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Ribeiro JH, Altinisik N, Rajan N, Verslegers M, Baatout S, Gopalakrishnan J, Quintens R. DNA damage and repair: underlying mechanisms leading to microcephaly. Front Cell Dev Biol 2023; 11:1268565. [PMID: 37881689 PMCID: PMC10597653 DOI: 10.3389/fcell.2023.1268565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 09/25/2023] [Indexed: 10/27/2023] Open
Abstract
DNA-damaging agents and endogenous DNA damage constantly harm genome integrity. Under genotoxic stress conditions, the DNA damage response (DDR) machinery is crucial in repairing lesions and preventing mutations in the basic structure of the DNA. Different repair pathways are implicated in the resolution of such lesions. For instance, the non-homologous DNA end joining and homologous recombination pathways are central cellular mechanisms by which eukaryotic cells maintain genome integrity. However, defects in these pathways are often associated with neurological disorders, indicating the pivotal role of DDR in normal brain development. Moreover, the brain is the most sensitive organ affected by DNA-damaging agents compared to other tissues during the prenatal period. The accumulation of lesions is believed to induce cell death, reduce proliferation and premature differentiation of neural stem and progenitor cells, and reduce brain size (microcephaly). Microcephaly is mainly caused by genetic mutations, especially genes encoding proteins involved in centrosomes and DNA repair pathways. However, it can also be induced by exposure to ionizing radiation and intrauterine infections such as the Zika virus. This review explains mammalian cortical development and the major DNA repair pathways that may lead to microcephaly when impaired. Next, we discuss the mechanisms and possible exposures leading to DNA damage and p53 hyperactivation culminating in microcephaly.
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Affiliation(s)
- Jessica Honorato Ribeiro
- Radiobiology Unit, Belgian Nuclear Research Centre (SCK CEN), Mol, Belgium
- Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Nazlican Altinisik
- Laboratory for Centrosome and Cytoskeleton Biology, Institute of Human Genetics, University Hospital, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Nicholas Rajan
- Radiobiology Unit, Belgian Nuclear Research Centre (SCK CEN), Mol, Belgium
| | - Mieke Verslegers
- Radiobiology Unit, Belgian Nuclear Research Centre (SCK CEN), Mol, Belgium
| | - Sarah Baatout
- Radiobiology Unit, Belgian Nuclear Research Centre (SCK CEN), Mol, Belgium
- Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Jay Gopalakrishnan
- Laboratory for Centrosome and Cytoskeleton Biology, Institute of Human Genetics, University Hospital, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Roel Quintens
- Radiobiology Unit, Belgian Nuclear Research Centre (SCK CEN), Mol, Belgium
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Bian X, Sun C, Cheng J, Hong B. Targeting DNA Damage Repair and Immune Checkpoint Proteins for Optimizing the Treatment of Endometrial Cancer. Pharmaceutics 2023; 15:2241. [PMID: 37765210 PMCID: PMC10536053 DOI: 10.3390/pharmaceutics15092241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 08/04/2023] [Accepted: 08/12/2023] [Indexed: 09/29/2023] Open
Abstract
The dependence of cancer cells on the DNA damage response (DDR) pathway for the repair of endogenous- or exogenous-factor-induced DNA damage has been extensively studied in various cancer types, including endometrial cancer (EC). Targeting one or more DNA damage repair protein with small molecules has shown encouraging treatment efficacy in preclinical and clinical models. However, the genes coding for DDR factors are rarely mutated in EC, limiting the utility of DDR inhibitors in this disease. In the current review, we recapitulate the functional role of the DNA repair system in the development and progression of cancer. Importantly, we discuss strategies that target DDR proteins, including PARP, CHK1 and WEE1, as monotherapies or in combination with cytotoxic agents in the treatment of EC and highlight the compounds currently being evaluated for their efficacy in EC in clinic. Recent studies indicate that the application of DNA damage agents in cancer cells leads to the activation of innate and adaptive immune responses; targeting immune checkpoint proteins could overcome the immune suppressive environment in tumors. We further summarize recently revolutionized immunotherapies that have been completed or are now being evaluated for their efficacy in advanced EC and propose future directions for the development of DDR-based cancer therapeutics in the treatment of EC.
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Affiliation(s)
- Xing Bian
- College of Biological and Pharmaceutical Engineering, West Anhui University, Lu’an 237012, China; (X.B.); (C.S.); (J.C.)
| | - Chuanbo Sun
- College of Biological and Pharmaceutical Engineering, West Anhui University, Lu’an 237012, China; (X.B.); (C.S.); (J.C.)
| | - Jin Cheng
- College of Biological and Pharmaceutical Engineering, West Anhui University, Lu’an 237012, China; (X.B.); (C.S.); (J.C.)
| | - Bo Hong
- Anhui Province Key Laboratory of Medical Physics and Technology, Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
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Talibova G, Bilmez Y, Ozturk S. DNA double-strand break repair in male germ cells during spermatogenesis and its association with male infertility development. DNA Repair (Amst) 2022; 118:103386. [DOI: 10.1016/j.dnarep.2022.103386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 08/01/2022] [Accepted: 08/03/2022] [Indexed: 11/16/2022]
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Roch B, Abramowski V, Etienne O, Musilli S, David P, Charbonnier JB, Callebaut I, Boussin FD, de Villartay JP. An XRCC4 mutant mouse, a model for human X4 syndrome, reveals interplays with Xlf, PAXX, and ATM in lymphoid development. eLife 2021; 10:e69353. [PMID: 34519267 PMCID: PMC8516412 DOI: 10.7554/elife.69353] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 09/13/2021] [Indexed: 12/17/2022] Open
Abstract
We developed an Xrcc4M61R separation of function mouse line to overcome the embryonic lethality of Xrcc4-deficient mice. XRCC4M61R protein does not interact with Xlf, thus obliterating XRCC4-Xlf filament formation while preserving the ability to stabilize DNA ligase IV. X4M61R mice, which are DNA repair deficient, phenocopy the Nhej1-/- (known as Xlf -/-) setting with a minor impact on the development of the adaptive immune system. The core non-homologous end-joining (NHEJ) DNA repair factor XRCC4 is therefore not mandatory for V(D)J recombination aside from its role in stabilizing DNA ligase IV. In contrast, Xrcc4M61R mice crossed on Paxx-/-, Nhej1-/-, or Atm-/- backgrounds are severely immunocompromised, owing to aborted V(D)J recombination as in Xlf-Paxx and Xlf-Atm double Knock Out (DKO) settings. Furthermore, massive apoptosis of post-mitotic neurons causes embryonic lethality of Xrcc4M61R -Nhej1-/- double mutants. These in vivo results reveal new functional interplays between XRCC4 and PAXX, ATM and Xlf in mouse development and provide new insights into the understanding of the clinical manifestations of human XRCC4-deficient condition, in particular its absence of immune deficiency.
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Affiliation(s)
- Benoit Roch
- Université de Paris, Imagine Institute, Laboratory “Genome Dynamics in the Immune System”, INSERM UMR 1163, F-75015ParisFrance
- Equipe Labellisée Ligue Nationale Contre le Cancer, F75015ParisFrance
| | - Vincent Abramowski
- Université de Paris, Imagine Institute, Laboratory “Genome Dynamics in the Immune System”, INSERM UMR 1163, F-75015ParisFrance
- Equipe Labellisée Ligue Nationale Contre le Cancer, F75015ParisFrance
| | - Olivier Etienne
- Université de Paris and Université Paris-Saclay, Inserm, LRP/iRCM/IBFJ CEA, UMR Stabilité Génétique Cellules Souches et Radiations, F-92265Fontenay-aux-RosesFrance
| | - Stefania Musilli
- Université de Paris, Imagine Institute, Laboratory “Genome Dynamics in the Immune System”, INSERM UMR 1163, F-75015ParisFrance
- Equipe Labellisée Ligue Nationale Contre le Cancer, F75015ParisFrance
| | - Pierre David
- Université de Paris, Imagine Institute, Transgenesis facility, INSERM UMR 1163, F-75015ParisFrance
| | - Jean-Baptiste Charbonnier
- Institute for Integrative Biology of the Cell (I2BC), Institute Joliot, CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, F-91198Gif-sur-Yvette CedexFrance
| | - Isabelle Callebaut
- Sorbonne Université, Muséum National d'Histoire Naturelle, CNRS UMR 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, F-75005ParisFrance
| | - François D Boussin
- Université de Paris and Université Paris-Saclay, Inserm, LRP/iRCM/IBFJ CEA, UMR Stabilité Génétique Cellules Souches et Radiations, F-92265Fontenay-aux-RosesFrance
| | - Jean-Pierre de Villartay
- Université de Paris, Imagine Institute, Laboratory “Genome Dynamics in the Immune System”, INSERM UMR 1163, F-75015ParisFrance
- Equipe Labellisée Ligue Nationale Contre le Cancer, F75015ParisFrance
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Asa ADDC, Wanotayan R, Sharma MK, Tsukada K, Shimada M, Matsumoto Y. Functional analysis of XRCC4 mutations in reported microcephaly and growth defect patients in terms of radiosensitivity. JOURNAL OF RADIATION RESEARCH 2021; 62:380-389. [PMID: 33842963 PMCID: PMC8127669 DOI: 10.1093/jrr/rrab016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Revised: 02/01/2021] [Indexed: 05/08/2023]
Abstract
Non-homologous end joining is one of the main pathways for DNA double-strand break (DSB) repair and is also implicated in V(D)J recombination in immune system. Therefore, mutations in non-homologous end-joining (NHEJ) proteins were found to be associated with immunodeficiency in human as well as in model animals. Several human patients with mutations in XRCC4 were reported to exhibit microcephaly and growth defects, but unexpectedly showed normal immune function. Here, to evaluate the functionality of these disease-associated mutations of XRCC4 in terms of radiosensitivity, we generated stable transfectants expressing these mutants in XRCC4-deficient murine M10 cells and measured their radiosensitivity by colony formation assay. V83_S105del, R225X and D254Mfs*68 were expressed at a similar level to wild-type XRCC4, while W43R, R161Q and R275X were expressed at even higher level than wild-type XRCC4. The expression levels of DNA ligase IV in the transfectants with these mutants were comparable to that in the wild-type XRCC4 transfectant. The V83S_S105del transfectant and, to a lesser extent, D254Mfs*68 transfectant, showed substantially increased radiosensitivity compared to the wild-type XRCC4 transfectant. The W43R, R161Q, R225X and R275X transfectants showed a slight but statistically significant increase in radiosensitivity compared to the wild-type XRCC4 transfectant. When expressed as fusion proteins with Green fluorescent protein (GFP), R225X, R275X and D254Mfs*68 localized to the cytoplasm, whereas other mutants localized to the nucleus. These results collectively indicated that the defects of XRCC4 in patients might be mainly due to insufficiency in protein quantity and impaired functionality, underscoring the importance of XRCC4's DSB repair function in normal development.
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Affiliation(s)
- Anie Day D C Asa
- Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, Tokyo 152-8550, Japan
| | - Rujira Wanotayan
- Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, Tokyo 152-8550, Japan
- Department of Radiological Technology, Mahidol University, Nakhon Pathom 73170, Thailand
| | - Mukesh Kumar Sharma
- Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, Tokyo 152-8550, Japan
- Department of Zoology, SPC Government College, Ajmer-305001, Rajasthan, India
| | - Kaima Tsukada
- Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, Tokyo 152-8550, Japan
| | - Mikio Shimada
- Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, Tokyo 152-8550, Japan
| | - Yoshihisa Matsumoto
- Corresponding author. Yoshihisa Matsumoto, Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 Japan. E-mail: ; FAX: +81-3-5734-3703
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The molecular basis and disease relevance of non-homologous DNA end joining. Nat Rev Mol Cell Biol 2020; 21:765-781. [PMID: 33077885 DOI: 10.1038/s41580-020-00297-8] [Citation(s) in RCA: 221] [Impact Index Per Article: 55.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/08/2020] [Indexed: 12/26/2022]
Abstract
Non-homologous DNA end joining (NHEJ) is the predominant repair mechanism of any type of DNA double-strand break (DSB) during most of the cell cycle and is essential for the development of antigen receptors. Defects in NHEJ result in sensitivity to ionizing radiation and loss of lymphocytes. The most critical step of NHEJ is synapsis, or the juxtaposition of the two DNA ends of a DSB, because all subsequent steps rely on it. Recent findings show that, like the end processing step, synapsis can be achieved through several mechanisms. In this Review, we first discuss repair pathway choice between NHEJ and other DSB repair pathways. We then integrate recent insights into the mechanisms of NHEJ synapsis with updates on other steps of NHEJ, such as DNA end processing and ligation. Finally, we discuss NHEJ-related human diseases, including inherited disorders and neoplasia, which arise from rare failures at different NHEJ steps.
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Fredette ME, Lombardi KC, Duker AL, Buck CO, Phornphutkul C, Bober MB, Quintos JB. NOVEL XRCC4 MUTATIONS IN AN INFANT WITH MICROCEPHALIC PRIMORDIAL DWARFISM, DILATED CARDIOMYOPATHY, SUBCLINICAL HYPOTHYROIDISM, AND EARLY DEATH: EXPANDING THE PHENOTYPE OF XRCC4 MUTATIONS. AACE Clin Case Rep 2020; 6:e1-e4. [PMID: 32524007 DOI: 10.4158/accr-2019-0283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 08/11/2019] [Indexed: 11/15/2022] Open
Abstract
Objective Microcephalic primordial dwarfism (MPD) is a group of clinically and genetically heterogeneous disorders which result in severe prenatal and postnatal growth failure. X-ray repair cross-complementing protein 4 (XRCC4) is a causative gene for an autosomal recessive form of MPD. The objective of this report is to describe novel XRCC4 mutations in a female infant with MPD, dilated cardiomyopathy, and subclinical hypothyroidism. Methods Genetic testing was performed using a comprehensive next generation sequencing panel for MPD, followed by targeted XRCC4 gene sequencing. Results We report the case of a 970-gram, 35-cm, female infant (weight z score -5.05, length z score -4.71) born at 36 weeks and 3 days gestation. Physical examination revealed triangular facies, micrognathism, clinodactyly, and second and third toe syndactyly. Initial echocardiogram at birth was normal. Follow-up echocardiogram at 60 days of life revealed dilated cardiomyopathy with moderate left ventricular systolic dysfunction (ejection fraction was 40 to 45%), and anticongestive therapy was initiated. Thyroid testing revealed subclinical hypothyroidism with elevated thyroid-stimulating hormone of 13.0 μIU/mL (reference range is 0.3 to 5.0 μIU/mL) and normal free thyroxine by dialysis of 1.6 ng/dL (reference range is 0.8 to 2.0 ng/dL). Levothyroxine was initiated. Postnatal growth remained poor (weight z score at 3 months -4.93, length z score at 3 months -6.48), including progressive microcephaly (head circumference z score at 3 months -10.94). Genetic testing revealed novel compound heterozygous XRCC4 variants in trans: c.628A>T and c.638+3A>G. The child ultimately had cardiopulmonary arrest and died at 6 months of life. Conclusion Molecular diagnosis in MPD is key to defining the natural history, management, and prognosis for patients with these rare disorders.
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Zhang XY, Wei XH, Wang BJ, Yao J. The XRCC4rs1805377 polymorphism is not associated with the risk of cancer: An updated meta-analysis. J Int Med Res 2020; 48:300060520926364. [PMID: 32493081 PMCID: PMC7273771 DOI: 10.1177/0300060520926364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
ObjectivesA growing number of studies have reported that genes involved in the repair of DNA double-strand breaks might be cancer-susceptibility genes. The x-ray cross-complementing group 4 gene ( XRCC4) encodes a protein that functions in the repair of DNA double-strand breaks, and this meta-analysis aimed to investigate the relationship between the XRCC4 rs1805377 polymorphism and cancer occurrence.MethodsWe retrieved case–control studies that met the inclusion criteria from PubMed, Web of Science, Embase, and China National Knowledge Infrastructure databases. Associations between rs1805377 and cancer risk were evaluated by odds ratios (ORs) using a random effects model and 95% confidence intervals (CIs) as well as sensitivity and subgroup analyses.ResultsAfter inclusion criteria were met, the meta-analysis involved 24 studies that included 9,633 cancer patients and 10,544 healthy controls. No significant association was found between rs1805377 and the risk of cancer (pooled OR = 1.107; 95% CI = 0.955–1.284) in the dominant genetic model. Similarly, no significant association was observed in the subgroup analysis.ConclusionsThrough this meta-analysis, we found no association between the rs1805377 polymorphism and cancer occurrence. This may provide useful information for relevant future studies into the etiology of cancer.
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Affiliation(s)
- Xin-yuan Zhang
- School of Forensic Medicine, China Medical University, Shenyang, Liaoning Province, P. R. China
| | - Xiao-han Wei
- School of Forensic Medicine, China Medical University, Shenyang, Liaoning Province, P. R. China
| | - Bao-jie Wang
- School of Forensic Medicine, China Medical University, Shenyang, Liaoning Province, P. R. China
| | - Jun Yao
- School of Forensic Medicine, China Medical University, Shenyang, Liaoning Province, P. R. China
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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: 335] [Impact Index Per Article: 47.9] [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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Blackford AN, Jackson SP. ATM, ATR, and DNA-PK: The Trinity at the Heart of the DNA Damage Response. Mol Cell 2017; 66:801-817. [PMID: 28622525 DOI: 10.1016/j.molcel.2017.05.015] [Citation(s) in RCA: 1209] [Impact Index Per Article: 172.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 04/28/2017] [Accepted: 05/16/2017] [Indexed: 01/09/2023]
Abstract
In vertebrate cells, the DNA damage response is controlled by three related kinases: ATM, ATR, and DNA-PK. It has been 20 years since the cloning of ATR, the last of the three to be identified. During this time, our understanding of how these kinases regulate DNA repair and associated events has grown profoundly, although major questions remain unanswered. Here, we provide a historical perspective of their discovery and discuss their established functions in sensing and responding to genotoxic stress. We also highlight what is known regarding their structural similarities and common mechanisms of regulation, as well as emerging non-canonical roles and how our knowledge of ATM, ATR, and DNA-PK is being translated to benefit human health.
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Affiliation(s)
- Andrew N Blackford
- Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK; Cancer Research UK and Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK; Wellcome Trust and Cancer Research UK Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK.
| | - Stephen P Jackson
- Wellcome Trust and Cancer Research UK Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK; Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK.
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Non-homologous DNA end joining and alternative pathways to double-strand break repair. Nat Rev Mol Cell Biol 2017; 18:495-506. [PMID: 28512351 DOI: 10.1038/nrm.2017.48] [Citation(s) in RCA: 1032] [Impact Index Per Article: 147.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
DNA double-strand breaks (DSBs) are the most dangerous type of DNA damage because they can result in the loss of large chromosomal regions. In all mammalian cells, DSBs that occur throughout the cell cycle are repaired predominantly by the non-homologous DNA end joining (NHEJ) pathway. Defects in NHEJ result in sensitivity to ionizing radiation and the ablation of lymphocytes. The NHEJ pathway utilizes proteins that recognize, resect, polymerize and ligate the DNA ends in a flexible manner. This flexibility permits NHEJ to function on a wide range of DNA-end configurations, with the resulting repaired DNA junctions often containing mutations. In this Review, we discuss the most recent findings regarding the relative involvement of the different NHEJ proteins in the repair of various DNA-end configurations. We also discuss the shunting of DNA-end repair to the auxiliary pathways of alternative end joining (a-EJ) or single-strand annealing (SSA) and the relevance of these different pathways to human disease.
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