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Kasaciunaite K, Fettes F, Levikova M, Daldrop P, Anand R, Cejka P, Seidel R. Competing interaction partners modulate the activity of Sgs1 helicase during DNA end resection. EMBO J 2019; 38:e101516. [PMID: 31268598 PMCID: PMC6601037 DOI: 10.15252/embj.2019101516] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 04/24/2019] [Accepted: 05/08/2019] [Indexed: 11/09/2022] Open
Abstract
DNA double-strand break repair by homologous recombination employs long-range resection of the 5' DNA ends at the break points. In Saccharomyces cerevisiae, this process can be performed by the RecQ helicase Sgs1 and the helicase-nuclease Dna2. Though functional interplay between them has been shown, it remains unclear whether and how these proteins cooperate on the molecular level. Here, we resolved the dynamics of DNA unwinding by Sgs1 at the single-molecule level and investigated Sgs1 regulation by Dna2, the single-stranded DNA-binding protein RPA, and the Top3-Rmi1 complex. We found that Dna2 modulates the velocity of Sgs1, indicating that during end resection both proteins form a functional complex and couple their activities. Sgs1 drives DNA unwinding and feeds single-stranded DNA to Dna2 for degradation. RPA was found to regulate the processivity and the affinity of Sgs1 to the DNA fork, while Top3-Rmi1 modulated the velocity of Sgs1. We hypothesize that the differential regulation of Sgs1 activity by its protein partners is important to support diverse cellular functions of Sgs1 during the maintenance of genome stability.
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Affiliation(s)
- Kristina Kasaciunaite
- Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, Germany
| | - Fergus Fettes
- Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, Germany
| | - Maryna Levikova
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Peter Daldrop
- Institute for Molecular Cell Biology, University of Münster, Münster, Germany
| | - Roopesh Anand
- Institute for Research in Biomedicine, Faculty of Biomedical Sciences, Università della Svizzera Italiana, Bellinzona, Switzerland
| | - Petr Cejka
- Institute for Research in Biomedicine, Faculty of Biomedical Sciences, Università della Svizzera Italiana, Bellinzona, Switzerland
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH), Zurich, Switzerland
| | - Ralf Seidel
- Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, Germany
- Institute for Molecular Cell Biology, University of Münster, Münster, Germany
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Lu R, O'Rourke JJ, Sobinoff AP, Allen JAM, Nelson CB, Tomlinson CG, Lee M, Reddel RR, Deans AJ, Pickett HA. The FANCM-BLM-TOP3A-RMI complex suppresses alternative lengthening of telomeres (ALT). Nat Commun 2019; 10:2252. [PMID: 31138797 PMCID: PMC6538672 DOI: 10.1038/s41467-019-10180-6] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 04/23/2019] [Indexed: 12/21/2022] Open
Abstract
The collapse of stalled replication forks is a major driver of genomic instability. Several committed mechanisms exist to resolve replication stress. These pathways are particularly pertinent at telomeres. Cancer cells that use Alternative Lengthening of Telomeres (ALT) display heightened levels of telomere-specific replication stress, and co-opt stalled replication forks as substrates for break-induced telomere synthesis. FANCM is a DNA translocase that can form independent functional interactions with the BLM-TOP3A-RMI (BTR) complex and the Fanconi anemia (FA) core complex. Here, we demonstrate that FANCM depletion provokes ALT activity, evident by increased break-induced telomere synthesis, and the induction of ALT biomarkers. FANCM-mediated attenuation of ALT requires its inherent DNA translocase activity and interaction with the BTR complex, but does not require the FA core complex, indicative of FANCM functioning to restrain excessive ALT activity by ameliorating replication stress at telomeres. Synthetic inhibition of FANCM-BTR complex formation is selectively toxic to ALT cancer cells.
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Affiliation(s)
- Robert Lu
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, 2145, NSW, Australia
| | - Julienne J O'Rourke
- Genome Stability Unit, St. Vincent's Institute, 9 Princes St, Fitzroy, 3065, VIC, Australia
- Department of Medicine (St. Vincent's), University of Melbourne, Parkville, 3052, VIC, Australia
| | - Alexander P Sobinoff
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, 2145, NSW, Australia
| | - Joshua A M Allen
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, 2145, NSW, Australia
| | - Christopher B Nelson
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, 2145, NSW, Australia
| | - Christopher G Tomlinson
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, 2145, NSW, Australia
| | - Michael Lee
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, 2145, NSW, Australia
| | - Roger R Reddel
- Cancer Research Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, 2145, NSW, Australia
| | - Andrew J Deans
- Genome Stability Unit, St. Vincent's Institute, 9 Princes St, Fitzroy, 3065, VIC, Australia.
- Department of Medicine (St. Vincent's), University of Melbourne, Parkville, 3052, VIC, Australia.
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, 2145, NSW, Australia.
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53
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Alfano L, Caporaso A, Altieri A, Dell’Aquila M, Landi C, Bini L, Pentimalli F, Giordano A. Depletion of the RNA binding protein HNRNPD impairs homologous recombination by inhibiting DNA-end resection and inducing R-loop accumulation. Nucleic Acids Res 2019; 47:4068-4085. [PMID: 30799487 PMCID: PMC6486545 DOI: 10.1093/nar/gkz076] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 01/24/2019] [Accepted: 02/01/2019] [Indexed: 12/12/2022] Open
Abstract
DNA double strand break (DSB) repair through homologous recombination (HR) is crucial to maintain genome stability. DSB resection generates a single strand DNA intermediate, which is crucial for the HR process. We used a synthetic DNA structure, mimicking a resection intermediate, as a bait to identify proteins involved in this process. Among these, LC/MS analysis identified the RNA binding protein, HNRNPD. We found that HNRNPD binds chromatin, although this binding occurred independently of DNA damage. However, upon damage, HNRNPD re-localized to γH2Ax foci and its silencing impaired CHK1 S345 phosphorylation and the DNA end resection process. Indeed, HNRNPD silencing reduced: the ssDNA fraction upon camptothecin treatment; AsiSI-induced DSB resection; and RPA32 S4/8 phosphorylation. CRISPR/Cas9-mediated HNRNPD knockout impaired in vitro DNA resection and sensitized cells to camptothecin and olaparib treatment. We found that HNRNPD interacts with the heterogeneous nuclear ribonucleoprotein SAF-A previously associated with DNA damage repair. HNRNPD depletion resulted in an increased amount of RNA:DNA hybrids upon DNA damage. Both the expression of RNase H1 and RNA pol II inhibition recovered the ability to phosphorylate RPA32 S4/8 in HNRNPD knockout cells upon DNA damage, suggesting that RNA:DNA hybrid resolution likely rescues the defective DNA damage response of HNRNPD-depleted cells.
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Affiliation(s)
- Luigi Alfano
- Oncology Research Center of Mercogliano (CROM); Istituto Nazionale Tumori, IRCCS, Fondazione G. Pascale, Napoli, Italia
| | - Antonella Caporaso
- Department of Medical Biotechnologies, University of Siena, Siena, Italia
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA, USA
| | - Angela Altieri
- Department of Medical Biotechnologies, University of Siena, Siena, Italia
| | - Milena Dell’Aquila
- Department of Medical Biotechnologies, University of Siena, Siena, Italia
| | - Claudia Landi
- Department of Life Sciences, University of Siena, Siena, Italia
| | - Luca Bini
- Department of Life Sciences, University of Siena, Siena, Italia
| | - Francesca Pentimalli
- Oncology Research Center of Mercogliano (CROM); Istituto Nazionale Tumori, IRCCS, Fondazione G. Pascale, Napoli, Italia
| | - Antonio Giordano
- Department of Medical Biotechnologies, University of Siena, Siena, Italia
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA, USA
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Setiaputra D, Durocher D. Shieldin - the protector of DNA ends. EMBO Rep 2019; 20:embr.201847560. [PMID: 30948458 DOI: 10.15252/embr.201847560] [Citation(s) in RCA: 143] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 01/26/2019] [Accepted: 02/06/2019] [Indexed: 12/29/2022] Open
Abstract
DNA double-strand breaks are a threat to genome integrity and cell viability. The nucleolytic processing of broken DNA ends plays a central role in dictating the repair processes that will mend these lesions. Usually, DNA end resection promotes repair by homologous recombination, whereas minimally processed ends are repaired by non-homologous end joining. Important in this process is the chromatin-binding protein 53BP1, which inhibits DNA end resection. How 53BP1 shields DNA ends from nucleases has been an enduring mystery. The recent discovery of shieldin, a four-subunit protein complex with single-stranded DNA-binding activity, illuminated a strong candidate for the ultimate effector of 53BP1-dependent end protection. Shieldin consists of REV7, a known 53BP1-pathway component, and three hitherto uncharacterized proteins: C20orf196 (SHLD1), FAM35A (SHLD2), and CTC-534A2.2 (SHLD3). Shieldin promotes many 53BP1-associated activities, such as the protection of DNA ends, non-homologous end joining, and immunoglobulin class switching. This review summarizes the identification of shieldin and the various models of shieldin action and highlights some outstanding questions requiring answers to gain a full molecular understanding of shieldin function.
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Affiliation(s)
- Dheva Setiaputra
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
| | - Daniel Durocher
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada .,Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
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55
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Regulatory control of Sgs1 and Dna2 during eukaryotic DNA end resection. Proc Natl Acad Sci U S A 2019; 116:6091-6100. [PMID: 30850524 DOI: 10.1073/pnas.1819276116] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In the repair of DNA double-strand breaks by homologous recombination, the DNA break ends must first be processed into 3' single-strand DNA overhangs. In budding yeast, end processing requires the helicase Sgs1 (BLM in humans), the nuclease/helicase Dna2, Top3-Rmi1, and replication protein A (RPA). Here, we use single-molecule imaging to visualize Sgs1-dependent end processing in real-time. We show that Sgs1 is recruited to DNA ends through Top3-Rmi1-dependent or -independent means, and in both cases Sgs1 is maintained in an immoble state at the DNA ends. Importantly, the addition of Dna2 triggers processive Sgs1 translocation, but DNA resection only occurs when RPA is also present. We also demonstrate that the Sgs1-Dna2-Top3-Rmi1-RPA ensemble can efficiently disrupt nucleosomes, and that Sgs1 itself possesses nucleosome remodeling activity. Together, these results shed light on the regulatory interplay among conserved protein factors that mediate the nucleolytic processing of DNA ends in preparation for homologous recombination-mediated chromosome damage repair.
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56
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Abstract
Fanconi anemia (FA) is a complex genetic disorder characterized by bone marrow failure (BMF), congenital defects, inability to repair DNA interstrand cross-links (ICLs), and cancer predisposition. FA presents two seemingly opposite characteristics: (a) massive cell death of the hematopoietic stem and progenitor cell (HSPC) compartment due to extensive genomic instability, leading to BMF, and (b) uncontrolled cell proliferation leading to FA-associated malignancies. The canonical function of the FA proteins is to collaborate with several other DNA repair proteins to eliminate clastogenic (chromosome-breaking) effects of DNA ICLs. Recent discoveries reveal that the FA pathway functions in a critical tumor-suppressor network to preserve genomic integrity by stabilizing replication forks, mitigating replication stress, and regulating cytokinesis. Homozygous germline mutations (biallelic) in 22 FANC genes cause FA, whereas heterozygous germline mutations in some of the FANC genes (monoallelic), such as BRCA1 and BRCA2, do not cause FA but significantly increase cancer susceptibility sporadically in the general population. In this review, we discuss our current understanding of the functions of the FA pathway in the maintenance of genomic stability, and we present an overview of the prevalence and clinical relevance of somatic mutations in FA genes.
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Affiliation(s)
- Joshi Niraj
- Department of Radiation Oncology and Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA;
| | - Anniina Färkkilä
- Department of Radiation Oncology and Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA;
| | - Alan D D'Andrea
- Department of Radiation Oncology and Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA;
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57
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Griffin WC, Trakselis MA. The MCM8/9 complex: A recent recruit to the roster of helicases involved in genome maintenance. DNA Repair (Amst) 2019; 76:1-10. [PMID: 30743181 DOI: 10.1016/j.dnarep.2019.02.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 02/03/2019] [Indexed: 12/11/2022]
Abstract
There are several DNA helicases involved in seemingly overlapping aspects of homologous and homoeologous recombination. Mutations of many of these helicases are directly implicated in genetic diseases including cancer, rapid aging, and infertility. MCM8/9 are recent additions to the catalog of helicases involved in recombination, and so far, the evidence is sparse, making assignment of function difficult. Mutations in MCM8/9 correlate principally with primary ovarian failure/insufficiency (POF/POI) and infertility indicating a meiotic defect. However, they also act when replication forks collapse/break shuttling products into mitotic recombination and several mutations are found in various somatic cancers. This review puts MCM8/9 in context with other replication and recombination helicases to narrow down its genomic maintenance role. We discuss the known structure/function relationship, the mutational spectrum, and dissect the available cellular and organismal data to better define its role in recombination.
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Affiliation(s)
- Wezley C Griffin
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas, 76798, USA
| | - Michael A Trakselis
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas, 76798, USA.
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58
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Wilkinson OJ, Martín-González A, Kang H, Northall SJ, Wigley DB, Moreno-Herrero F, Dillingham MS. CtIP forms a tetrameric dumbbell-shaped particle which bridges complex DNA end structures for double-strand break repair. eLife 2019; 8:42129. [PMID: 30601117 PMCID: PMC6344080 DOI: 10.7554/elife.42129] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 01/01/2019] [Indexed: 12/16/2022] Open
Abstract
CtIP is involved in the resection of broken DNA during the S and G2 phases of the cell cycle for repair by recombination. Acting with the MRN complex, it plays a particularly important role in handling complex DNA end structures by localised nucleolytic processing of DNA termini in preparation for longer range resection. Here we show that human CtIP is a tetrameric protein adopting a dumbbell architecture in which DNA binding domains are connected by long coiled-coils. The protein complex binds two short DNA duplexes with high affinity and bridges DNA molecules in trans. DNA binding is potentiated by dephosphorylation and is not specific for DNA end structures per se. However, the affinity for linear DNA molecules is increased if the DNA terminates with complex structures including forked ssDNA overhangs and nucleoprotein conjugates. This work provides a biochemical and structural basis for the function of CtIP at complex DNA breaks.
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Affiliation(s)
| | - Alejandro Martín-González
- Department of Macromolecular Structures, Centro Nacional de Biotecnologia, Consejo Superior de Investigaciones Cientificas, Madrid, Spain
| | - Haejoo Kang
- Department of Medicine, Imperial College London, London, United Kingdom
| | - Sarah J Northall
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Dale B Wigley
- Department of Medicine, Imperial College London, London, United Kingdom
| | - Fernando Moreno-Herrero
- Department of Macromolecular Structures, Centro Nacional de Biotecnologia, Consejo Superior de Investigaciones Cientificas, Madrid, Spain
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59
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Jimeno S, Mejías-Navarro F, Prados-Carvajal R, Huertas P. Controlling the balance between chromosome break repair pathways. DNA Repair (Amst) 2019; 115:95-134. [DOI: 10.1016/bs.apcsb.2018.10.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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60
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Sae2 antagonizes Rad9 accumulation at DNA double-strand breaks to attenuate checkpoint signaling and facilitate end resection. Proc Natl Acad Sci U S A 2018; 115:E11961-E11969. [PMID: 30510002 DOI: 10.1073/pnas.1816539115] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The Mre11-Rad50-Xrs2NBS1 complex plays important roles in the DNA damage response by activating the Tel1ATM kinase and catalyzing 5'-3' resection at DNA double-strand breaks (DSBs). To initiate resection, Mre11 endonuclease nicks the 5' strands at DSB ends in a reaction stimulated by Sae2CtIP Accordingly, Mre11-nuclease deficient (mre11-nd) and sae2Δ mutants are expected to exhibit similar phenotypes; however, we found several notable differences. First, sae2Δ cells exhibit greater sensitivity to genotoxins than mre11-nd cells. Second, sae2Δ is synthetic lethal with sgs1Δ, whereas the mre11-nd sgs1Δ mutant is viable. Third, Sae2 attenuates the Tel1-Rad53CHK2 checkpoint and antagonizes Rad953BP1 accumulation at DSBs independent of Mre11 nuclease. We show that Sae2 competes with other Tel1 substrates, thus reducing Rad9 binding to chromatin and to Rad53. We suggest that persistent Sae2 binding at DSBs in the mre11-nd mutant counteracts the inhibitory effects of Rad9 and Rad53 on Exo1 and Dna2-Sgs1-mediated resection, accounting for the different phenotypes conferred by mre11-nd and sae2Δ mutations. Collectively, these data show a resection initiation independent role for Sae2 at DSBs by modulating the DNA damage checkpoint.
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61
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Wang H, Qiu Z, Liu B, Wu Y, Ren J, Liu Y, Zhao Y, Wang Y, Hao S, Li Z, Peng B, Xu X. PLK1 targets CtIP to promote microhomology-mediated end joining. Nucleic Acids Res 2018; 46:10724-10739. [PMID: 30202980 PMCID: PMC6237753 DOI: 10.1093/nar/gky810] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 08/08/2018] [Accepted: 08/30/2018] [Indexed: 12/12/2022] Open
Abstract
Proper DNA double-strand break (DSB) repair is essential for maintaining genome integrity. Microhomology-mediated end joining (MMEJ) is an error-prone repair mechanism, which introduces mutations at break sites and contributes to chromosomal translocations and telomere fusions, thus driving carcinogenesis. Mitotic kinases PLK1, CDK1 and Aurora A are important for supporting MMEJ and are often overexpressed in various tumors. However, the functional interplay between these kinases and MMEJ has not been explored. Here, we found that MMEJ is preferentially employed to fix DSBs in cells arrested in mitosis following nocodazole treatment. We further showed that the DSB repair factor CtIP is jointly phosphorylated by CDK1/Aurora A and PLK1. CDK1/Aurora A-mediated CtIP phosphorylation at serine 327 triggers CtIP binding to the PLK1 polo-box domain, which in turn facilitates PLK1 to phosphorylate CtIP mainly at serine 723. A PLK1 phosphor-mimic CtIP mutant fails to initiate extended end resection and is thus unable to mediate homologous recombination and the G2/M checkpoint but can mediate MMEJ. These data imply that PLK1 may target CtIP to promote error-prone MMEJ and inactivate the G2/M checkpoint. These findings have helped elucidate the oncogenic roles of these factors.
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Affiliation(s)
- Hailong Wang
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Zhiyu Qiu
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Bo Liu
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Yan Wu
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Jianping Ren
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Yaqing Liu
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Yuqin Zhao
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Ya Wang
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Shuailin Hao
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Zheng Li
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Bin Peng
- Guangdong Key Laboratory for Genome Stability & Disease Prevention, Shenzhen University School of Medicine, Shenzhen, Guangdong 518060, China
| | - Xingzhi Xu
- Guangdong Key Laboratory for Genome Stability & Disease Prevention, Shenzhen University School of Medicine, Shenzhen, Guangdong 518060, China
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62
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Pannunzio NR, Watanabe G, Lieber MR. Nonhomologous DNA end-joining for repair of DNA double-strand breaks. J Biol Chem 2017; 293:10512-10523. [PMID: 29247009 DOI: 10.1074/jbc.tm117.000374] [Citation(s) in RCA: 326] [Impact Index Per Article: 46.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Nonhomologous DNA end-joining (NHEJ) is the predominant double-strand break (DSB) repair pathway throughout the cell cycle and accounts for nearly all DSB repair outside of the S and G2 phases. NHEJ relies on Ku to thread onto DNA termini and thereby improve the affinity of the NHEJ enzymatic components consisting of polymerases (Pol μ and Pol λ), a nuclease (the Artemis·DNA-PKcs complex), and a ligase (XLF·XRCC4·Lig4 complex). Each of the enzymatic components is distinctive for its versatility in acting on diverse incompatible DNA end configurations coupled with a flexibility in loading order, resulting in many possible junctional outcomes from one DSB. DNA ends can either be directly ligated or, if the ends are incompatible, processed until a ligatable configuration is achieved that is often stabilized by up to 4 bp of terminal microhomology. Processing of DNA ends results in nucleotide loss or addition, explaining why DSBs repaired by NHEJ are rarely restored to their original DNA sequence. Thus, NHEJ is a single pathway with multiple enzymes at its disposal to repair DSBs, resulting in a diversity of repair outcomes.
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Affiliation(s)
- Nicholas R Pannunzio
- From the Departments of Pathology, Biochemistry and Molecular Biology, and Molecular Microbiology and Immunology, Section of Molecular and Computational Biology, Department of Biological Sciences, Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California 90033
| | - Go Watanabe
- From the Departments of Pathology, Biochemistry and Molecular Biology, and Molecular Microbiology and Immunology, Section of Molecular and Computational Biology, Department of Biological Sciences, Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California 90033
| | - Michael R Lieber
- From the Departments of Pathology, Biochemistry and Molecular Biology, and Molecular Microbiology and Immunology, Section of Molecular and Computational Biology, Department of Biological Sciences, Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California 90033
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