and internal chromatin–chromatin tethers. Together with microtubule dynamics, these can mobilize the genome in response to DNA damage. Chromatin exhibits increased mobility on DNA damage, but the biophysical basis for this behavior remains unknown. To explore the mechanisms that drive DNA damage–induced chromosome mobility, we use single-particle tracking of tagged chromosomal loci during interphase in live yeast cells together with polymer models of chromatin chains. Telomeres become mobilized from sites on the nuclear envelope and the pericentromere expands after exposure to DNA-damaging agents. The magnitude of chromatin mobility induced by a single double-strand break requires active microtubule function. These findings reveal how relaxation of external tethers to the nuclear envelope and internal chromatin–chromatin tethers, together with microtubule dynamics, can mobilize the genome in response to DNA damage.
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Affiliation(s)
- Josh Lawrimore
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Timothy M Barry
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Raymond M Barry
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Alyssa C York
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Brandon Friedman
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Diana M Cook
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Kristen Akialis
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Jolien Tyler
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Paula Vasquez
- Department of Mathematics, University of South Carolina, Columbia, SC 29208
| | - Elaine Yeh
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Kerry Bloom
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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53
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Abstract
Chromosomes underlie a dynamic organization that fulfills functional roles in processes like transcription, DNA repair, nuclear envelope stability, and cell division. Chromosome dynamics depend on chromosome structure and cannot freely diffuse. Furthermore, chromosomes interact closely with their surrounding nuclear environment, which further constrains chromosome dynamics. Recently, several studies enlighten that cytoskeletal proteins regulate dynamic chromosome organization. Cytoskeletal polymers that include actin filaments, microtubules and intermediate filaments can connect to the nuclear envelope via Linker of the Nucleoskeleton and Cytoskeleton (LINC) complexes and transfer forces onto chromosomes inside the nucleus. Monomers of these cytoplasmic polymers and related proteins can also enter the nucleus and play different roles in the interior of the nucleus than they do in the cytoplasm. Nuclear cytoskeletal proteins can act as chromatin remodelers alone or in complexes with other nuclear proteins. They can also act as transcription factors. Many of these mechanisms have been conserved during evolution, indicating that the cytoskeletal regulation of chromosome dynamics is an essential process. In this review, we discuss the different influences of cytoskeletal proteins on chromosome dynamics by focusing on the well-studied model organism budding yeast.
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Affiliation(s)
- Maya Spichal
- Department of Genetics, University of North Carolina, Chapel HillNC, United States
| | - Emmanuelle Fabre
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, CNRS UMR 7212, INSERM U944, Hôpital St. Louis 1Paris, France
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54
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Tarrant DJ, Stirpe M, Rowe M, Howard MJ, von der Haar T, Gourlay CW. Inappropriate expression of the translation elongation factor 1A disrupts genome stability and metabolism. J Cell Sci 2016; 129:4455-4465. [PMID: 27807005 PMCID: PMC5201016 DOI: 10.1242/jcs.192831] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Accepted: 10/26/2016] [Indexed: 02/02/2023] Open
Abstract
The translation elongation factor eEF1A is one of the most abundant proteins found within cells, and its role within protein synthesis is well documented. Levels of eEF1A are tightly controlled, with inappropriate expression linked to oncogenesis. However, the mechanisms by which increased eEF1A expression alters cell behaviour are unknown. Our analyses in yeast suggest that elevation of eEF1A levels leads to stabilisation of the spindle pole body and changes in nuclear organisation. Elevation of the eEF1A2 isoform also leads to altered nuclear morphology in cultured human cells, suggesting a conserved role in maintaining genome stability. Gene expression and metabolomic analyses reveal that the level of eEF1A is crucial for the maintenance of metabolism and amino acid levels in yeast, most likely because of its role in the control of vacuole function. Increased eEF1A2 levels trigger lysosome biogenesis in cultured human cells, also suggesting a conserved role within metabolic control mechanisms. Taken together, our data suggest that the control of eEF1A levels is important for the maintenance of a number of cell functions beyond translation and that its de-regulation might contribute to its oncogenic properties. Summary: The translation elongation factor eEF1A is elevated in some cancers. We use yeast and human cell models to show that eEF1A elevation leads to genome instability and metabolic alterations that might affect its oncogenic properties.
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Affiliation(s)
- Daniel J Tarrant
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
| | - Mariarita Stirpe
- Department of Biology and Biotechnology, Sapienza, University of Rome, 00185 Rome, Italy
| | - Michelle Rowe
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
| | - Mark J Howard
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
| | - Tobias von der Haar
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
| | - Campbell W Gourlay
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
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55
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Seeber A, Gasser SM. Chromatin organization and dynamics in double-strand break repair. Curr Opin Genet Dev 2016; 43:9-16. [PMID: 27810555 DOI: 10.1016/j.gde.2016.10.005] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 10/17/2016] [Indexed: 01/17/2023]
Abstract
Chromatin is organized and segmented into a landscape of domains that serve multiple purposes. In contrast to transcription, which is controlled by defined sequences at distinct sites, DNA damage can occur anywhere. Repair accordingly must occur everywhere, yet it is inevitably affected by its chromatin environment. In this review, we summarize recent work investigating how changes in chromatin organization facilitate and/or guide DNA double-strand break repair. In addition, we examine new live cell studies on the dynamics of chromatin and the mechanisms that regulate its movement.
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Affiliation(s)
- Andrew Seeber
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland; University of Basel, Faculty of Natural Sciences, Klingelbergstrasse 50, CH-4056 Basel, Switzerland
| | - Susan M Gasser
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland; University of Basel, Faculty of Natural Sciences, Klingelbergstrasse 50, CH-4056 Basel, Switzerland.
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56
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De Loof A. The cell's self-generated "electrome": The biophysical essence of the immaterial dimension of Life? Commun Integr Biol 2016; 9:e1197446. [PMID: 27829975 PMCID: PMC5100658 DOI: 10.1080/19420889.2016.1197446] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 05/30/2016] [Accepted: 05/31/2016] [Indexed: 11/16/2022] Open
Abstract
In the classical “mind-body” wording, “body” is usually associated with the “mass aspect” of living entities and “mind” with the “immaterial” one. Thoughts, consciousness and soul are classified as immaterial. A most challenging question emerges: Can something that is truly immaterial, thus that in the wording of physics has no mass, exist at all? Many will answer: “No, impossible.” My answer is that it is very well possible, that no esoteric mechanisms need to be invoked, but that this possibility is inherent to 2 well established but undervalued physiological mechanisms. The first one is electrical in nature. In analogy with “genome,” “proteome” etc. “electrome” (a novel term) stands for the totality of all ionic currents of any living entity, from the cellular to the organismal level. Cellular electricity is truly vital. Death of any cell ensues at the very moment that it irreversibly (excluding regeneration) loses its ability to realize its electrical dimension. The second mechanism involves communication activity that is invariably executed by sender-receiver entities that incessantly handle information. Information itself is immaterial (= no mass). Both mechanisms are instrumental to the functioning of all cells, in particular to their still enigmatic cognitive memory system. Ionic/electrical currents associated with the cytoskeleton likely play a key role but have been largely overlooked. This paper aims at initiating a discussion platform from which students with different backgrounds but all interested in the immaterial dimension of life could engage in elaborating an integrating vocabulary and in initiating experimental approaches.
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Affiliation(s)
- Arnold De Loof
- Functional Genomics and Proteomics Group, Department of Biology, KU Leuven-University of Leuven , Leuven, Belgium
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57
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Harding SM, Greenberg RA. Choreographing the Double Strand Break Response: Ubiquitin and SUMO Control of Nuclear Architecture. Front Genet 2016; 7:103. [PMID: 27375678 PMCID: PMC4894868 DOI: 10.3389/fgene.2016.00103] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 05/24/2016] [Indexed: 12/16/2022] Open
Abstract
The cellular response to DNA double strand breaks (DSBs) is a multifaceted signaling program that centers on post-translational modifications including phosphorylation, ubiquitylation and SUMOylation. In this review we discuss how ubiquitin and SUMO orchestrate the recognition of DSBs and explore how this influences chromatin organization. We discuss functional outcomes of this response including transcriptional silencing and how pre-existing chromatin states may control the DSB response and the maintenance of genomic stability.
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Affiliation(s)
- Shane M Harding
- Departments of Cancer Biology and Pathology, Abramson Family Cancer Research Institute, Basser Research Center for BRCA, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA USA
| | - Roger A Greenberg
- Departments of Cancer Biology and Pathology, Abramson Family Cancer Research Institute, Basser Research Center for BRCA, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA USA
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58
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Joyner RP, Tang JH, Helenius J, Dultz E, Brune C, Holt LJ, Huet S, Müller DJ, Weis K. A glucose-starvation response regulates the diffusion of macromolecules. eLife 2016; 5. [PMID: 27003290 PMCID: PMC4811765 DOI: 10.7554/elife.09376] [Citation(s) in RCA: 125] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 03/02/2016] [Indexed: 01/19/2023] Open
Abstract
The organization and biophysical properties of the cytosol implicitly govern molecular interactions within cells. However, little is known about mechanisms by which cells regulate cytosolic properties and intracellular diffusion rates. Here, we demonstrate that the intracellular environment of budding yeast undertakes a startling transition upon glucose starvation in which macromolecular mobility is dramatically restricted, reducing the movement of both chromatin in the nucleus and mRNPs in the cytoplasm. This confinement cannot be explained by an ATP decrease or the physiological drop in intracellular pH. Rather, our results suggest that the regulation of diffusional mobility is induced by a reduction in cell volume and subsequent increase in molecular crowding which severely alters the biophysical properties of the intracellular environment. A similar response can be observed in fission yeast and bacteria. This reveals a novel mechanism by which cells globally alter their properties to establish a unique homeostasis during starvation. DOI:http://dx.doi.org/10.7554/eLife.09376.001 Most organisms live in unpredictable environments, which can often lead to nutrient shortages and other conditions that limit their ability to grow. To survive in these harsh conditions, many organisms adopt a dormant state in which their metabolism slows down to conserve vital energy. When the environmental conditions improve, the organisms can return to their normal state and continue to grow. The interior of cells is known as the cytoplasm. It is very crowded and contains many molecules and compartments that carry out a variety of vital processes. The cytoplasm has long been considered to be fluid-like in nature, but recent evidence suggests that in bacterial cells it can solidify to resemble a glass-like material under certain conditions. When cells experience stress they stop dividing and alter their metabolism. However, it was not clear whether cells also alter their physical properties in response to changes in the environment. Now, Joyner et al. starve yeast cells of sugar and track the movements of two large molecules called mRNPs and chromatin. Chromatin is found in a cell compartment known as the nucleus, while mRNPs are found in the cytoplasm. The experiments show that during starvation, both molecules are less able to move around in their respective areas of the cell. This appears to be due to water loss from the cells, which causes the cells to become smaller and leads to the interior of the cell becoming more crowded. Joyner et al. also observed a similar response in bacteria. Furthermore, Joyner et al. suggest that the changes in physical properties are critical for cells to survive the stress caused by starvation. A separate study by Munder et al. found that when cells become dormant the cytoplasm becomes more acidic, which causes many proteins to bind to each other and form large clumps. Together, the findings of the studies suggest that the interior of cells can undergo a transition from a fluid-like to a more solid-like state to protect the cells from damage when energy is in short supply. The next challenge is to understand the molecular mechanisms that cause the physical properties of the cells to change under different conditions. DOI:http://dx.doi.org/10.7554/eLife.09376.002
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Affiliation(s)
- Ryan P Joyner
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Jeffrey H Tang
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zürich, Switzerland
| | - Jonne Helenius
- Department of Biosystems Science and Engineering, ETH Zurich, Zürich, Switzerland
| | - Elisa Dultz
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Christiane Brune
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Liam J Holt
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Sebastien Huet
- CNRS, UMR 6290, Institut Génétique et Développement, University of Rennes, Rennes, France
| | - Daniel J Müller
- Department of Biosystems Science and Engineering, ETH Zurich, Zürich, Switzerland
| | - Karsten Weis
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.,Institute of Biochemistry, Department of Biology, ETH Zurich, Zürich, Switzerland
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