1
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Horsfield JA. Full circle: a brief history of cohesin and the regulation of gene expression. FEBS J 2023; 290:1670-1687. [PMID: 35048511 DOI: 10.1111/febs.16362] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/21/2021] [Accepted: 01/18/2022] [Indexed: 12/17/2022]
Abstract
The cohesin complex has a range of crucial functions in the cell. Cohesin is essential for mediating chromatid cohesion during mitosis, for repair of double-strand DNA breaks, and for control of gene transcription. This last function has been the subject of intense research ever since the discovery of cohesin's role in the long-range regulation of the cut gene in Drosophila. Subsequent research showed that the expression of some genes is exquisitely sensitive to cohesin depletion, while others remain relatively unperturbed. Sensitivity to cohesin depletion is also remarkably cell type- and/or condition-specific. The relatively recent discovery that cohesin is integral to forming chromatin loops via loop extrusion should explain much of cohesin's gene regulatory properties, but surprisingly, loop extrusion has failed to identify a 'one size fits all' mechanism for how cohesin controls gene expression. This review will illustrate how early examples of cohesin-dependent gene expression integrate with later work on cohesin's role in genome organization to explain mechanisms by which cohesin regulates gene expression.
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Affiliation(s)
- Julia A Horsfield
- Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
- Genetics Otago Research Centre, University of Otago, Dunedin, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, New Zealand
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2
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Emerson DJ, Zhao PA, Cook AL, Barnett RJ, Klein KN, Saulebekova D, Ge C, Zhou L, Simandi Z, Minsk MK, Titus KR, Wang W, Gong W, Zhang D, Yang L, Venev SV, Gibcus JH, Yang H, Sasaki T, Kanemaki MT, Yue F, Dekker J, Chen CL, Gilbert DM, Phillips-Cremins JE. Cohesin-mediated loop anchors confine the locations of human replication origins. Nature 2022; 606:812-819. [PMID: 35676475 PMCID: PMC9217744 DOI: 10.1038/s41586-022-04803-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 04/26/2022] [Indexed: 12/18/2022]
Abstract
DNA replication occurs through an intricately regulated series of molecular events and is fundamental for genome stability1,2. At present, it is unknown how the locations of replication origins are determined in the human genome. Here we dissect the role of topologically associating domains (TADs)3-6, subTADs7 and loops8 in the positioning of replication initiation zones (IZs). We stratify TADs and subTADs by the presence of corner-dots indicative of loops and the orientation of CTCF motifs. We find that high-efficiency, early replicating IZs localize to boundaries between adjacent corner-dot TADs anchored by high-density arrays of divergently and convergently oriented CTCF motifs. By contrast, low-efficiency IZs localize to weaker dotless boundaries. Following ablation of cohesin-mediated loop extrusion during G1, high-efficiency IZs become diffuse and delocalized at boundaries with complex CTCF motif orientations. Moreover, G1 knockdown of the cohesin unloading factor WAPL results in gained long-range loops and narrowed localization of IZs at the same boundaries. Finally, targeted deletion or insertion of specific boundaries causes local replication timing shifts consistent with IZ loss or gain, respectively. Our data support a model in which cohesin-mediated loop extrusion and stalling at a subset of genetically encoded TAD and subTAD boundaries is an essential determinant of the locations of replication origins in human S phase.
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Affiliation(s)
- Daniel J Emerson
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Peiyao A Zhao
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Ashley L Cook
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - R Jordan Barnett
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Kyle N Klein
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Dalila Saulebekova
- Institut Curie, PSL Research University, CNRS UMR3244, Dynamics of Genetic Information, Sorbonne Université, Paris, France
| | - Chunmin Ge
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Linda Zhou
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Zoltan Simandi
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Miriam K Minsk
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Katelyn R Titus
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Weitao Wang
- Institut Curie, PSL Research University, CNRS UMR3244, Dynamics of Genetic Information, Sorbonne Université, Paris, France
| | - Wanfeng Gong
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Di Zhang
- Children's Hospital of Pennsylvania, Philadelphia, PA, USA
| | - Liyan Yang
- University of Massachusetts Chan Medical School, Worcester, MA, USA
| | - Sergey V Venev
- University of Massachusetts Chan Medical School, Worcester, MA, USA
| | - Johan H Gibcus
- University of Massachusetts Chan Medical School, Worcester, MA, USA
| | - Hongbo Yang
- Department of Biochemistry and Molecular Genetics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Takayo Sasaki
- San Diego Biomedical Research Institute, San Diego, CA, USA
| | - Masato T Kanemaki
- Department of Chromosome Science, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Mishima, Japan
- Department of Genetics, The Graduate University for Advanced Studies (Sokendai), Mishima, Japan
| | - Feng Yue
- Department of Biochemistry and Molecular Genetics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Job Dekker
- University of Massachusetts Chan Medical School, Worcester, MA, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Chun-Long Chen
- Institut Curie, PSL Research University, CNRS UMR3244, Dynamics of Genetic Information, Sorbonne Université, Paris, France
| | - David M Gilbert
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
- San Diego Biomedical Research Institute, San Diego, CA, USA
| | - Jennifer E Phillips-Cremins
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA.
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
- New York Stem Cell Foundation Robertson Investigator, New York, NY, USA.
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3
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Antony J, Chin CV, Horsfield JA. Cohesin Mutations in Cancer: Emerging Therapeutic Targets. Int J Mol Sci 2021; 22:6788. [PMID: 34202641 PMCID: PMC8269296 DOI: 10.3390/ijms22136788] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 06/08/2021] [Accepted: 06/18/2021] [Indexed: 12/12/2022] Open
Abstract
The cohesin complex is crucial for mediating sister chromatid cohesion and for hierarchal three-dimensional organization of the genome. Mutations in cohesin genes are present in a range of cancers. Extensive research over the last few years has shown that cohesin mutations are key events that contribute to neoplastic transformation. Cohesin is involved in a range of cellular processes; therefore, the impact of cohesin mutations in cancer is complex and can be cell context dependent. Candidate targets with therapeutic potential in cohesin mutant cells are emerging from functional studies. Here, we review emerging targets and pharmacological agents that have therapeutic potential in cohesin mutant cells.
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Affiliation(s)
- Jisha Antony
- Department of Pathology, Otago Medical School, University of Otago, Dunedin 9016, New Zealand;
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland 1010, New Zealand
| | - Chue Vin Chin
- Department of Pathology, Otago Medical School, University of Otago, Dunedin 9016, New Zealand;
| | - Julia A. Horsfield
- Department of Pathology, Otago Medical School, University of Otago, Dunedin 9016, New Zealand;
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland 1010, New Zealand
- Genetics Otago Research Centre, University of Otago, Dunedin 9016, New Zealand
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4
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Cheng H, Zhang N, Pati D. Cohesin subunit RAD21: From biology to disease. Gene 2020; 758:144966. [PMID: 32687945 PMCID: PMC7949736 DOI: 10.1016/j.gene.2020.144966] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 07/13/2020] [Accepted: 07/14/2020] [Indexed: 02/06/2023]
Abstract
RAD21 (also known as KIAA0078, NXP1, HR21, Mcd1, Scc1, and hereafter called RAD21), an essential gene, encodes a DNA double-strand break (DSB) repair protein that is evolutionarily conserved in all eukaryotes from budding yeast to humans. RAD21 protein is a structural component of the highly conserved cohesin complex consisting of RAD21, SMC1a, SMC3, and SCC3 [STAG1 (SA1) and STAG2 (SA2) in metazoans] proteins, involved in sister chromatid cohesion. This function is essential for proper chromosome segregation, post-replicative DNA repair, and prevention of inappropriate recombination between repetitive regions. In interphase, cohesin also functions in the control of gene expression by binding to numerous sites within the genome. In addition to playing roles in the normal cell cycle and DNA DSB repair, RAD21 is also linked to the apoptotic pathways. Germline heterozygous or homozygous missense mutations in RAD21 have been associated with human genetic disorders, including developmental diseases such as Cornelia de Lange syndrome (CdLS) and chronic intestinal pseudo-obstruction (CIPO) called Mungan syndrome, respectively, and collectively termed as cohesinopathies. Somatic mutations and amplification of the RAD21 have also been widely reported in both human solid and hematopoietic tumors. Considering the role of RAD21 in a broad range of cellular processes that are hot spots in neoplasm, it is not surprising that the deregulation of RAD21 has been increasingly evident in human cancers. Herein, we review the biology of RAD21 and the cellular processes that this important protein regulates and discuss the significance of RAD21 deregulation in cancer and cohesinopathies.
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Affiliation(s)
- Haizi Cheng
- Texas Children's Cancer Center, Baylor College of Medicine, Houston, TX, United States; Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Nenggang Zhang
- Texas Children's Cancer Center, Baylor College of Medicine, Houston, TX, United States; Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Debananda Pati
- Texas Children's Cancer Center, Baylor College of Medicine, Houston, TX, United States; Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States; Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, United States.
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5
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Cucco F, Palumbo E, Camerini S, D’Alessio B, Quarantotti V, Casella ML, Rizzo IM, Cukrov D, Delia D, Russo A, Crescenzi M, Musio A. Separase prevents genomic instability by controlling replication fork speed. Nucleic Acids Res 2018; 46:267-278. [PMID: 29165708 PMCID: PMC5758895 DOI: 10.1093/nar/gkx1172] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Revised: 10/26/2017] [Accepted: 11/10/2017] [Indexed: 01/21/2023] Open
Abstract
Proper chromosome segregation is crucial for preserving genomic integrity, and errors in this process cause chromosome mis-segregation, which may contribute to cancer development. Sister chromatid separation is triggered by Separase, an evolutionary conserved protease that cleaves the cohesin complex, allowing the dissolution of sister chromatid cohesion. Here we provide evidence that Separase participates in genomic stability maintenance by controlling replication fork speed. We found that Separase interacted with the replication licensing factors MCM2-7, and genome-wide data showed that Separase co-localized with MCM complex and cohesin. Unexpectedly, the depletion of Separase increased the fork velocity about 1.5-fold and caused a strong acetylation of cohesin's SMC3 subunit and altered checkpoint response. Notably, Separase silencing triggered genomic instability in both HeLa and human primary fibroblast cells. Our results show a novel mechanism for fork progression mediated by Separase and thus the basis for genomic instability associated with tumorigenesis.
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Affiliation(s)
- Francesco Cucco
- Institute for Biomedical and Genetic Research, National Research Council, Pisa, Italy
| | - Elisa Palumbo
- Department of Biology, University of Padua, Padua, Italy
| | - Serena Camerini
- Department of Cell Biology and Neurosciences, National Institute of Health, Rome, Italy
| | - Barbara D’Alessio
- Institute for Biomedical and Genetic Research, National Research Council, Pisa, Italy
| | - Valentina Quarantotti
- Institute for Biomedical and Genetic Research, National Research Council, Pisa, Italy
| | - Maria Luisa Casella
- Department of Cell Biology and Neurosciences, National Institute of Health, Rome, Italy
| | - Ilaria Maria Rizzo
- Institute for Biomedical and Genetic Research, National Research Council, Pisa, Italy
| | - Dubravka Cukrov
- Institute for Biomedical and Genetic Research, National Research Council, Pisa, Italy
| | - Domenico Delia
- Fondazione IRCCS Istituto Nazionale Tumori, Department of Experimental Oncology, Milan, Italy
| | - Antonella Russo
- Department of Biology, University of Padua, Padua, Italy
- Department of Molecular Medicine, University of Padua, Padua, Italy
| | - Marco Crescenzi
- Department of Cell Biology and Neurosciences, National Institute of Health, Rome, Italy
| | - Antonio Musio
- Institute for Biomedical and Genetic Research, National Research Council, Pisa, Italy
- Tumour Institute of Tuscany, Florence, Italy
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6
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Forsburg SL, Shen KF. Centromere Stability: The Replication Connection. Genes (Basel) 2017; 8:genes8010037. [PMID: 28106789 PMCID: PMC5295031 DOI: 10.3390/genes8010037] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 01/10/2017] [Accepted: 01/12/2017] [Indexed: 11/16/2022] Open
Abstract
The fission yeast centromere, which is similar to metazoan centromeres, contains highly repetitive pericentromere sequences that are assembled into heterochromatin. This is required for the recruitment of cohesin and proper chromosome segregation. Surprisingly, the pericentromere replicates early in the S phase. Loss of heterochromatin causes this domain to become very sensitive to replication fork defects, leading to gross chromosome rearrangements. This review examines the interplay between components of DNA replication, heterochromatin assembly, and cohesin dynamics that ensures maintenance of genome stability and proper chromosome segregation.
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Affiliation(s)
- Susan L Forsburg
- Program in Molecular & Computational Biology, University of Southern California, Los Angeles, CA 90089-2910, USA.
| | - Kuo-Fang Shen
- Program in Molecular & Computational Biology, University of Southern California, Los Angeles, CA 90089-2910, USA.
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7
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Kusunoki S, Ishimi Y. Interaction of human minichromosome maintenance protein-binding protein with minichromosome maintenance 2-7. FEBS J 2014; 281:1057-67. [PMID: 24299456 DOI: 10.1111/febs.12668] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Accepted: 11/29/2013] [Indexed: 11/29/2022]
Abstract
It has been reported that minichromosome maintenance protein-binding protein (MCM-BP) functions in the formation of the pre-replication complex, unloading of minichromosome maintenance (MCM)2-7 from chromatin in late S phase, and formation of the cohesion complex by interacting with MCM3-7 proteins, suggesting that MCM-BP functions in several different reactions during the cell cycle. Here, we examined the interaction of human MCM-BP with MCM2-7 and structural maintenance of chromosome 3 in synchronized HeLa cells by immunoprecipitation. The results show that MCM-BP mainly interacts with MCM7 in the Triton-soluble fraction from S phase and G(2) phase cells, and it also interacts with structural maintenance of chromosome 3 in the fraction from G(2) phase cells. In vitro studies show that MCM-BP disassembles MCM2-7 bound to DNA with a fork-like structure by interacting with MCM3, MCM5, and MCM7. These results suggest that MCM-BP functions in disassembling MCM2-7 on chromatin during S phase and G2 phase by interacting with MCM3, MCM5, and MCM7.
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8
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Berkowitz KM, Sowash AR, Koenig LR, Urcuyo D, Khan F, Yang F, Wang PJ, Jongens TA, Kaestner KH. Disruption of CHTF18 causes defective meiotic recombination in male mice. PLoS Genet 2012; 8:e1002996. [PMID: 23133398 PMCID: PMC3486840 DOI: 10.1371/journal.pgen.1002996] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Accepted: 08/13/2012] [Indexed: 12/23/2022] Open
Abstract
CHTF18 (chromosome transmission fidelity factor 18) is an evolutionarily conserved subunit of the Replication Factor C-like complex, CTF18-RLC. CHTF18 is necessary for the faithful passage of chromosomes from one daughter cell to the next during mitosis in yeast, and it is crucial for germline development in the fruitfly. Previously, we showed that mouse Chtf18 is expressed throughout the germline, suggesting a role for CHTF18 in mammalian gametogenesis. To determine the role of CHTF18 in mammalian germ cell development, we derived mice carrying null and conditional mutations in the Chtf18 gene. Chtf18-null males exhibit 5-fold decreased sperm concentrations compared to wild-type controls, resulting in subfertility. Loss of Chtf18 results in impaired spermatogenesis; spermatogenic cells display abnormal morphology, and the stereotypical arrangement of cells within seminiferous tubules is perturbed. Meiotic recombination is defective and homologous chromosomes separate prematurely during prophase I. Repair of DNA double-strand breaks is delayed and incomplete; both RAD51 and γH2AX persist in prophase I. In addition, MLH1 foci are decreased in pachynema. These findings demonstrate essential roles for CHTF18 in mammalian spermatogenesis and meiosis, and suggest that CHTF18 may function during the double-strand break repair pathway to promote the formation of crossovers. Meiosis is the specialized process of cell division during germ cell development that results in formation of eggs and sperm. Genetic exchange between maternal and paternal chromosomes occurs during meiosis in a process called homologous recombination, in which DNA double- strand breaks are made and then repaired to allow DNA crossovers to form. These are essential processes that keep homologous chromosomes joined until anaphase I and ensure proper chromosome segregation. Errors in meiotic recombination lead to chromosome mis-segregation and ultimately aneuploidy, an abnormal chromosome number. Although it is well known that defects in these processes contribute greatly to infertility, birth defects, and pregnancy loss in humans, their molecular basis is not well understood. We demonstrate here a Chtf18 mutant mouse that exhibits subfertility and defects in meiotic recombination. Specifically, DNA double-strand breaks are incompletely repaired, DNA crossovers are significantly decreased, and homologous chromosomes separate during prophase I in Chtf18-null males. Our findings suggest roles for CHTF18 in DNA double-strand break repair and crossover formation, functions in mammals not previously known.
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Affiliation(s)
- Karen M Berkowitz
- Department of Obstetrics and Gynecology, Drexel University College of Medicine, Philadelphia, PA, USA.
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9
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Abstract
The cohesin complex holds the sister chromatids together from S-phase until the metaphase-to-anaphase transition, and ensures both their proper cohesion and timely separation. In addition to its canonical function in chromosomal segregation, cohesin has been suggested by several lines of investigation in recent years to play additional roles in apoptosis, DNA-damage response, transcriptional regulation and haematopoiesis. To better understand the basis of the disparate cellular functions of cohesin in these various processes, we have characterized a comprehensive protein interactome of cohesin-RAD21 by using three independent approaches: Y2H (yeast two-hybrid) screening, immunoprecipitation-coupled-MS of cytoplasmic and nuclear extracts from MOLT-4 T-lymphocytes in the presence and absence of etoposide-induced apoptosis, and affinity pull-down assays of chromatographically purified nuclear extracts from pro-apoptotic MOLT-4 cells. Our analyses revealed 112 novel protein interactors of cohesin-RAD21 that function in different cellular processes, including mitosis, regulation of apoptosis, chromosome dynamics, replication, transcription regulation, RNA processing, DNA-damage response, protein modification and degradation, and cytoskeleton and cell motility. Identification of cohesin interactors provides a framework for explaining the various non-canonical functions of the cohesin complex.
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Affiliation(s)
- Anil K Panigrahi
- Texas Children's Cancer Center, Department of Pediatric Hematology/Oncology, Baylor College of Medicine, Houston, 77030, USA
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10
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Abstract
Stability and function of eukaryotic genomes are closely linked to chromatin structure and organization. During cell division the entire genome must be accurately replicated and the chromatin landscape reproduced on new DNA. Chromatin and nuclear structure influence where and when DNA replication initiates, whereas the replication process itself disrupts chromatin and challenges established patterns of genome regulation. Specialized replication-coupled mechanisms assemble new DNA into chromatin, but epigenome maintenance is a continuous process taking place throughout the cell cycle. If DNA synthesis is perturbed, cells can suffer loss of both genome and epigenome integrity with severe consequences for the organism.
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11
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Abstract
In eukaryotes, the Mcm2-7 complex forms the core of the replicative helicase - the molecular motor that uses ATP binding and hydrolysis to fuel the unwinding of double-stranded DNA at the replication fork. Although it is a toroidal hexameric helicase superficially resembling better-studied homohexameric helicases from prokaryotes and viruses, Mcm2-7 is the only known helicase formed from six unique and essential subunits. Recent biochemical and structural analyses of both Mcm2-7 and a higher-order complex containing additional activator proteins (the CMG complex) shed light on the reason behind this unique subunit assembly: whereas only a limited number of specific ATPase active sites are needed for DNA unwinding, one particular ATPase active site has evolved to form a reversible discontinuity (gate) in the toroidal complex. The activation of Mcm2-7 helicase during S-phase requires physical association of the accessory proteins Cdc45 and GINS; structural data suggest that these accessory factors activate DNA unwinding through closure of the Mcm2-7 gate. Moreover, studies capitalizing on advances in the biochemical reconstitution of eukaryotic DNA replication demonstrate that Mcm2-7 loads onto origins during initiation as a double hexamer, yet does not act as a double-stranded DNA pump during elongation.
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Affiliation(s)
- Sriram Vijayraghavan
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, USA
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12
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Guillou E, Ibarra A, Coulon V, Casado-Vela J, Rico D, Casal I, Schwob E, Losada A, Méndez J. Cohesin organizes chromatin loops at DNA replication factories. Genes Dev 2010; 24:2812-22. [PMID: 21159821 PMCID: PMC3003199 DOI: 10.1101/gad.608210] [Citation(s) in RCA: 170] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 10/22/2010] [Indexed: 12/23/2022]
Abstract
Genomic DNA is packed in chromatin fibers organized in higher-order structures within the interphase nucleus. One level of organization involves the formation of chromatin loops that may provide a favorable environment to processes such as DNA replication, transcription, and repair. However, little is known about the mechanistic basis of this structuration. Here we demonstrate that cohesin participates in the spatial organization of DNA replication factories in human cells. Cohesin is enriched at replication origins and interacts with prereplication complex proteins. Down-regulation of cohesin slows down S-phase progression by limiting the number of active origins and increasing the length of chromatin loops that correspond with replicon units. These results give a new dimension to the role of cohesin in the architectural organization of interphase chromatin, by showing its participation in DNA replication.
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Affiliation(s)
- Emmanuelle Guillou
- DNA Replication Group, Spanish National Cancer Research Centre (CNIO), E-28029 Madrid, Spain
| | - Arkaitz Ibarra
- DNA Replication Group, Spanish National Cancer Research Centre (CNIO), E-28029 Madrid, Spain
| | - Vincent Coulon
- Institut de Génétique Moléculaire de Montpellier, CNRS-Université Montpellier 1 et 2, 34293 Montpellier, Cedex 5, France
| | - Juan Casado-Vela
- Protein Technology Unit, Biotechnology Programme, Spanish National Cancer Research Centre (CNIO), E-28029 Madrid, Spain
| | - Daniel Rico
- Structural Computational Biology Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), E-28029 Madrid, Spain
| | - Ignacio Casal
- Protein Technology Unit, Biotechnology Programme, Spanish National Cancer Research Centre (CNIO), E-28029 Madrid, Spain
| | - Etienne Schwob
- Institut de Génétique Moléculaire de Montpellier, CNRS-Université Montpellier 1 et 2, 34293 Montpellier, Cedex 5, France
| | - Ana Losada
- Chromosome Dynamics Group, Molecular Oncology Programme, Spanish National Cancer Research Centre (CNIO), E-28029 Madrid, Spain
| | - Juan Méndez
- DNA Replication Group, Spanish National Cancer Research Centre (CNIO), E-28029 Madrid, Spain
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13
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Uhlmann F. A matter of choice: the establishment of sister chromatid cohesion. EMBO Rep 2009; 10:1095-102. [PMID: 19745840 PMCID: PMC2744122 DOI: 10.1038/embor.2009.207] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Accepted: 08/19/2009] [Indexed: 11/09/2022] Open
Abstract
Sister chromatid cohesion is the basis for the recognition of chromosomal DNA replication products for their bipolar segregation in mitosis. Fundamental to sister chromatid cohesion is the ring-shaped cohesin complex, which is loaded onto chromosomes long before the initiation of DNA replication and is thought to hold replicated sister chromatids together by topological embrace. What happens to cohesin when the replication fork approaches, and how cohesin recognizes newly synthesized sister chromatids, is poorly understood. The characterization of a number of cohesion establishment factors has begun to provide hints as to the reactions involved. Cohesin is a member of the evolutionarily conserved family of Smc subunit-based protein complexes that contribute to many aspects of chromosome biology by mediating long-range DNA interactions. I propose that the establishment of cohesion equates to the selective stabilization of those cohesin-mediated DNA interactions that link sister chromatids in the wake of replication forks.
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Affiliation(s)
- Frank Uhlmann
- Chromosome Segregation Laboratory, Cancer Research UK London Research Institute, London, UK.
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14
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Abstract
Cohesin is a chromosome-associated multisubunit protein complex that is highly conserved in eukaryotes and has close homologs in bacteria. Cohesin mediates cohesion between replicated sister chromatids and is therefore essential for chromosome segregation in dividing cells. Cohesin is also required for efficient repair of damaged DNA and has important functions in regulating gene expression in both proliferating and post-mitotic cells. Here we discuss how cohesin associates with DNA, how these interactions are controlled during the cell cycle; how binding of cohesin to DNA may mediate sister chromatid cohesion, DNA repair, and gene regulation; and how defects in these processes can lead to human disease.
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Affiliation(s)
- Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), A-1030 Vienna, Austria.
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15
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Xu H, Boone C, Brown GW. Genetic dissection of parallel sister-chromatid cohesion pathways. Genetics 2007; 176:1417-29. [PMID: 17483413 PMCID: PMC1931553 DOI: 10.1534/genetics.107.072876] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2007] [Accepted: 04/25/2007] [Indexed: 11/18/2022] Open
Abstract
Sister-chromatid cohesion, the process of pairing replicated chromosomes during mitosis and meiosis, is mediated through the essential cohesin complex and a number of nonessential cohesion genes, but the specific roles of these nonessential genes in sister-chromatid cohesion remain to be clarified. We analyzed sister-chromatid cohesion in double mutants of mrc1Delta, tof1Delta, and csm3Delta and identified additive cohesion defects that indicated the existence of at least two pathways that contribute to sister-chromatid cohesion. To understand the relationship of other nonessential cohesion genes with respect to these two pathways, pairwise combinations of deletion and temperature-sensitive alleles were tested for cohesion defects. These data defined two cohesion pathways, one containing CSM3, TOF1, CTF4, and CHL1, and the second containing MRC1, CTF18, CTF8, and DCC1. Furthermore, we found that the nonessential genes are not important for the maintenance of cohesion at G(2)/M. Thus, our data suggest that nonessential cohesion genes make critical redundant contributions to the establishment of sister-chromatid cohesion and define two cohesion pathways, thereby establishing a framework for understanding the role of nonessential genes in sister-chromatid cohesion.
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Affiliation(s)
- Hong Xu
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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16
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Lake CM, Teeter K, Page SL, Nielsen R, Hawley RS. A genetic analysis of the Drosophila mcm5 gene defines a domain specifically required for meiotic recombination. Genetics 2007; 176:2151-63. [PMID: 17565942 PMCID: PMC1950621 DOI: 10.1534/genetics.107.073551] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Members of the minichromosome maintenance (MCM) family have pivotal roles in many biological processes. Although originally studied for their role in DNA replication, it is becoming increasingly apparent that certain members of this family are multifunctional and also play roles in transcription, cohesion, condensation, and recombination. Here we provide a genetic dissection of the mcm5 gene in Drosophila that demonstrates an unexpected function for this protein. First, we show that homozygotes for a null allele of mcm5 die as third instar larvae, apparently as a result of blocking those replication events that lead to mitotic divisions without impairing endo-reduplication. However, we have also recovered a viable and fertile allele of mcm5 (denoted mcm5(A7)) that specifically impairs the meiotic recombination process. We demonstrate that the decrease in recombination observed in females homozygous for mcm5(A7) is not due to a failure to create or repair meiotically induced double strand breaks (DSBs), but rather to a failure to resolve those DSBs into meiotic crossovers. Consistent with their ability to repair meiotically induced DSBs, flies homozygous for mcm5(A7) are fully proficient in somatic DNA repair. These results strengthen the observation that members of the prereplicative complex have multiple functions and provide evidence that mcm5 plays a critical role in the meiotic recombination pathway.
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Affiliation(s)
- Cathleen M Lake
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA.
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