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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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Pellegrini L. The CMG DNA helicase and the core replisome. Curr Opin Struct Biol 2023; 81:102612. [PMID: 37244171 DOI: 10.1016/j.sbi.2023.102612] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 04/19/2023] [Accepted: 04/25/2023] [Indexed: 05/29/2023]
Abstract
Eukaryotic DNA replication is performed by the replisome, a large and dynamic multi-protein machine endowed with the required enzymatic components for the synthesis of new DNA. Recent cryo-electron microscopy (cryoEM) analyses have revealed the conserved architecture of the core eukaryotic replisome, comprising the CMG (Cdc45-MCM-GINS) DNA helicase, the leading-strand DNA polymerase epsilon, the Timeless-Tipin heterodimer, the hub protein AND-1 and the checkpoint protein Claspin. These results bid well for arriving soon at an integrated understanding of the structural basis of semi-discontinuous DNA replication. They further set the scene for the characterisation of the mechanisms that interface DNA synthesis with concurrent processes such as DNA repair, propagation of chromatin structure and establishment of sister chromatid cohesion.
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Oberdoerffer P, Miller KM. Histone H2A variants: Diversifying chromatin to ensure genome integrity. Semin Cell Dev Biol 2023; 135:59-72. [PMID: 35331626 PMCID: PMC9489817 DOI: 10.1016/j.semcdb.2022.03.011] [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: 11/24/2021] [Revised: 03/07/2022] [Accepted: 03/08/2022] [Indexed: 12/12/2022]
Abstract
Histone variants represent chromatin components that diversify the structure and function of the genome. The variants of H2A, primarily H2A.X, H2A.Z and macroH2A, are well-established participants in DNA damage response (DDR) pathways, which function to protect the integrity of the genome. Through their deposition, post-translational modifications and unique protein interaction networks, these variants guard DNA from endogenous threats including replication stress and genome fragility as well as from DNA lesions inflicted by exogenous sources. A growing body of work is now providing a clearer picture on the involvement and mechanistic basis of H2A variant contribution to genome integrity. Beyond their well-documented role in gene regulation, we review here how histone H2A variants promote genome stability and how alterations in these pathways contribute to human diseases including cancer.
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Affiliation(s)
- Philipp Oberdoerffer
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21287 USA.
| | - Kyle M Miller
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA; Livestrong Cancer Institutes, Dell Medical School, The University of Texas at Austin, Austin, TX 78712, USA.
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Zagelbaum J, Schooley A, Zhao J, Schrank BR, Callen E, Zha S, Gottesman ME, Nussenzweig A, Rabadan R, Dekker J, Gautier J. Multiscale reorganization of the genome following DNA damage facilitates chromosome translocations via nuclear actin polymerization. Nat Struct Mol Biol 2023; 30:99-106. [PMID: 36564591 PMCID: PMC10104780 DOI: 10.1038/s41594-022-00893-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 11/04/2022] [Indexed: 12/24/2022]
Abstract
Nuclear actin-based movements have been shown to orchestrate clustering of DNA double-strand breaks (DSBs) into homology-directed repair domains. Here we describe multiscale three-dimensional genome reorganization following DNA damage and analyze the contribution of the nuclear WASP-ARP2/3-actin pathway toward chromatin topology alterations and pathologic repair. Hi-C analysis reveals genome-wide, DNA damage-induced chromatin compartment flips facilitated by ARP2/3 that enrich for open, A compartments. Damage promotes interactions between DSBs, which in turn facilitate aberrant, actin-dependent intra- and inter-chromosomal rearrangements. Our work establishes that clustering of resected DSBs into repair domains by nuclear actin assembly is coordinated with multiscale alterations in genome architecture that enable homology-directed repair while also increasing nonhomologous end-joining-dependent translocation frequency.
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Affiliation(s)
- Jennifer Zagelbaum
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Integrated Program in Cellular, Molecular, and Biomedical Studies, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Allana Schooley
- Department of Systems Biology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Junfei Zhao
- Department of Systems Biology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Benjamin R Schrank
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Elsa Callen
- Laboratory of Genome Integrity, National Institutes of Health, Bethesda, MD, USA
| | - Shan Zha
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Pathology and Cell Biology and Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Herbert Irving Comprehensive Cancer Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Max E Gottesman
- Department of Biochemistry and Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - André Nussenzweig
- Laboratory of Genome Integrity, National Institutes of Health, Bethesda, MD, USA
| | - Raul Rabadan
- Department of Systems Biology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Herbert Irving Comprehensive Cancer Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Job Dekker
- Department of Systems Biology, University of Massachusetts Medical School, Worcester, MA, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Jean Gautier
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA.
- Herbert Irving Comprehensive Cancer Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA.
- Department of Genetics and Development, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA.
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