1
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Tortora MMC, Fudenberg G. The physical chemistry of interphase loop extrusion. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.23.609419. [PMID: 39229088 PMCID: PMC11370536 DOI: 10.1101/2024.08.23.609419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2024]
Abstract
Loop extrusion constitutes a universal mechanism of genome organization, whereby structural maintenance of chromosomes (SMC) protein complexes load onto the chromatin fiber and generate DNA loops of increasingly-larger sizes until their eventual release. In mammalian interphase cells, loop extrusion is mediated by the cohesin complex, which is dynamically regulated by the interchange of multiple accessory proteins. Although these regulators bind the core cohesin complex only transiently, their disruption can dramatically alter cohesin dynamics, gene expression, chromosome morphology and contact patterns. Still, a theory of how cohesin regulators and their molecular interplay with the core complex modulate genome folding remains at large. Here we derive a model of cohesin loop extrusion from first principles, based on in vivo measurements of the abundance and dynamics of cohesin regulators. We systematically evaluate potential chemical reaction networks that describe the association of cohesin with its regulators and with the chromatin fiber. Remarkably, experimental observations are consistent with only a single biochemical reaction cycle, which results in a unique minimal model that may be fully parameterized by quantitative protein measurements. We demonstrate how distinct roles for cohesin regulators emerge simply from the structure of the reaction network, and how their dynamic exchange can regulate loop extrusion kinetics over time-scales that far exceed their own chromatin residence times. By embedding our cohesin biochemical reaction network within biophysical chromatin simulations, we evidence how variations in regulatory protein abundance can alter chromatin architecture across multiple length- and time-scales. Predictions from our model are corroborated by biophysical and biochemical assays, optical microscopy observations, and Hi-C conformation capture techniques. More broadly, our theoretical and numerical framework bridges the gap between in vitro observations of extrusion motor dynamics at the molecular scale and their structural consequences at the genome-wide level.
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Affiliation(s)
- Maxime M C Tortora
- Department of Quantitative and Computational Biology, University of Southern California, Los Angeles, USA
| | - Geoffrey Fudenberg
- Department of Quantitative and Computational Biology, University of Southern California, Los Angeles, USA
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2
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Salari H, Fourel G, Jost D. Transcription regulates the spatio-temporal dynamics of genes through micro-compartmentalization. Nat Commun 2024; 15:5393. [PMID: 38918438 PMCID: PMC11199603 DOI: 10.1038/s41467-024-49727-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 06/17/2024] [Indexed: 06/27/2024] Open
Abstract
Although our understanding of the involvement of heterochromatin architectural factors in shaping nuclear organization is improving, there is still ongoing debate regarding the role of active genes in this process. In this study, we utilize publicly-available Micro-C data from mouse embryonic stem cells to investigate the relationship between gene transcription and 3D gene folding. Our analysis uncovers a nonmonotonic - globally positive - correlation between intragenic contact density and Pol II occupancy, independent of cohesin-based loop extrusion. Through the development of a biophysical model integrating the role of transcription dynamics within a polymer model of chromosome organization, we demonstrate that Pol II-mediated attractive interactions with limited valency between transcribed regions yield quantitative predictions consistent with chromosome-conformation-capture and live-imaging experiments. Our work provides compelling evidence that transcriptional activity shapes the 4D genome through Pol II-mediated micro-compartmentalization.
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Affiliation(s)
- Hossein Salari
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR5239, Inserm U1293, Université Claude Bernard Lyon 1, 46 Allée d'Italie, 69007, Lyon, France.
- École Normale Supérieure de Lyon, CNRS, Laboratoire de Physique, 46 Allée d'Italie, 69007, Lyon, France.
| | - Geneviève Fourel
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR5239, Inserm U1293, Université Claude Bernard Lyon 1, 46 Allée d'Italie, 69007, Lyon, France
| | - Daniel Jost
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR5239, Inserm U1293, Université Claude Bernard Lyon 1, 46 Allée d'Italie, 69007, Lyon, France.
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3
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Fouziya S, Krietenstein N, Mir US, Mieczkowski J, Khan MA, Baba A, Dar MA, Altaf M, Wani AH. Genome wide nucleosome landscape shapes 3D chromatin organization. SCIENCE ADVANCES 2024; 10:eadn2955. [PMID: 38848364 PMCID: PMC11160460 DOI: 10.1126/sciadv.adn2955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Accepted: 05/03/2024] [Indexed: 06/09/2024]
Abstract
The hierarchical chromatin organization begins with formation of nucleosomes, which fold into chromatin domains punctuated by boundaries and ultimately chromosomes. In a hierarchal organization, lower levels shape higher levels. However, the dependence of higher-order 3D chromatin organization on the nucleosome-level organization has not been studied in cells. We investigated the relationship between nucleosome-level organization and higher-order chromatin organization by perturbing nucleosomes across the genome by deleting Imitation SWItch (ISWI) and Chromodomain Helicase DNA-binding (CHD1) chromatin remodeling factors in budding yeast. We find that changes in nucleosome-level properties are accompanied by changes in 3D chromatin organization. Short-range chromatin contacts up to a few kilo-base pairs decrease, chromatin domains weaken, and boundary strength decreases. Boundary strength scales with accessibility and moderately with width of nucleosome-depleted region. Change in nucleosome positioning seems to alter the stiffness of chromatin, which can affect formation of chromatin contacts. Our results suggest a biomechanical "bottom-up" mechanism by which nucleosome distribution across genome shapes 3D chromatin organization.
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Affiliation(s)
- Shah Fouziya
- Department of Biotechnology, School of Biological Sciences, University of Kashmir, Srinagar, J&K, 190006, India
| | - Nils Krietenstein
- Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Denmark
| | - Ulfat Syed Mir
- Centre for Interdisciplinary Research and Innovations, University of Kashmir, Srinagar, J&K, 190006, India
| | - Jakub Mieczkowski
- International Research Agenda 3P Medicine Laboratory, Medical University of Gdansk, Gdansk, Poland
| | - Masood A. Khan
- Department of Biotechnology, School of Biological Sciences, University of Kashmir, Srinagar, J&K, 190006, India
| | - Aemon Baba
- Department of Biotechnology, School of Biological Sciences, University of Kashmir, Srinagar, J&K, 190006, India
| | - Mohmmad Abaas Dar
- Department of Biotechnology, School of Biological Sciences, University of Kashmir, Srinagar, J&K, 190006, India
| | - Mohammad Altaf
- Centre for Interdisciplinary Research and Innovations, University of Kashmir, Srinagar, J&K, 190006, India
| | - Ajazul H. Wani
- Department of Biotechnology, School of Biological Sciences, University of Kashmir, Srinagar, J&K, 190006, India
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4
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Hildebrand EM, Polovnikov K, Dekker B, Liu Y, Lafontaine DL, Fox AN, Li Y, Venev SV, Mirny LA, Dekker J. Mitotic chromosomes are self-entangled and disentangle through a topoisomerase-II-dependent two-stage exit from mitosis. Mol Cell 2024; 84:1422-1441.e14. [PMID: 38521067 DOI: 10.1016/j.molcel.2024.02.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 10/23/2023] [Accepted: 02/24/2024] [Indexed: 03/25/2024]
Abstract
The topological state of chromosomes determines their mechanical properties, dynamics, and function. Recent work indicated that interphase chromosomes are largely free of entanglements. Here, we use Hi-C, polymer simulations, and multi-contact 3C and find that, by contrast, mitotic chromosomes are self-entangled. We explore how a mitotic self-entangled state is converted into an unentangled interphase state during mitotic exit. Most mitotic entanglements are removed during anaphase/telophase, with remaining ones removed during early G1, in a topoisomerase-II-dependent process. Polymer models suggest a two-stage disentanglement pathway: first, decondensation of mitotic chromosomes with remaining condensin loops produces entropic forces that bias topoisomerase II activity toward decatenation. At the second stage, the loops are released, and the formation of new entanglements is prevented by lower topoisomerase II activity, allowing the establishment of unentangled and territorial G1 chromosomes. When mitotic entanglements are not removed in experiments and models, a normal interphase state cannot be acquired.
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Affiliation(s)
- Erica M Hildebrand
- Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | | | - Bastiaan Dekker
- Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Yu Liu
- Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA; Nuclear Dynamics and Cancer Program, Cancer Epigenetics Institute, Fox Chase Cancer Center, Temple Health, Philadelphia, PA 19111, USA
| | - Denis L Lafontaine
- Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - A Nicole Fox
- Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Ying Li
- Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Sergey V Venev
- Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Leonid A Mirny
- Institute for Medical Engineering and Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - Job Dekker
- Department of Systems Biology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
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5
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Yuan T, Yan H, Bailey MLP, Williams JF, Surovtsev I, King MC, Mochrie SGJ. Effect of loops on the mean-square displacement of Rouse-model chromatin. Phys Rev E 2024; 109:044502. [PMID: 38755928 DOI: 10.1103/physreve.109.044502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 02/16/2024] [Indexed: 05/18/2024]
Abstract
Chromatin polymer dynamics are commonly described using the classical Rouse model. The subsequent discovery, however, of intermediate-scale chromatin organization known as topologically associating domains (TADs) in experimental Hi-C contact maps for chromosomes across the tree of life, together with the success of loop extrusion factor (LEF) model in explaining TAD formation, motivates efforts to understand the effect of loops and loop extrusion on chromatin dynamics. This paper seeks to fulfill this need by combining LEF-model simulations with extended Rouse-model polymer simulations to investigate the dynamics of chromatin with loops and dynamic loop extrusion. We show that loops significantly suppress the averaged mean-square displacement (MSD) of a gene locus, consistent with recent experiments that track fluorescently labeled chromatin loci. We also find that loops reduce the MSD's stretching exponent from the classical Rouse-model value of 1/2 to a loop-density-dependent value in the 0.45-0.40 range. Remarkably, stretching exponent values in this range have also been observed in recent experiments [Weber et al., Phys. Rev. Lett. 104, 238102 (2010)0031-900710.1103/PhysRevLett.104.238102; Bailey et al., Mol. Biol. Cell 34, ar78 (2023)1059-152410.1091/mbc.E23-04-0119]. We also show that the dynamics of loop extrusion itself negligibly affects chromatin mobility. By studying static "rosette" loop configurations, we also demonstrate that chromatin MSDs and stretching exponents depend on the location of the locus in question relative to the position of the loops and on the local friction environment.
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Affiliation(s)
- Tianyu Yuan
- Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, Connecticut 06520, USA
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Hao Yan
- Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, Connecticut 06520, USA
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Mary Lou P Bailey
- Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, Connecticut 06520, USA
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Jessica F Williams
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
| | - Ivan Surovtsev
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
| | - Megan C King
- Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, Connecticut 06520, USA
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA
- Department of Molecular, Cell and Developmental Biology, Yale University, New Haven, Connecticut 06511, USA
| | - Simon G J Mochrie
- Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, Connecticut 06520, USA
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
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6
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Kolbin D, Walker BL, Hult C, Stanton JD, Adalsteinsson D, Forest MG, Bloom K. Polymer Modeling Reveals Interplay between Physical Properties of Chromosomal DNA and the Size and Distribution of Condensin-Based Chromatin Loops. Genes (Basel) 2023; 14:2193. [PMID: 38137015 PMCID: PMC10742461 DOI: 10.3390/genes14122193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 11/28/2023] [Accepted: 12/06/2023] [Indexed: 12/24/2023] Open
Abstract
Transient DNA loops occur throughout the genome due to thermal fluctuations of DNA and the function of SMC complex proteins such as condensin and cohesin. Transient crosslinking within and between chromosomes and loop extrusion by SMCs have profound effects on high-order chromatin organization and exhibit specificity in cell type, cell cycle stage, and cellular environment. SMC complexes anchor one end to DNA with the other extending some distance and retracting to form a loop. How cells regulate loop sizes and how loops distribute along chromatin are emerging questions. To understand loop size regulation, we employed bead-spring polymer chain models of chromatin and the activity of an SMC complex on chromatin. Our study shows that (1) the stiffness of the chromatin polymer chain, (2) the tensile stiffness of chromatin crosslinking complexes such as condensin, and (3) the strength of the internal or external tethering of chromatin chains cooperatively dictate the loop size distribution and compaction volume of induced chromatin domains. When strong DNA tethers are invoked, loop size distributions are tuned by condensin stiffness. When DNA tethers are released, loop size distributions are tuned by chromatin stiffness. In this three-way interaction, the presence and strength of tethering unexpectedly dictates chromatin conformation within a topological domain.
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Affiliation(s)
- Daniel Kolbin
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; (D.K.); (J.D.S.)
| | - Benjamin L. Walker
- Department of Mathematics, University of California-Irvine, Irvine, CA 92697, USA;
| | - Caitlin Hult
- Department of Mathematics, Gettysburg College, Gettysburg, PA 17325, USA
| | - John Donoghue Stanton
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; (D.K.); (J.D.S.)
| | - David Adalsteinsson
- Department of Mathematics and Carolina Center for Interdisciplinary Applied Mathematics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; (D.A.); (M.G.F.)
| | - M. Gregory Forest
- Department of Mathematics and Carolina Center for Interdisciplinary Applied Mathematics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; (D.A.); (M.G.F.)
- Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Kerry Bloom
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; (D.K.); (J.D.S.)
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7
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Liu S, Miné-Hattab J, Villemeur M, Guerois R, Pinholt HD, Mirny LA, Taddei A. In vivo tracking of functionally tagged Rad51 unveils a robust strategy of homology search. Nat Struct Mol Biol 2023; 30:1582-1591. [PMID: 37605042 DOI: 10.1038/s41594-023-01065-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 07/12/2023] [Indexed: 08/23/2023]
Abstract
Homologous recombination (HR) is a major pathway to repair DNA double-strand breaks (DSB). HR uses an undamaged homologous DNA sequence as a template for copying the missing information, which requires identifying a homologous sequence among megabases of DNA within the crowded nucleus. In eukaryotes, the conserved Rad51-single-stranded DNA nucleoprotein filament (NPF) performs this homology search. Although NPFs have been extensively studied in vitro by molecular and genetic approaches, their in vivo formation and dynamics could not thus far be assessed due to the lack of functional tagged versions of Rad51. Here we develop and characterize in budding yeast the first fully functional, tagged version of Rad51. Following induction of a unique DSB, we observe Rad51-ssDNA forming exceedingly long filaments, spanning the whole nucleus and eventually contacting the donor sequence. Emerging filaments adopt a variety of shapes not seen in vitro and are modulated by Rad54 and Srs2, shedding new light on the function of these factors. The filaments are also dynamic, undergoing rounds of compaction and extension. Our biophysical models demonstrate that formation of extended filaments, and particularly their compaction-extension dynamics, constitute a robust search strategy, allowing DSB to rapidly explore the nuclear volume and thus enable efficient HR.
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Affiliation(s)
- Siyu Liu
- Institut Curie, Université PSL, Sorbonne University, CNRS, Nuclear Dynamics, Paris, France
| | - Judith Miné-Hattab
- Institut Curie, Université PSL, Sorbonne University, CNRS, Nuclear Dynamics, Paris, France
| | - Marie Villemeur
- Institut Curie, Université PSL, Sorbonne University, CNRS, Nuclear Dynamics, Paris, France
| | - Raphaël Guerois
- Institute for Integrative Biology of the Cell (I2BC), University of Paris-Saclay, CEA, CNRS, Gif-sur-Yvette, France
| | - Henrik Dahl Pinholt
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Leonid A Mirny
- Institut Curie, Université PSL, Sorbonne University, CNRS, Nuclear Dynamics, Paris, France
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Angela Taddei
- Institut Curie, Université PSL, Sorbonne University, CNRS, Nuclear Dynamics, Paris, France.
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8
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Tortora MMC, Brennan LD, Karpen G, Jost D. HP1-driven phase separation recapitulates the thermodynamics and kinetics of heterochromatin condensate formation. Proc Natl Acad Sci U S A 2023; 120:e2211855120. [PMID: 37549295 PMCID: PMC10438847 DOI: 10.1073/pnas.2211855120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 06/28/2023] [Indexed: 08/09/2023] Open
Abstract
The spatial segregation of pericentromeric heterochromatin (PCH) into distinct, membrane-less nuclear compartments involves the binding of Heterochromatin Protein 1 (HP1) to H3K9me2/3-rich genomic regions. While HP1 exhibits liquid-liquid phase separation properties in vitro, its mechanistic impact on the structure and dynamics of PCH condensate formation in vivo remains largely unresolved. Here, using a minimal theoretical framework, we systematically investigate the mutual coupling between self-interacting HP1-like molecules and the chromatin polymer. We reveal that the specific affinity of HP1 for H3K9me2/3 loci facilitates coacervation in nucleo and promotes the formation of stable PCH condensates at HP1 levels far below the concentration required to observe phase separation in purified protein assays in vitro. These heterotypic HP1-chromatin interactions give rise to a strong dependence of the nucleoplasmic HP1 density on HP1-H3K9me2/3 stoichiometry, consistent with the thermodynamics of multicomponent phase separation. The dynamical cross talk between HP1 and the viscoelastic chromatin scaffold also leads to anomalously slow equilibration kinetics, which strongly depend on the genomic distribution of H3K9me2/3 domains and result in the coexistence of multiple long-lived, microphase-separated PCH compartments. The morphology of these complex coacervates is further found to be governed by the dynamic establishment of the underlying H3K9me2/3 landscape, which may drive their increasingly abnormal, aspherical shapes during cell development. These findings compare favorably to 4D microscopy measurements of HP1 condensate formation in live Drosophila embryos and suggest a general quantitative model of PCH formation based on the interplay between HP1-based phase separation and chromatin polymer mechanics.
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Affiliation(s)
- Maxime M. C. Tortora
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR5239, Inserm U1293, Université Claude Bernard Lyon 1, 69007Lyon, France
| | - Lucy D. Brennan
- Department of Molecular and Cell Biology, University of California, Berkeley, CA94720
| | - Gary Karpen
- Department of Molecular and Cell Biology, University of California, Berkeley, CA94720
- Department of BioEngineering and BioMedical Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA94720
| | - Daniel Jost
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR5239, Inserm U1293, Université Claude Bernard Lyon 1, 69007Lyon, France
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9
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Bailey MLP, Surovtsev I, Williams JF, Yan H, Yuan T, Li K, Duseau K, Mochrie SGJ, King MC. Loops and the activity of loop extrusion factors constrain chromatin dynamics. Mol Biol Cell 2023; 34:ar78. [PMID: 37126401 PMCID: PMC10398873 DOI: 10.1091/mbc.e23-04-0119] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 04/19/2023] [Accepted: 04/20/2023] [Indexed: 05/02/2023] Open
Abstract
The chromosomes-DNA polymers and their binding proteins-are compacted into a spatially organized, yet dynamic, three-dimensional structure. Recent genome-wide chromatin conformation capture experiments reveal a hierarchical organization of the DNA structure that is imposed, at least in part, by looping interactions arising from the activity of loop extrusion factors. The dynamics of chromatin reflects the response of the polymer to a combination of thermal fluctuations and active processes. However, how chromosome structure and enzymes acting on chromatin together define its dynamics remains poorly understood. To gain insight into the structure-dynamics relationship of chromatin, we combine high-precision microscopy in living Schizosaccharomyces pombe cells with systematic genetic perturbations and Rouse model polymer simulations. We first investigated how the activity of two loop extrusion factors, the cohesin and condensin complexes, influences chromatin dynamics. We observed that deactivating cohesin, or to a lesser extent condensin, increased chromatin mobility, suggesting that loop extrusion constrains rather than agitates chromatin motion. Our corresponding simulations reveal that the introduction of loops is sufficient to explain the constraining activity of loop extrusion factors, highlighting that the conformation adopted by the polymer plays a key role in defining its dynamics. Moreover, we find that the number of loops or residence times of loop extrusion factors influence the dynamic behavior of the chromatin polymer. Last, we observe that the activity of the INO80 chromatin remodeler, but not the SWI/SNF or RSC complexes, is critical for ATP-dependent chromatin mobility in fission yeast. Taking the data together, we suggest that thermal and INO80-dependent activities exert forces that drive chromatin fluctuations, which are constrained by the organization of the chromosome into loops.
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Affiliation(s)
- Mary Lou P. Bailey
- Department of Applied Physics, Yale University, New Haven, CT 06511
- Integrated Graduate Program in Physics Engineering Biology, Yale University, New Haven, CT 06511
| | - Ivan Surovtsev
- Department of Physics, Yale University, New Haven, CT 06511
- Department of Cell Biology, Yale School of Medicine, New Haven, CT 06520
| | | | - Hao Yan
- Integrated Graduate Program in Physics Engineering Biology, Yale University, New Haven, CT 06511
- Department of Physics, Yale University, New Haven, CT 06511
| | - Tianyu Yuan
- Integrated Graduate Program in Physics Engineering Biology, Yale University, New Haven, CT 06511
- Department of Physics, Yale University, New Haven, CT 06511
| | - Kevin Li
- Department of Cell Biology, Yale School of Medicine, New Haven, CT 06520
| | - Katherine Duseau
- Department of Cell Biology, Yale School of Medicine, New Haven, CT 06520
| | - Simon G. J. Mochrie
- Department of Applied Physics, Yale University, New Haven, CT 06511
- Integrated Graduate Program in Physics Engineering Biology, Yale University, New Haven, CT 06511
- Department of Physics, Yale University, New Haven, CT 06511
| | - Megan C. King
- Integrated Graduate Program in Physics Engineering Biology, Yale University, New Haven, CT 06511
- Department of Molecular, Cell and Developmental Biology, Yale University, New Haven, CT 06511
- Department of Cell Biology, Yale School of Medicine, New Haven, CT 06520
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10
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Mansisidor AR, Risca VI. Chromatin accessibility: methods, mechanisms, and biological insights. Nucleus 2022; 13:236-276. [PMID: 36404679 PMCID: PMC9683059 DOI: 10.1080/19491034.2022.2143106] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/23/2022] [Accepted: 10/30/2022] [Indexed: 11/22/2022] Open
Abstract
Access to DNA is a prerequisite to the execution of essential cellular processes that include transcription, replication, chromosomal segregation, and DNA repair. How the proteins that regulate these processes function in the context of chromatin and its dynamic architectures is an intensive field of study. Over the past decade, genome-wide assays and new imaging approaches have enabled a greater understanding of how access to the genome is regulated by nucleosomes and associated proteins. Additional mechanisms that may control DNA accessibility in vivo include chromatin compaction and phase separation - processes that are beginning to be understood. Here, we review the ongoing development of accessibility measurements, we summarize the different molecular and structural mechanisms that shape the accessibility landscape, and we detail the many important biological functions that are linked to chromatin accessibility.
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Affiliation(s)
- Andrés R. Mansisidor
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
| | - Viviana I. Risca
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
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11
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Navarro EJ, Marshall WF, Fung JC. Modeling cell biological features of meiotic chromosome pairing to study interlock resolution. PLoS Comput Biol 2022; 18:e1010252. [PMID: 35696428 PMCID: PMC9232156 DOI: 10.1371/journal.pcbi.1010252] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 06/24/2022] [Accepted: 05/25/2022] [Indexed: 11/17/2022] Open
Abstract
During meiosis, homologous chromosomes become associated side by side in a process known as homologous chromosome pairing. Pairing requires long range chromosome motion through a nucleus that is full of other chromosomes. It remains unclear how the cell manages to align each pair of chromosomes quickly while mitigating and resolving interlocks. Here, we use a coarse-grained molecular dynamics model to investigate how specific features of meiosis, including motor-driven telomere motion, nuclear envelope interactions, and increased nuclear size, affect the rate of pairing and the mitigation/resolution of interlocks. By creating in silico versions of three yeast strains and comparing the results of our model to experimental data, we find that a more distributed placement of pairing sites along the chromosome is necessary to replicate experimental findings. Active motion of the telomeric ends speeds up pairing only if binding sites are spread along the chromosome length. Adding a meiotic bouquet significantly speeds up pairing but does not significantly change the number of interlocks. An increase in nuclear size slows down pairing while greatly reducing the number of interlocks. Interestingly, active forces increase the number of interlocks, which raises the question: How do these interlocks resolve? Our model gives us detailed movies of interlock resolution events which we then analyze to build a step-by-step recipe for interlock resolution. In our model, interlocks must first translocate to the ends, where they are held in a quasi-stable state by a large number of paired sites on one side. To completely resolve an interlock, the telomeres of the involved chromosomes must come in close proximity so that the cooperativity of pairing coupled with random motion causes the telomeres to unwind. Together our results indicate that computational modeling of homolog pairing provides insight into the specific cell biological changes that occur during meiosis.
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Affiliation(s)
- Erik J. Navarro
- Department of Obstetrics, Gynecology and Reproductive Sciences and Center of Reproductive Sciences, University of California, San Francisco, California, United States of America
| | - Wallace F. Marshall
- Department of Biochemistry and Biophysics, University of California, San Francisco, California, United States of America
| | - Jennifer C. Fung
- Department of Obstetrics, Gynecology and Reproductive Sciences and Center of Reproductive Sciences, University of California, San Francisco, California, United States of America
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12
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Gabriele M, Brandão HB, Grosse-Holz S, Jha A, Dailey GM, Cattoglio C, Hsieh THS, Mirny L, Zechner C, Hansen AS. Dynamics of CTCF- and cohesin-mediated chromatin looping revealed by live-cell imaging. Science 2022; 376:496-501. [PMID: 35420890 PMCID: PMC9069445 DOI: 10.1126/science.abn6583] [Citation(s) in RCA: 190] [Impact Index Per Article: 95.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Animal genomes are folded into loops and topologically associating domains (TADs) by CTCF and loop-extruding cohesins, but the live dynamics of loop formation and stability remain unknown. Here, we directly visualized chromatin looping at the Fbn2 TAD in mouse embryonic stem cells using super-resolution live-cell imaging and quantified looping dynamics by Bayesian inference. Unexpectedly, the Fbn2 loop was both rare and dynamic, with a looped fraction of approximately 3 to 6.5% and a median loop lifetime of approximately 10 to 30 minutes. Our results establish that the Fbn2 TAD is highly dynamic, and about 92% of the time, cohesin-extruded loops exist within the TAD without bridging both CTCF boundaries. This suggests that single CTCF boundaries, rather than the fully CTCF-CTCF looped state, may be the primary regulators of functional interactions.
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Affiliation(s)
- Michele Gabriele
- Department of Biological Engineering, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
- The Broad Institute of MIT and Harvard; Cambridge, MA 02139, USA
- Koch Institute for Integrative Cancer Research; Cambridge, MA, 02139, USA
| | - Hugo B. Brandão
- Department of Biological Engineering, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
- The Broad Institute of MIT and Harvard; Cambridge, MA 02139, USA
- Koch Institute for Integrative Cancer Research; Cambridge, MA, 02139, USA
| | - Simon Grosse-Holz
- Department of Physics, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
- Institut Curie; Paris 75005, France
| | - Asmita Jha
- Department of Biological Engineering, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
- The Broad Institute of MIT and Harvard; Cambridge, MA 02139, USA
- Koch Institute for Integrative Cancer Research; Cambridge, MA, 02139, USA
| | - Gina M. Dailey
- Department of Molecular and Cell Biology, University of California, Berkeley; Berkeley, CA 94720, USA
| | - Claudia Cattoglio
- Department of Molecular and Cell Biology, University of California, Berkeley; Berkeley, CA 94720, USA
- Howard Hughes Medical Institute, University of California, Berkeley; Berkeley, CA 94720, USA
| | - Tsung-Han S. Hsieh
- Department of Molecular and Cell Biology, University of California, Berkeley; Berkeley, CA 94720, USA
- Howard Hughes Medical Institute, University of California, Berkeley; Berkeley, CA 94720, USA
| | - Leonid Mirny
- Department of Physics, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
- Institut Curie; Paris 75005, France
- Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
| | - Christoph Zechner
- Max Planck Institute of Molecular Cell Biology & Genetics; Dresden, Germany
- Center for Systems Biology Dresden; Dresden, Germany
- Cluster of Excellence Physics of Life and Faculty of Computer Science, TU Dresden; Dresden, Germany
| | - Anders S. Hansen
- Department of Biological Engineering, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
- The Broad Institute of MIT and Harvard; Cambridge, MA 02139, USA
- Koch Institute for Integrative Cancer Research; Cambridge, MA, 02139, USA
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13
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Diffusion and distal linkages govern interchromosomal dynamics during meiotic prophase. Proc Natl Acad Sci U S A 2022; 119:e2115883119. [PMID: 35302885 PMCID: PMC8944930 DOI: 10.1073/pnas.2115883119] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
SignificanceEssential for sexual reproduction, meiosis is a specialized cell division required for the production of haploid gametes. Critical to this process are the pairing, recombination, and segregation of homologous chromosomes (homologs). While pairing and recombination are linked, it is not known how many linkages are sufficient to hold homologs in proximity. Here, we reveal that random diffusion and the placement of a small number of linkages are sufficient to establish the apparent "pairing" of homologs. We also show that colocalization between any two loci is more dynamic than anticipated. Our study provides observations of live interchromosomal dynamics during meiosis and illustrates the power of combining single-cell measurements with theoretical polymer modeling.
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14
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García Fernández F, Fabre E. The Dynamic Behavior of Chromatin in Response to DNA Double-Strand Breaks. Genes (Basel) 2022; 13:genes13020215. [PMID: 35205260 PMCID: PMC8872016 DOI: 10.3390/genes13020215] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 01/18/2022] [Accepted: 01/19/2022] [Indexed: 02/05/2023] Open
Abstract
The primary functions of the eukaryotic nucleus as a site for the storage, retrieval, and replication of information require a highly dynamic chromatin organization, which can be affected by the presence of DNA damage. In response to double-strand breaks (DSBs), the mobility of chromatin at the break site is severely affected and, to a lesser extent, that of other chromosomes. The how and why of such movement has been widely studied over the last two decades, leading to different mechanistic models and proposed potential roles underlying both local and global mobility. Here, we review the state of the knowledge on current issues affecting chromatin mobility upon DSBs, and highlight its role as a crucial step in the DNA damage response (DDR).
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Affiliation(s)
- Fabiola García Fernández
- Institut Curie, CNRS UMR3664, Sorbonne Université, F-75005 Paris, France
- Correspondence: (F.G.F.); (E.F.)
| | - Emmanuelle Fabre
- Génomes Biologie Cellulaire et Thérapeutiques, CNRS UMR7212, INSERM U944, Université de Paris, F-75010 Paris, France
- Correspondence: (F.G.F.); (E.F.)
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15
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Spatial organization of chromosomes leads to heterogeneous chromatin motion and drives the liquid- or gel-like dynamical behavior of chromatin. Genome Res 2021; 32:28-43. [PMID: 34963660 PMCID: PMC8744683 DOI: 10.1101/gr.275827.121] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 12/02/2021] [Indexed: 11/25/2022]
Abstract
Chromosome organization and dynamics are involved in regulating many fundamental processes such as gene transcription and DNA repair. Experiments unveiled that chromatin motion is highly heterogeneous inside cell nuclei, ranging from a liquid-like, mobile state to a gel-like, rigid regime. Using polymer modeling, we investigate how these different physical states and dynamical heterogeneities may emerge from the same structural mechanisms. We found that the formation of topologically associating domains (TADs) is a key driver of chromatin motion heterogeneity. In particular, we showed that the local degree of compaction of the TAD regulates the transition from a weakly compact, fluid state of chromatin to a more compact, gel state exhibiting anomalous diffusion and coherent motion. Our work provides a comprehensive study of chromosome dynamics and a unified view of chromatin motion enabling interpretation of the wide variety of dynamical behaviors observed experimentally across different biological conditions, suggesting that the "liquid" or "solid" state of chromatin are in fact two sides of the same coin.
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16
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Hedley JG, Teif VB, Kornyshev AA. Nucleosome-induced homology recognition in chromatin. J R Soc Interface 2021; 18:20210147. [PMID: 34129789 PMCID: PMC8205524 DOI: 10.1098/rsif.2021.0147] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 05/04/2021] [Indexed: 02/07/2023] Open
Abstract
One of the least understood properties of chromatin is the ability of its similar regions to recognize each other through weak interactions. Theories based on electrostatic interactions between helical macromolecules suggest that the ability to recognize sequence homology is an innate property of the non-ideal helical structure of DNA. However, this theory does not account for the nucleosomal packing of DNA. Can homologous DNA sequences recognize each other while wrapped up in the nucleosomes? Can structural homology arise at the level of nucleosome arrays? Here, we present a theoretical model for the recognition potential well between chromatin fibres sliding against each other. This well is different from the one predicted for bare DNA; the minima in energy do not correspond to literal juxtaposition, but are shifted by approximately half the nucleosome repeat length. The presence of this potential well suggests that nucleosome positioning may induce mutual sequence recognition between chromatin fibres and facilitate the formation of chromatin nanodomains. This has implications for nucleosome arrays enclosed between CTCF-cohesin boundaries, which may form stiffer stem-like structures instead of flexible entropically favourable loops. We also consider switches between chromatin states, e.g. through acetylation/deacetylation of histones, and discuss nucleosome-induced recognition as a precursory stage of genetic recombination.
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Affiliation(s)
- Jonathan G. Hedley
- Department of Chemistry, Faculty of Natural Sciences, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London W12 0BZ, UK
| | - Vladimir B. Teif
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK
| | - Alexei A. Kornyshev
- Department of Chemistry, Faculty of Natural Sciences, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London W12 0BZ, UK
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17
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Sumner MC, Torrisi SB, Brickner DG, Brickner JH. Random sub-diffusion and capture of genes by the nuclear pore reduces dynamics and coordinates inter-chromosomal movement. eLife 2021; 10:66238. [PMID: 34002694 PMCID: PMC8195609 DOI: 10.7554/elife.66238] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 05/17/2021] [Indexed: 11/13/2022] Open
Abstract
Hundreds of genes interact with the yeast nuclear pore complex (NPC), localizing at the nuclear periphery and clustering with co-regulated genes. Dynamic tracking of peripheral genes shows that they cycle on and off the NPC and that interaction with the NPC slows their sub-diffusive movement. Furthermore, NPC-dependent inter-chromosomal clustering leads to coordinated movement of pairs of loci separated by hundreds of nanometers. We developed fractional Brownian motion simulations for chromosomal loci in the nucleoplasm and interacting with NPCs. These simulations predict the rate and nature of random sub-diffusion during repositioning from nucleoplasm to periphery and match measurements from two different experimental models, arguing that recruitment to the nuclear periphery is due to random sub-diffusion and transient capture by NPCs. Finally, the simulations do not lead to inter-chromosomal clustering or coordinated movement, suggesting that interaction with the NPC is necessary, but not sufficient, to cause clustering.
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Affiliation(s)
- Michael Chas Sumner
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
| | - Steven B Torrisi
- Department of Physics, Harvard University, Cambridge, United States
| | - Donna G Brickner
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
| | - Jason H Brickner
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
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18
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Hao X, Parmar JJ, Lelandais B, Aristov A, Ouyang W, Weber C, Zimmer C. Super-resolution visualization and modeling of human chromosomal regions reveals cohesin-dependent loop structures. Genome Biol 2021; 22:150. [PMID: 33975635 PMCID: PMC8111965 DOI: 10.1186/s13059-021-02343-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Accepted: 04/08/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The 3D organization of the chromatin fiber in cell nuclei plays a key role in the regulation of gene expression. Genome-wide techniques to score DNA-DNA contacts, such as Hi-C, reveal the partitioning of chromosomes into epigenetically defined active and repressed compartments and smaller "topologically associated" domains. These domains are often associated with chromatin loops, which largely disappear upon removal of cohesin. Because most Hi-C implementations average contact frequencies over millions of cells and do not provide direct spatial information, it remains unclear whether and how frequently chromatin domains and loops exist in single cells. RESULTS We combine 3D single-molecule localization microscopy with a low-cost fluorescence labeling strategy that does not denature the DNA, to visualize large portions of single human chromosomes in situ at high resolution. In parallel, we develop multi-scale, whole nucleus polymer simulations, that predict chromatin structures at scales ranging from 5 kb up to entire chromosomes. We image chromosomes in G1 and M phase and examine the effect of cohesin on interphase chromatin structure. Depletion of cohesin leads to increased prevalence of loose chromatin stretches, increased gyration radii, and reduced smoothness of imaged chromatin regions. By comparison to model predictions, we estimate that 6-25 or more purely cohesin-dependent chromatin loops coexist per megabase of DNA in single cells, suggesting that the vast majority of the genome is enclosed in loops. CONCLUSION Our results provide new constraints on chromatin structure and showcase an affordable non-invasive approach to study genome organization in single cells.
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Affiliation(s)
- Xian Hao
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
- School of Public Health & Jiangxi Provincial Key Laboratory of Preventive Medicine, Nanchang University, Nanchang, 330006, China
| | - Jyotsana J Parmar
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
- Simons Center for the Study of Living Machines, National Center for Biological Sciences (TIFR), Bangalore, Karnataka, 560065, India
| | - Benoît Lelandais
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
| | - Andrey Aristov
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
| | - Wei Ouyang
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
- Université de Paris, F-75013, Paris, France
| | - Christian Weber
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
| | - Christophe Zimmer
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France.
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19
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García Fernández F, Lemos B, Khalil Y, Batrin R, Haber JE, Fabre E. Modified chromosome structure caused by phosphomimetic H2A modulates the DNA damage response by increasing chromatin mobility in yeast. J Cell Sci 2021; 134:jcs.258500. [PMID: 33622771 DOI: 10.1242/jcs.258500] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 02/06/2021] [Indexed: 12/23/2022] Open
Abstract
In budding yeast and mammals, double-strand breaks (DSBs) trigger global chromatin mobility together with rapid phosphorylation of histone H2A over an extensive region of the chromatin. To assess the role of H2A phosphorylation in this response to DNA damage, we have constructed strains where H2A has been mutated to the phosphomimetic H2A-S129E. We show that mimicking H2A phosphorylation leads to an increase in global chromatin mobility in the absence of DNA damage. The intrinsic chromatin mobility of H2A-S129E is not due to downstream checkpoint activation, histone degradation or kinetochore anchoring. Rather, the increased intrachromosomal distances observed in the H2A-S129E mutant are consistent with chromatin structural changes. Strikingly, in this context the Rad9-dependent checkpoint becomes dispensable. Moreover, increased chromatin dynamics in the H2A-S129E mutant correlates with improved DSB repair by non-homologous end joining and a sharp decrease in interchromosomal translocation rate. We propose that changes in chromosomal conformation due to H2A phosphorylation are sufficient to modulate the DNA damage response and maintain genome integrity.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Fabiola García Fernández
- Institut de recherche Saint-Louis (IRSL), Université de Paris, INSERM U944, CNRS UMR7212, Genome and Cell Biology of Diseases Unit, F-75010 Paris, France
| | - Brenda Lemos
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454-9110, USA
| | - Yasmine Khalil
- Institut de recherche Saint-Louis (IRSL), Université de Paris, INSERM U944, CNRS UMR7212, Genome and Cell Biology of Diseases Unit, F-75010 Paris, France
| | - Renaud Batrin
- Institut de recherche Saint-Louis (IRSL), Université de Paris, INSERM U944, CNRS UMR7212, Genome and Cell Biology of Diseases Unit, F-75010 Paris, France
| | - James E Haber
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454-9110, USA
| | - Emmanuelle Fabre
- Institut de recherche Saint-Louis (IRSL), Université de Paris, INSERM U944, CNRS UMR7212, Genome and Cell Biology of Diseases Unit, F-75010 Paris, France
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20
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Pease NA, Nguyen PHB, Woodworth MA, Ng KKH, Irwin B, Vaughan JC, Kueh HY. Tunable, division-independent control of gene activation timing by a polycomb switch. Cell Rep 2021; 34:108888. [PMID: 33761349 PMCID: PMC8024876 DOI: 10.1016/j.celrep.2021.108888] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 12/17/2020] [Accepted: 03/01/2021] [Indexed: 01/09/2023] Open
Abstract
During development, progenitors often differentiate many cell generations after receiving signals. These delays must be robust yet tunable for precise population size control. Polycomb repressive mechanisms, involving histone H3 lysine-27 trimethylation (H3K27me3), restrain the expression of lineage-specifying genes in progenitors and may delay their activation and ensuing differentiation. Here, we elucidate an epigenetic switch controlling the T cell commitment gene Bcl11b that holds its locus in a heritable inactive state for multiple cell generations before activation. Integrating experiments and modeling, we identify a mechanism where H3K27me3 levels at Bcl11b, regulated by methyltransferase and demethylase activities, set the time delay at which the locus switches from a compacted, silent state to an extended, active state. This activation delay robustly spans many cell generations, is tunable by chromatin modifiers and transcription factors, and is independent of cell division. With their regulatory flexibility, such timed epigenetic switches may broadly control timing in development.
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Affiliation(s)
- Nicholas A Pease
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA; Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA
| | - Phuc H B Nguyen
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA; Molecular Engineering and Sciences Institute, University of Washington, Seattle, WA 98195, USA
| | - Marcus A Woodworth
- Biological Physics, Structure and Design Program, University of Washington, Seattle, WA 98195, USA; Department of Chemistry, University of Washington, Seattle, WA 98195, USA
| | - Kenneth K H Ng
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
| | - Blythe Irwin
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
| | - Joshua C Vaughan
- Department of Chemistry, University of Washington, Seattle, WA 98195, USA; Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
| | - Hao Yuan Kueh
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA; Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98195, USA.
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21
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Brunet A, Destainville N, Collas P. Physical constraints in polymer modeling of chromatin associations with the nuclear periphery at kilobase scale. Nucleus 2021; 12:6-20. [PMID: 33435761 PMCID: PMC7808377 DOI: 10.1080/19491034.2020.1868105] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Interactions of chromatin with the nuclear lamina imposes a radial genome distribution important for nuclear functions. How physical properties of chromatin affect these interactions is unclear. We used polymer simulations to model how physical parameters of chromatin affect its interaction with the lamina. Impact of polymer stiffness is greater than stretching on its configurations at the lamina; these are manifested as trains describing extended interactions, and loops describing desorbed regions . Conferring an attraction potential leads to persistent interaction and adsorption-desorption regimes manifested by fluctuations between trains and loops. These are modulated by polymer stiffness and stretching, with a dominant impact of stiffness on resulting structural configurations. We infer that flexible euchromatin is more prone to stochastic interactions with lamins than rigid heterochromatin characterizing constitutive LADs. Our models provide insights on the physical properties of chromatin as a polymer which affect the dynamics and patterns of interactions with the nuclear lamina.
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Affiliation(s)
- Annaël Brunet
- Department of Molecular Medicine, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo , Oslo, Norway
| | - Nicolas Destainville
- Laboratoire De Physique Théorique, IRSAMC, Université De Toulouse (UPS) , CNRS, Toulouse, France
| | - Philippe Collas
- Department of Molecular Medicine, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo , Oslo, Norway.,Department of Immunology and Transfusion Medicine, Oslo University Hospital , Oslo, Norway
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22
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Rensen E, Mueller F, Scoca V, Parmar JJ, Souque P, Zimmer C, Di Nunzio F. Clustering and reverse transcription of HIV-1 genomes in nuclear niches of macrophages. EMBO J 2021; 40:e105247. [PMID: 33270250 PMCID: PMC7780146 DOI: 10.15252/embj.2020105247] [Citation(s) in RCA: 70] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 10/04/2020] [Accepted: 10/16/2020] [Indexed: 01/07/2023] Open
Abstract
In order to replicate, human immunodeficiency virus (HIV-1) reverse-transcribes its RNA genome into DNA, which subsequently integrates into host cell chromosomes. These two key events of the viral life cycle are commonly viewed as separate not only in time, but also in cellular space, since reverse transcription (RT) is thought to be completed in the cytoplasm before nuclear import and integration. However, the spatiotemporal organization of the early viral replication cycle in macrophages, the natural non-dividing target cells that constitute reservoirs of HIV-1 and an obstacle to curing AIDS, remains unclear. Here, we demonstrate that infected macrophages display large nuclear foci of viral DNA (vDNA) and viral RNA, in which multiple viral genomes cluster together. These clusters form in the absence of chromosomal integration, sequester the paraspeckle protein CPSF6, and localize to nuclear speckles. Surprisingly, these viral RNA clusters consist mostly of genomic, incoming RNA, both in cells where reverse transcription is pharmacologically suppressed and in untreated cells. We demonstrate that following temporary inhibition, reverse transcription can resume in the nucleus and lead to vDNA accumulation in these clusters. We further show that nuclear reverse transcription can result in transcription-competent viral DNA. These findings change our understanding of the early HIV-1 replication cycle and may have implications for addressing HIV-1 persistence.
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Affiliation(s)
- Elena Rensen
- Imaging and Modeling UnitInstitut PasteurUMR 3691 CNRSC3BI USR 3756 IP CNRSParisFrance
- Molecular Virology and VaccinologyInstitut PasteurParisFrance
| | - Florian Mueller
- Imaging and Modeling UnitInstitut PasteurUMR 3691 CNRSC3BI USR 3756 IP CNRSParisFrance
| | - Viviana Scoca
- Molecular Virology and VaccinologyInstitut PasteurParisFrance
| | - Jyotsana J Parmar
- Imaging and Modeling UnitInstitut PasteurUMR 3691 CNRSC3BI USR 3756 IP CNRSParisFrance
| | - Philippe Souque
- Molecular Virology and VaccinologyInstitut PasteurParisFrance
| | - Christophe Zimmer
- Imaging and Modeling UnitInstitut PasteurUMR 3691 CNRSC3BI USR 3756 IP CNRSParisFrance
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23
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Di Stefano M, Paulsen J, Jost D, Marti-Renom MA. 4D nucleome modeling. Curr Opin Genet Dev 2020; 67:25-32. [PMID: 33253996 PMCID: PMC8098745 DOI: 10.1016/j.gde.2020.10.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 10/18/2020] [Accepted: 10/24/2020] [Indexed: 02/01/2023]
Abstract
The intrinsic dynamic nature of chromosomes is emerging as a fundamental component in regulating DNA transcription, replication, and damage-repair among other nuclear functions. With this increased awareness, reinforced over the last ten years, many new experimental techniques, mainly based on microscopy and chromosome conformation capture, have been introduced to study the genome in space and time. Owing to the increasing complexity of these cutting-edge techniques, computational approaches have become of paramount importance to interpret, contextualize, and complement such experiments with new insights. Hence, it is becoming crucial for experimental biologists to have a clear understanding of the diverse theoretical modeling approaches available and the biological information each of them can provide.
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Affiliation(s)
- Marco Di Stefano
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Baldiri i Reixac 4, 08028 Barcelona, Spain.
| | - Jonas Paulsen
- EVOGENE, Department of Biosciences, Faculty of Natural Sciences, University of Oslo, 0316 Oslo, Norway
| | - Daniel Jost
- Université de Lyon, ENS de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Biologie et Modélisation de la Cellule, Lyon, France
| | - Marc A Marti-Renom
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Baldiri i Reixac 4, 08028 Barcelona, Spain; Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Dr. Aiguader 88, 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain; ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain.
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24
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Miné-Hattab J, Chiolo I. Complex Chromatin Motions for DNA Repair. Front Genet 2020; 11:800. [PMID: 33061931 PMCID: PMC7481375 DOI: 10.3389/fgene.2020.00800] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 07/06/2020] [Indexed: 12/26/2022] Open
Abstract
A number of studies across different model systems revealed that chromatin undergoes significant changes in dynamics in response to DNA damage. These include local motion changes at damage sites, increased nuclear exploration of both damaged and undamaged loci, and directed motions to new nuclear locations associated with certain repair pathways. These studies also revealed the need for new analytical methods to identify directed motions in a context of mixed trajectories, and the importance of investigating nuclear dynamics over different time scales to identify diffusion regimes. Here we provide an overview of the current understanding of this field, including imaging and analytical methods developed to investigate nuclear dynamics in different contexts. These dynamics are essential for genome integrity. Identifying the molecular mechanisms responsible for these movements is key to understanding how their misregulation contributes to cancer and other genome instability disorders.
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Affiliation(s)
- Judith Miné-Hattab
- UMR 3664, CNRS, Institut Curie, PSL Research University, Paris, France
- UMR 3664, CNRS, Institut Curie, Sorbonne Université, Paris, France
| | - Irene Chiolo
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, United States
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25
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Yeast ATM and ATR kinases use different mechanisms to spread histone H2A phosphorylation around a DNA double-strand break. Proc Natl Acad Sci U S A 2020; 117:21354-21363. [PMID: 32817543 PMCID: PMC7474660 DOI: 10.1073/pnas.2002126117] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
One of the hallmarks of DNA damage is the rapid spreading of phosphorylated histone H2A (γ-H2AX) around a DNA double-strand break (DSB). In the budding yeast Saccharomyces cerevisiae, nearly all H2A isoforms can be phosphorylated, either by Mec1ATR or Tel1ATM checkpoint kinases. We induced a site-specific DSB with HO endonuclease at the MAT locus on chromosome III and monitored the formation of γ-H2AX by chromatin immunoprecipitation (ChIP)-qPCR in order to uncover the mechanisms by which Mec1ATR and Tel1ATM propagate histone modifications across chromatin. With either kinase, γ-H2AX spreads as far as ∼50 kb on both sides of the lesion within 1 h; but the kinetics and distribution of modification around the DSB are significantly different. The total accumulation of phosphorylation is reduced by about half when either of the two H2A genes is mutated to the nonphosphorylatable S129A allele. Mec1 activity is limited by the abundance of its ATRIP partner, Ddc2. Moreover, Mec1 is more efficient than Tel1 at phosphorylating chromatin in trans-at distant undamaged sites that are brought into physical proximity to the DSB. We compared experimental data to mathematical models of spreading mechanisms to determine whether the kinases search for target nucleosomes by primarily moving in three dimensions through the nucleoplasm or in one dimension along the chromatin. Bayesian model selection indicates that Mec1 primarily uses a three-dimensional diffusive mechanism, whereas Tel1 undergoes directed motion along the chromatin.
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Quantitative Analysis of Spatial Distributions of All tRNA Genes in Budding Yeast. Biophys J 2020; 118:2181-2192. [PMID: 31951810 DOI: 10.1016/j.bpj.2019.12.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 12/17/2019] [Accepted: 12/18/2019] [Indexed: 10/25/2022] Open
Abstract
In the budding yeast nucleus, transfer RNA (tRNA) genes are considered to localize in the vicinity of the nucleolus; however, the use of Hi-C and fluorescent repressor-operator system techniques has clearly indicated that the tRNA genes are distributed not only around the nucleolus but also at other nuclear locations. However, there are some discrepancies between Hi-C data analysis and the results indicated from fluorescence microscopy data. To fill these gaps, we systematically clarified the spatial arrangements of all tRNA genes in the budding yeast nucleus using the genome simulation model developed by us. The simulation results revealed that out of 275 tRNA genes, 58% were found to be spatially distributed around the centromeres, 16% were distributed around the ribosomal DNA regions, and the remaining 26% were distributed between the centromeres and ribosomal DNA regions. Furthermore, 1% of all tRNA genes were found to be spatially distributed around the nuclear envelope, 30% were distributed around the center of the nucleus, and the remaining 69% were distributed between the nuclear envelope and the center of the nucleus. The percentage distributions were highly similar to those of the 176 tRNA genes encoding tRNAs having an anticodon for the optimal codons. The simulation results also revealed that the spatial arrangements of tRNA genes were affected by linear genomic distance from the tethering elements such as the centromeres or telomeres; however, the distance was only one of the factors to determine spatial distribution. This study also investigates whether tRNA gene transcriptional levels depend on the arrangements in the budding yeast nucleus by integrating the genome simulation model with tRNA sequencing data. The results suggest that the transcriptional levels did not depend on the arrangements in the nucleus. By using the genome simulation model, we showed the possibility of quantitatively analyzing genome structures.
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Moller J, de Pablo JJ. Bottom-Up Meets Top-Down: The Crossroads of Multiscale Chromatin Modeling. Biophys J 2020; 118:2057-2065. [PMID: 32320675 DOI: 10.1016/j.bpj.2020.03.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 03/04/2020] [Accepted: 03/20/2020] [Indexed: 01/19/2023] Open
Abstract
Chromatin can be viewed as a hierarchically structured fiber that regulates gene expression. It consists of a complex network of DNA and proteins whose characteristic dynamical modes facilitate compaction and rearrangement in the cell nucleus. These modes stem from chromatin's fundamental unit, the nucleosome, and their effects are propagated across length scales. Understanding the effects of nucleosome dynamics on the chromatin fiber, primarily through post-translational modifications that occur on the histones, is of central importance to epigenetics. Within the last decade, imaging and chromosome conformation capture techniques have revealed a number of structural and statistical features of the packaged chromatin fiber at a hitherto unavailable level of resolution. Such experiments have led to increased efforts to develop polymer models that aim to reproduce, explain, and predict the contact probability scaling and density heterogeneity. At nanometer scales, available models have focused on the role of the nucleosome and epigenetic marks on local chromatin structure. At micrometer scales, existing models have sought to explain scaling laws and density heterogeneity. Less work, however, has been done to reconcile these two approaches: bottom-up and top-down models of chromatin. In this perspective, we highlight the multiscale simulation models that are driving toward an understanding of chromatin structure and function, from the nanometer to the micron scale, and we highlight areas of opportunity and some of the prospects for new frameworks that bridge these two scales. Taken together, experimental and modeling advances over the last few years have established a robust platform for the study of chromatin fiber structure and dynamics, which will be of considerable use to the chromatin community in developing an understanding of the interplay between epigenomic regulation and molecular structure.
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Affiliation(s)
- Joshua Moller
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois
| | - Juan J de Pablo
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois; Material Science Division, Argonne National Laboratory, Lemont, Illinois.
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Tortora MMC, Salari H, Jost D. Chromosome dynamics during interphase: a biophysical perspective. Curr Opin Genet Dev 2020; 61:37-43. [DOI: 10.1016/j.gde.2020.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 02/24/2020] [Accepted: 03/02/2020] [Indexed: 12/29/2022]
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Abstract
Maintaining the integrity of the genome in the face of DNA damage is crucial to ensure the survival of the cell and normal development. DNA lesions and repair occur in the context of the chromatin fiber, whose 3D organization and movements in the restricted volume of the nucleus are under intense scrutiny. Here, we highlight work from our and other labs that addresses how the dynamic organization of the chromatin fiber affects the repair of damaged DNA and how, conversely, DNA damage and repair affect the structure and dynamics of chromatin in the budding yeast nucleus.
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Affiliation(s)
- Emmanuelle Fabre
- a Equipe Biologie et Dynamique des Chromosomes , Institut Universitaire d'Hématologie, Hôpital St. Louis , Paris , France.,b CNRS, UMR 7212 INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité , Paris , France
| | - Christophe Zimmer
- c Institut Pasteur, Unité Imagerie et Modélisation , 25 rue du Docteur Roux, 75015 , Paris , France.,d UMR 3691, CNRS; C3BI, USR 3756, IP CNRS , Paris , France
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Abstract
DNA is packaged into chromosomes, which are further organized into domains: Regions of the genome which are more likely to self-interact. Domains have been observed in species ranging from bacteria to humans and are thought to play an important role in gene regulation. Yet the mechanisms of domain formation are not fully understood. Here we use computer simulations to investigate domain formation in yeast. Our model reproduces the experimentally observed domains using only nucleosome positioning information as an input, implying that (unlike in higher eukaryotes) domain boundary locations are largely determined at this level. Our results reveal how irregular nucleosome spacing impacts the 3D chromosome organization, pointing to a direct link between nucleosome positioning and genome regulation at the large scale. We use molecular dynamics simulations based on publicly available micrococcal nuclease sequencing data for nucleosome positions to predict the 3D structure of chromatin in the yeast genome. Our main aim is to shed light on the mechanism underlying the formation of chromosomal interaction domains, chromosome regions of around 0.5 to 10 kbp which show enriched self-interactions, which were experimentally observed in recent MicroC experiments (importantly these are at a different length scale from the 100- to 1,000-kbp–sized domains observed in higher eukaryotes). We show that the sole input of nucleosome positioning data is already sufficient to determine the patterns of chromatin interactions and domain boundaries seen experimentally to a high degree of accuracy. Since the nucleosome spacing so strongly affects the larger-scale domain structure, we next examine the genome-wide linker-length distribution in more detail, finding that it is highly irregular and varies in different genomic regions such as gene bodies, promoters, and active and inactive genes. Finally we use our simple simulation model to characterize in more detail how irregular nucleosome spacing may affect local chromatin structure.
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31
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Socol M, Wang R, Jost D, Carrivain P, Vaillant C, Le Cam E, Dahirel V, Normand C, Bystricky K, Victor JM, Gadal O, Bancaud A. Rouse model with transient intramolecular contacts on a timescale of seconds recapitulates folding and fluctuation of yeast chromosomes. Nucleic Acids Res 2019; 47:6195-6207. [PMID: 31114898 PMCID: PMC6614813 DOI: 10.1093/nar/gkz374] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 04/25/2019] [Accepted: 05/09/2019] [Indexed: 01/08/2023] Open
Abstract
DNA folding and dynamics along with major nuclear functions are determined by chromosome structural properties, which remain, thus far, elusive in vivo. Here, we combine polymer modeling and single particle tracking experiments to determine the physico-chemical parameters of chromatin in vitro and in living yeast. We find that the motion of reconstituted chromatin fibers can be recapitulated by the Rouse model using mechanical parameters of nucleosome arrays deduced from structural simulations. Conversely, we report that the Rouse model shows some inconsistencies to analyze the motion and structural properties inferred from yeast chromosomes determined with chromosome conformation capture techniques (specifically, Hi-C). We hence introduce the Rouse model with Transient Internal Contacts (RouseTIC), in which random association and dissociation occurs along the chromosome contour. The parametrization of this model by fitting motion and Hi-C data allows us to measure the kinetic parameters of the contact formation reaction. Chromosome contacts appear to be transient; associated to a lifetime of seconds and characterized by an attractive energy of -0.3 to -0.5 kBT. We suggest attributing this energy to the occurrence of histone tail-DNA contacts and notice that its amplitude sets chromosomes in 'theta' conditions, in which they are poised for compartmentalization and phase separation.
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Affiliation(s)
- Marius Socol
- LAAS-CNRS, Université de Toulouse, CNRS, F-31400 Toulouse, France
- IRIM, CNRS, University of Montpellier, France
| | - Renjie Wang
- Laboratoire de Biologie Moléculaire Eucaryote (LBME), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, F-31062 Toulouse, France
- Material Science & Engineering School, Henan University of Technology, 450001 Zhengzhou, P.R. China
| | - Daniel Jost
- Univ. Grenoble Alpes, CNRS, CHU Grenoble Alpes, Grenoble INP, TIMC-IMAG, F-38000 Grenoble, France
| | - Pascal Carrivain
- Laboratoire de Physique, Ecole Normale Supérieure de Lyon, CNRS UMR 5672, Lyon 69007, France
| | - Cédric Vaillant
- Laboratoire de Physique, Ecole Normale Supérieure de Lyon, CNRS UMR 5672, Lyon 69007, France
| | - Eric Le Cam
- Genome Maintenance and Molecular Microscopy UMR8126, CNRS, Université Paris-Sud, Université Paris-Saclay, Gustave Roussy, F-94805 Villejuif Cedex France
| | - Vincent Dahirel
- Sorbonne Université, CNRS, Physicochimie des Electrolytes et Nanosystèmes interfaciaux, laboratoire PHENIX, F-75005 Paris, France
| | - Christophe Normand
- Laboratoire de Biologie Moléculaire Eucaryote (LBME), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, F-31062 Toulouse, France
| | - Kerstin Bystricky
- Laboratoire de Biologie Moléculaire Eucaryote (LBME), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, F-31062 Toulouse, France
| | - Jean-Marc Victor
- Sorbonne Université, CNRS, Laboratoire de Physique Théorique de la Matière Condensée, LPTMC, F-75005 Paris, France
| | - Olivier Gadal
- Laboratoire de Biologie Moléculaire Eucaryote (LBME), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, F-31062 Toulouse, France
| | - Aurélien Bancaud
- LAAS-CNRS, Université de Toulouse, CNRS, F-31400 Toulouse, France
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Parmar JJ, Woringer M, Zimmer C. How the Genome Folds: The Biophysics of Four-Dimensional Chromatin Organization. Annu Rev Biophys 2019; 48:231-253. [DOI: 10.1146/annurev-biophys-052118-115638] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The genetic information that instructs transcription and other cellular functions is carried by the chromosomes, polymers of DNA in complex with histones and other proteins. These polymers are folded inside nuclei five orders of magnitude smaller than their linear length, and many facets of this folding correlate with or are causally related to transcription and other cellular functions. Recent advances in sequencing and imaging-based techniques have enabled new views into several layers of chromatin organization. These experimental findings are accompanied by computational modeling efforts based on polymer physics that can provide mechanistic insights and quantitative predictions. Here, we review current knowledge of the main levels of chromatin organization, from the scale of nucleosomes to the entire nucleus, our current understanding of their underlying biophysical and molecular mechanisms, and some of their functional implications.
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Affiliation(s)
- Jyotsana J. Parmar
- Unité Imagerie et Modélisation, CNRS UMR 3691, and C3BI (Center of Bioinformatics, Biostatistics and Integrative Biology), CNRS USR 3756, Institut Pasteur, 75015 Paris, France;, ,
| | - Maxime Woringer
- Unité Imagerie et Modélisation, CNRS UMR 3691, and C3BI (Center of Bioinformatics, Biostatistics and Integrative Biology), CNRS USR 3756, Institut Pasteur, 75015 Paris, France;, ,
- Sorbonne Universités, CNRS, 75005 Paris, France
- Department of Molecular and Cell Biology, Li Ka Shing Center for Biomedical and Health Sciences, and CIRM Center of Excellence in Stem Cell Genomics, University of California, Berkeley, California 94720, USA
| | - Christophe Zimmer
- Unité Imagerie et Modélisation, CNRS UMR 3691, and C3BI (Center of Bioinformatics, Biostatistics and Integrative Biology), CNRS USR 3756, Institut Pasteur, 75015 Paris, France;, ,
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Miné-Hattab J, Taddei A. Physical principles and functional consequences of nuclear compartmentalization in budding yeast. Curr Opin Cell Biol 2019; 58:105-113. [PMID: 30928833 DOI: 10.1016/j.ceb.2019.02.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 01/28/2019] [Accepted: 02/20/2019] [Indexed: 12/19/2022]
Abstract
One striking feature of eukaryotic nuclei is the existence of discrete regions, in which specific factors concentrate while others are excluded, thus forming microenvironments with different molecular compositions and biological functions. These domains are often referred to as subcompartments even though they are not membrane enclosed. Despite their functional importance the physical nature of these structures remains largely unknown. Here, we describe how the Saccharomyces cerevisiae nucleus is compartmentalized and discuss possible physical models underlying the formation and maintenance of chromatin associated subcompartments. Focusing on three particular examples, the nucleolus, silencing foci, and repair foci, we discuss the biological implications of these different models as well as possible approaches to challenge them in living cells.
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Affiliation(s)
- Judith Miné-Hattab
- Institut Curi-PSL Research University, CNRS, Sorbonne Université, UMR3664, F-75005, Paris, France
| | - Angela Taddei
- Institut Curi-PSL Research University, CNRS, Sorbonne Université, UMR3664, F-75005, Paris, France.
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34
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Arifulin EA, Musinova YR, Vassetzky YS, Sheval EV. Mobility of Nuclear Components and Genome Functioning. BIOCHEMISTRY (MOSCOW) 2018; 83:690-700. [PMID: 30195325 DOI: 10.1134/s0006297918060068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cell nucleus is characterized by strong compartmentalization of structural components in its three-dimensional space. Certain genomic functions are accompanied by changes in the localization of chromatin loci and nuclear bodies. Here we review recent data on the mobility of nuclear components and the role of this mobility in genome functioning.
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Affiliation(s)
- E A Arifulin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
| | - Y R Musinova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.,LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, Villejuif, 94805, France.,Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, 119334, Russia
| | - Y S Vassetzky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.,LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, Villejuif, 94805, France.,Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, 119334, Russia.,UMR8126, CNRS, Université Paris-Sud, Institut de Cancérologie Gustave Roussy, Villejuif, 94805, France
| | - E V Sheval
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.,LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, Villejuif, 94805, France
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35
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Dultz E, Mancini R, Polles G, Vallotton P, Alber F, Weis K. Quantitative imaging of chromatin decompaction in living cells. Mol Biol Cell 2018; 29:1763-1777. [PMID: 29771637 DOI: 10.1101/219253] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023] Open
Abstract
Chromatin organization is highly dynamic and regulates transcription. Upon transcriptional activation, chromatin is remodeled and referred to as "open," but quantitative and dynamic data of this decompaction process are lacking. Here, we have developed a quantitative high resolution-microscopy assay in living yeast cells to visualize and quantify chromatin dynamics using the GAL7-10-1 locus as a model system. Upon transcriptional activation of these three clustered genes, we detect an increase of the mean distance across this locus by >100 nm. This decompaction is linked to active transcription but is not sensitive to the histone deacetylase inhibitor trichostatin A or to deletion of the histone acetyl transferase Gcn5. In contrast, the deletion of SNF2 (encoding the ATPase of the SWI/SNF chromatin remodeling complex) or the deactivation of the histone chaperone complex FACT lead to a strongly reduced decompaction without significant effects on transcriptional induction in FACT mutants. Our findings are consistent with nucleosome remodeling and eviction activities being major contributors to chromatin reorganization during transcription but also suggest that transcription can occur in the absence of detectable decompaction.
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Affiliation(s)
- Elisa Dultz
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Roberta Mancini
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Guido Polles
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089
| | - Pascal Vallotton
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Frank Alber
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089
| | - Karsten Weis
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
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36
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Zimmer C, Fabre E. Chromatin mobility upon DNA damage: state of the art and remaining questions. Curr Genet 2018; 65:1-9. [DOI: 10.1007/s00294-018-0852-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 05/30/2018] [Accepted: 06/04/2018] [Indexed: 12/14/2022]
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37
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Arbona JM, Goldar A, Hyrien O, Arneodo A, Audit B. The eukaryotic bell-shaped temporal rate of DNA replication origin firing emanates from a balance between origin activation and passivation. eLife 2018; 7:35192. [PMID: 29856315 PMCID: PMC6033540 DOI: 10.7554/elife.35192] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 05/31/2018] [Indexed: 01/22/2023] Open
Abstract
The time-dependent rate I(t) of origin firing per length of unreplicated DNA presents a universal bell shape in eukaryotes that has been interpreted as the result of a complex time-evolving interaction between origins and limiting firing factors. Here, we show that a normal diffusion of replication fork components towards localized potential replication origins (p-oris) can more simply account for the I(t) universal bell shape, as a consequence of a competition between the origin firing time and the time needed to replicate DNA separating two neighboring p-oris. We predict the I(t) maximal value to be the product of the replication fork speed with the squared p-ori density. We show that this relation is robustly observed in simulations and in experimental data for several eukaryotes. Our work underlines that fork-component recycling and potential origins localization are sufficient spatial ingredients to explain the universality of DNA replication kinetics. Before a cell can divide, it must duplicate its DNA. In eukaryotes – organisms such as animals and fungi, which store their DNA in the cell’s nucleus – DNA replication starts at specific sites in the genome called replication origins. At each origin sits a protein complex that will activate when it randomly captures an activating protein that diffuses within the nucleus. Once a replication origin activates or “fires”, the complex then splits into two new complexes that move away from each other as they duplicate the DNA. If an active complex collides with an inactive one at another origin, the latter is inactivated – a phenomenon known as origin passivation. When two active complexes meet, they release the activating proteins, which diffuse away and eventually activate other origins in unreplicated DNA. The number of origins that activate each minute divided by the length of unreplicated DNA is referred to as the “rate of origin firing”. In all eukaryotes, this rate – also known as I(t) – follows the same pattern. First, it increases until more than half of the DNA is duplicated. Then it decreases until everything is duplicated. This means that, if plotted out, the graph of origin firing rate would always be a bell-shaped curve, even for organisms with genomes of different sizes that have different numbers of origins. The reason for this universal shape remained unclear. Scientists had tried to create numerical simulations that model the rate of origin firing. However, for these simulations to reproduce the bell-shape curve, a number of untested assumptions had to be made about how DNA replication takes place. In addition, these models ignored the fact that it takes time to replicate the DNA between origins. To take this time into account, Arbona et al. instead decided to model the replication origins as discrete and distinct entities. This way of building the mathematical model succeeded in reproducing the universal bell curve shape without additional assumptions. With this simulation, the balance between origin activation and passivation is enough to achieve the observed pattern. The new model also predicts that the maximum rate of origin firing is determined by the speed of DNA replication and the density of origins in the genome. Arbona et al. verified this prediction in yeast, fly, frog and human cells – organisms with different sized genomes that take between 20 minutes and 8 hours to replicate their DNA. Lastly, the prediction also held true in yeast treated with hydroxyurea, an anticancer drug that slows DNA replication. A better understanding of DNA replication can help scientists to understand how this process is perturbed in cancers and how drugs that target DNA replication can treat these diseases. Future work will explore how the 3D organization of the genome affects the diffusion of activating proteins within the cell nucleus.
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Affiliation(s)
- Jean-Michel Arbona
- Laboratoire de Physique, Université de Lyon, Ens de Lyon, Université Claude Bernard Lyon 1, CNRS, Lyon, France
| | | | - Olivier Hyrien
- Institut de Biologie de l'Ecole Normale Supérieure, Ecole Normale Supérieure, CNRS, INSERM, PSL Research University, Paris, France
| | - Alain Arneodo
- LOMA, Univ de Bordeaux, CNRS, UMR 5798, Talence, France
| | - Benjamin Audit
- Laboratoire de Physique, Université de Lyon, Ens de Lyon, Université Claude Bernard Lyon 1, CNRS, Lyon, France
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38
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Dultz E, Mancini R, Polles G, Vallotton P, Alber F, Weis K. Quantitative imaging of chromatin decompaction in living cells. Mol Biol Cell 2018; 29:1763-1777. [PMID: 29771637 PMCID: PMC6080713 DOI: 10.1091/mbc.e17-11-0648] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Chromatin organization is highly dynamic and regulates transcription. Upon transcriptional activation, chromatin is remodeled and referred to as “open,” but quantitative and dynamic data of this decompaction process are lacking. Here, we have developed a quantitative high resolution–microscopy assay in living yeast cells to visualize and quantify chromatin dynamics using the GAL7-10-1 locus as a model system. Upon transcriptional activation of these three clustered genes, we detect an increase of the mean distance across this locus by >100 nm. This decompaction is linked to active transcription but is not sensitive to the histone deacetylase inhibitor trichostatin A or to deletion of the histone acetyl transferase Gcn5. In contrast, the deletion of SNF2 (encoding the ATPase of the SWI/SNF chromatin remodeling complex) or the deactivation of the histone chaperone complex FACT lead to a strongly reduced decompaction without significant effects on transcriptional induction in FACT mutants. Our findings are consistent with nucleosome remodeling and eviction activities being major contributors to chromatin reorganization during transcription but also suggest that transcription can occur in the absence of detectable decompaction.
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Affiliation(s)
- Elisa Dultz
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Roberta Mancini
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Guido Polles
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089
| | - Pascal Vallotton
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Frank Alber
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089
| | - Karsten Weis
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
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39
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Abstract
The repair of chromosomal double-strand breaks (DSBs) by homologous recombination is essential to maintain genome integrity. The key step in DSB repair is the RecA/Rad51-mediated process to match sequences at the broken end to homologous donor sequences that can be used as a template to repair the lesion. Here, in reviewing research about DSB repair, I consider the many factors that appear to play important roles in the successful search for homology by several homologous recombination mechanisms. See also the video abstract here: https://youtu.be/vm7-X5uIzS8.
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Affiliation(s)
- James E Haber
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454-9110, USA
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40
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Deep learning massively accelerates super-resolution localization microscopy. Nat Biotechnol 2018; 36:460-468. [PMID: 29658943 DOI: 10.1038/nbt.4106] [Citation(s) in RCA: 283] [Impact Index Per Article: 47.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 02/16/2018] [Indexed: 02/07/2023]
Abstract
The speed of super-resolution microscopy methods based on single-molecule localization, for example, PALM and STORM, is limited by the need to record many thousands of frames with a small number of observed molecules in each. Here, we present ANNA-PALM, a computational strategy that uses artificial neural networks to reconstruct super-resolution views from sparse, rapidly acquired localization images and/or widefield images. Simulations and experimental imaging of microtubules, nuclear pores, and mitochondria show that high-quality, super-resolution images can be reconstructed from up to two orders of magnitude fewer frames than usually needed, without compromising spatial resolution. Super-resolution reconstructions are even possible from widefield images alone, though adding localization data improves image quality. We demonstrate super-resolution imaging of >1,000 fields of view containing >1,000 cells in ∼3 h, yielding an image spanning spatial scales from ∼20 nm to ∼2 mm. The drastic reduction in acquisition time and sample irradiation afforded by ANNA-PALM enables faster and gentler high-throughput and live-cell super-resolution imaging.
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Herbert S, Brion A, Arbona JM, Lelek M, Veillet A, Lelandais B, Parmar J, Fernández FG, Almayrac E, Khalil Y, Birgy E, Fabre E, Zimmer C. Chromatin stiffening underlies enhanced locus mobility after DNA damage in budding yeast. EMBO J 2017; 36:2595-2608. [PMID: 28694242 PMCID: PMC5579376 DOI: 10.15252/embj.201695842] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 05/15/2017] [Accepted: 05/18/2017] [Indexed: 12/31/2022] Open
Abstract
DNA double-strand breaks (DSBs) induce a cellular response that involves histone modifications and chromatin remodeling at the damaged site and increases chromosome dynamics both locally at the damaged site and globally in the nucleus. In parallel, it has become clear that the spatial organization and dynamics of chromosomes can be largely explained by the statistical properties of tethered, but randomly moving, polymer chains, characterized mainly by their rigidity and compaction. How these properties of chromatin are affected during DNA damage remains, however, unclear. Here, we use live cell microscopy to track chromatin loci and measure distances between loci on yeast chromosome IV in thousands of cells, in the presence or absence of genotoxic stress. We confirm that DSBs result in enhanced chromatin subdiffusion and show that intrachromosomal distances increase with DNA damage all along the chromosome. Our data can be explained by an increase in chromatin rigidity, but not by chromatin decondensation or centromeric untethering only. We provide evidence that chromatin stiffening is mediated in part by histone H2A phosphorylation. Our results support a genome-wide stiffening of the chromatin fiber as a consequence of DNA damage and as a novel mechanism underlying increased chromatin mobility.
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Affiliation(s)
- Sébastien Herbert
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Alice Brion
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Jean-Michel Arbona
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Mickaël Lelek
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Adeline Veillet
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Benoît Lelandais
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Jyotsana Parmar
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Fabiola García Fernández
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Etienne Almayrac
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Yasmine Khalil
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Eleonore Birgy
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Emmanuelle Fabre
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Christophe Zimmer
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
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