1
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Fan J, Dhingra N, Yang T, Yang V, Zhao X. Srs2 binding to PCNA and its sumoylation contribute to RPA antagonism during the DNA damage response. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.28.587206. [PMID: 38586001 PMCID: PMC10996639 DOI: 10.1101/2024.03.28.587206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Activation of the DNA damage checkpoint upon genotoxin treatment induces a multitude of cellular changes, such as cell cycle arrest, to cope with genome stress. After prolonged genotoxin treatment, the checkpoint can be downregulated to allow cell cycle and growth resumption. In yeast, downregulation of the DNA damage checkpoint requires the Srs2 DNA helicase, which removes the ssDNA binding complex RPA and the associated Mec1 checkpoint kinase from DNA, thus dampening Mec1 activation. However, it is unclear whether the 'anti-checkpoint' role of Srs2 is temporally and spatially regulated to both allow timely checkpoint termination and to prevent superfluous RPA removal. Here we address this question by examining regulatory elements of Srs2, including its phosphorylation, sumoylation, and protein-interaction sites. Our genetic analyses and checkpoint level assessment suggest that the RPA countering role of Srs2 is promoted by Srs2 binding to PCNA, which is known to recruit Srs2 to subsets of ssDNA regions. RPA antagonism is further fostered by Srs2 sumoylation, which we found depends on the Srs2-PCNA interaction. Srs2 sumoylation is additionally reliant on Mec1 and peaks after Mec1 activity reaches maximal levels. Collectively, our data provide evidence for a two-step model wherein checkpoint downregulation is facilitated by PCNA-mediated Srs2 recruitment to ssDNA-RPA filaments and the subsequent Srs2 sumoylation stimulated upon Mec1 hyperactivation. We propose that this mechanism allows Mec1 hyperactivation to trigger checkpoint recovery.
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Affiliation(s)
- Jiayi Fan
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Nalini Dhingra
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Tammy Yang
- City University of New York Hunter College, New York, NY 10065
| | - Vicki Yang
- City University of New York Hunter College, New York, NY 10065
| | - Xiaolan Zhao
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
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2
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Tang N, Wen W, Liu Z, Xiong X, Wu Y. HELQ as a DNA helicase: Its novel role in normal cell function and tumorigenesis (Review). Oncol Rep 2023; 50:220. [PMID: 37921071 PMCID: PMC10652244 DOI: 10.3892/or.2023.8657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 08/08/2023] [Indexed: 11/04/2023] Open
Abstract
Helicase POLQ‑like (HELQ or Hel308), is a highly conserved, 3'‑5' superfamily II DNA helicase that contributes to diverse DNA processes, including DNA repair, unwinding, and strand annealing. HELQ deficiency leads to subfertility, due to its critical role in germ cell stability. In addition, the abnormal expression of HELQ has been observed in multiple tumors and a number of molecular pathways, including the nucleotide excision repair, checkpoint kinase 1‑DNA repair protein RAD51 homolog 1 and ATM/ATR pathways, have been shown to be involved in HELQ. In the present review, the structure and characteristics of HELQ, as well as its major functions in DNA processing, were described. Molecular mechanisms involving HELQ in the context of tumorigenesis were also described. It was deduced that HELQ biology warrants investigation, and that its critical roles in the regulation of various DNA processes and participation in tumorigenesis are clinically relevant.
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Affiliation(s)
- Nan Tang
- Department of Traditional Chinese Medicine, Guangzhou Red Cross Hospital of Jinan University, Guangzhou, Guangdong 510220, P.R. China
| | - Weilun Wen
- Department of Traditional Chinese Medicine, Guangzhou Red Cross Hospital of Jinan University, Guangzhou, Guangdong 510220, P.R. China
| | - Zhihe Liu
- Guangzhou Institute of Traumatic Surgery, Guangzhou Red Cross Hospital of Jinan University, Guangzhou, Guangdong 510220, P.R. China
| | - Xifeng Xiong
- Guangzhou Institute of Traumatic Surgery, Guangzhou Red Cross Hospital of Jinan University, Guangzhou, Guangdong 510220, P.R. China
| | - Yanhua Wu
- Department of Traditional Chinese Medicine, Guangzhou Red Cross Hospital of Jinan University, Guangzhou, Guangdong 510220, P.R. China
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3
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Lever R, Simmons E, Gamble-Milner R, Buckley R, Harrison C, Parkes A, Mitchell L, Gausden J, Škulj S, Bertoša B, Bolt E, Allers T. Archaeal Hel308 suppresses recombination through a catalytic switch that controls DNA annealing. Nucleic Acids Res 2023; 51:8563-8574. [PMID: 37409572 PMCID: PMC10484726 DOI: 10.1093/nar/gkad572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Revised: 06/14/2023] [Accepted: 06/23/2023] [Indexed: 07/07/2023] Open
Abstract
Hel308 helicases promote genome stability in archaea and are conserved in metazoans, where they are known as HELQ. Their helicase mechanism is well characterised, but it is unclear how they specifically contribute to genome stability in archaea. We show here that a highly conserved motif of Hel308/HELQ helicases (motif IVa, F/YHHAGL) modulates both DNA unwinding and a newly identified strand annealing function of archaeal Hel308. A single amino acid substitution in motif IVa results in hyper-active DNA helicase and annealase activities of purified Hel308 in vitro. All-atom molecular dynamics simulations using Hel308 crystal structures provided a molecular basis for these differences between mutant and wild type Hel308. In archaeal cells, the same mutation results in 160000-fold increased recombination, exclusively as gene conversion (non-crossover) events. However, crossover recombination is unaffected by the motif IVa mutation, as is cell viability or DNA damage sensitivity. By contrast, cells lacking Hel308 show impaired growth, increased sensitivity to DNA cross-linking agents, and only moderately increased recombination. Our data reveal that archaeal Hel308 suppresses recombination and promotes DNA repair, and that motif IVa in the RecA2 domain acts as a catalytic switch to modulate the separable recombination and repair activities of Hel308.
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Affiliation(s)
- Rebecca J Lever
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | - Emily Simmons
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | | | - Ryan J Buckley
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | - Catherine Harrison
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | - Ashley J Parkes
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | - Laura Mitchell
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | - Jacob A Gausden
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | - Sanja Škulj
- Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia
| | - Branimir Bertoša
- Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia
| | - Edward L Bolt
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | - Thorsten Allers
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
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4
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He L, Lever R, Cubbon A, Tehseen M, Jenkins T, Nottingham AO, Horton A, Betts H, Fisher M, Hamdan SM, Soultanas P, Bolt EL. Interaction of human HelQ with DNA polymerase delta halts DNA synthesis and stimulates DNA single-strand annealing. Nucleic Acids Res 2023; 51:1740-1749. [PMID: 36718939 PMCID: PMC9976902 DOI: 10.1093/nar/gkad032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 01/05/2023] [Accepted: 01/10/2023] [Indexed: 02/01/2023] Open
Abstract
DNA strand breaks are repaired by DNA synthesis from an exposed DNA end paired with a homologous DNA template. DNA polymerase delta (Pol δ) catalyses DNA synthesis in multiple eukaryotic DNA break repair pathways but triggers genome instability unless its activity is restrained. We show that human HelQ halts DNA synthesis by isolated Pol δ and Pol δ-PCNA-RPA holoenzyme. Using novel HelQ mutant proteins we identify that inhibition of Pol δ is independent of DNA binding, and maps to a 70 amino acid intrinsically disordered region of HelQ. Pol δ and its POLD3 subunit robustly stimulated DNA single-strand annealing by HelQ, and POLD3 and HelQ interact physically via the intrinsically disordered HelQ region. This data, and inability of HelQ to inhibit DNA synthesis by the POLD1 catalytic subunit of Pol δ, reveal a mechanism for limiting DNA synthesis and promoting DNA strand annealing during human DNA break repair, which centres on POLD3.
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Affiliation(s)
- Liu He
- School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Rebecca Lever
- School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Andrew Cubbon
- School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Muhammad Tehseen
- Bioscience Program, Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Tabitha Jenkins
- School of Life Sciences, University of Nottingham, Nottingham, UK
| | | | - Anya Horton
- School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Hannah Betts
- Biodiscovery Institute, School of Chemistry, University of Nottingham, Nottingham, UK
| | | | - Samir M Hamdan
- Bioscience Program, Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Panos Soultanas
- Biodiscovery Institute, School of Chemistry, University of Nottingham, Nottingham, UK
| | - Edward L Bolt
- School of Life Sciences, University of Nottingham, Nottingham, UK
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5
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Vanson S, Li Y, Wood RD, Doublié S. Probing the structure and function of polymerase θ helicase-like domain. DNA Repair (Amst) 2022; 116:103358. [PMID: 35753097 PMCID: PMC10329254 DOI: 10.1016/j.dnarep.2022.103358] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 06/09/2022] [Accepted: 06/09/2022] [Indexed: 11/19/2022]
Abstract
DNA Polymerase θ is the key actuator of the recently identified double-strand break repair pathway, theta-mediated end joining (TMEJ). It is the only known polymerase to have a 3-domain architecture containing an independently functional family A DNA polymerase tethered by a long central region to an N-terminal helicase-like domain (HLD). Full-length polymerase θ and the isolated HLD hydrolyze ATP in the presence of DNA, but no processive DNA duplex unwinding has been observed. Based on sequence and structure conservation, the HLD is classified as a member of helicase superfamily II and, more specifically, the Ski2-like family. The specific subdomain composition and organization most closely resemble that of archaeal DNA repair helicases Hel308 and Hjm. The underlying structural basis as to why the HLD is not able to processively unwind duplex DNA, despite its similarity to bona fide helicases, remains elusive. Activities of the HLD include ATP hydrolysis, protein displacement, and annealing of complementary DNA. These observations have led to speculation about the role of the HLD within the context of double-strand break repair via TMEJ, such as removal of single-stranded DNA binding proteins like RPA and RAD51 and microhomology alignment. This review summarizes the structural classification and organization of the polymerase θ HLD and its homologs and explores emerging data on its biochemical activities. We conclude with a simple, speculative model for the HLD's role in TMEJ.
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Affiliation(s)
- Scott Vanson
- Department of Microbiology and Molecular Genetics, University of Vermont, 89 Beaumont Ave, Burlington, VT 05405, USA
| | - Yuzhen Li
- Department of Epigenetics & Molecular Carcinogenesis, The University of Texas MD Anderson Center, Houston, TX 77230, USA
| | - Richard D Wood
- Department of Epigenetics & Molecular Carcinogenesis, The University of Texas MD Anderson Center, Houston, TX 77230, USA.
| | - Sylvie Doublié
- Department of Microbiology and Molecular Genetics, University of Vermont, 89 Beaumont Ave, Burlington, VT 05405, USA.
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6
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Moyret-Lalle C, Prodhomme MK, Burlet D, Kashiwagi A, Petrilli V, Puisieux A, Seimiya H, Tissier A. Role of EMT in the DNA damage response, double-strand break repair pathway choice and its implications in cancer treatment. Cancer Sci 2022; 113:2214-2223. [PMID: 35534984 PMCID: PMC9277259 DOI: 10.1111/cas.15389] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/20/2022] [Accepted: 04/25/2022] [Indexed: 11/30/2022] Open
Abstract
Numerous epithelial–mesenchymal transition (EMT) characteristics have now been demonstrated to participate in tumor development. Indeed, EMT is involved in invasion, acquisition of stem cell properties, and therapy‐associated resistance of cancer cells. Together, these mechanisms offer advantages in adapting to changes in the tumor microenvironment. However, recent findings have shown that EMT‐associated transcription factors (EMT‐TFs) may also be involved in DNA repair. A better understanding of the coordination between the DNA repair pathways and the role played by some EMT‐TFs in the DNA damage response (DDR) should pave the way for new treatments targeting tumor‐specific molecular vulnerabilities, which result in selective destruction of cancer cells. Here we review recent advances, providing novel insights into the role of EMT in the DDR and repair pathways, with a particular focus on the influence of EMT on cellular sensitivity to damage, as well as the implications of these relationships for improving the efficacy of cancer treatments.
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Affiliation(s)
- Caroline Moyret-Lalle
- Université de Lyon, Université Claude Bernard Lyon 1, INSERM 1052, CNRS 5286, Centre Léon Bérard, Cancer Research Centre of Lyon, Lyon, France.,LabEx DEVweCAN, Université de Lyon, Lyon, France
| | - Mélanie K Prodhomme
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Delphine Burlet
- Université de Lyon, Université Claude Bernard Lyon 1, INSERM 1052, CNRS 5286, Centre Léon Bérard, Cancer Research Centre of Lyon, Lyon, France
| | - Ayaka Kashiwagi
- Division of Molecular Biotherapy, Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, Tokyo, Japan.,Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan
| | - Virginie Petrilli
- Université de Lyon, Université Claude Bernard Lyon 1, INSERM 1052, CNRS 5286, Centre Léon Bérard, Cancer Research Centre of Lyon, Lyon, France
| | - Alain Puisieux
- Institut Curie, Versailles Saint-Quentin-en-Yvelines University, PSL Research University, Paris, France
| | - Hiroyuki Seimiya
- Division of Molecular Biotherapy, Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, Tokyo, Japan.,Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan
| | - Agnès Tissier
- Université de Lyon, Université Claude Bernard Lyon 1, INSERM 1052, CNRS 5286, Centre Léon Bérard, Cancer Research Centre of Lyon, Lyon, France
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7
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Hormeno S, Wilkinson OJ, Aicart-Ramos C, Kuppa S, Antony E, Dillingham MS, Moreno-Herrero F. Human HELB is a processive motor protein that catalyzes RPA clearance from single-stranded DNA. Proc Natl Acad Sci U S A 2022; 119:e2112376119. [PMID: 35385349 PMCID: PMC9169624 DOI: 10.1073/pnas.2112376119] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 03/01/2022] [Indexed: 01/17/2023] Open
Abstract
Human DNA helicase B (HELB) is a poorly characterized helicase suggested to play both positive and negative regulatory roles in DNA replication and recombination. In this work, we used bulk and single-molecule approaches to characterize the biochemical activities of HELB protein with a particular focus on its interactions with Replication Protein A (RPA) and RPA–single-stranded DNA (ssDNA) filaments. HELB is a monomeric protein that binds tightly to ssDNA with a site size of ∼20 nucleotides. It couples ATP hydrolysis to translocation along ssDNA in the 5′ to 3′ direction accompanied by the formation of DNA loops. HELB also displays classical helicase activity, but this is very weak in the absence of an assisting force. HELB binds specifically to human RPA, which enhances its ATPase and ssDNA translocase activities but inhibits DNA unwinding. Direct observation of HELB on RPA nucleoprotein filaments shows that translocating HELB concomitantly clears RPA from ssDNA. This activity, which can allow other proteins access to ssDNA intermediates despite their shielding by RPA, may underpin the diverse roles of HELB in cellular DNA transactions.
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Affiliation(s)
- Silvia Hormeno
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain
| | - Oliver J. Wilkinson
- DNA:Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Clara Aicart-Ramos
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain
| | - Sahiti Kuppa
- Department of Biochemistry, Saint Louis University, St. Louis, MO 63104
| | - Edwin Antony
- Department of Biochemistry, Saint Louis University, St. Louis, MO 63104
| | - Mark S. Dillingham
- DNA:Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Fernando Moreno-Herrero
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain
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8
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Anand R, Buechelmaier E, Belan O, Newton M, Vancevska A, Kaczmarczyk A, Takaki T, Rueda DS, Powell SN, Boulton SJ. HELQ is a dual-function DSB repair enzyme modulated by RPA and RAD51. Nature 2022; 601:268-273. [PMID: 34937945 PMCID: PMC8755542 DOI: 10.1038/s41586-021-04261-0] [Citation(s) in RCA: 24] [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: 06/02/2021] [Accepted: 11/17/2021] [Indexed: 02/04/2023]
Abstract
DNA double-stranded breaks (DSBs) are deleterious lesions, and their incorrect repair can drive cancer development1. HELQ is a superfamily 2 helicase with 3' to 5' polarity, and its disruption in mice confers germ cells loss, infertility and increased predisposition to ovarian and pituitary tumours2-4. At the cellular level, defects in HELQ result in hypersensitivity to cisplatin and mitomycin C, and persistence of RAD51 foci after DNA damage3,5. Notably, HELQ binds to RPA and the RAD51-paralogue BCDX2 complex, but the relevance of these interactions and how HELQ functions in DSB repair remains unclear3,5,6. Here we show that HELQ helicase activity and a previously unappreciated DNA strand annealing function are differentially regulated by RPA and RAD51. Using biochemistry analyses and single-molecule imaging, we establish that RAD51 forms a complex with and strongly stimulates HELQ as it translocates during DNA unwinding. By contrast, RPA inhibits DNA unwinding by HELQ but strongly stimulates DNA strand annealing. Mechanistically, we show that HELQ possesses an intrinsic ability to capture RPA-bound DNA strands and then displace RPA to facilitate annealing of complementary sequences. Finally, we show that HELQ deficiency in cells compromises single-strand annealing and microhomology-mediated end-joining pathways and leads to bias towards long-tract gene conversion tracts during homologous recombination. Thus, our results implicate HELQ in multiple arms of DSB repair through co-factor-dependent modulation of intrinsic translocase and DNA strand annealing activities.
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Affiliation(s)
- Roopesh Anand
- DSB Repair Metabolism Laboratory, The Francis Crick Institute, London, UK
| | - Erika Buechelmaier
- Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Graduate School of Medical Sciences, Weill Cornell Medicine, New York, NY, USA
| | - Ondrej Belan
- DSB Repair Metabolism Laboratory, The Francis Crick Institute, London, UK
| | - Matthew Newton
- DSB Repair Metabolism Laboratory, The Francis Crick Institute, London, UK
| | | | - Artur Kaczmarczyk
- Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, UK
- Single Molecule Imaging Group, MRC-London Institute of Medical Sciences, London, UK
| | - Tohru Takaki
- DSB Repair Metabolism Laboratory, The Francis Crick Institute, London, UK
| | - David S Rueda
- Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, UK.
- Single Molecule Imaging Group, MRC-London Institute of Medical Sciences, London, UK.
| | - Simon N Powell
- Memorial Sloan Kettering Cancer Center, New York, NY, USA.
| | - Simon J Boulton
- DSB Repair Metabolism Laboratory, The Francis Crick Institute, London, UK.
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9
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Helicase Q promotes homology-driven DNA double-strand break repair and prevents tandem duplications. Nat Commun 2021; 12:7126. [PMID: 34880204 PMCID: PMC8654963 DOI: 10.1038/s41467-021-27408-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Accepted: 11/16/2021] [Indexed: 11/09/2022] Open
Abstract
DNA double-strand breaks are a major threat to cellular survival and genetic integrity. In addition to high fidelity repair, three intrinsically mutagenic DNA break repair routes have been described, i.e. single-strand annealing (SSA), polymerase theta-mediated end-joining (TMEJ) and residual ill-defined microhomology-mediated end-joining (MMEJ) activity. Here, we identify C. elegans Helicase Q (HELQ-1) as being essential for MMEJ as well as for SSA. We also find HELQ-1 to be crucial for the synthesis-dependent strand annealing (SDSA) mode of homologous recombination (HR). Loss of HELQ-1 leads to increased genome instability: patchwork insertions arise at deletion junctions due to abortive rounds of polymerase theta activity, and tandem duplications spontaneously accumulate in genomes of helq-1 mutant animals as a result of TMEJ of abrogated HR intermediates. Our work thus implicates HELQ activity for all DSB repair modes guided by complementary base pairs and provides mechanistic insight into mutational signatures common in HR-defective cancers.
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10
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Zahn KE, Jensen RB. Polymerase θ Coordinates Multiple Intrinsic Enzymatic Activities during DNA Repair. Genes (Basel) 2021; 12:1310. [PMID: 34573292 PMCID: PMC8470613 DOI: 10.3390/genes12091310] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 08/19/2021] [Accepted: 08/20/2021] [Indexed: 11/16/2022] Open
Abstract
The POLQ gene encodes DNA polymerase θ, a 2590 amino acid protein product harboring DNA-dependent ATPase, template-dependent DNA polymerase, dNTP-dependent endonuclease, and 5'-dRP lyase functions. Polymerase θ participates at an essential step of a DNA double-strand break repair pathway able to join 5'-resected substrates by locating and pairing microhomologies present in 3'-overhanging single-stranded tails, cleaving the extraneous 3'-DNA by dNTP-dependent end-processing, before extending the nascent 3' end from the microhomology annealing site. Metazoans require polymerase θ for full resistance to DNA double-strand break inducing agents but can survive knockout of the POLQ gene. Cancer cells with compromised homologous recombination, or other DNA repair defects, over-utilize end-joining by polymerase θ and often over-express the POLQ gene. This dependency points to polymerase θ as an ideal drug target candidate and multiple drug-development programs are now preparing to enter clinical trials with small-molecule inhibitors. Specific inhibitors of polymerase θ would not only be predicted to treat BRCA-mutant cancers, but could thwart accumulated resistance to current standard-of-care cancer therapies and overcome PARP-inhibitor resistance in patients. This article will discuss synthetic lethal strategies targeting polymerase θ in DNA damage-response-deficient cancers and summarize data, describing molecular structures and enzymatic functions.
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Affiliation(s)
- Karl E. Zahn
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA
- Repare Therapeutics, 7210 Rue Frederick Banting, Montreal, QC H4S 2A1, Canada
| | - Ryan B. Jensen
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA
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