51
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Batenburg NL, Mersaoui SY, Walker JR, Coulombe Y, Hammond-Martel I, Wurtele H, Masson JY, Zhu XD. Cockayne syndrome group B protein regulates fork restart, fork progression and MRE11-dependent fork degradation in BRCA1/2-deficient cells. Nucleic Acids Res 2021; 49:12836-12854. [PMID: 34871413 PMCID: PMC8682776 DOI: 10.1093/nar/gkab1173] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2021] [Revised: 11/08/2021] [Accepted: 11/30/2021] [Indexed: 11/25/2022] Open
Abstract
Cockayne syndrome group B (CSB) protein has been implicated in the repair of a variety of DNA lesions that induce replication stress. However, little is known about its role at stalled replication forks. Here, we report that CSB is recruited to stalled forks in a manner dependent upon its T1031 phosphorylation by CDK. While dispensable for MRE11 association with stalled forks in wild-type cells, CSB is required for further accumulation of MRE11 at stalled forks in BRCA1/2-deficient cells. CSB promotes MRE11-mediated fork degradation in BRCA1/2-deficient cells. CSB possesses an intrinsic ATP-dependent fork reversal activity in vitro, which is activated upon removal of its N-terminal region that is known to autoinhibit CSB’s ATPase domain. CSB functions similarly to fork reversal factors SMARCAL1, ZRANB3 and HLTF to regulate slowdown in fork progression upon exposure to replication stress, indicative of a role of CSB in fork reversal in vivo. Furthermore, CSB not only acts epistatically with MRE11 to facilitate fork restart but also promotes RAD52-mediated break-induced replication repair of double-strand breaks arising from cleavage of stalled forks by MUS81 in BRCA1/2-deficient cells. Loss of CSB exacerbates chemosensitivity in BRCA1/2-deficient cells, underscoring an important role of CSB in the treatment of cancer lacking functional BRCA1/2.
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Affiliation(s)
- Nicole L Batenburg
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Sofiane Y Mersaoui
- CHU de Québec-Université Laval, Oncology Division, Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, 9 McMahon, Québec City, Québec G1R 3S3, Canada
| | - John R Walker
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Yan Coulombe
- CHU de Québec-Université Laval, Oncology Division, Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, 9 McMahon, Québec City, Québec G1R 3S3, Canada
| | - Ian Hammond-Martel
- Centre de recherche, de l'Hôpital Maisonneuve-Rosemont, 5415 boulevard de l'Assomption, Montréal, Québec H1T 2M4, Canada
| | - Hugo Wurtele
- Centre de recherche, de l'Hôpital Maisonneuve-Rosemont, 5415 boulevard de l'Assomption, Montréal, Québec H1T 2M4, Canada.,Department of Medicine, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Jean-Yves Masson
- CHU de Québec-Université Laval, Oncology Division, Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, 9 McMahon, Québec City, Québec G1R 3S3, Canada
| | - Xu-Dong Zhu
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada
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52
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Lei KH, Yang HL, Chang HY, Yeh HY, Nguyen DD, Lee TY, Lyu X, Chastain M, Chai W, Li HW, Chi P. Crosstalk between CST and RPA regulates RAD51 activity during replication stress. Nat Commun 2021; 12:6412. [PMID: 34741010 PMCID: PMC8571288 DOI: 10.1038/s41467-021-26624-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 10/06/2021] [Indexed: 11/09/2022] Open
Abstract
Replication stress causes replication fork stalling, resulting in an accumulation of single-stranded DNA (ssDNA). Replication protein A (RPA) and CTC1-STN1-TEN1 (CST) complex bind ssDNA and are found at stalled forks, where they regulate RAD51 recruitment and foci formation in vivo. Here, we investigate crosstalk between RPA, CST, and RAD51. We show that CST and RPA localize in close proximity in cells. Although CST stably binds to ssDNA with a high affinity at low ionic strength, the interaction becomes more dynamic and enables facilitated dissociation at high ionic strength. CST can coexist with RPA on the same ssDNA and target RAD51 to RPA-coated ssDNA. Notably, whereas RPA-coated ssDNA inhibits RAD51 activity, RAD51 can assemble a functional filament and exhibit strand-exchange activity on CST-coated ssDNA at high ionic strength. Our findings provide mechanistic insights into how CST targets and tethers RAD51 to RPA-coated ssDNA in response to replication stress.
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Affiliation(s)
- Kai-Hang Lei
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Han-Lin Yang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
| | - Hao-Yen Chang
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Hsin-Yi Yeh
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Dinh Duc Nguyen
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Tzu-Yu Lee
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
| | - Xinxing Lyu
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Megan Chastain
- Office of Research, Washington State University, Spokane, WA, USA
| | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Hung-Wen Li
- Department of Chemistry, National Taiwan University, Taipei, Taiwan.
| | - Peter Chi
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan. .,Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.
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53
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Keuper K, Wieland A, Räschle M, Storchova Z. Processes shaping cancer genomes - From mitotic defects to chromosomal rearrangements. DNA Repair (Amst) 2021; 107:103207. [PMID: 34425515 DOI: 10.1016/j.dnarep.2021.103207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 08/06/2021] [Accepted: 08/07/2021] [Indexed: 11/19/2022]
Abstract
Sequencing of cancer genomes revealed a rich landscape of somatic single nucleotide variants, structural changes of chromosomes, as well as chromosomal copy number alterations. These chromosome changes are highly variable, and simple translocations, deletions or duplications have been identified, as well as complex events that likely arise through activity of several interconnected processes. Comparison of the cancer genome sequencing data with our knowledge about processes important for maintenance of genome stability, namely DNA replication, repair and chromosome segregation, provides insights into the mechanisms that may give rise to complex chromosomal patterns, such as chromothripsis, a complex form of multiple focal chromosome rearrangements. In addition, observations gained from model systems that recapitulate the rearrangements patterns under defined experimental conditions suggest that mitotic errors and defective DNA replication and repair contribute to their formation. Here, we review the molecular mechanisms that contribute to formation of chromosomal aberrations observed in cancer genomes.
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Affiliation(s)
- Kristina Keuper
- Department of Molecular Genetics, Paul-Ehrlich Strasse 24, University of Kaiserslautern, 67663, Kaiserslautern, Germany
| | - Angela Wieland
- Department of Molecular Genetics, Paul-Ehrlich Strasse 24, University of Kaiserslautern, 67663, Kaiserslautern, Germany
| | - Markus Räschle
- Department of Molecular Genetics, Paul-Ehrlich Strasse 24, University of Kaiserslautern, 67663, Kaiserslautern, Germany
| | - Zuzana Storchova
- Department of Molecular Genetics, Paul-Ehrlich Strasse 24, University of Kaiserslautern, 67663, Kaiserslautern, Germany.
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54
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Kent T, Clynes D. Alternative Lengthening of Telomeres: Lessons to Be Learned from Telomeric DNA Double-Strand Break Repair. Genes (Basel) 2021; 12:1734. [PMID: 34828344 PMCID: PMC8619803 DOI: 10.3390/genes12111734] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 10/22/2021] [Accepted: 10/28/2021] [Indexed: 12/25/2022] Open
Abstract
The study of the molecular pathways underlying cancer has given us important insights into how breaks in our DNA are repaired and the dire consequences that can occur when these processes are perturbed. Extensive research over the past 20 years has shown that the key molecular event underpinning a subset of cancers involves the deregulated repair of DNA double-strand breaks (DSBs) at telomeres, which in turn leads to telomere lengthening and the potential for replicative immortality. Here we discuss, in-depth, recent major breakthroughs in our understanding of the mechanisms underpinning this pathway known as the alternative lengthening of telomeres (ALT). We explore how this gives us important insights into how DSB repair at telomeres is regulated, with relevance to the cell-cycle-dependent regulation of repair, repair of stalled replication forks and the spatial regulation of DSB repair.
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Affiliation(s)
- Thomas Kent
- Molecular Haematology Unit, Radcliffe Department of Medicine, The MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK;
| | - David Clynes
- Department of Oncology, The MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
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55
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Kang Z, Fu P, Alcivar AL, Fu H, Redon C, Foo TK, Zuo Y, Ye C, Baxley R, Madireddy A, Buisson R, Bielinsky AK, Zou L, Shen Z, Aladjem MI, Xia B. BRCA2 associates with MCM10 to suppress PRIMPOL-mediated repriming and single-stranded gap formation after DNA damage. Nat Commun 2021; 12:5966. [PMID: 34645815 PMCID: PMC8514439 DOI: 10.1038/s41467-021-26227-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 09/23/2021] [Indexed: 11/28/2022] Open
Abstract
The BRCA2 tumor suppressor protects genome integrity by promoting homologous recombination-based repair of DNA breaks, stability of stalled DNA replication forks and DNA damage-induced cell cycle checkpoints. BRCA2 deficient cells display the radio-resistant DNA synthesis (RDS) phenotype, however the mechanism has remained elusive. Here we show that cells without BRCA2 are unable to sufficiently restrain DNA replication fork progression after DNA damage, and the underrestrained fork progression is due primarily to Primase-Polymerase (PRIMPOL)-mediated repriming of DNA synthesis downstream of lesions, leaving behind single-stranded DNA gaps. Moreover, we find that BRCA2 associates with the essential DNA replication factor MCM10 and this association suppresses PRIMPOL-mediated repriming and ssDNA gap formation, while having no impact on the stability of stalled replication forks. Our findings establish an important function for BRCA2, provide insights into replication fork control during the DNA damage response, and may have implications in tumor suppression and therapy response. Tumor suppressor BRCA2 is known to stabilize and restart stalled DNA replication forks. Here the authors show that BRCA2 is recruited to the replication fork through its interaction with MCM10 and inhibits Primase-Polymerase-mediated repriming, lesion bypass and single strand DNA gap formation after DNA damage.
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Affiliation(s)
- Zhihua Kang
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA
| | - Pan Fu
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA.,Department of Clinical Microbiology Laboratory, Children's Hospital of Fudan University, Shanghai, China
| | - Allen L Alcivar
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA.,Bristol-Myers Squibb Company, Bloomsbury, NJ, 08804, USA
| | - Haiqing Fu
- Developmental Therapeutics Group, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
| | - Christophe Redon
- Developmental Therapeutics Group, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
| | - Tzeh Keong Foo
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA
| | - Yamei Zuo
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA
| | - Caiyong Ye
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA.,School of Radiation Medicine and Protection, Soochow University, Suzhou, China
| | - Ryan Baxley
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Advaitha Madireddy
- Department of Pediatric Hematology/Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA
| | - Remi Buisson
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Boston, MA, USA.,Department of Biological Chemistry, University of California Irvine, Irvine, CA, USA
| | - Anja-Katrin Bielinsky
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Lee Zou
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Boston, MA, USA
| | - Zhiyuan Shen
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA
| | - Mirit I Aladjem
- Developmental Therapeutics Group, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
| | - Bing Xia
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA.
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56
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Le HP, Heyer WD, Liu J. Guardians of the Genome: BRCA2 and Its Partners. Genes (Basel) 2021; 12:genes12081229. [PMID: 34440403 PMCID: PMC8394001 DOI: 10.3390/genes12081229] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/04/2021] [Accepted: 08/06/2021] [Indexed: 12/28/2022] Open
Abstract
The tumor suppressor BRCA2 functions as a central caretaker of genome stability, and individuals who carry BRCA2 mutations are predisposed to breast, ovarian, and other cancers. Recent research advanced our mechanistic understanding of BRCA2 and its various interaction partners in DNA repair, DNA replication support, and DNA double-strand break repair pathway choice. In this review, we discuss the biochemical and structural properties of BRCA2 and examine how these fundamental properties contribute to DNA repair and replication fork stabilization in living cells. We highlight selected BRCA2 binding partners and discuss their role in BRCA2-mediated homologous recombination and fork protection. Improved mechanistic understanding of how BRCA2 functions in genome stability maintenance can enable experimental evidence-based evaluation of pathogenic BRCA2 mutations and BRCA2 pseudo-revertants to support targeted therapy.
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Affiliation(s)
- Hang Phuong Le
- Department of Microbiology and Molecular Genetics, University of California, Davis, CA 95616, USA; (H.P.L.); (W.-D.H.)
| | - Wolf-Dietrich Heyer
- Department of Microbiology and Molecular Genetics, University of California, Davis, CA 95616, USA; (H.P.L.); (W.-D.H.)
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Jie Liu
- Department of Microbiology and Molecular Genetics, University of California, Davis, CA 95616, USA; (H.P.L.); (W.-D.H.)
- Correspondence: ; Tel.: +1-530-752-3016
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57
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Muraszko J, Kramarz K, Argunhan B, Ito K, Baranowska G, Kurokawa Y, Murayama Y, Tsubouchi H, Lambert S, Iwasaki H, Dziadkowiec D. Rrp1 translocase and ubiquitin ligase activities restrict the genome destabilising effects of Rad51 in fission yeast. Nucleic Acids Res 2021; 49:6832-6848. [PMID: 34157114 PMCID: PMC8266636 DOI: 10.1093/nar/gkab511] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 05/27/2021] [Accepted: 06/06/2021] [Indexed: 11/20/2022] Open
Abstract
Rad51 is the key protein in homologous recombination that plays important roles during DNA replication and repair. Auxiliary factors regulate Rad51 activity to facilitate productive recombination, and prevent inappropriate, untimely or excessive events, which could lead to genome instability. Previous genetic analyses identified a function for Rrp1 (a member of the Rad5/16-like group of SWI2/SNF2 translocases) in modulating Rad51 function, shared with the Rad51 mediator Swi5-Sfr1 and the Srs2 anti-recombinase. Here, we show that Rrp1 overproduction alleviates the toxicity associated with excessive Rad51 levels in a manner dependent on Rrp1 ATPase domain. Purified Rrp1 binds to DNA and has a DNA-dependent ATPase activity. Importantly, Rrp1 directly interacts with Rad51 and removes it from double-stranded DNA, confirming that Rrp1 is a translocase capable of modulating Rad51 function. Rrp1 affects Rad51 binding at centromeres. Additionally, we demonstrate in vivo and in vitro that Rrp1 possesses E3 ubiquitin ligase activity with Rad51 as a substrate, suggesting that Rrp1 regulates Rad51 in a multi-tiered fashion.
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Affiliation(s)
| | - Karol Kramarz
- Institut Curie, Université PSL, CNRS UMR3348, 91400 Orsay, France.,Université Paris-Saclay, CNRS UMR3348, 91400 Orsay, France
| | - Bilge Argunhan
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Japan
| | - Kentaro Ito
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Japan
| | | | - Yumiko Kurokawa
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Japan
| | - Yasuto Murayama
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Japan
| | - Hideo Tsubouchi
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Japan
| | - Sarah Lambert
- Institut Curie, Université PSL, CNRS UMR3348, 91400 Orsay, France.,Université Paris-Saclay, CNRS UMR3348, 91400 Orsay, France
| | - Hiroshi Iwasaki
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Japan
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58
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Abraxas suppresses DNA end resection and limits break-induced replication by controlling SLX4/MUS81 chromatin loading in response to TOP1 inhibitor-induced DNA damage. Nat Commun 2021; 12:4373. [PMID: 34272385 PMCID: PMC8285526 DOI: 10.1038/s41467-021-24665-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 06/28/2021] [Indexed: 11/08/2022] Open
Abstract
Although homologous recombination (HR) is indicated as a high-fidelity repair mechanism, break-induced replication (BIR), a subtype of HR, is a mutagenic mechanism that leads to chromosome rearrangements. It remains poorly understood how cells suppress mutagenic BIR. Trapping of Topoisomerase 1 by camptothecin (CPT) in a cleavage complex on the DNA can be transformed into single-ended double-strand breaks (seDSBs) upon DNA replication or colliding with transcriptional machinery. Here, we demonstrate a role of Abraxas in limiting seDSBs undergoing BIR-dependent mitotic DNA synthesis. Through counteracting K63-linked ubiquitin modification, Abraxas restricts SLX4/Mus81 recruitment to CPT damage sites for cleavage and subsequent resection processed by MRE11 endonuclease, CtIP, and DNA2/BLM. Uncontrolled SLX4/MUS81 loading and excessive end resection due to Abraxas-deficiency leads to increased mitotic DNA synthesis via RAD52- and POLD3- dependent, RAD51-independent BIR and extensive chromosome aberrations. Our work implicates Abraxas/BRCA1-A complex as a critical regulator that restrains BIR for protection of genome stability.
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59
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Técher H, Pasero P. The Replication Stress Response on a Narrow Path Between Genomic Instability and Inflammation. Front Cell Dev Biol 2021; 9:702584. [PMID: 34249949 PMCID: PMC8270677 DOI: 10.3389/fcell.2021.702584] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 06/03/2021] [Indexed: 02/06/2023] Open
Abstract
The genome of eukaryotic cells is particularly at risk during the S phase of the cell cycle, when megabases of chromosomal DNA are unwound to generate two identical copies of the genome. This daunting task is executed by thousands of micro-machines called replisomes, acting at fragile structures called replication forks. The correct execution of this replication program depends on the coordinated action of hundreds of different enzymes, from the licensing of replication origins to the termination of DNA replication. This review focuses on the mechanisms that ensure the completion of DNA replication under challenging conditions of endogenous or exogenous origin. It also covers new findings connecting the processing of stalled forks to the release of small DNA fragments into the cytoplasm, activating the cGAS-STING pathway. DNA damage and fork repair comes therefore at a price, which is the activation of an inflammatory response that has both positive and negative impacts on the fate of stressed cells. These new findings have broad implications for the etiology of interferonopathies and for cancer treatment.
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Affiliation(s)
- Hervé Técher
- Institut de Génétique Humaine, CNRS, Université de Montpellier, Equipe Labellisée Ligue Contre le Cancer, Montpellier, France
| | - Philippe Pasero
- Institut de Génétique Humaine, CNRS, Université de Montpellier, Equipe Labellisée Ligue Contre le Cancer, Montpellier, France
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60
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Abstract
Unlike bacteria, mammalian cells need to complete DNA replication before segregating their chromosomes for the maintenance of genome integrity. Thus, cells have evolved efficient pathways to restore stalled and/or collapsed replication forks during S-phase, and when necessary, also to delay cell cycle progression to ensure replication completion. However, strong evidence shows that cells can proceed to mitosis with incompletely replicated DNA when under mild replication stress (RS) conditions. Consequently, the incompletely replicated genomic gaps form, predominantly at common fragile site regions, where the converging fork-like DNA structures accumulate. These branched structures pose a severe threat to the faithful disjunction of chromosomes as they physically interlink the partially duplicated sister chromatids. In this review, we provide an overview discussing how cells respond and deal with the under-replicated DNA structures that escape from the S/G2 surveillance system. We also focus on recent research of a mitotic break-induced replication pathway (also known as mitotic DNA repair synthesis), which has been proposed to operate during prophase in an attempt to finish DNA synthesis at the under-replicated genomic regions. Finally, we discuss recent data on how mild RS may cause chromosome instability and mutations that accelerate cancer genome evolution.
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Affiliation(s)
- Camelia Mocanu
- Chromosome Dynamics and Stability Group, Genome Damage and Stability Centre, University of Sussex, Brighton BN1 7BG, UK
| | - Kok-Lung Chan
- Chromosome Dynamics and Stability Group, Genome Damage and Stability Centre, University of Sussex, Brighton BN1 7BG, UK
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61
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Krishnamoorthy A, Jackson J, Mohamed T, Adolph M, Vindigni A, Cortez D. RADX prevents genome instability by confining replication fork reversal to stalled forks. Mol Cell 2021; 81:3007-3017.e5. [PMID: 34107305 DOI: 10.1016/j.molcel.2021.05.014] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 04/02/2021] [Accepted: 05/10/2021] [Indexed: 12/16/2022]
Abstract
RAD51 facilitates replication fork reversal and protects reversed forks from nuclease degradation. Although potentially a useful replication stress response mechanism, unregulated fork reversal can cause genome instability. Here we show that RADX, a single-strand DNA binding protein that binds to and destabilizes RAD51 nucleofilaments, can either inhibit or promote fork reversal depending on replication stress levels. RADX inhibits fork reversal at elongating forks, thereby preventing fork slowing and collapse. Paradoxically, in the presence of persistent replication stress, RADX localizes to stalled forks to generate reversed fork structures. Consequently, inactivating RADX prevents fork-reversal-dependent telomere dysfunction in the absence of RTEL1 and blocks nascent strand degradation when fork protection factors are inactivated. Addition of RADX increases SMARCAL1-dependent fork reversal in conditions in which pre-binding RAD51 to a model fork substrate is inhibitory. Thus, RADX directly interacts with RAD51 and single-strand DNA to confine fork reversal to persistently stalled forks.
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Affiliation(s)
- Archana Krishnamoorthy
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37237, USA
| | - Jessica Jackson
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Taha Mohamed
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37237, USA
| | - Madison Adolph
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37237, USA
| | - Alessandro Vindigni
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - David Cortez
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37237, USA.
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62
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Qiu S, Jiang G, Cao L, Huang J. Replication Fork Reversal and Protection. Front Cell Dev Biol 2021; 9:670392. [PMID: 34041245 PMCID: PMC8141627 DOI: 10.3389/fcell.2021.670392] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Accepted: 04/19/2021] [Indexed: 12/12/2022] Open
Abstract
During genome replication, replication forks often encounter obstacles that impede their progression. Arrested forks are unstable structures that can give rise to collapse and rearrange if they are not properly processed and restarted. Replication fork reversal is a critical protective mechanism in higher eukaryotic cells in response to replication stress, in which forks reverse their direction to form a Holliday junction-like structure. The reversed replication forks are protected from nuclease degradation by DNA damage repair proteins, such as BRCA1, BRCA2, and RAD51. Some of these molecules work cooperatively, while others have unique functions. Once the stress is resolved, the replication forks can restart with the help of enzymes, including human RECQ1 helicase, but restart will not be considered here. Here, we review research on the key factors and mechanisms required for the remodeling and protection of stalled replication forks in mammalian cells.
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Affiliation(s)
- Shan Qiu
- Department of General Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.,The MOE Key Laboratory of Biosystems Homeostasis and Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, China.,Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Zhejiang University, Haining, China
| | - Guixing Jiang
- Department of General Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Liping Cao
- Department of General Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Jun Huang
- Department of General Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.,The MOE Key Laboratory of Biosystems Homeostasis and Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, China
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63
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Stok C, Kok Y, van den Tempel N, van Vugt MATM. Shaping the BRCAness mutational landscape by alternative double-strand break repair, replication stress and mitotic aberrancies. Nucleic Acids Res 2021; 49:4239-4257. [PMID: 33744950 PMCID: PMC8096281 DOI: 10.1093/nar/gkab151] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 02/18/2021] [Accepted: 03/05/2021] [Indexed: 12/16/2022] Open
Abstract
Tumours with mutations in the BRCA1/BRCA2 genes have impaired double-stranded DNA break repair, compromised replication fork protection and increased sensitivity to replication blocking agents, a phenotype collectively known as 'BRCAness'. Tumours with a BRCAness phenotype become dependent on alternative repair pathways that are error-prone and introduce specific patterns of somatic mutations across the genome. The increasing availability of next-generation sequencing data of tumour samples has enabled identification of distinct mutational signatures associated with BRCAness. These signatures reveal that alternative repair pathways, including Polymerase θ-mediated alternative end-joining and RAD52-mediated single strand annealing are active in BRCA1/2-deficient tumours, pointing towards potential therapeutic targets in these tumours. Additionally, insight into the mutations and consequences of unrepaired DNA lesions may also aid in the identification of BRCA-like tumours lacking BRCA1/BRCA2 gene inactivation. This is clinically relevant, as these tumours respond favourably to treatment with DNA-damaging agents, including PARP inhibitors or cisplatin, which have been successfully used to treat patients with BRCA1/2-defective tumours. In this review, we aim to provide insight in the origins of the mutational landscape associated with BRCAness by exploring the molecular biology of alternative DNA repair pathways, which may represent actionable therapeutic targets in in these cells.
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Affiliation(s)
- Colin Stok
- Department of Medical Oncology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ, Groningen, The Netherlands
| | - Yannick P Kok
- Department of Medical Oncology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ, Groningen, The Netherlands
| | - Nathalie van den Tempel
- Department of Medical Oncology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ, Groningen, The Netherlands
| | - Marcel A T M van Vugt
- Department of Medical Oncology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ, Groningen, The Netherlands
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64
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Tye S, Ronson GE, Morris JR. A fork in the road: Where homologous recombination and stalled replication fork protection part ways. Semin Cell Dev Biol 2021; 113:14-26. [PMID: 32653304 PMCID: PMC8082280 DOI: 10.1016/j.semcdb.2020.07.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 07/06/2020] [Accepted: 07/06/2020] [Indexed: 12/14/2022]
Abstract
In response to replication hindrances, DNA replication forks frequently stall and are remodelled into a four-way junction. In such a structure the annealed nascent strand is thought to resemble a DNA double-strand break and remodelled forks are vulnerable to nuclease attack by MRE11 and DNA2. Proteins that promote the recruitment, loading and stabilisation of RAD51 onto single-stranded DNA for homology search and strand exchange in homologous recombination (HR) repair and inter-strand cross-link repair also act to set up RAD51-mediated protection of nascent DNA at stalled replication forks. However, despite the similarities of these pathways, several lines of evidence indicate that fork protection is not simply analogous to the RAD51 loading step of HR. Protection of stalled forks not only requires separate functions of a number of recombination proteins, but also utilises nucleases important for the resection steps of HR in alternative ways. Here we discuss how fork protection arises and how its differences with HR give insights into the differing contexts of these two pathways.
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Affiliation(s)
- Stephanie Tye
- Section of Structural and Synthetic Biology, Department of Infectious Disease, Imperial College London, London, SW7 2AZ, UK
| | - George E Ronson
- University of Birmingham, College of Medical Dental Schools, Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, Vincent Drive, Edgbaston, Birmingham, B15 2TT, UK
| | - Joanna R Morris
- University of Birmingham, College of Medical Dental Schools, Institute of Cancer and Genomics Sciences, Birmingham Centre for Genome Biology, Vincent Drive, Edgbaston, Birmingham, B15 2TT, UK.
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65
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Quinet A, Tirman S, Cybulla E, Meroni A, Vindigni A. To skip or not to skip: choosing repriming to tolerate DNA damage. Mol Cell 2021; 81:649-658. [PMID: 33515486 PMCID: PMC7935405 DOI: 10.1016/j.molcel.2021.01.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 11/21/2020] [Accepted: 01/06/2021] [Indexed: 12/14/2022]
Abstract
Accurate DNA replication is constantly threatened by DNA lesions arising from endogenous and exogenous sources. Specialized DNA replication stress response pathways ensure replication fork progression in the presence of DNA lesions with minimal delay in fork elongation. These pathways broadly include translesion DNA synthesis, template switching, and replication fork repriming. Here, we discuss recent advances toward our understanding of the mechanisms that regulate the fine-tuned balance between these different replication stress response pathways. We also discuss the molecular pathways required to fill single-stranded DNA gaps that accumulate throughout the genome after repriming and the biological consequences of using repriming instead of other DNA damage tolerance pathways on genome integrity and cell fitness.
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Affiliation(s)
- Annabel Quinet
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Stephanie Tirman
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Emily Cybulla
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Alice Meroni
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Alessandro Vindigni
- Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
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66
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Lyu X, Lei K, Biak Sang P, Shiva O, Chastain M, Chi P, Chai W. Human CST complex protects stalled replication forks by directly blocking MRE11 degradation of nascent-strand DNA. EMBO J 2021; 40:e103654. [PMID: 33210317 PMCID: PMC7809791 DOI: 10.15252/embj.2019103654] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 10/07/2020] [Accepted: 10/20/2020] [Indexed: 01/31/2023] Open
Abstract
Degradation and collapse of stalled replication forks are main sources of genomic instability, yet the molecular mechanisms for protecting forks from degradation/collapse are not well understood. Here, we report that human CST (CTC1-STN1-TEN1) proteins, which form a single-stranded DNA-binding complex, localize at stalled forks and protect stalled forks from degradation by the MRE11 nuclease. CST deficiency increases MRE11 binding to stalled forks, leading to nascent-strand degradation at reversed forks and ssDNA accumulation. In addition, purified CST complex binds to 5' DNA overhangs and directly blocks MRE11 degradation in vitro, and the DNA-binding ability of CST is required for blocking MRE11-mediated nascent-strand degradation. Our results suggest that CST inhibits MRE11 binding to reversed forks, thus antagonizing excessive nascent-strand degradation. Finally, we uncover that CST complex inactivation exacerbates genome instability in BRCA2 deficient cells. Collectively, our findings identify the CST complex as an important fork protector that preserves genome integrity under replication perturbation.
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Affiliation(s)
- Xinxing Lyu
- Department of Cancer BiologyCardinal Bernardin Cancer CenterLoyola University Chicago Stritch School of MedicineMaywoodILUSA
- Department of Biomedical SciencesESF College of MedicineWashington State UniversitySpokaneWAUSA
| | - Kai‐Hang Lei
- Institute of Biochemical SciencesNational Taiwan UniversityTaipeiTaiwan
| | - Pau Biak Sang
- Department of Cancer BiologyCardinal Bernardin Cancer CenterLoyola University Chicago Stritch School of MedicineMaywoodILUSA
| | - Olga Shiva
- Department of Biomedical SciencesESF College of MedicineWashington State UniversitySpokaneWAUSA
| | - Megan Chastain
- Department of Biomedical SciencesESF College of MedicineWashington State UniversitySpokaneWAUSA
| | - Peter Chi
- Institute of Biochemical SciencesNational Taiwan UniversityTaipeiTaiwan
- Institute of Biological ChemistryAcademia SinicaTaipeiTaiwan
| | - Weihang Chai
- Department of Cancer BiologyCardinal Bernardin Cancer CenterLoyola University Chicago Stritch School of MedicineMaywoodILUSA
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67
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DCAF14 promotes stalled fork stability to maintain genome integrity. Cell Rep 2021; 34:108669. [PMID: 33503431 PMCID: PMC7941590 DOI: 10.1016/j.celrep.2020.108669] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 11/24/2020] [Accepted: 12/29/2020] [Indexed: 12/15/2022] Open
Abstract
Replication stress response ensures impediments to DNA replication do not compromise replication fork stability and genome integrity. In a process termed replication fork protection, newly synthesized DNA at stalled replication forks is stabilized and protected from nuclease-mediated degradation. We report the identification of DDB1- and CUL4-associated factor 14 (DCAF14), a substrate receptor for Cullin4-RING E3 ligase (CRL4) complex, integral in stabilizing stalled replication forks. DCAF14 localizes rapidly to stalled forks and promotes genome integrity by preventing fork collapse into double-strand breaks (DSBs). Importantly, CRL4DCAF14 mediates stalled fork protection in a RAD51-dependent manner to protect nascent DNA from MRE11 and DNA2 nucleases. Thus, our study shows replication stress response functions of DCAF14 in genome maintenance. Townsend et al. find that DDB1- and CUL4-associated factor DCAF14 is recruited to stalled replication forks. DCAF14 prevents replication fork collapse in a CRL4-dependent manner to promote genome stability and cell survival. DCAF14 depletion triggers nascent strand degradation that is reversible by enhancing RAD51 levels at forks.
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68
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Tian T, Bu M, Chen X, Ding L, Yang Y, Han J, Feng XH, Xu P, Liu T, Ying S, Lei Y, Li Q, Huang J. The ZATT-TOP2A-PICH Axis Drives Extensive Replication Fork Reversal to Promote Genome Stability. Mol Cell 2020; 81:198-211.e6. [PMID: 33296677 DOI: 10.1016/j.molcel.2020.11.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 09/03/2020] [Accepted: 11/03/2020] [Indexed: 12/15/2022]
Abstract
Replication fork reversal is a global response to replication stress in mammalian cells, but precisely how it occurs remains poorly understood. Here, we show that, upon replication stress, DNA topoisomerase IIalpha (TOP2A) is recruited to stalled forks in a manner dependent on the SNF2-family DNA translocases HLTF, ZRANB3, and SMARCAL1. This is accompanied by an increase in TOP2A SUMOylation mediated by the SUMO E3 ligase ZATT and followed by recruitment of a SUMO-targeted DNA translocase, PICH. Disruption of the ZATT-TOP2A-PICH axis results in accumulation of partially reversed forks and enhanced genome instability. These results suggest that fork reversal occurs via a sequential two-step process. First, HLTF, ZRANB3, and SMARCAL1 initiate limited fork reversal, creating superhelical strain in the newly replicated sister chromatids. Second, TOP2A drives extensive fork reversal by resolving the resulting topological barriers and via its role in recruiting PICH to stalled forks.
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Affiliation(s)
- Tian Tian
- The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Min Bu
- The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Xu Chen
- The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Linli Ding
- The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Yulan Yang
- The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Jinhua Han
- The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Xin-Hua Feng
- The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Pinglong Xu
- The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Ting Liu
- Department of Cell Biology and Department of General Surgery of Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Songmin Ying
- Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Yang Lei
- Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Qing Li
- Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Jun Huang
- The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China.
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69
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Shiu JL, Wu CK, Chang SB, Sun YJ, Chen YJ, Lai CC, Chiu WT, Chang WT, Myung K, Su WP, Liaw H. The HLTF-PARP1 interaction in the progression and stability of damaged replication forks caused by methyl methanesulfonate. Oncogenesis 2020; 9:104. [PMID: 33281189 PMCID: PMC7719709 DOI: 10.1038/s41389-020-00289-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 11/04/2020] [Accepted: 11/17/2020] [Indexed: 11/27/2022] Open
Abstract
Human HLTF participates in the lesion-bypass mechanism through the fork reversal structure, known as template switching of post-replication repair. However, the mechanism by which HLTF promotes the replication progression and fork stability of damaged forks remains unclear. Here, we identify a novel protein–protein interaction between HLTF and PARP1. The depletion of HLTF and PARP1 increases chromosome breaks, further reduces the length of replication tracks, and concomitantly increases the number of stalled forks after methyl methanesulfonate treatment according to a DNA fiber analysis. The progression of replication also depends on BARD1 in the presence of MMS treatment. By combining 5-ethynyl-2′-deoxyuridine with a proximity ligation assay, we revealed that the HLTF, PARP1, and BRCA1/BARD1/RAD51 proteins were initially recruited to damaged forks. However, prolonged stalling of damaged forks results in fork collapse. HLTF and PCNA dissociate from the collapsed forks, with increased accumulation of PARP1 and BRCA1/BARD1/RAD51 at the collapsed forks. Our results reveal that HLTF together with PARP1 and BARD1 participates in the stabilization of damaged forks, and the PARP1–BARD1 interaction is further involved in the repair of collapse forks.
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Affiliation(s)
- Jia-Lin Shiu
- Department of Life Sciences, National Cheng Kung University, No.1 University Road, Tainan City, 701, Taiwan
| | - Cheng-Kuei Wu
- Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, No.138, Sheng Li Road, Tainan City, 704, Taiwan
| | - Song-Bin Chang
- Department of Life Sciences, National Cheng Kung University, No.1 University Road, Tainan City, 701, Taiwan
| | - Yan-Jhih Sun
- Department of Life Sciences, National Cheng Kung University, No.1 University Road, Tainan City, 701, Taiwan
| | - Yen-Ju Chen
- Department of Life Sciences, National Cheng Kung University, No.1 University Road, Tainan City, 701, Taiwan
| | - Chien-Chen Lai
- Institute of Molecular Biology, College of Life Science, National Chung Hsing University, No.145 Xingda Rd. South Dist., Taichung City, Taiwan
| | - Wen-Tai Chiu
- Department of Biomedical Engineering, National Cheng Kung University, Tainan City, Taiwan
| | - Wen-Tsan Chang
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
| | - Kyungjae Myung
- IBS Center for Genomic Integrity, UNIST-gil 50, Ulsan, 689-798, Republic of Korea
| | - Wen-Pin Su
- Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, No.138, Sheng Li Road, Tainan City, 704, Taiwan. .,Departments of Oncology and Internal Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan City, 704, Taiwan.
| | - Hungjiun Liaw
- Department of Life Sciences, National Cheng Kung University, No.1 University Road, Tainan City, 701, Taiwan.
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70
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Development and validation of a nomogram with an epigenetic signature for predicting survival in patients with lung adenocarcinoma. Aging (Albany NY) 2020; 12:23200-23216. [PMID: 33221751 PMCID: PMC7746339 DOI: 10.18632/aging.104090] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 08/25/2020] [Indexed: 02/07/2023]
Abstract
Epigenetic factors play crucial roles in carcinogenesis by modifying chromatin architecture. Here, we established an epigenetic biosignature-based model for examining survival in patients with lung adenocarcinoma (LUAD). We retrieved gene-expression profiles and clinical data from The Cancer Genome Atlas and Gene Expression Omnibus and clustered the data into training (n = 490) and Validation (n = 226) datasets, respectively. To establish an epigenetic model, we identified prognostic epigenetic regulation-related genes by LASSO and Cox regression analyses, and established a novel 11-gene signature, including EPC1, GADD45A, HCFC2, RCOR1, SMARCAL1, TLE2, TRIM28, and ZNF516, for predicting LUAD overall survival (OS). The biosignature performed optimally in both the training and validation sets according to receiver operating characteristic and calibration plots. Moreover, the biosignature classified patients into high- and low-risk clusters with distinct survival times, with Cox regression analysis revealing the biosignature as an independent LUAD prognostic index. Furthermore, the generated nomogram integrating the prognostic gene biosignature and clinical indices predicted LUAD OS with high efficiency and outperformed tumor-node-metastasis staging in LUAD survival prediction. These results demonstrated the efficacy of the epigenetic signature prognostic nomogram for reliably predicting LUAD OS and its potential application for informing clinical decision making and individualized treatment.
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71
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Conti BA, Smogorzewska A. Mechanisms of direct replication restart at stressed replisomes. DNA Repair (Amst) 2020; 95:102947. [PMID: 32853827 PMCID: PMC7669714 DOI: 10.1016/j.dnarep.2020.102947] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 08/02/2020] [Accepted: 08/04/2020] [Indexed: 02/09/2023]
Affiliation(s)
- Brooke A Conti
- Laboratory of Genome Maintenance, The Rockefeller University, New York 10065, USA
| | - Agata Smogorzewska
- Laboratory of Genome Maintenance, The Rockefeller University, New York 10065, USA.
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72
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Liu W, Krishnamoorthy A, Zhao R, Cortez D. Two replication fork remodeling pathways generate nuclease substrates for distinct fork protection factors. SCIENCE ADVANCES 2020; 6:6/46/eabc3598. [PMID: 33188024 PMCID: PMC7673757 DOI: 10.1126/sciadv.abc3598] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 09/23/2020] [Indexed: 05/11/2023]
Abstract
Fork reversal is a common response to replication stress, but it generates a DNA end that is susceptible to degradation. Many fork protection factors block degradation, but how they work remains unclear. Here, we find that 53BP1 protects forks from DNA2-mediated degradation in a cell type-specific manner. Fork protection by 53BP1 reduces S-phase DNA damage and hypersensitivity to replication stress. Unlike BRCA2, FANCD2, and ABRO1 that protect reversed forks generated by SMARCAL1, ZRANB3, and HLTF, 53BP1 protects forks remodeled by FBH1. This property is shared by the fork protection factors FANCA, FANCC, FANCG, BOD1L, and VHL. RAD51 is required to generate the resection substrate in all cases. Unexpectedly, BRCA2 is also required for fork degradation in the FBH1 pathway or when RAD51 activity is partially compromised. We conclude that there are multiple fork protection mechanisms that operate downstream of at least two RAD51-dependent fork remodeling pathways.
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Affiliation(s)
- W Liu
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37237, USA
| | - A Krishnamoorthy
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37237, USA
| | - R Zhao
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37237, USA
| | - D Cortez
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37237, USA.
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73
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Kondratick CM, Washington MT, Spies M. Making Choices: DNA Replication Fork Recovery Mechanisms. Semin Cell Dev Biol 2020; 113:27-37. [PMID: 33967572 DOI: 10.1016/j.semcdb.2020.10.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
DNA replication is laden with obstacles that slow, stall, collapse, and break DNA replication forks. At each obstacle, there is a decision to be made whether to bypass the lesion, repair or restart the damaged fork, or to protect stalled forks from further demise. Each "decision" draws upon multitude of proteins participating in various mechanisms that allow repair and restart of replication forks. Specific functions for many of these proteins have been described and an understanding of how they come together in supporting replication forks is starting to emerge. Many questions, however, remain regarding selection of the mechanisms that enable faithful genome duplication and how "normal" intermediates in these mechanisms are sometimes funneled into "rogue" processes that destabilize the genome and lead to cancer, cell death, and emergence of chemotherapeutic resistance. In this review we will discuss molecular mechanisms of DNA damage bypass and replication fork protection and repair. We will specifically focus on the key players that define which mechanism is employed including: PCNA and its control by posttranslational modifications, translesion synthesis DNA polymerases, molecular motors that catalyze reversal of stalled replication forks, proteins that antagonize fork reversal and protect reversed forks from nucleolytic degradation, and the machinery of homologous recombination that helps to reestablish broken forks. We will also discuss risks to genome integrity inherent in each of these mechanisms.
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Affiliation(s)
- Christine M Kondratick
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - M Todd Washington
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242.,Department of Radiation Oncology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Maria Spies
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242.,Department of Radiation Oncology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
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74
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Nguyen DD, Kim EY, Sang PB, Chai W. Roles of OB-Fold Proteins in Replication Stress. Front Cell Dev Biol 2020; 8:574466. [PMID: 33043007 PMCID: PMC7517361 DOI: 10.3389/fcell.2020.574466] [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: 06/19/2020] [Accepted: 08/25/2020] [Indexed: 12/20/2022] Open
Abstract
Accurate DNA replication is essential for maintaining genome stability. However, this stability becomes vulnerable when replication fork progression is stalled or slowed - a condition known as replication stress. Prolonged fork stalling can cause DNA damage, leading to genome instabilities. Thus, cells have developed several pathways and a complex set of proteins to overcome the challenge at stalled replication forks. Oligonucleotide/oligosaccharide binding (OB)-fold containing proteins are a group of proteins that play a crucial role in fork protection and fork restart. These proteins bind to single-stranded DNA with high affinity and prevent premature annealing and unwanted nuclease digestion. Among these OB-fold containing proteins, the best studied in eukaryotic cells are replication protein A (RPA) and breast cancer susceptibility protein 2 (BRCA2). Recently, another RPA-like protein complex CTC1-STN1-TEN1 (CST) complex has been found to counter replication perturbation. In this review, we discuss the latest findings on how these OB-fold containing proteins (RPA, BRCA2, CST) cooperate to safeguard DNA replication and maintain genome stability.
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Affiliation(s)
| | | | | | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, United States
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75
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Joseph SA, Taglialatela A, Leuzzi G, Huang JW, Cuella-Martin R, Ciccia A. Time for remodeling: SNF2-family DNA translocases in replication fork metabolism and human disease. DNA Repair (Amst) 2020; 95:102943. [PMID: 32971328 DOI: 10.1016/j.dnarep.2020.102943] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 07/24/2020] [Accepted: 07/26/2020] [Indexed: 02/07/2023]
Abstract
Over the course of DNA replication, DNA lesions, transcriptional intermediates and protein-DNA complexes can impair the progression of replication forks, thus resulting in replication stress. Failure to maintain replication fork integrity in response to replication stress leads to genomic instability and predisposes to the development of cancer and other genetic disorders. Multiple DNA damage and repair pathways have evolved to allow completion of DNA replication following replication stress, thus preserving genomic integrity. One of the processes commonly induced in response to replication stress is fork reversal, which consists in the remodeling of stalled replication forks into four-way DNA junctions. In normal conditions, fork reversal slows down replication fork progression to ensure accurate repair of DNA lesions and facilitates replication fork restart once the DNA lesions have been removed. However, in certain pathological situations, such as the deficiency of DNA repair factors that protect regressed forks from nuclease-mediated degradation, fork reversal can cause genomic instability. In this review, we describe the complex molecular mechanisms regulating fork reversal, with a focus on the role of the SNF2-family fork remodelers SMARCAL1, ZRANB3 and HLTF, and highlight the implications of fork reversal for tumorigenesis and cancer therapy.
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Affiliation(s)
- Sarah A Joseph
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Angelo Taglialatela
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Giuseppe Leuzzi
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Jen-Wei Huang
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Raquel Cuella-Martin
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Alberto Ciccia
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA.
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76
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Bansal R, Hussain S, Chanana UB, Bisht D, Goel I, Muthuswami R. SMARCAL1, the annealing helicase and the transcriptional co-regulator. IUBMB Life 2020; 72:2080-2096. [PMID: 32754981 DOI: 10.1002/iub.2354] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 06/26/2020] [Accepted: 07/07/2020] [Indexed: 12/15/2022]
Abstract
The ATP-dependent chromatin remodeling proteins play an important role in DNA repair. The energy released by ATP hydrolysis is used for myriad functions ranging from nucleosome repositioning and nucleosome eviction to histone variant exchange. In addition, the distant member of the family, SMARCAL1, uses the energy to reanneal stalled replication forks in response to DNA damage. Biophysical studies have shown that this protein has the unique ability to recognize and bind specifically to DNA structures possessing double-strand to single-strand transition regions. Mutations in SMARCAL1 have been linked to Schimke immuno-osseous dysplasia, an autosomal recessive disorder that exhibits variable penetrance and expressivity. It has long been hypothesized that the variable expressivity and pleiotropic phenotypes observed in the patients might be due to the ability of SMARCAL1 to co-regulate the expression of a subset of genes within the genome. Recently, the role of SMARCAL1 in regulating transcription has been delineated. In this review, we discuss the biophysical and functional properties of the protein that help it to transcriptionally co-regulate DNA damage response as well as to bind to the stalled replication fork and stabilize it, thus ensuring genomic stability. We also discuss the role of SMARCAL1 in cancer and the possibility of using this protein as a chemotherapeutic target.
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Affiliation(s)
- Ritu Bansal
- Chromatin Remodeling Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Saddam Hussain
- Chromatin Remodeling Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Upasana Bedi Chanana
- Chromatin Remodeling Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Deepa Bisht
- Chromatin Remodeling Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Isha Goel
- Chromatin Remodeling Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Rohini Muthuswami
- Chromatin Remodeling Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
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77
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Sequential role of RAD51 paralog complexes in replication fork remodeling and restart. Nat Commun 2020; 11:3531. [PMID: 32669601 PMCID: PMC7363682 DOI: 10.1038/s41467-020-17324-z] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 06/16/2020] [Indexed: 12/19/2022] Open
Abstract
Homologous recombination (HR) factors were recently implicated in DNA replication fork remodeling and protection. While maintaining genome stability, HR-mediated fork remodeling promotes cancer chemoresistance, by as-yet elusive mechanisms. Five HR cofactors – the RAD51 paralogs RAD51B, RAD51C, RAD51D, XRCC2 and XRCC3 – recently emerged as crucial tumor suppressors. Albeit extensively characterized in DNA repair, their role in replication has not been addressed systematically. Here, we identify all RAD51 paralogs while screening for modulators of RAD51 recombinase upon replication stress. Single-molecule analysis of fork progression and architecture in isogenic cellular systems shows that the BCDX2 subcomplex restrains fork progression upon stress, promoting fork reversal. Accordingly, BCDX2 primes unscheduled degradation of reversed forks in BRCA2-defective cells, boosting genomic instability. Conversely, the CX3 subcomplex is dispensable for fork reversal, but mediates efficient restart of reversed forks. We propose that RAD51 paralogs sequentially orchestrate clinically relevant transactions at replication forks, cooperatively promoting fork remodeling and restart. Replication stress has been associated with transient remodelling of replication intermediates into reversed forks, followed by efficient fork restart. Here the authors systematically analyse the role of RAD51 paralogs in these transactions, providing insights on the mechanistic role of different complexes of these proteins.
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78
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Berti M, Cortez D, Lopes M. The plasticity of DNA replication forks in response to clinically relevant genotoxic stress. Nat Rev Mol Cell Biol 2020; 21:633-651. [PMID: 32612242 DOI: 10.1038/s41580-020-0257-5] [Citation(s) in RCA: 186] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2020] [Indexed: 12/28/2022]
Abstract
Complete and accurate DNA replication requires the progression of replication forks through DNA damage, actively transcribed regions, structured DNA and compact chromatin. Recent studies have revealed a remarkable plasticity of the replication process in dealing with these obstacles, which includes modulation of replication origin firing, of the architecture of replication forks, and of the functional organization of the replication machinery in response to replication stress. However, these specialized mechanisms also expose cells to potentially dangerous transactions while replicating DNA. In this Review, we discuss how replication forks are actively stalled, remodelled, processed, protected and restarted in response to specific types of stress. We also discuss adaptations of the replication machinery and the role of chromatin modifications during these transactions. Finally, we discuss interesting recent data on the relevance of replication fork plasticity to human health, covering its role in tumorigenesis, its crosstalk with innate immunity responses and its potential as an effective cancer therapy target.
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Affiliation(s)
- Matteo Berti
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - David Cortez
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Massimo Lopes
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland.
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79
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Bai G, Kermi C, Stoy H, Schiltz CJ, Bacal J, Zaino AM, Hadden MK, Eichman BF, Lopes M, Cimprich KA. HLTF Promotes Fork Reversal, Limiting Replication Stress Resistance and Preventing Multiple Mechanisms of Unrestrained DNA Synthesis. Mol Cell 2020; 78:1237-1251.e7. [PMID: 32442397 PMCID: PMC7305998 DOI: 10.1016/j.molcel.2020.04.031] [Citation(s) in RCA: 115] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 03/12/2020] [Accepted: 04/24/2020] [Indexed: 01/06/2023]
Abstract
DNA replication stress can stall replication forks, leading to genome instability. DNA damage tolerance pathways assist fork progression, promoting replication fork reversal, translesion DNA synthesis (TLS), and repriming. In the absence of the fork remodeler HLTF, forks fail to slow following replication stress, but underlying mechanisms and cellular consequences remain elusive. Here, we demonstrate that HLTF-deficient cells fail to undergo fork reversal in vivo and rely on the primase-polymerase PRIMPOL for repriming, unrestrained replication, and S phase progression upon limiting nucleotide levels. By contrast, in an HLTF-HIRAN mutant, unrestrained replication relies on the TLS protein REV1. Importantly, HLTF-deficient cells also exhibit reduced double-strand break (DSB) formation and increased survival upon replication stress. Our findings suggest that HLTF promotes fork remodeling, preventing other mechanisms of replication stress tolerance in cancer cells. This remarkable plasticity of the replication fork may determine the outcome of replication stress in terms of genome integrity, tumorigenesis, and response to chemotherapy.
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Affiliation(s)
- Gongshi Bai
- Department of Chemical and Systems Biology, Stanford University School of Medicine, 318 Campus Drive, Stanford, CA 94305-5441, USA
| | - Chames Kermi
- Department of Chemical and Systems Biology, Stanford University School of Medicine, 318 Campus Drive, Stanford, CA 94305-5441, USA
| | - Henriette Stoy
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Carl J Schiltz
- Department of Biological Sciences and Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Julien Bacal
- Department of Chemical and Systems Biology, Stanford University School of Medicine, 318 Campus Drive, Stanford, CA 94305-5441, USA
| | - Angela M Zaino
- Department of Pharmaceutical Sciences, University of Connecticut, 69 North Eagleville Road, Storrs, CT 06029-3092, USA
| | - M Kyle Hadden
- Department of Pharmaceutical Sciences, University of Connecticut, 69 North Eagleville Road, Storrs, CT 06029-3092, USA
| | - Brandt F Eichman
- Department of Biological Sciences and Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Massimo Lopes
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Karlene A Cimprich
- Department of Chemical and Systems Biology, Stanford University School of Medicine, 318 Campus Drive, Stanford, CA 94305-5441, USA.
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80
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Jain CK, Mukhopadhyay S, Ganguly A. RecQ Family Helicases in Replication Fork Remodeling and Repair: Opening New Avenues towards the Identification of Potential Targets for Cancer Chemotherapy. Anticancer Agents Med Chem 2020; 20:1311-1326. [PMID: 32418530 DOI: 10.2174/1871520620666200518082433] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 08/08/2019] [Accepted: 12/30/2019] [Indexed: 11/22/2022]
Abstract
Replication fork reversal and restart has gained immense interest as a central response mechanism to replication stress following DNA damage. Although the exact mechanism of fork reversal has not been elucidated precisely, the involvement of diverse pathways and different factors has been demonstrated, which are central to this phenomenon. RecQ helicases known for their vital role in DNA repair and maintaining genome stability has recently been implicated in the restart of regressed replication forks. Through interaction with vital proteins like Poly (ADP) ribose polymerase 1 (PARP1), these helicases participate in the replication fork reversal and restart phenomenon. Most therapeutic agents used for cancer chemotherapy act by causing DNA damage in replicating cells and subsequent cell death. These DNA damages can be repaired by mechanisms involving fork reversal as the key phenomenon eventually reducing the efficacy of the therapeutic agent. Hence the factors contributing to this repair process can be good selective targets for developing more efficient chemotherapeutic agents. In this review, we have discussed in detail the role of various proteins in replication fork reversal and restart with special emphasis on RecQ helicases. Involvement of other proteins like PARP1, recombinase rad51, SWI/SNF complex has also been discussed. Since RecQ helicases play a central role in the DNA damage response following chemotherapeutic treatment, we propose that targeting these helicases can emerge as an alternative to available intervention strategies. We have also summarized the current research status of available RecQ inhibitors and siRNA based therapeutic approaches that targets RecQ helicases. In summary, our review gives an overview of the DNA damage responses involving replication fork reversal and provides new directions for the development of more efficient and sustainable chemotherapeutic approaches.
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Affiliation(s)
- Chetan K Jain
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, 721302, India
| | - Swagata Mukhopadhyay
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, 721302, India
| | - Agneyo Ganguly
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, 721302, India
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81
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Liptay M, Barbosa JS, Rottenberg S. Replication Fork Remodeling and Therapy Escape in DNA Damage Response-Deficient Cancers. Front Oncol 2020; 10:670. [PMID: 32432041 PMCID: PMC7214843 DOI: 10.3389/fonc.2020.00670] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 04/09/2020] [Indexed: 12/27/2022] Open
Abstract
Most cancers have lost a critical DNA damage response (DDR) pathway during tumor evolution. These alterations provide a useful explanation for the initial sensitivity of tumors to DNA-targeting chemotherapy. A striking example is dysfunctional homology-directed repair (HDR), e.g., due to inactivating mutations in BRCA1 and BRCA2 genes. Extensive efforts are being made to develop novel targeted therapies exploiting such an HDR defect. Inhibitors of poly(ADP-ribose) polymerase (PARP) are an instructive example of this approach. Despite the success of PARP inhibitors, the presence of primary or acquired therapy resistance remains a major challenge in clinical oncology. To move the field of precision medicine forward, we need to understand the precise mechanisms causing therapy resistance. Using preclinical models, various mechanisms underlying chemotherapy resistance have been identified. Restoration of HDR seems to be a prevalent mechanism but this does not explain resistance in all cases. Interestingly, some factors involved in DNA damage response (DDR) have independent functions in replication fork (RF) biology and their loss causes RF instability and therapy sensitivity. However, in BRCA-deficient tumors, loss of these factors leads to restored stability of RFs and acquired drug resistance. In this review we discuss the recent advances in the field of RF biology and its potential implications for chemotherapy response in DDR-defective cancers. Additionally, we review the role of DNA damage tolerance (DDT) pathways in maintenance of genome integrity and their alterations in cancer. Furthermore, we refer to novel tools that, combined with a better understanding of drug resistance mechanisms, may constitute a great advance in personalized diagnosis and therapeutic strategies for patients with HDR-deficient tumors.
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Affiliation(s)
- Martin Liptay
- Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Joana S. Barbosa
- Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Sven Rottenberg
- Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Bern Center for Precision Medicine, University of Bern, Bern, Switzerland
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82
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Kurashima K, Kashiwagi H, Shimomura I, Suzuki A, Takeshita F, Mazevet M, Harata M, Yamashita T, Yamamoto Y, Kohno T, Shiotani B. SMARCA4 deficiency-associated heterochromatin induces intrinsic DNA replication stress and susceptibility to ATR inhibition in lung adenocarcinoma. NAR Cancer 2020; 2:zcaa005. [PMID: 34316685 PMCID: PMC8210217 DOI: 10.1093/narcan/zcaa005] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2019] [Revised: 03/28/2020] [Accepted: 04/16/2020] [Indexed: 12/31/2022] Open
Abstract
The SWI/SNF chromatin remodeling complex regulates transcription through the control of chromatin structure and is increasingly thought to play an important role in human cancer. Lung adenocarcinoma (LADC) patients frequently harbor mutations in SMARCA4, a core component of this multisubunit complex. Most of these mutations are loss-of-function mutations, which disrupt critical functions in the regulation of chromatin architecture and can cause DNA replication stress. This study reports that LADC cells deficient in SMARCA4 showed increased DNA replication stress and greater sensitivity to the ATR inhibitor (ATRi) in vitro and in vivo. Mechanistically, loss of SMARCA4 increased heterochromatin formation, resulting in stalled forks, a typical DNA replication stress. In the absence of SMARCA4, severe ATRi-induced single-stranded DNA, which caused replication catastrophe, was generated on nascent DNA near the reversed forks around heterochromatin in an Mre11-dependent manner. Thus, loss of SMARCA4 confers susceptibility to ATRi, both by increasing heterochromatin-associated replication stress and by allowing Mre11 to destabilize reversed forks. These two mechanisms synergistically increase susceptibility of SMARCA4-deficient LADC cells to ATRi. These results provide a preclinical basis for assessing SMARCA4 defects as a biomarker of ATRi efficacy.
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Affiliation(s)
- Kiminori Kurashima
- Division of Cellular Signaling, National Cancer Center Research Institute, Chuo-ku, Tokyo 104-0045, Japan
| | - Hideto Kashiwagi
- Division of Cellular Signaling, National Cancer Center Research Institute, Chuo-ku, Tokyo 104-0045, Japan
| | - Iwao Shimomura
- Division of Molecular and Cellular Medicine, National Cancer Center Research Institute, Chuo-ku, Tokyo 104-0045, Japan
- Department of Respirology, Graduate School of Medicine, Chiba University, Chiba-shi, Chiba 260-8670, Japan
| | - Ayako Suzuki
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa-shi, Chiba 277-8562, Japan
| | - Fumitaka Takeshita
- Department of Functional Analysis, National Cancer Center Research Institute, Chuo-ku, Tokyo 104-0045, Japan
| | - Marianne Mazevet
- Division of Cellular Signaling, National Cancer Center Research Institute, Chuo-ku, Tokyo 104-0045, Japan
| | - Masahiko Harata
- Graduate School of Agricultural Science, Tohoku University, Sendai-shi, Miyagi 980-0845, Japan
| | - Takayuki Yamashita
- Laboratory of Molecular Genetics, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi-shi, Gunma 371-8512, Japan
| | - Yusuke Yamamoto
- Division of Molecular and Cellular Medicine, National Cancer Center Research Institute, Chuo-ku, Tokyo 104-0045, Japan
| | - Takashi Kohno
- Division of Genome Biology, National Cancer Center Research Institute, Chuo-ku, Tokyo 104-0045, Japan
| | - Bunsyo Shiotani
- To whom correspondence should be addressed. Tel: +81 3 3547 5201 (Ext. 3681); Fax: +81 3 3543 9305;
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83
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Huselid E, Bunting SF. The Regulation of Homologous Recombination by Helicases. Genes (Basel) 2020; 11:genes11050498. [PMID: 32369918 PMCID: PMC7290689 DOI: 10.3390/genes11050498] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 04/29/2020] [Accepted: 04/29/2020] [Indexed: 11/16/2022] Open
Abstract
Homologous recombination is essential for DNA repair, replication and the exchange of genetic material between parental chromosomes during meiosis. The stages of recombination involve complex reorganization of DNA structures, and the successful completion of these steps is dependent on the activities of multiple helicase enzymes. Helicases of many different families coordinate the processing of broken DNA ends, and the subsequent formation and disassembly of the recombination intermediates that are necessary for template-based DNA repair. Loss of recombination-associated helicase activities can therefore lead to genomic instability, cell death and increased risk of tumor formation. The efficiency of recombination is also influenced by the ‘anti-recombinase’ effect of certain helicases, which can direct DNA breaks toward repair by other pathways. Other helicases regulate the crossover versus non-crossover outcomes of repair. The use of recombination is increased when replication forks and the transcription machinery collide, or encounter lesions in the DNA template. Successful completion of recombination in these situations is also regulated by helicases, allowing normal cell growth, and the maintenance of genomic integrity.
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84
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Prato G, De Grandis E, Mancardi MM, Cordani R, Giacomini T, Pisciotta L, Uccella S, Severino M, Tortora D, Pavanello M, Bertamino M, Verrina E, Caridi G, Di Rocco M, Nobili L. Schimke immuno-osseous dysplasia, two new cases with peculiar EEG pattern. Brain Dev 2020; 42:408-413. [PMID: 32115305 DOI: 10.1016/j.braindev.2020.01.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 01/09/2020] [Accepted: 01/29/2020] [Indexed: 10/24/2022]
Abstract
Schimke Immuno-Osseous Dysplasia (SIOD) is an autosomal recessive multisystem disorder caused by pathogenic variants in the gene SMARCAL1. The clinical picture is characterized by spondyloepiphyseal dysplasia resulting in growth failure, nephropathy and T-cell deficiency. Neurologic manifestations include microcephaly, cognitive impairment, migraine-like headaches and cerebrovascular manifestations such as cerebral atherosclerotic vascular disease and reversible cerebral vasoconstriction. The role of SMARCAL1 deficiency in non-vascular neurological complications is still under debate. Epilepsy has been reported in a few patients, even in the absence of brain abnormalities. Data regarding electroencephalographic (EEG) patterns in SIOD are scarce METHODS: We describe the clinical, neuroradiological and EEG findings in two unrelated patients with SIOD showing a peculiar pseudo-periodic EEG pattern apparently not related to the cerebrovascular complications, since it was recognized both before and after cerebrovascular events CONCLUSION: Our observations support the hypothesis that SMARCAL1plays an important role in neurodevelopment and brain function and expand the spectrum of neurological abnormalities related to SIOD.
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Affiliation(s)
- Giulia Prato
- Unit of Child Neuropsychiatry, Epilepsy Centre, Department of Medical and Surgical Neuroscience and Rehabilitation, IRCCS Istituto Giannina Gaslini, Genoa, Italy.
| | - Elisa De Grandis
- Unit of Child Neuropsychiatry, Epilepsy Centre, Department of Medical and Surgical Neuroscience and Rehabilitation, IRCCS Istituto Giannina Gaslini, Genoa, Italy; Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genoa, Genoa, Italy.
| | - Maria Margherita Mancardi
- Unit of Child Neuropsychiatry, Epilepsy Centre, Department of Medical and Surgical Neuroscience and Rehabilitation, IRCCS Istituto Giannina Gaslini, Genoa, Italy.
| | - Ramona Cordani
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genoa, Genoa, Italy.
| | - Thea Giacomini
- Unit of Child Neuropsychiatry, Epilepsy Centre, Department of Medical and Surgical Neuroscience and Rehabilitation, IRCCS Istituto Giannina Gaslini, Genoa, Italy; Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genoa, Genoa, Italy.
| | - Livia Pisciotta
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genoa, Genoa, Italy.
| | - Sara Uccella
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genoa, Genoa, Italy
| | | | - Domenico Tortora
- Neuroradiology Unit, IRCCS Istituto Giannina Gaslini, Genoa, Italy.
| | - Marco Pavanello
- Neurosurgery Unit, Department of Clinical and Surgical Neurosciences and Rehabilitation, IRCCS Istituto Giannina Gaslini, Genoa, Italy.
| | - Marta Bertamino
- Physical Medicine and Rehabilitation Unit, Department of Clinical and Surgical Neurosciences and Rehabilitation, IRCCS Istituto Giannina Gaslini, Genoa, Italy.
| | - Enrico Verrina
- Dialysis Unit, Department of Paediatrics, IRCCS Istituto Giannina Gaslini, Genoa, Italy.
| | - Gianluca Caridi
- Laboratory of Molecular Nephrology, IRCCS Istituto Giannina Gaslini, Genoa, Italy.
| | - Maja Di Rocco
- Unit of Rare Diseases, Department of Pediatrics, IRCCS Istituto Giannina Gaslini, Genoa, Italy.
| | - Lino Nobili
- Unit of Child Neuropsychiatry, Epilepsy Centre, Department of Medical and Surgical Neuroscience and Rehabilitation, IRCCS Istituto Giannina Gaslini, Genoa, Italy; Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genoa, Genoa, Italy.
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85
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Zhang JM, Zou L. Alternative lengthening of telomeres: from molecular mechanisms to therapeutic outlooks. Cell Biosci 2020; 10:30. [PMID: 32175073 PMCID: PMC7063710 DOI: 10.1186/s13578-020-00391-6] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Accepted: 02/23/2020] [Indexed: 02/06/2023] Open
Abstract
To escape replicative senescence, cancer cells have to overcome telomere attrition during DNA replication. Most of cancers rely on telomerase to extend and maintain telomeres, but 4-11% of cancers use a homologous recombination-based pathway called alternative lengthening of telomeres (ALT). ALT is prevalent in cancers from the mesenchymal origin and usually associates with poor clinical outcome. Given its critical role in protecting telomeres and genomic integrity in tumor cells, ALT is an Achilles heel of tumors and an attractive target for cancer therapy. Here, we review the recent progress in the mechanistic studies of ALT, and discuss the emerging therapeutic strategies to target ALT-positive cancers.
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Affiliation(s)
- Jia-Min Zhang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129 USA
| | - Lee Zou
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129 USA.,2Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114 USA
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86
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Kelso AA, Goodson SD, Sehorn MG. In Vitro Assays for DNA Branch Migration. Methods Mol Biol 2020; 1999:271-284. [PMID: 31127584 DOI: 10.1007/978-1-4939-9500-4_18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Homologous recombination is a high-fidelity DNA double-strand break repair pathway that uses a homologous template to repair the break. Recombinases are the central enzymes that facilitate the strand invasion step of homologous recombination, which forms a DNA joint molecule. These DNA joint molecules can be moved through branch migration activity. In this chapter, we describe two assays to determine the branch migration activity and directionality of an enzyme. Monitoring the branch migration activity of an enzyme can provide insight into the roles of these factors in homologous recombination.
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Affiliation(s)
- Andrew A Kelso
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC, USA
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, SC, USA
| | - Steven D Goodson
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC, USA
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, SC, USA
| | - Michael G Sehorn
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC, USA.
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, SC, USA.
- Center for Optical Materials Science and Engineering Technologies, Clemson University, Clemson, SC, USA.
- Clemson University School of Health Research, Clemson, SC, USA.
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87
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Brosh RM, Matson SW. History of DNA Helicases. Genes (Basel) 2020; 11:genes11030255. [PMID: 32120966 PMCID: PMC7140857 DOI: 10.3390/genes11030255] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 02/18/2020] [Accepted: 02/20/2020] [Indexed: 12/13/2022] Open
Abstract
Since the discovery of the DNA double helix, there has been a fascination in understanding the molecular mechanisms and cellular processes that account for: (i) the transmission of genetic information from one generation to the next and (ii) the remarkable stability of the genome. Nucleic acid biologists have endeavored to unravel the mysteries of DNA not only to understand the processes of DNA replication, repair, recombination, and transcription but to also characterize the underlying basis of genetic diseases characterized by chromosomal instability. Perhaps unexpectedly at first, DNA helicases have arisen as a key class of enzymes to study in this latter capacity. From the first discovery of ATP-dependent DNA unwinding enzymes in the mid 1970's to the burgeoning of helicase-dependent pathways found to be prevalent in all kingdoms of life, the story of scientific discovery in helicase research is rich and informative. Over four decades after their discovery, we take this opportunity to provide a history of DNA helicases. No doubt, many chapters are left to be written. Nonetheless, at this juncture we are privileged to share our perspective on the DNA helicase field - where it has been, its current state, and where it is headed.
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Affiliation(s)
- Robert M. Brosh
- Section on DNA Helicases, Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
- Correspondence: (R.M.B.J.); (S.W.M.); Tel.: +1-410-558-8578 (R.M.B.J.); +1-919-962-0005 (S.W.M.)
| | - Steven W. Matson
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Correspondence: (R.M.B.J.); (S.W.M.); Tel.: +1-410-558-8578 (R.M.B.J.); +1-919-962-0005 (S.W.M.)
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88
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Feng E, Batenburg NL, Walker JR, Ho A, Mitchell TRH, Qin J, Zhu XD. CSB cooperates with SMARCAL1 to maintain telomere stability in ALT cells. J Cell Sci 2020; 133:jcs234914. [PMID: 31974116 DOI: 10.1242/jcs.234914] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 01/13/2020] [Indexed: 01/01/2023] Open
Abstract
Elevated replication stress is evident at telomeres of about 10-15% of cancer cells, which maintain their telomeres via a homologous recombination (HR)-based mechanism, referred to as alternative lengthening of telomeres (ALT). How ALT cells resolve replication stress to support their growth remains incompletely characterized. Here, we report that CSB (also known as ERCC6) promotes recruitment of HR repair proteins (MRN, BRCA1, BLM and RPA32) and POLD3 to ALT telomeres, a process that requires the ATPase activity of CSB and is controlled by ATM- and CDK2-dependent phosphorylation. Loss of CSB stimulates telomeric recruitment of MUS81 and SLX4, components of the structure-specific MUS81-EME1-SLX1-SLX4 (MUS-SLX) endonuclease complex, suggesting that CSB restricts MUS-SLX-mediated processing of stalled forks at ALT telomeres. Loss of CSB coupled with depletion of SMARCAL1, a chromatin remodeler implicated in catalyzing regression of stalled forks, synergistically promotes not only telomeric recruitment of MUS81 but also the formation of fragile telomeres, the latter of which is reported to arise from fork stalling. These results altogether suggest that CSB-mediated HR repair and SMARCAL1-mediated fork regression cooperate to prevent stalled forks from being processed into fragile telomeres in ALT cells.
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Affiliation(s)
- Emily Feng
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Nicole L Batenburg
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - John R Walker
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Angus Ho
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Taylor R H Mitchell
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Jian Qin
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Xu-Dong Zhu
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
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89
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Physiological and Pathological Roles of RAD52 at DNA Replication Forks. Cancers (Basel) 2020; 12:cancers12020402. [PMID: 32050645 PMCID: PMC7072239 DOI: 10.3390/cancers12020402] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 02/06/2020] [Accepted: 02/07/2020] [Indexed: 02/07/2023] Open
Abstract
Understanding basic molecular mechanisms underlying the biology of cancer cells is of outmost importance for identification of novel therapeutic targets and biomarkers for patient stratification and better therapy selection. One of these mechanisms, the response to replication stress, fuels cancer genomic instability. It is also an Achille’s heel of cancer. Thus, identification of pathways used by the cancer cells to respond to replication-stress may assist in the identification of new biomarkers and discovery of new therapeutic targets. Alternative mechanisms that act at perturbed DNA replication forks and involve fork degradation by nucleases emerged as crucial for sensitivity of cancer cells to chemotherapeutics agents inducing replication stress. Despite its important role in homologous recombination and recombinational repair of DNA double strand breaks in lower eukaryotes, RAD52 protein has been considered dispensable in human cells and the full range of its cellular functions remained unclear. Very recently, however, human RAD52 emerged as an important player in multiple aspects of replication fork metabolism under physiological and pathological conditions. In this review, we describe recent advances on RAD52’s key functions at stalled or collapsed DNA replication forks, in particular, the unexpected role of RAD52 as a gatekeeper, which prevents unscheduled processing of DNA. Last, we will discuss how these functions can be exploited using specific inhibitors in targeted therapy or for an informed therapy selection.
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90
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Warren NJH, Eastman A. Comparison of the different mechanisms of cytotoxicity induced by checkpoint kinase I inhibitors when used as single agents or in combination with DNA damage. Oncogene 2020; 39:1389-1401. [PMID: 31659257 PMCID: PMC7023985 DOI: 10.1038/s41388-019-1079-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 10/14/2019] [Accepted: 10/15/2019] [Indexed: 12/31/2022]
Abstract
Inhibition of the DNA damage response is an emerging strategy to treat cancer. Understanding how DNA damage response inhibitors cause cytotoxicity in cancer cells is crucial to their further clinical development. This review focuses on three different mechanisms of cell killing by checkpoint kinase I inhibitors (CHK1i). DNA damage induced by chemotherapy drugs, such as topoisomerase I inhibitors, results in S and G2 phase arrest. Addition of CHK1i promotes cell cycle progression before repair is completed resulting in mitotic catastrophe. Ribonucleotide reductase inhibitors such as gemcitabine also arrest cells in S phase by preventing dNTP synthesis. Addition of CHK1i re-activates the DNA helicase to unwind DNA, but in the absence of dNTPs, this leads to excessive single-strand DNA that exceeds the protective capacity of the single-strand-binding protein RPA. Unprotected DNA is subjected to nuclease cleavage, resulting in replication catastrophe. CHK1i alone also kills a subset of cell lines through MRE11 and MUS81-mediated DNA cleavage in S phase cells. The choice of mechanism depends on the activation state of CDK2. Low level activation of CDK2 mediates helicase activation, cell cycle progression, and both replication and mitotic catastrophe. In contrast, high CDK2 activity is required for sensitivity to CHK1i as monotherapy. This high CDK2 activity threshold usually occurs late in the cell cycle to prepare for mitosis, but in CHK1i-sensitive cells, high activity can be attained in early S phase, resulting in DNA cleavage and cell death. This sensitivity to CHK1i has previously been associated with endogenous replication stress, but the dependence on high CDK2 activity, as well as MRE11, contradicts this hypothesis. The major unresolved question is why some cell lines fail to restrain their high CDK2 activity and hence succumb to CHK1i in S phase. Resolving this question will facilitate stratification of patients for treatment with CHK1i as monotherapy.
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Affiliation(s)
- Nicholas J H Warren
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Lebanon, NH, 03756, USA
| | - Alan Eastman
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Lebanon, NH, 03756, USA.
- Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, NH, 03756, USA.
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91
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Kent T, Gracias D, Shepherd S, Clynes D. Alternative Lengthening of Telomeres in Pediatric Cancer: Mechanisms to Therapies. Front Oncol 2020; 9:1518. [PMID: 32039009 PMCID: PMC6985284 DOI: 10.3389/fonc.2019.01518] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 12/17/2019] [Indexed: 12/26/2022] Open
Abstract
Achieving replicative immortality is a crucial step in tumorigenesis and requires both bypassing cell cycle checkpoints and the extension of telomeres, sequences that protect the distal ends of chromosomes during replication. In the majority of cancers this is achieved through the enzyme telomerase, however a subset of cancers instead utilize a telomerase-independent mechanism of telomere elongation-the Alternative Lengthening of Telomeres (ALT) pathway. Recent work has aimed to decipher the exact mechanism that underlies this pathway. To this end, this pathway has now been shown to extend telomeres through exploitation of DNA repair machinery in a unique process that may present a number of druggable targets. The identification of such targets, and the subsequent development or repurposing of therapies to these targets may be crucial to improving the prognosis for many ALT-positive cancers, wherein mean survival is lower than non-ALT counterparts and the cancers themselves are particularly unresponsive to standard of care therapies. In this review we summarize the recent identification of many aspects of the ALT pathway, and the therapies that may be employed to exploit these new targets.
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Affiliation(s)
- Thomas Kent
- MRC Molecular Haematology Unit, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - Deanne Gracias
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - Samuel Shepherd
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - David Clynes
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
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92
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Morales C, Ruiz-Torres M, Rodríguez-Acebes S, Lafarga V, Rodríguez-Corsino M, Megías D, Cisneros DA, Peters JM, Méndez J, Losada A. PDS5 proteins are required for proper cohesin dynamics and participate in replication fork protection. J Biol Chem 2020; 295:146-157. [PMID: 31757807 PMCID: PMC6952610 DOI: 10.1074/jbc.ra119.011099] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 11/20/2019] [Indexed: 12/11/2022] Open
Abstract
Cohesin is a chromatin-bound complex that mediates sister chromatid cohesion and facilitates long-range interactions through DNA looping. How the transcription and replication machineries deal with the presence of cohesin on chromatin remains unclear. The dynamic association of cohesin with chromatin depends on WAPL cohesin release factor (WAPL) and on PDS5 cohesin-associated factor (PDS5), which exists in two versions in vertebrate cells, PDS5A and PDS5B. Using genetic deletion in mouse embryo fibroblasts and a combination of CRISPR-mediated gene editing and RNAi-mediated gene silencing in human cells, here we analyzed the consequences of PDS5 depletion for DNA replication. We found that either PDS5A or PDS5B is sufficient for proper cohesin dynamics and that their simultaneous removal increases cohesin's residence time on chromatin and slows down DNA replication. A similar phenotype was observed in WAPL-depleted cells. Cohesin down-regulation restored normal replication fork rates in PDS5-deficient cells, suggesting that chromatin-bound cohesin hinders the advance of the replisome. We further show that PDS5 proteins are required to recruit WRN helicase-interacting protein 1 (WRNIP1), RAD51 recombinase (RAD51), and BRCA2 DNA repair associated (BRCA2) to stalled forks and that in their absence, nascent DNA strands at unprotected forks are degraded by MRE11 homolog double-strand break repair nuclease (MRE11). These findings indicate that PDS5 proteins participate in replication fork protection and also provide insights into how cohesin and its regulators contribute to the response to replication stress, a common feature of cancer cells.
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Affiliation(s)
- Carmen Morales
- Chromosome Dynamics Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Miguel Ruiz-Torres
- Chromosome Dynamics Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Sara Rodríguez-Acebes
- DNA Replication Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Vanesa Lafarga
- Genome Instability Group, Molecular Oncology Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Miriam Rodríguez-Corsino
- Chromosome Dynamics Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Diego Megías
- Confocal Microscopy Unit, Biotechnology Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - David A Cisneros
- Research Institute for Molecular Pathology (IMP), Campus Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Jan-Michael Peters
- Research Institute for Molecular Pathology (IMP), Campus Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Juan Méndez
- DNA Replication Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Ana Losada
- Chromosome Dynamics Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain.
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93
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Shin S, Hyun K, Kim J, Hohng S. ATP Binding to Rad5 Initiates Replication Fork Reversal by Inducing the Unwinding of the Leading Arm and the Formation of the Holliday Junction. Cell Rep 2019; 23:1831-1839. [PMID: 29742437 DOI: 10.1016/j.celrep.2018.04.029] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 02/20/2018] [Accepted: 04/05/2018] [Indexed: 11/30/2022] Open
Abstract
Replication fork reversal is one of the major pathways for reactivating stalled DNA replication. Many enzymes with replication fork reversal activity have DNA-unwinding activity as well, but none of the fork reversal enzymes in the SWI/SNF family shows a separate DNA-unwinding activity, raising the question of how they initiate the remodeling process. Here, we found ATP binding to Rad5 induces the unwinding of the leading arm of the replication fork and proximally positions the leading and lagging arms. This facilitates the spontaneous remodeling of the replication fork into a four-way junction. Once the four-way junction is formed, Rad5 migrates the four-way junction at a speed of 7.1 ± 0.14 nt/s. The 3' end anchoring of the leading arm by Rad5's HIRAN domain is critical for both branch migration and the recovery of the three-way junction, but not for the structural transition to the four-way junction.
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Affiliation(s)
- Soochul Shin
- Department of Physics and Astronomy, Institute of Applied Physics, National Center of Creative Research Initiatives, Seoul National University, Seoul 08826, Republic of Korea
| | - Kwangbeom Hyun
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Jaehoon Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.
| | - Sungchul Hohng
- Department of Physics and Astronomy, Institute of Applied Physics, National Center of Creative Research Initiatives, Seoul National University, Seoul 08826, Republic of Korea.
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94
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Bhat KP, Krishnamoorthy A, Dungrawala H, Garcin EB, Modesti M, Cortez D. RADX Modulates RAD51 Activity to Control Replication Fork Protection. Cell Rep 2019; 24:538-545. [PMID: 30021152 DOI: 10.1016/j.celrep.2018.06.061] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 05/25/2018] [Accepted: 06/13/2018] [Indexed: 10/28/2022] Open
Abstract
RAD51 promotes homologous recombination repair (HR) of double-strand breaks and acts during DNA replication to facilitate fork reversal and protect nascent DNA strands from nuclease digestion. Several additional HR proteins regulate fork protection by promoting RAD51 filament formation. Here, we show that RADX modulates stalled fork protection by antagonizing RAD51. Consequently, silencing RADX restores fork protection in cells deficient for BRCA1, BRCA2, FANCA, FANCD2, or BOD1L. Inactivating RADX prevents both MRE11- and DNA2-dependent fork degradation. Furthermore, RADX overexpression causes fork degradation that is dependent on these nucleases and fork reversal. The amount of RAD51 determines the fate of stalled replication forks, with more RAD51 required for fork protection than fork reversal. Finally, we find that RADX effectively competes with RAD51 for binding to single-stranded DNA, supporting a model in which RADX buffers RAD51 to ensure the right amount of reversal and protection to maintain genome stability.
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Affiliation(s)
- Kamakoti P Bhat
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Archana Krishnamoorthy
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Huzefa Dungrawala
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Edwige B Garcin
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université U105, Marseille, France
| | - Mauro Modesti
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université U105, Marseille, France
| | - David Cortez
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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95
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Pilzecker B, Buoninfante OA, Jacobs H. DNA damage tolerance in stem cells, ageing, mutagenesis, disease and cancer therapy. Nucleic Acids Res 2019; 47:7163-7181. [PMID: 31251805 PMCID: PMC6698745 DOI: 10.1093/nar/gkz531] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 05/22/2019] [Accepted: 06/26/2019] [Indexed: 12/12/2022] Open
Abstract
The DNA damage response network guards the stability of the genome from a plethora of exogenous and endogenous insults. An essential feature of the DNA damage response network is its capacity to tolerate DNA damage and structural impediments during DNA synthesis. This capacity, referred to as DNA damage tolerance (DDT), contributes to replication fork progression and stability in the presence of blocking structures or DNA lesions. Defective DDT can lead to a prolonged fork arrest and eventually cumulate in a fork collapse that involves the formation of DNA double strand breaks. Four principal modes of DDT have been distinguished: translesion synthesis, fork reversal, template switching and repriming. All DDT modes warrant continuation of replication through bypassing the fork stalling impediment or repriming downstream of the impediment in combination with filling of the single-stranded DNA gaps. In this way, DDT prevents secondary DNA damage and critically contributes to genome stability and cellular fitness. DDT plays a key role in mutagenesis, stem cell maintenance, ageing and the prevention of cancer. This review provides an overview of the role of DDT in these aspects.
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Affiliation(s)
- Bas Pilzecker
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Olimpia Alessandra Buoninfante
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Heinz Jacobs
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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96
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Long MJC, Van Hall-Beauvais A, Aye Y. The more the merrier: how homo-oligomerization alters the interactome and function of ribonucleotide reductase. Curr Opin Chem Biol 2019; 54:10-18. [PMID: 31734537 DOI: 10.1016/j.cbpa.2019.09.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 09/03/2019] [Accepted: 09/19/2019] [Indexed: 02/05/2023]
Abstract
Stereotyped as a nexus of dNTP synthesis, the dual-subunit enzyme - ribonucleotide reductase (RNR) - is coming into view as a paradigm of oligomerization and moonlighting behavior. In the present issue of 'omics', we discuss what makes the larger subunit of this enzyme (RNR-α) so interesting, highlighting its emerging cellular interactome based on its unique oligomeric dynamism that dictates its compartment-specific occupations. Linking the history of the field with the multivariable nature of this exceedingly sophisticated enzyme, we further discuss implications of new data pertaining to DNA-damage response, S-phase checkpoints, and ultimately tumor suppression. We hereby hope to provide ideas for those interested in these fields and exemplify conceptual frameworks and tools that are useful to study RNR's broader roles in biology.
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Affiliation(s)
| | - Alexandra Van Hall-Beauvais
- Swiss Federal Institute of Technology Lausanne (EPFL), Institute of Chemical Sciences and Engineering, 1015, Lausanne, Switzerland
| | - Yimon Aye
- Swiss Federal Institute of Technology Lausanne (EPFL), Institute of Chemical Sciences and Engineering, 1015, Lausanne, Switzerland.
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97
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Matos DA, Zhang JM, Ouyang J, Nguyen HD, Genois MM, Zou L. ATR Protects the Genome against R Loops through a MUS81-Triggered Feedback Loop. Mol Cell 2019; 77:514-527.e4. [PMID: 31708417 DOI: 10.1016/j.molcel.2019.10.010] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 08/11/2019] [Accepted: 10/08/2019] [Indexed: 12/20/2022]
Abstract
R loops arising during transcription induce genomic instability, but how cells respond to the R loop-associated genomic stress is still poorly understood. Here, we show that cells harboring high levels of R loops rely on the ATR kinase for survival. In response to aberrant R loop accumulation, the ataxia telangiectasia and Rad3-related (ATR)-Chk1 pathway is activated by R loop-induced reversed replication forks. In contrast to the activation of ATR by replication inhibitors, R loop-induced ATR activation requires the MUS81 endonuclease. ATR protects the genome from R loops by suppressing transcription-replication collisions, promoting replication fork recovery, and enforcing a G2/M cell-cycle arrest. Furthermore, ATR prevents excessive cleavage of reversed forks by MUS81, revealing a MUS81-triggered and ATR-mediated feedback loop that fine-tunes MUS81 activity at replication forks. These results suggest that ATR is a key sensor and suppressor of R loop-induced genomic instability, uncovering a signaling circuitry that safeguards the genome against R loops.
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Affiliation(s)
- Dominick A Matos
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Jia-Min Zhang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Jian Ouyang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Hai Dang Nguyen
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Marie-Michelle Genois
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Lee Zou
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA; Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
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98
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Quinet A, Tirman S, Jackson J, Šviković S, Lemaçon D, Carvajal-Maldonado D, González-Acosta D, Vessoni AT, Cybulla E, Wood M, Tavis S, Batista LFZ, Méndez J, Sale JE, Vindigni A. PRIMPOL-Mediated Adaptive Response Suppresses Replication Fork Reversal in BRCA-Deficient Cells. Mol Cell 2019; 77:461-474.e9. [PMID: 31676232 PMCID: PMC7007862 DOI: 10.1016/j.molcel.2019.10.008] [Citation(s) in RCA: 151] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 07/29/2019] [Accepted: 10/07/2019] [Indexed: 12/20/2022]
Abstract
Acute treatment with replication-stalling chemotherapeutics causes reversal of replication forks. BRCA proteins protect reversed forks from nucleolytic degradation, and their loss leads to chemosensitivity. Here, we show that fork degradation is no longer detectable in BRCA1-deficient cancer cells exposed to multiple cisplatin doses, mimicking a clinical treatment regimen. This effect depends on increased expression and chromatin loading of PRIMPOL and is regulated by ATR activity. Electron microscopy and single-molecule DNA fiber analyses reveal that PRIMPOL rescues fork degradation by reinitiating DNA synthesis past DNA lesions. PRIMPOL repriming leads to accumulation of ssDNA gaps while suppressing fork reversal. We propose that cells adapt to repeated cisplatin doses by activating PRIMPOL repriming under conditions that would otherwise promote pathological reversed fork degradation. This effect is generalizable to other conditions of impaired fork reversal (e.g., SMARCAL1 loss or PARP inhibition) and suggests a new strategy to modulate cisplatin chemosensitivity by targeting the PRIMPOL pathway. Multiple cisplatin doses suppress reversed fork degradation in BRCA-deficient cells The PRIMPOL adaptive response suppresses fork reversal and leads to ssDNA gaps The ATR kinase regulates the PRIMPOL-mediated adaptive response Impaired fork reversal shifts the balance toward PRIMPOL-mediated repriming
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Affiliation(s)
- Annabel Quinet
- Division of Oncology, Department of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Stephanie Tirman
- Division of Oncology, Department of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA; Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Jessica Jackson
- Division of Oncology, Department of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Saša Šviković
- Division of Protein & Nucleic Acid Chemistry, Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Delphine Lemaçon
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Denisse Carvajal-Maldonado
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | | | - Alexandre T Vessoni
- Division of Hematology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Emily Cybulla
- Division of Oncology, Department of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA; Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Matthew Wood
- Division of Oncology, Department of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA; Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Steven Tavis
- Division of Oncology, Department of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Luis F Z Batista
- Division of Hematology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Juan Méndez
- Spanish National Cancer Research Centre (CNIO), Madrid 28029, Spain
| | - Julian E Sale
- Division of Protein & Nucleic Acid Chemistry, Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Alessandro Vindigni
- Division of Oncology, Department of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA; Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA.
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99
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Abstract
The replisome quickly and accurately copies billions of DNA bases each cell division cycle. However, it can make errors, especially when the template DNA is damaged. In these cases, replication-coupled repair mechanisms remove the mistake or repair the template lesions to ensure high fidelity and complete copying of the genome. Failures in these genome maintenance activities generate mutations, rearrangements, and chromosome segregation problems that cause many human diseases. In this review, I provide a broad overview of replication-coupled repair pathways, explaining how they fix polymerase mistakes, respond to template damage that acts as obstacles to the replisome, deal with broken forks, and impact human health and disease.
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100
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Pugliese GM, Salaris F, Palermo V, Marabitti V, Morina N, Rosa A, Franchitto A, Pichierri P. Inducible SMARCAL1 knockdown in iPSC reveals a link between replication stress and altered expression of master differentiation genes. Dis Model Mech 2019; 12:dmm.039487. [PMID: 31515241 PMCID: PMC6826020 DOI: 10.1242/dmm.039487] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 08/30/2019] [Indexed: 12/15/2022] Open
Abstract
Schimke immuno-osseous dysplasia is an autosomal recessive genetic osteochondrodysplasia characterized by dysmorphism, spondyloepiphyseal dysplasia, nephrotic syndrome and frequently T cell immunodeficiency. Several hypotheses have been proposed to explain the pathophysiology of the disease; however, the mechanism by which SMARCAL1 mutations cause the syndrome is elusive. Here, we generated a conditional SMARCAL1 knockdown model in induced pluripotent stem cells (iPSCs) to mimic conditions associated with the severe form the disease. Using multiple cellular endpoints, we characterized this model for the presence of phenotypes linked to the replication caretaker role of SMARCAL1. Our data show that conditional knockdown of SMARCAL1 in human iPSCs induces replication-dependent and chronic accumulation of DNA damage triggering the DNA damage response. Furthermore, they indicate that accumulation of DNA damage and activation of the DNA damage response correlates with increased levels of R-loops and replication-transcription interference. Finally, we provide evidence that SMARCAL1-deficient iPSCs maintain active DNA damage response beyond differentiation, possibly contributing to the observed altered expression of a subset of germ layer-specific master genes. Confirming the relevance of SMARCAL1 loss for the observed phenotypes, they are prevented or rescued after re-expression of wild-type SMARCAL1 in our iPSC model. In conclusion, our conditional SMARCAL1 knockdown model in iPSCs may represent a powerful model when studying pathogenetic mechanisms of severe Schimke immuno-osseous dysplasia.
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Affiliation(s)
- Giusj Monia Pugliese
- Mechanisms, Biomarkers and Models Unit, Department of Environment and Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
| | - Federico Salaris
- Center for Life Nano Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy.,Department of Biology and Biotechnology Charles Darwin, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Valentina Palermo
- Mechanisms, Biomarkers and Models Unit, Department of Environment and Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
| | - Veronica Marabitti
- Mechanisms, Biomarkers and Models Unit, Department of Environment and Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
| | - Nicolò Morina
- Mechanisms, Biomarkers and Models Unit, Department of Environment and Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
| | - Alessandro Rosa
- Center for Life Nano Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy.,Department of Biology and Biotechnology Charles Darwin, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Annapaola Franchitto
- Mechanisms, Biomarkers and Models Unit, Department of Environment and Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
| | - Pietro Pichierri
- Mechanisms, Biomarkers and Models Unit, Department of Environment and Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy .,Istituto Nazionale Biostrutture e Biosistemi, Via delle Medaglie d'Oro, 00136 Rome, Italy
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