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Xia D, Zhu X, Wang Y, Gong P, Su HS, Xu X. Implications of ubiquitination and the maintenance of replication fork stability in cancer therapy. Biosci Rep 2023; 43:BSR20222591. [PMID: 37728310 PMCID: PMC10550789 DOI: 10.1042/bsr20222591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Revised: 08/21/2023] [Accepted: 09/19/2023] [Indexed: 09/21/2023] Open
Abstract
DNA replication forks are subject to intricate surveillance and strict regulation by sophisticated cellular machinery. Such close regulation is necessary to ensure the accurate duplication of genetic information and to tackle the diverse endogenous and exogenous stresses that impede this process. Stalled replication forks are vulnerable to collapse, which is a major cause of genomic instability and carcinogenesis. Replication stress responses, which are organized via a series of coordinated molecular events, stabilize stalled replication forks and carry out fork reversal and restoration. DNA damage tolerance and repair pathways such as homologous recombination and Fanconi anemia also contribute to replication fork stabilization. The signaling network that mediates the transduction and interplay of these pathways is regulated by a series of post-translational modifications, including ubiquitination, which affects the activity, stability, and interactome of substrates. In particular, the ubiquitination of replication protein A and proliferating cell nuclear antigen at stalled replication forks promotes the recruitment of downstream regulators. In this review, we describe the ubiquitination-mediated signaling cascades that regulate replication fork progression and stabilization. In addition, we discuss the targeting of replication fork stability and ubiquitination system components as a potential therapeutic approach for the treatment of cancer.
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Affiliation(s)
- Donghui Xia
- Shenzhen University General Hospital-Dehua Hospital Joint Research Center on Precision Medicine (sgh-dhhCPM), Dehua Hospital, Dehua, Quanzhou 362500, China
- Guangdong Key Laboratory for Genome Stability and Disease Prevention, Carson International Cancer Center, Marshall Laboratory of Biomedical Engineering, Shenzhen University Medical School, Shenzhen University, Shenzhen, Guangdong 518060, China
- State Key Laboratory of Agro-biotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Xuefei Zhu
- Department of General Surgery, Institute of Precision Diagnosis and Treatment of Gastrointestinal Tumors and Carson International Cancer Center, Shenzhen University General Hospital, Shenzhen University Medical School, Shenzhen University, Shenzhen, Guangdong 518060, China
| | - Ying Wang
- State Key Laboratory of Agro-biotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Peng Gong
- Department of General Surgery, Institute of Precision Diagnosis and Treatment of Gastrointestinal Tumors and Carson International Cancer Center, Shenzhen University General Hospital, Shenzhen University Medical School, Shenzhen University, Shenzhen, Guangdong 518060, China
| | - Hong-Shu Su
- Shenzhen University General Hospital-Dehua Hospital Joint Research Center on Precision Medicine (sgh-dhhCPM), Dehua Hospital, Dehua, Quanzhou 362500, China
| | - Xingzhi Xu
- Shenzhen University General Hospital-Dehua Hospital Joint Research Center on Precision Medicine (sgh-dhhCPM), Dehua Hospital, Dehua, Quanzhou 362500, China
- Guangdong Key Laboratory for Genome Stability and Disease Prevention, Carson International Cancer Center, Marshall Laboratory of Biomedical Engineering, Shenzhen University Medical School, Shenzhen University, Shenzhen, Guangdong 518060, China
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Zhang J, Zhao X, Liu L, Li HD, Gu L, Castrillon DH, Li GM. The mismatch recognition protein MutSα promotes nascent strand degradation at stalled replication forks. Proc Natl Acad Sci U S A 2022; 119:e2201738119. [PMID: 36161943 DOI: 10.1073/pnas.2201738119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
DNA mismatch repair (MMR) is well known for its role in maintaining replication fidelity by correcting mispairs generated during replication. Here, we identify an unusual MMR function to promote genome instability in the replication stress response. Under replication stress, binding of the mismatch recognition protein MutSα to replication forks blocks the loading of fork protection factors FANCD2 and BRCA1 to replication forks and promotes the recruitment of exonuclease MRE11 onto DNA to nascent strand degradation. This MutSα-dependent MRE11-catalyzed DNA degradation causes DNA breaks and chromosome abnormalities, contributing to an ultramutator phenotype. Mismatch repair (MMR) is a replication-coupled DNA repair mechanism and plays multiple roles at the replication fork. The well-established MMR functions include correcting misincorporated nucleotides that have escaped the proofreading activity of DNA polymerases, recognizing nonmismatched DNA adducts, and triggering a DNA damage response. In an attempt to determine whether MMR regulates replication progression in cells expressing an ultramutable DNA polymerase ɛ (Polɛ), carrying a proline-to-arginine substitution at amino acid 286 (Polɛ-P286R), we identified an unusual MMR function in response to hydroxyurea (HU)-induced replication stress. Polɛ-P286R cells treated with hydroxyurea exhibit increased MRE11-catalyzed nascent strand degradation. This degradation by MRE11 depends on the mismatch recognition protein MutSα and its binding to stalled replication forks. Increased MutSα binding at replication forks is also associated with decreased loading of replication fork protection factors FANCD2 and BRCA1, suggesting blockage of these fork protection factors from loading to replication forks by MutSα. We find that the MutSα-dependent MRE11-catalyzed fork degradation induces DNA breaks and various chromosome abnormalities. Therefore, unlike the well-known MMR functions of ensuring replication fidelity, the newly identified MMR activity of promoting genome instability may also play a role in cancer avoidance by eliminating rogue cells.
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Liu Y, Wang L, Xu X, Yuan Y, Zhang B, Li Z, Xie Y, Yan R, Zheng Z, Ji J, Murray JM, Carr AM, Kong D. The intra-S phase checkpoint directly regulates replication elongation to preserve the integrity of stalled replisomes. Proc Natl Acad Sci U S A 2021; 118:e2019183118. [PMID: 34108240 PMCID: PMC8214678 DOI: 10.1073/pnas.2019183118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
DNA replication is dramatically slowed down under replication stress. The regulation of replication speed is a conserved response in eukaryotes and, in fission yeast, requires the checkpoint kinases Rad3ATR and Cds1Chk2 However, the underlying mechanism of this checkpoint regulation remains unresolved. Here, we report that the Rad3ATR-Cds1Chk2 checkpoint directly targets the Cdc45-MCM-GINS (CMG) replicative helicase under replication stress. When replication forks stall, the Cds1Chk2 kinase directly phosphorylates Cdc45 on the S275, S322, and S397 residues, which significantly reduces CMG helicase activity. Furthermore, in cds1Chk2 -mutated cells, the CMG helicase and DNA polymerases are physically separated, potentially disrupting replisomes and collapsing replication forks. This study demonstrates that the intra-S phase checkpoint directly regulates replication elongation, reduces CMG helicase processivity, prevents CMG helicase delinking from DNA polymerases, and therefore helps preserve the integrity of stalled replisomes and replication forks.
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Affiliation(s)
- Yang Liu
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
- National Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Lu Wang
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
- National Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Xin Xu
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
- National Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Yue Yuan
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
- National Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Bo Zhang
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
- National Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Zeyang Li
- National Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Yuchen Xie
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
- National Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Rui Yan
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
- National Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Zeqi Zheng
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
- National Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Jianguo Ji
- National Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
| | - Johanne M Murray
- Genome Damage and Stability Center, School of Life Sciences, University of Sussex, Brighton BN1 9RQ, United Kingdom
| | - Antony M Carr
- Genome Damage and Stability Center, School of Life Sciences, University of Sussex, Brighton BN1 9RQ, United Kingdom
| | - Daochun Kong
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China;
- National Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
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Abstract
Eukaryotic genomes are highly complex and divided into linear chromosomes that require end protection from unwarranted fusions, recombination, and degradation in order to maintain genomic stability. This is accomplished through the conserved specialized nucleoprotein structure of telomeres. Due to the repetitive nature of telomeric DNA, and the unusual terminal structure, namely a protruding single stranded 3′ DNA end, completing telomeric DNA replication in a timely and efficient manner is a challenge. For example, the end replication problem causes a progressive shortening of telomeric DNA at each round of DNA replication, thus telomeres eventually lose their protective capacity. This phenomenon is counteracted by the recruitment and the activation at telomeres of the specialized reverse transcriptase telomerase. Despite the importance of telomerase in providing a mechanism for complete replication of telomeric ends, the majority of telomere replication is in fact carried out by the conventional DNA replication machinery. There is significant evidence demonstrating that progression of replication forks is hampered at chromosomal ends due to telomeric sequences prone to form secondary structures, tightly DNA-bound proteins, and the heterochromatic nature of telomeres. The telomeric loop (t-loop) formed by invasion of the 3′-end into telomeric duplex sequences may also impede the passage of replication fork. Replication fork stalling can lead to fork collapse and DNA breaks, a major cause of genomic instability triggered notably by unwanted repair events. Moreover, at chromosomal ends, unreplicated DNA distal to a stalled fork cannot be rescued by a fork coming from the opposite direction. This highlights the importance of the multiple mechanisms involved in overcoming fork progression obstacles at telomeres. Consequently, numerous factors participate in efficient telomeric DNA duplication by preventing replication fork stalling or promoting the restart of a stalled replication fork at telomeres. In this review, we will discuss difficulties associated with the passage of the replication fork through telomeres in both fission and budding yeasts as well as mammals, highlighting conserved mechanisms implicated in maintaining telomere integrity during replication, thus preserving a stable genome.
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Affiliation(s)
- Erin Bonnell
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Cancer Research Pavilion, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Emeline Pasquier
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Cancer Research Pavilion, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Raymund J Wellinger
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Cancer Research Pavilion, Université de Sherbrooke, Sherbrooke, QC, Canada
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Abstract
Chemoresistance remains to be a common and significant hurdle with all chemotherapies. Tumors gain resistance by acquiring additional mutations. Some of the chemoresistance mechanisms are known and can be tackled. However, the majority of chemoresistance mechanisms are unknown. Our recent findings shed light on one such unknown mechanism. We identified a novel role for 5-hydroxymethycytosine (5hmC), an epigenetic mark on the DNA, in maintaining the integrity of stalled replication forks and its impact on genomic stability and chemoresistance.
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Affiliation(s)
- Suhas S Kharat
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, Maryland USA
| | - Shyam K Sharan
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, Maryland USA
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Kim JJ, Lee SY, Choi JH, Woo HG, Xhemalce B, Miller KM. PCAF-Mediated Histone Acetylation Promotes Replication Fork Degradation by MRE11 and EXO1 in BRCA-Deficient Cells. Mol Cell 2020; 80:327-344.e8. [PMID: 32966758 DOI: 10.1016/j.molcel.2020.08.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 07/22/2020] [Accepted: 08/26/2020] [Indexed: 12/12/2022]
Abstract
Stabilization of stalled replication forks is a prominent mechanism of PARP (Poly(ADP-ribose) Polymerase) inhibitor (PARPi) resistance in BRCA-deficient tumors. Epigenetic mechanisms of replication fork stability are emerging but remain poorly understood. Here, we report the histone acetyltransferase PCAF (p300/CBP-associated) as a fork-associated protein that promotes fork degradation in BRCA-deficient cells by acetylating H4K8 at stalled replication forks, which recruits MRE11 and EXO1. A H4K8ac binding domain within MRE11/EXO1 is required for their recruitment to stalled forks. Low PCAF levels, which we identify in a subset of BRCA2-deficient tumors, stabilize stalled forks, resulting in PARPi resistance in BRCA-deficient cells. Furthermore, PCAF activity is tightly regulated by ATR (ataxia telangiectasia and Rad3-related), which phosphorylates PCAF on serine 264 (S264) to limit its association and activity at stalled forks. Our results reveal PCAF and histone acetylation as critical regulators of fork stability and PARPi responses in BRCA-deficient cells, which provides key insights into targeting BRCA-deficient tumors and identifying epigenetic modulators of chemotherapeutic responses.
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Parmar K, Kochupurakkal BS, Lazaro JB, Wang ZC, Palakurthi S, Kirschmeier PT, Yang C, Sambel LA, Farkkila A, Reznichenko E, Reavis HD, Dunn CE, Zou L, Do KT, Konstantinopoulos PA, Matulonis UA, Liu JF, D’Andrea AD, Shapiro GI. The CHK1 Inhibitor Prexasertib Exhibits Monotherapy Activity in High-Grade Serous Ovarian Cancer Models and Sensitizes to PARP Inhibition. Clin Cancer Res 2019; 25:6127-6140. [PMID: 31409614 PMCID: PMC6801076 DOI: 10.1158/1078-0432.ccr-19-0448] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 04/24/2019] [Accepted: 07/16/2019] [Indexed: 12/15/2022]
Abstract
PURPOSE PARP inhibitors are approved for the treatment of high-grade serous ovarian cancers (HGSOC). Therapeutic resistance, resulting from restoration of homologous recombination (HR) repair or replication fork stabilization, is a pressing clinical problem. We assessed the activity of prexasertib, a checkpoint kinase 1 (CHK1) inhibitor known to cause replication catastrophe, as monotherapy and in combination with the PARP inhibitor olaparib in preclinical models of HGSOC, including those with acquired PARP inhibitor resistance. EXPERIMENTAL DESIGN Prexasertib was tested as a single agent or in combination with olaparib in 14 clinically annotated and molecularly characterized luciferized HGSOC patient-derived xenograft (PDX) models and in a panel of ovarian cancer cell lines. The ability of prexasertib to impair HR repair and replication fork stability was also assessed. RESULTS Prexasertib monotherapy demonstrated antitumor activity across the 14 PDX models. Thirteen models were resistant to olaparib monotherapy, including 4 carrying BRCA1 mutation. The combination of olaparib with prexasertib was synergistic and produced significant tumor growth inhibition in an olaparib-resistant model and further augmented the degree and durability of response in the olaparib-sensitive model. HGSOC cell lines, including those with acquired PARP inhibitor resistance, were also sensitive to prexasertib, associated with induction of DNA damage and replication stress. Prexasertib also sensitized these cell lines to PARP inhibition and compromised both HR repair and replication fork stability. CONCLUSIONS Prexasertib exhibits monotherapy activity in PARP inhibitor-resistant HGSOC PDX and cell line models, reverses restored HR and replication fork stability, and synergizes with PARP inhibition.
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Affiliation(s)
- Kalindi Parmar
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Bose S. Kochupurakkal
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Jean-Bernard Lazaro
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Zhigang C. Wang
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Sangeetha Palakurthi
- Belfer Center for Applied Cancer Science, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Paul T. Kirschmeier
- Belfer Center for Applied Cancer Science, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Chunyu Yang
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Larissa A. Sambel
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Anniina Farkkila
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Elizaveta Reznichenko
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Hunter D Reavis
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Connor E. Dunn
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Lee Zou
- Department of Pathology, Massachusetts General Hospital Cancer Center and Harvard Medical School, Charlestown, Massachusetts
| | - Khanh T. Do
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
| | - Panagiotis A. Konstantinopoulos
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
| | - Ursula A. Matulonis
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
| | - Joyce F. Liu
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
| | - Alan D. D’Andrea
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Geoffrey I. Shapiro
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts,Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
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Feng G, Yuan Y, Li Z, Wang L, Zhang B, Luo J, Ji J, Kong D. Replication fork stalling elicits chromatin compaction for the stability of stalling replication forks. Proc Natl Acad Sci U S A 2019; 116:14563-72. [PMID: 31262821 DOI: 10.1073/pnas.1821475116] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
DNA replication forks in eukaryotic cells stall at a variety of replication barriers. Stalling forks require strict cellular regulations to prevent fork collapse. However, the mechanism underlying these cellular regulations is poorly understood. In this study, a cellular mechanism was uncovered that regulates chromatin structures to stabilize stalling forks. When replication forks stall, H2BK33, a newly identified acetylation site, is deacetylated and H3K9 trimethylated in the nucleosomes surrounding stalling forks, which results in chromatin compaction around forks. Acetylation-mimic H2BK33Q and its deacetylase clr6-1 mutations compromise this fork stalling-induced chromatin compaction, cause physical separation of replicative helicase and DNA polymerases, and significantly increase the frequency of stalling fork collapse. Furthermore, this fork stalling-induced H2BK33 deacetylation is independent of checkpoint. In summary, these results suggest that eukaryotic cells have developed a cellular mechanism that stabilizes stalling forks by targeting nucleosomes and inducing chromatin compaction around stalling forks. This mechanism is named the "Chromsfork" control: Chromatin Compaction Stabilizes Stalling Replication Forks.
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9
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Son MY, Hasty P. Homologous recombination defects and how they affect replication fork maintenance. AIMS Genet 2019; 5:192-211. [PMID: 31435521 PMCID: PMC6690234 DOI: 10.3934/genet.2018.4.192] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 03/18/2019] [Indexed: 01/07/2023]
Abstract
Homologous recombination (HR) repairs DNA double strand breaks (DSBs) and stabilizes replication forks (RFs). RAD51 is the recombinase for the HR pathway. To preserve genomic integrity, RAD51 forms a filament on the 3′ end of a DSB and on a single-stranded DNA (ssDNA) gap. But unregulated HR results in undesirable chromosomal rearrangements. This review describes the multiple mechanisms that regulate HR with a focus on those mechanisms that promote and contain RAD51 filaments to limit chromosomal rearrangements. If any of these pathways break down and HR becomes unregulated then disease, primarily cancer, can result.
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Affiliation(s)
- Mi Young Son
- Department of Molecular Medicine and Institute of Biotechnology, UT Health San Antonio, 15355 Lambda Drive, San Antonio, USA
| | - Paul Hasty
- Department of Molecular Medicine and Institute of Biotechnology, UT Health San Antonio, 15355 Lambda Drive, San Antonio, USA.,The Mays Cancer Center, USA.,Sam and Ann Barshop Institute for Longevity and Aging Studies, USA
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10
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Prado F, Maya D. Regulation of Replication Fork Advance and Stability by Nucleosome Assembly. Genes (Basel) 2017; 8:genes8020049. [PMID: 28125036 PMCID: PMC5333038 DOI: 10.3390/genes8020049] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 01/04/2017] [Accepted: 01/16/2017] [Indexed: 12/13/2022] Open
Abstract
The advance of replication forks to duplicate chromosomes in dividing cells requires the disassembly of nucleosomes ahead of the fork and the rapid assembly of parental and de novo histones at the newly synthesized strands behind the fork. Replication-coupled chromatin assembly provides a unique opportunity to regulate fork advance and stability. Through post-translational histone modifications and tightly regulated physical and genetic interactions between chromatin assembly factors and replisome components, chromatin assembly: (1) controls the rate of DNA synthesis and adjusts it to histone availability; (2) provides a mechanism to protect the integrity of the advancing fork; and (3) regulates the mechanisms of DNA damage tolerance in response to replication-blocking lesions. Uncoupling DNA synthesis from nucleosome assembly has deleterious effects on genome integrity and cell cycle progression and is linked to genetic diseases, cancer, and aging.
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Affiliation(s)
- Felix Prado
- Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), Spanish National Research Council (CSIC), Seville 41092, Spain.
| | - Douglas Maya
- Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), Spanish National Research Council (CSIC), Seville 41092, Spain.
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11
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Affiliation(s)
- Anja-Katrin Bielinsky
- a Department of Biochemistry , Molecular Biology, and Biophysics, University of Minnesota , Minneapolis , MN , USA
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12
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Ouyang KJ, Yagle MK, Matunis MJ, Ellis NA. BLM SUMOylation regulates ssDNA accumulation at stalled replication forks. Front Genet 2013; 4:167. [PMID: 24027577 PMCID: PMC3761158 DOI: 10.3389/fgene.2013.00167] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 08/12/2013] [Indexed: 12/22/2022] Open
Abstract
Polymerase stalling results in uncoupling of DNA polymerase and the replicative helicase, which generates single-stranded DNA (ssDNA). After stalling, RAD51 accumulates at stalled replication forks to stabilize the fork and to repair by homologous recombination (HR) double-strand breaks (DSBs) that accumulate there. We showed recently that SUMO modification of the BLM helicase is required in order for RAD51 to accumulate at stalled forks. In order to investigate how BLM SUMOylation controls RAD51 accumulation, we characterized the function of HR proteins and ssDNA-binding protein RPA in cells that stably expressed either normal BLM (BLM+) or SUMO-mutant BLM (SM-BLM). In HU-treated SM-BLM cells, mediators BRCA2 and RAD52, which normally substitute RAD51 for RPA on ssDNA, failed to accumulate normally at stalled forks; instead, excess RPA accumulated. SM-BLM cells also exhibited higher levels of HU-induced chromatin-bound RPA than BLM+ cells did. The excess RPA did not result from excessive intrinsic BLM helicase activity, because in vitro SUMOylated BLM unwound similar amounts of replication-fork substrate as unSUMOylated BLM. Nor did BLM SUMOylation inhibit binding of RPA to BLM in vitro; however, in immunoprecipitation experiments, more BLM-RPA complex formed in HU-treated SM-BLM cells, indicating that BLM SUMOylation controls the amount of BLM-RPA complex normally formed at stalled forks. Together, these results showed that BLM SUMOylation regulates the amount of ssDNA that accumulates during polymerase stalling. We conclude that BLM SUMOylation functions as a licensing mechanism that permits and regulates HR at damaged replication forks.
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Affiliation(s)
- Karen J Ouyang
- Department of Medicine, University of Chicago Chicago, IL, USA
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