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DNA Repair and Ovarian Carcinogenesis: Impact on Risk, Prognosis and Therapy Outcome. Cancers (Basel) 2020; 12:cancers12071713. [PMID: 32605254 PMCID: PMC7408288 DOI: 10.3390/cancers12071713] [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: 05/30/2020] [Accepted: 06/24/2020] [Indexed: 12/13/2022] Open
Abstract
There is ample evidence for the essential involvement of DNA repair and DNA damage response in the onset of solid malignancies, including ovarian cancer. Indeed, high-penetrance germline mutations in DNA repair genes are important players in familial cancers: BRCA1, BRCA2 mutations or mismatch repair, and polymerase deficiency in colorectal, breast, and ovarian cancers. Recently, some molecular hallmarks (e.g., TP53, KRAS, BRAF, RAD51C/D or PTEN mutations) of ovarian carcinomas were identified. The manuscript overviews the role of DNA repair machinery in ovarian cancer, its risk, prognosis, and therapy outcome. We have attempted to expose molecular hallmarks of ovarian cancer with a focus on DNA repair system and scrutinized genetic, epigenetic, functional, and protein alterations in individual DNA repair pathways (homologous recombination, non-homologous end-joining, DNA mismatch repair, base- and nucleotide-excision repair, and direct repair). We suggest that lack of knowledge particularly in non-homologous end joining repair pathway and the interplay between DNA repair pathways needs to be confronted. The most important genes of the DNA repair system are emphasized and their targeting in ovarian cancer will deserve further attention. The function of those genes, as well as the functional status of the entire DNA repair pathways, should be investigated in detail in the near future.
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Skowron MA, Petzsch P, Hardt K, Wagner N, Beier M, Stepanow S, Drechsler M, Rieder H, Köhrer K, Niegisch G, Hoffmann MJ, Schulz WA. Distinctive mutational spectrum and karyotype disruption in long-term cisplatin-treated urothelial carcinoma cell lines. Sci Rep 2019; 9:14476. [PMID: 31597922 PMCID: PMC6785536 DOI: 10.1038/s41598-019-50891-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 09/09/2019] [Indexed: 12/12/2022] Open
Abstract
The DNA-damaging compound cisplatin is broadly employed for cancer chemotherapy. The mutagenic effects of cisplatin on cancer cell genomes are poorly studied and might even contribute to drug resistance. We have therefore analyzed mutations and chromosomal alterations in four cisplatin-resistant bladder cancer cell lines (LTTs) by whole-exome-sequencing and array-CGH. 720–7479 genes in the LTTs contained point mutations, with a characteristic mutational signature. Only 53 genes were mutated in all LTTs, including the presumed cisplatin exporter ATP7B. Chromosomal alterations were characterized by segmented deletions and gains leading to severely altered karyotypes. The few chromosomal changes shared among LTTs included gains involving the anti-apoptotic BCL2L1 gene and losses involving the NRF2 regulator KEAP1. Overall, the extent of genomic changes paralleled cisplatin treatment concentrations. In conclusion, bladder cancer cell lines selected for cisplatin-resistance contain abundant and characteristic drug-induced genomic changes. Cisplatin treatment may therefore generate novel tumor genomes during patient treatment.
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Affiliation(s)
- Margaretha A Skowron
- Department of Urology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Patrick Petzsch
- Biological and Medical Research Center (BMFZ), Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Karin Hardt
- Institute for Human Genetics, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Nicholas Wagner
- Department of Urology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Manfred Beier
- Institute for Human Genetics, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Stefanie Stepanow
- Biological and Medical Research Center (BMFZ), Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Matthias Drechsler
- Institute for Human Genetics, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Harald Rieder
- Institute for Human Genetics, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Karl Köhrer
- Biological and Medical Research Center (BMFZ), Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Günter Niegisch
- Department of Urology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Michèle J Hoffmann
- Department of Urology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Wolfgang A Schulz
- Department of Urology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
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McCormick A, Donoghue P, Dixon M, O'Sullivan R, O'Donnell RL, Murray J, Kaufmann A, Curtin NJ, Edmondson RJ. Ovarian Cancers Harbor Defects in Nonhomologous End Joining Resulting in Resistance to Rucaparib. Clin Cancer Res 2017. [PMID: 27702817 DOI: 10.1158/1078-0432.ccr-16-0564] [] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Purpose: DNA damage defects are common in ovarian cancer and can be used to stratify treatment. Although most work has focused on homologous recombination (HR), DNA double-strand breaks are repaired primarily by nonhomologous end joining (NHEJ). Defects in NHEJ have been shown to contribute to genomic instability and have been associated with the development of chemoresistance.Experimental Design: NHEJ was assessed in a panel of ovarian cancer cell lines and 47 primary ascetic-derived ovarian cancer cultures, by measuring the ability of cell extracts to end-join linearized plasmid monomers into multimers. mRNA and protein expression of components of NHEJ was determined using RT-qPCR and Western blotting. Cytotoxicities of cisplatin and the PARP inhibitor rucaparib were assessed using sulforhodamine B (SRB) assays. HR function was assessed using γH2AX/RAD51 foci assay.Results: NHEJ was defective (D) in four of six cell lines and 20 of 47 primary cultures. NHEJ function was independent of HR competence (C). NHEJD cultures were resistant to rucaparib (P = 0.0022). When HR and NHEJ functions were taken into account, only NHEJC/HRD cultures were sensitive to rucaparib (compared with NHEJC/HRC P = 0.034, NHEJD/HRC P = 0.0002, and NHEJD/HRD P = 0.0045). The DNA-PK inhibitor, NU7441, induced resistance to rucaparib (P = 0.014) and HR function recovery in a BRCA1-defective cell line.Conclusions: This study has shown that NHEJ is defective in 40% of ovarian cancers, which is independent of HR function and associated with resistance to PARP inhibitors in ex vivo primary cultures. Clin Cancer Res; 23(8); 2050-60. ©2016 AACR.
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Affiliation(s)
- Aiste McCormick
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom
| | - Peter Donoghue
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom
| | - Michelle Dixon
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom
| | - Richard O'Sullivan
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom
| | - Rachel L O'Donnell
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.,Northern Gynaecological Oncology Centre, Queen Elizabeth Hospital, Gateshead, United Kingdom
| | - James Murray
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom
| | - Angelika Kaufmann
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.,Northern Gynaecological Oncology Centre, Queen Elizabeth Hospital, Gateshead, United Kingdom
| | - Nicola J Curtin
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.
| | - Richard J Edmondson
- Faculty Institute for Cancer Studies, University of Manchester, St Mary's Hospital, Oxford Road, Manchester, United Kingdom.
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4
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McCormick A, Donoghue P, Dixon M, O'Sullivan R, O'Donnell RL, Murray J, Kaufmann A, Curtin NJ, Edmondson RJ. Ovarian Cancers Harbor Defects in Nonhomologous End Joining Resulting in Resistance to Rucaparib. Clin Cancer Res 2016; 23:2050-2060. [PMID: 27702817 DOI: 10.1158/1078-0432.ccr-16-0564] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 09/28/2016] [Accepted: 09/28/2016] [Indexed: 11/16/2022]
Abstract
Purpose: DNA damage defects are common in ovarian cancer and can be used to stratify treatment. Although most work has focused on homologous recombination (HR), DNA double-strand breaks are repaired primarily by nonhomologous end joining (NHEJ). Defects in NHEJ have been shown to contribute to genomic instability and have been associated with the development of chemoresistance.Experimental Design: NHEJ was assessed in a panel of ovarian cancer cell lines and 47 primary ascetic-derived ovarian cancer cultures, by measuring the ability of cell extracts to end-join linearized plasmid monomers into multimers. mRNA and protein expression of components of NHEJ was determined using RT-qPCR and Western blotting. Cytotoxicities of cisplatin and the PARP inhibitor rucaparib were assessed using sulforhodamine B (SRB) assays. HR function was assessed using γH2AX/RAD51 foci assay.Results: NHEJ was defective (D) in four of six cell lines and 20 of 47 primary cultures. NHEJ function was independent of HR competence (C). NHEJD cultures were resistant to rucaparib (P = 0.0022). When HR and NHEJ functions were taken into account, only NHEJC/HRD cultures were sensitive to rucaparib (compared with NHEJC/HRC P = 0.034, NHEJD/HRC P = 0.0002, and NHEJD/HRD P = 0.0045). The DNA-PK inhibitor, NU7441, induced resistance to rucaparib (P = 0.014) and HR function recovery in a BRCA1-defective cell line.Conclusions: This study has shown that NHEJ is defective in 40% of ovarian cancers, which is independent of HR function and associated with resistance to PARP inhibitors in ex vivo primary cultures. Clin Cancer Res; 23(8); 2050-60. ©2016 AACR.
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Affiliation(s)
- Aiste McCormick
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom
| | - Peter Donoghue
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom
| | - Michelle Dixon
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom
| | - Richard O'Sullivan
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom
| | - Rachel L O'Donnell
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.,Northern Gynaecological Oncology Centre, Queen Elizabeth Hospital, Gateshead, United Kingdom
| | - James Murray
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom
| | - Angelika Kaufmann
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.,Northern Gynaecological Oncology Centre, Queen Elizabeth Hospital, Gateshead, United Kingdom
| | - Nicola J Curtin
- Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.
| | - Richard J Edmondson
- Faculty Institute for Cancer Studies, University of Manchester, St Mary's Hospital, Oxford Road, Manchester, United Kingdom.
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DNA polymerases δ and λ cooperate in repairing double-strand breaks by microhomology-mediated end-joining in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2015; 112:E6907-16. [PMID: 26607450 DOI: 10.1073/pnas.1507833112] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Maintenance of genome stability is carried out by a suite of DNA repair pathways that ensure the repair of damaged DNA and faithful replication of the genome. Of particular importance are the repair pathways, which respond to DNA double-strand breaks (DSBs), and how the efficiency of repair is influenced by sequence homology. In this study, we developed a genetic assay in diploid Saccharomyces cerevisiae cells to analyze DSBs requiring microhomologies for repair, known as microhomology-mediated end-joining (MMEJ). MMEJ repair efficiency increased concomitant with microhomology length and decreased upon introduction of mismatches. The central proteins in homologous recombination (HR), Rad52 and Rad51, suppressed MMEJ in this system, suggesting a competition between HR and MMEJ for the repair of a DSB. Importantly, we found that DNA polymerase delta (Pol δ) is critical for MMEJ, independent of microhomology length and base-pairing continuity. MMEJ recombinants showed evidence that Pol δ proofreading function is active during MMEJ-mediated DSB repair. Furthermore, mutations in Pol δ and DNA polymerase 4 (Pol λ), the DNA polymerase previously implicated in MMEJ, cause a synergistic decrease in MMEJ repair. Pol λ showed faster kinetics associating with MMEJ substrates following DSB induction than Pol δ. The association of Pol δ depended on RAD1, which encodes the flap endonuclease needed to cleave MMEJ intermediates before DNA synthesis. Moreover, Pol δ recruitment was diminished in cells lacking Pol λ. These data suggest cooperative involvement of both polymerases in MMEJ.
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Differential requirement for SUB1 in chromosomal and plasmid double-strand DNA break repair. PLoS One 2013; 8:e58015. [PMID: 23554872 PMCID: PMC3595253 DOI: 10.1371/journal.pone.0058015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 01/29/2013] [Indexed: 11/19/2022] Open
Abstract
Non homologous end joining (NHEJ) is an important process that repairs double strand DNA breaks (DSBs) in eukaryotic cells. Cells defective in NHEJ are unable to join chromosomal breaks. Two different NHEJ assays are typically used to determine the efficiency of NHEJ. One requires NHEJ of linearized plasmid DNA transformed into the test organism; the other requires NHEJ of a single chromosomal break induced either by HO endonuclease or the I-SceI restriction enzyme. These two assays are generally considered equivalent and rely on the same set of NHEJ genes. PC4 is an abundant DNA binding protein that has been suggested to stimulate NHEJ. Here we tested the role of PC4's yeast homolog SUB1 in repair of DNA double strand breaks using different assays. We found SUB1 is required for NHEJ repair of DSBs in plasmid DNA, but not in chromosomal DNA. Our results suggest that these two assays, while similar are not equivalent and that repair of plasmid DNA requires additional factor(s) that are not required for NHEJ repair of chromosomal double-strand DNA breaks. Possible roles for Sub1 proteins in NHEJ of plasmid DNA are discussed.
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Boboila C, Alt FW, Schwer B. Classical and alternative end-joining pathways for repair of lymphocyte-specific and general DNA double-strand breaks. Adv Immunol 2013; 116:1-49. [PMID: 23063072 DOI: 10.1016/b978-0-12-394300-2.00001-6] [Citation(s) in RCA: 203] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Classical nonhomologous end joining (C-NHEJ) is one of the two major known pathways for the repair of DNA double-strand breaks (DSBs) in mammalian cells. Our understanding of C-NHEJ has been derived, in significant part, through studies of programmed physiologic DNA DSBs formed during V(D)J recombination in the developing immune system. Studies of immunoglobulin heavy-chain (IgH) class-switch recombination (CSR) also have revealed that there is an "alternative" end-joining process (A-EJ) that can function, relatively robustly, in the repair of DSBs in activated mature B lymphocytes. This A-EJ process has also been implicated in the formation of oncogenic translocations found in lymphoid tumors. In this review, we discuss our current understanding of C-NHEJ and A-EJ in the context of V(D)J recombination, CSR, and the formation of chromosomal translocations.
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Affiliation(s)
- Cristian Boboila
- Howard Hughes Medical Institute, Immune Disease Institute, Program in Cellular and Molecular Medicine, Children's Hospital Boston, Boston, Massachusetts, USA
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HTLV-I tax increases genetic instability by inducing DNA double strand breaks during DNA replication and switching repair to NHEJ. PLoS One 2012; 7:e42226. [PMID: 22916124 PMCID: PMC3423393 DOI: 10.1371/journal.pone.0042226] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 07/02/2012] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Appropriate responses to damaged DNA are indispensible for preserving genome stability and preventing cancer. Tumor viruses often target DNA repair machinery to achieve transformation. The Human T-cell leukemia virus type I (HTLV-I) is the only known transforming human retrovirus and the etiological agent of Adult T-cell Leukemia (ATLL). Although HTLV-I-transformed leukemic cells have numerous genetic lesions, the precise role of the viral tax gene in this process is not fully understood. RESULTS Our results show a novel function of HTLV-I oncoprotein Tax as an inducer of genomic DNA double strand breaks (DDSB) during DNA replication. We also found that Tax acts as a potent inhibitor of homologous recombination (HR) DNA repair through the activation of the NF-kB pathway. These results were confirmed using HTLV-I molecular clones expressing Tax at physiological levels in a natural context. We further found that HTLV-I- and Tax-transformed cells are not more susceptible to DNA damaging agents and repair DNA lesions at a rate similar to that of normal cells. Finally, we demonstrated that during S phase, Tax-associated DDSB are preferentially repaired using the error-prone non-homologous end joining (NHEJ) pathway. CONCLUSIONS This study provides new insights in Tax effects on DNA repair and genome instability. Although it may not be self sufficient, the creation of DNA breaks and subsequent abnormal use of the non-conservative NHEJ DNA repair during the S phase in HTLV-I-infected Tax-expressing cells may cooperate with other factors to increase genetic and genome instability and favor transformation.
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Kienzler A, Tronchère X, Devaux A, Bony S. Assessment of RTG-W1, RTL-W1, and PLHC-1 fish cell lines for genotoxicity testing of environmental pollutants by means of a Fpg-modified comet assay. Toxicol In Vitro 2012; 26:500-10. [DOI: 10.1016/j.tiv.2012.01.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 12/13/2011] [Accepted: 01/04/2012] [Indexed: 11/16/2022]
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Yasaei H, Gilham E, Pickles JC, Roberts TP, O'Donovan M, Newbold RF. Carcinogen-specific mutational and epigenetic alterations in INK4A, INK4B and p53 tumour-suppressor genes drive induced senescence bypass in normal diploid mammalian cells. Oncogene 2012; 32:171-9. [DOI: 10.1038/onc.2012.45] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Nambiar M, Raghavan SC. How does DNA break during chromosomal translocations? Nucleic Acids Res 2011; 39:5813-25. [PMID: 21498543 PMCID: PMC3152359 DOI: 10.1093/nar/gkr223] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Revised: 03/25/2011] [Accepted: 03/29/2011] [Indexed: 12/20/2022] Open
Abstract
Chromosomal translocations are one of the most common types of genetic rearrangements and are molecular signatures for many types of cancers. They are considered as primary causes for cancers, especially lymphoma and leukemia. Although many translocations have been reported in the last four decades, the mechanism by which chromosomes break during a translocation remains largely unknown. In this review, we summarize recent advances made in understanding the molecular mechanism of chromosomal translocations.
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Affiliation(s)
- Mridula Nambiar
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
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Rahal EA, Henricksen LA, Li Y, Williams RS, Tainer JA, Dixon K. ATM regulates Mre11-dependent DNA end-degradation and microhomology-mediated end joining. Cell Cycle 2010; 9:2866-77. [PMID: 20647759 DOI: 10.4161/cc.9.14.12363] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The human disorder ataxia telangiectasia (AT), which is characterized by genetic instability and neurodegeneration, results from mutation of the ataxia telangiectasia mutated (ATM) kinase. The loss of ATM leads to cell cycle checkpoint deficiencies and other DNA damage signaling defects that do not fully explain all pathologies associated with A-T including neuronal loss. In addressing this enigma, we find here that ATM suppresses DNA double-strand break (DSB) repair by microhomology-mediated end joining (MMEJ). We show that ATM repression of DNA end-degradation is dependent on its kinase activities and that Mre11 is the major nuclease behind increased DNA end-degradation and MMEJ repair in A-T. Assessment of MMEJ by an in vivo reporter assay system reveals decreased levels of MMEJ repair in Mre11-knockdown cells and in cells treated with Mre11-nuclease inhibitor mirin. Structure-based modeling of Mre11 dimer engaging DNA ends suggests the 5' ends of a bridged DSB are juxtaposed such that DNA unwinding and 3'-5' exonuclease activities may collaborate to facilitate simultaneous pairing of extended 5' termini and exonucleolytic degradation of the 3' ends in MMEJ. Together our results provide an integrated understanding of ATM and Mre11 in MMEJ: ATM has a critical regulatory function in controlling DNA end-stability and error-prone DSB repair and Mre11 nuclease plays a major role in initiating MMEJ in mammalian cells. These functions of ATM and Mre11 could be particularly important in neuronal cells, which are post-mitotic and therefore depend on mechanisms other than homologous recombination between sister chromatids to repair DSBs.
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Affiliation(s)
- Elias A Rahal
- Department of Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
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Chan SH, Yu AM, McVey M. Dual roles for DNA polymerase theta in alternative end-joining repair of double-strand breaks in Drosophila. PLoS Genet 2010; 6:e1001005. [PMID: 20617203 PMCID: PMC2895639 DOI: 10.1371/journal.pgen.1001005] [Citation(s) in RCA: 178] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Accepted: 05/27/2010] [Indexed: 11/25/2022] Open
Abstract
DNA double-strand breaks are repaired by multiple mechanisms that are roughly grouped into the categories of homology-directed repair and non-homologous end joining. End-joining repair can be further classified as either classical non-homologous end joining, which requires DNA ligase 4, or “alternative” end joining, which does not. Alternative end joining has been associated with genomic deletions and translocations, but its molecular mechanism(s) are largely uncharacterized. Here, we report that Drosophila melanogaster DNA polymerase theta (pol theta), encoded by the mus308 gene and previously implicated in DNA interstrand crosslink repair, plays a crucial role in DNA ligase 4-independent alternative end joining. In the absence of pol theta, end joining is impaired and residual repair often creates large deletions flanking the break site. Analysis of break repair junctions from flies with mus308 separation-of-function alleles suggests that pol theta promotes the use of long microhomologies during alternative end joining and increases the likelihood of complex insertion events. Our results establish pol theta as a key protein in alternative end joining in Drosophila and suggest a potential mechanistic link between alternative end joining and interstrand crosslink repair. DNA double-strand breaks, in which both strands of the DNA double helix are cut, must be recognized and accurately repaired in order to promote cell survival and prevent the accumulation of mutations. However, error-prone repair occasionally occurs, even when accurate repair is possible. We have investigated the genetic requirements of an error-prone break-repair mechanism called alternative end joining. We have previously shown that alternative end joining is frequently used in the fruit fly, Drosophila melanogaster. Here, we demonstrate that a fruit fly protein named DNA polymerase theta is a key player in this inaccurate repair mechanism. Genetic analysis suggests that polymerase theta may be important for two processes associated with alternative end joining: (1) annealing at short, complementary DNA sequences, and (2) DNA synthesis that creates small insertions at break-repair sites. In the absence of polymerase theta, a backup repair mechanism that frequently results in large chromosome deletions is revealed. Because DNA polymerase theta is highly expressed in many types of human cancers, our findings lay the groundwork for further investigations into how polymerase theta is involved in repair processes that may promote the development of cancer.
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Affiliation(s)
- Sze Ham Chan
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Amy Marie Yu
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Mitch McVey
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
- Program in Genetics, Tufts Sackler School of Graduate Biomedical Sciences, Boston, Massachusetts, United States of America
- * E-mail:
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Gandhi M, Evdokimova V, Nikiforov YE. Mechanisms of chromosomal rearrangements in solid tumors: the model of papillary thyroid carcinoma. Mol Cell Endocrinol 2010; 321:36-43. [PMID: 19766698 PMCID: PMC2849910 DOI: 10.1016/j.mce.2009.09.013] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 09/07/2009] [Accepted: 09/10/2009] [Indexed: 11/24/2022]
Abstract
Thyroid cancer, and its most common type, papillary carcinoma, frequently have chromosomal rearrangements and therefore represent a good model for the understanding of mechanisms of chromosomal rearrangements in solid tumors. Several types of rearrangement known to occur in thyroid cancer, including RET/PTC, NTRK1 and BRAF/AKAP9, are more common in radiation-associated thyroid tumors and RET/PTC can be induced experimentally by exposing human thyroid cells to ionizing radiation. In this review, the molecular mechanisms of generation of RET/PTC and other chromosomal rearrangements are discussed, with the emphasis on the role of nuclear architecture and interphase gene proximity in the generation of intrachromosomal rearrangements in thyroid cells.
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Affiliation(s)
| | | | - Yuri E. Nikiforov
- Corresponding author: Dr. Yuri Nikiforov, Department of Pathology, University of Pittsburgh, 200 Lothrop Street, PUH, Room C-606, Pittsburgh, PA 15213, Telephone: 412-802-6083, Fax: 412-802-6799,
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Alternative end-joining catalyzes robust IgH locus deletions and translocations in the combined absence of ligase 4 and Ku70. Proc Natl Acad Sci U S A 2010; 107:3034-9. [PMID: 20133803 DOI: 10.1073/pnas.0915067107] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Class switch recombination (CSR) in B lymphocytes is initiated by introduction of multiple DNA double-strand breaks (DSBs) into switch (S) regions that flank immunoglobulin heavy chain (IgH) constant region exons. CSR is completed by joining a DSB in the donor S mu to a DSB in a downstream acceptor S region (e.g., S gamma1) by end-joining. In normal cells, many CSR junctions are mediated by classical nonhomologous end-joining (C-NHEJ), which employs the Ku70/80 complex for DSB recognition and XRCC4/DNA ligase 4 for ligation. Alternative end-joining (A-EJ) mediates CSR, at reduced levels, in the absence of C-NHEJ, even in combined absence of Ku70 and ligase 4, demonstrating an A-EJ pathway totally distinct from C-NHEJ. Multiple DSBs are introduced into S mu during CSR, with some being rejoined or joined to each other to generate internal switch deletions (ISDs). In addition, S-region DSBs can be joined to other chromosomes to generate translocations, the level of which is increased by absence of a single C-NHEJ component (e.g., XRCC4). We asked whether ISD and S-region translocations occur in the complete absence of C-NHEJ (e.g., in Ku70/ligase 4 double-deficient B cells). We found, unexpectedly, that B-cell activation for CSR generates substantial ISD in both S mu and S gamma1 and that ISD in both is greatly increased by the absence of C-NHEJ. IgH chromosomal translocations to the c-myc oncogene also are augmented in the combined absence of Ku70 and ligase 4. We discuss the implications of these findings for A-EJ in normal and abnormal DSB repair.
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DNA repair by homologous recombination, but not by nonhomologous end joining, is elevated in breast cancer cells. Neoplasia 2009; 11:683-91. [PMID: 19568413 DOI: 10.1593/neo.09312] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Revised: 04/12/2009] [Accepted: 04/13/2009] [Indexed: 11/18/2022]
Abstract
Aberrant double-stranded break (DSB) repair leads to genomic instability, which is a hallmark of malignant cells. Double-stranded breaks are repaired by two pathways: homologous recombination (HR) and nonhomologous DNA end joining (NHEJ). It is not known whether these repair pathways are affected in sporadic breast tumors. Here, we examined the efficiency of HR and NHEJ repair in a panel of sporadic breast cancer cell lines and tested whether the efficiency of HR or NHEJ correlates with radioresistance. Homologous recombination and NHEJ in breast cancer cells were analyzed using in vivo fluorescent assays. Unexpectedly, our analysis revealed that the efficiency of HR is significantly elevated in breast cancer cells compared with normal mammary epithelial cells. In contrast, the efficiency of NHEJ in breast cancer cells is not different from normal cells. Overall, breast cancer cells were more sensitive to radiation than normal cells, but the levels of resistance did not correlate with either HR or NHEJ efficiency. Thus, we demonstrate that sporadic breast cancers are not associated with a deficiency in DSB repair, but rather with upregulation of the HR pathway. Our finding of elevated HR in sporadic breast cancer cell lines suggests that therapies directed against the components of HR will be highly tumor-specific.
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Chromosomal instability in bladder cancer. Arch Toxicol 2008; 82:173-82. [PMID: 18253719 DOI: 10.1007/s00204-008-0280-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Accepted: 01/09/2008] [Indexed: 01/10/2023]
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