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Kazadi D, Lim J, Rothschild G, Grinstein V, Laffleur B, Becherel O, Lavin MJ, Basu U. Effects of senataxin and RNA exosome on B-cell chromosomal integrity. Heliyon 2020; 6:e03442. [PMID: 32195383 PMCID: PMC7075999 DOI: 10.1016/j.heliyon.2020.e03442] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 01/07/2020] [Accepted: 02/13/2020] [Indexed: 11/10/2022] Open
Abstract
Loss of function of senataxin (SETX), a bona-fide RNA/DNA helicase, is associated with neuronal degeneration leading to Ataxia and Ocular Apraxia (AOA) in human patients. SETX is proposed to promote transcription termination, DNA replication, DNA repair, and to unwind deleterious RNA:DNA hybrids in the genome. In all the above-mentioned mechanisms, SETX unwinds transcription complex-associated nascent RNA which is then degraded by the RNA exosome complex. Here we have used B cells isolated from a SETX mutant mouse model and compared genomic instability and immunoglobulin heavy chain locus (IgH) class switch recombination (CSR) to evaluate aberrant and programmed genomic rearrangements, respectively. Similar to RNA exosome mutant primary B cells, SETX mutant primary B cells display genomic instability but a modest decrease in efficiency of CSR. Furthermore, knockdown of Setx mRNAs from CH12–F3 B-cell lines leads to a defect in IgA CSR and accumulation of aberrant patterns of mutations in IgH switch sequences. Given that SETX mutant mice do not recapitulate the AOA neurodegenerative phenotype, it is possible that some aspects of SETX biology are rescued by redundant helicases in mice. Overall, our study provides new insights into the role of the SETX/RNA exosome axis in suppressing genomic instability so that programmed DNA breaks are properly orchestrated.
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Affiliation(s)
- David Kazadi
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Junghyun Lim
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Gerson Rothschild
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Veronika Grinstein
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Brice Laffleur
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Olivier Becherel
- Centre for Clinical Research, University of Queensland, Brisbane, Qld, Australia
| | - Martin J Lavin
- Centre for Clinical Research, University of Queensland, Brisbane, Qld, Australia
| | - Uttiya Basu
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
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2
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Lieberman HB, Panigrahi SK, Hopkins KM, Wang L, Broustas CG. p53 and RAD9, the DNA Damage Response, and Regulation of Transcription Networks. Radiat Res 2017; 187:424-432. [PMID: 28140789 DOI: 10.1667/rr003cc.1] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The way cells respond to DNA damage is important since inefficient repair or misrepair of lesions can have deleterious consequences, including mutation, genomic instability, neurodegenerative disorders, premature aging, cancer or death. Whether damage occurs spontaneously as a byproduct of normal metabolic processes, or after exposure to exogenous agents, cells muster a coordinated, complex DNA damage response (DDR) to mitigate potential harmful effects. A variety of activities are involved to promote cell survival, and include DNA repair, DNA damage tolerance, as well as transient cell cycle arrest to provide time for repair before entry into critical cell cycle phases, an event that could be lethal if traversal occurs while damage is present. When such damage is prolonged or not repairable, senescence, apoptosis or autophagy is induced. One major level of DDR regulation occurs via the orchestrated transcriptional control of select sets of genes encoding proteins that mediate the response. p53 is a transcription factor that transactivates specific DDR downstream genes through binding DNA consensus sequences usually in or near target gene promoter regions. The profile of p53-regulated genes activated at any given time varies, and is dependent upon type of DNA damage or stress experienced, exact composition of the consensus DNA binding sequence, presence of other DNA binding proteins, as well as cell context. RAD9 is another protein critical for the response of cells to DNA damage, and can also selectively regulate gene transcription. The limited studies addressing the role of RAD9 in transcription regulation indicate that the protein transactivates at least one of its target genes, p21/waf1/cip1, by binding to DNA sequences demonstrated to be a p53 response element. NEIL1 is also regulated by RAD9 through a similar DNA sequence, though not yet directly verified as a bonafide p53 response element. These findings suggest a novel pathway whereby p53 and RAD9 control the DDR through a shared mechanism involving an overlapping network of downstream target genes. Details and unresolved questions about how these proteins coordinate or compete to execute the DDR through transcriptional reprogramming, as well as biological implications, are discussed.
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Affiliation(s)
- Howard B Lieberman
- a Center for Radiological Research, Columbia University College of Physicians and Surgeons, New York, New York 10032; and.,b Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York 10032
| | - Sunil K Panigrahi
- a Center for Radiological Research, Columbia University College of Physicians and Surgeons, New York, New York 10032; and
| | - Kevin M Hopkins
- a Center for Radiological Research, Columbia University College of Physicians and Surgeons, New York, New York 10032; and
| | - Li Wang
- a Center for Radiological Research, Columbia University College of Physicians and Surgeons, New York, New York 10032; and
| | - Constantinos G Broustas
- a Center for Radiological Research, Columbia University College of Physicians and Surgeons, New York, New York 10032; and
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3
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Iijima M, Banno K, Okawa R, Yanokura M, Iida M, Takeda T, Kunitomi-Irie H, Adachi M, Nakamura K, Umene K, Nogami Y, Masuda K, Tominaga E, Aoki D. Genome-wide analysis of gynecologic cancer: The Cancer Genome Atlas in ovarian and endometrial cancer. Oncol Lett 2017; 13:1063-1070. [PMID: 28454214 DOI: 10.3892/ol.2017.5582] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Accepted: 09/12/2016] [Indexed: 12/26/2022] Open
Abstract
Cancer typically develops due to genetic abnormalities, but a single gene abnormality cannot completely account for the onset of cancer. The Cancer Genome Atlas (CGA) project was conducted for the cross-sectional genome-wide analysis of numerous genetic abnormalities in various types of cancer. This approach has facilitated the identification of novel AT-rich interaction domain 1A gene mutations in ovarian clear cell carcinoma, frequent tumor protein 53 (TP53) gene mutations in high-grade ovarian serous carcinoma, and Kirsten rat sarcoma and B-rapidly accelerated fibrosarcoma proto-oncogene, serine/threonine kinase gene mutations in low-grade ovarian serous carcinoma. Genome-wide analysis of endometrial cancers has led to the establishment of four subgroups: Polymerase ultramutated, microsatellite instability hypermutated, genome copy-number low and genome copy-number high. These results may facilitate the improvement of the prediction of patient prognosis and therapeutic sensitivity in various types of gynecologic cancer. The enhanced use of currently available therapeutic agents and the development of novel drugs may be facilitated by the novel classification of ovarian cancer based on TP53 mutations, the efficacy of poly (ADP-ribose) polymerase inhibitors for tumors with breast cancer 1/2 mutations and the effect of phosphoinositide-3-kinase (PI3K)/mammalian target of rapamycin inhibitors for tumors with mutations in the PI3K/protein kinase B signaling pathway. Important results have been revealed by genome-wide analyses; however, the pathogenic underlying mechanisms of gynecologic cancer will require further studies and multilateral evaluation using epigenetic, transcriptomic and proteomic analyses, in addition to genomic analysis.
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Affiliation(s)
- Moito Iijima
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Kouji Banno
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Ryuichiro Okawa
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Megumi Yanokura
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Miho Iida
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Takashi Takeda
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Haruko Kunitomi-Irie
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Masataka Adachi
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Kanako Nakamura
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Kiyoko Umene
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Yuya Nogami
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Kenta Masuda
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Eiichiro Tominaga
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Daisuke Aoki
- Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo 160-8582, Japan
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Filipović J, Joksić G, Vujić D, Joksić I, Mrasek K, Weise A, Liehr T. First molecular-cytogenetic characterization of Fanconi anemia fragile sites in primary lymphocytes of FA-D2 patients in different stages of the disease. Mol Cytogenet 2016; 9:70. [PMID: 27625703 PMCID: PMC5020439 DOI: 10.1186/s13039-016-0280-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 08/26/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Fanconi anemia (FA) is a chromosomal instability syndrome characterized by increased frequency of chromosomal breakages, chromosomal radial figures and accelerated telomere shortening. In this work we performed detailed molecular-cytogenetic characterization of breakpoints in primary lymphocytes of FA-D2 patients in different stages of the disease using fluorescent in situ hybridization. RESULTS We found that chromosomal breakpoints co-localize on the molecular level with common fragile sites, whereas their distribution pattern depends on the severity of the disease. Telomere quantitative fluorescent in situ hybridization revealed that telomere fusions and radial figures, especially radials which involve telomere sequences are the consequence of critically shortened telomeres that increase with the disease progression and could be considered as a predictive parameter during the course of the disease. Sex chromosomes in FA cells are also involved in radial formation indicating that specific X chromosome regions share homology with autosomes and also could serve as repair templates in resolving DNA damage. CONCLUSIONS FA-D2 chromosomal breakpoints co-localize with common fragile sites, but their distribution pattern depends on the disease stage. Telomere fusions and radials figures which involve telomere sequences are the consequence of shortened telomeres, increase with disease progression and could be of predictive value.
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Affiliation(s)
- Jelena Filipović
- Vinca Institute of Nuclear Sciences, University of Belgrade, Mike Petrovica Alasa 12-14, Belgrade, 11001 Serbia
| | - Gordana Joksić
- Vinca Institute of Nuclear Sciences, University of Belgrade, Mike Petrovica Alasa 12-14, Belgrade, 11001 Serbia
| | - Dragana Vujić
- Mother and Child Health Care Institute of Serbia, "Dr Vukan Cupic", Radoja Dakica 6, Belgrade, 11070 Serbia
| | - Ivana Joksić
- Vinca Institute of Nuclear Sciences, University of Belgrade, Mike Petrovica Alasa 12-14, Belgrade, 11001 Serbia
| | - Kristin Mrasek
- Institute of Human Genetics, Jena University Hospital, Friedrich Schiller University, Kollegiengasse 10, Jena, D-07743 Germany
| | - Anja Weise
- Institute of Human Genetics, Jena University Hospital, Friedrich Schiller University, Kollegiengasse 10, Jena, D-07743 Germany
| | - Thomas Liehr
- Institute of Human Genetics, Jena University Hospital, Friedrich Schiller University, Kollegiengasse 10, Jena, D-07743 Germany
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5
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Lysines 3241 and 3260 of DNA-PKcs are important for genomic stability and radioresistance. Biochem Biophys Res Commun 2016; 477:235-40. [PMID: 27297111 DOI: 10.1016/j.bbrc.2016.06.048] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 06/09/2016] [Indexed: 11/22/2022]
Abstract
DNA-dependent protein kinase (DNA-PK) is a serine/threonine kinase that plays an essential role in the repair of DNA double-strand breaks (DSBs) in the non-homologous end-joining (NHEJ) pathway. The DNA-PK holoenzyme consists of a catalytic subunit (DNA-PKcs) and DNA-binding subunit (Ku70/80, Ku). Ku is a molecular sensor for double-stranded DNA and once bound to DSB ends it recruits DNA-PKcs to the DSB site. Subsequently, DNA-PKcs is activated and heavily phosphorylated, with these phosphorylations modulating DNA-PKcs. Although phosphorylation of DNA-PKcs is well studied, other post-translational modifications of DNA-PKcs are not. In this study, we aimed to determine if acetylation of DNA-PKcs regulates DNA-PKcs-dependent DSB repair. We report that DNA-PKcs is acetylated in vivo and identified two putative acetylation sites, lysine residues 3241 and 3260. Mutating these sites to block potential acetylation results in increased radiosensitive, a slight decrease in DSB repair capacity as assessed by γH2AX resolution, and increased chromosomal aberrations, especially quadriradial chromosomes. Together, our results provide evidence that acetylation potentially regulates DNA-PKcs.
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6
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Reisz JA, Bansal N, Qian J, Zhao W, Furdui CM. Effects of ionizing radiation on biological molecules--mechanisms of damage and emerging methods of detection. Antioxid Redox Signal 2014; 21:260-92. [PMID: 24382094 PMCID: PMC4060780 DOI: 10.1089/ars.2013.5489] [Citation(s) in RCA: 414] [Impact Index Per Article: 41.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 12/07/2013] [Accepted: 01/01/2014] [Indexed: 12/13/2022]
Abstract
SIGNIFICANCE The detrimental effects of ionizing radiation (IR) involve a highly orchestrated series of events that are amplified by endogenous signaling and culminating in oxidative damage to DNA, lipids, proteins, and many metabolites. Despite the global impact of IR, the molecular mechanisms underlying tissue damage reveal that many biomolecules are chemoselectively modified by IR. RECENT ADVANCES The development of high-throughput "omics" technologies for mapping DNA and protein modifications have revolutionized the study of IR effects on biological systems. Studies in cells, tissues, and biological fluids are used to identify molecular features or biomarkers of IR exposure and response and the molecular mechanisms that regulate their expression or synthesis. CRITICAL ISSUES In this review, chemical mechanisms are described for IR-induced modifications of biomolecules along with methods for their detection. Included with the detection methods are crucial experimental considerations and caveats for their use. Additional factors critical to the cellular response to radiation, including alterations in protein expression, metabolomics, and epigenetic factors, are also discussed. FUTURE DIRECTIONS Throughout the review, the synergy of combined "omics" technologies such as genomics and epigenomics, proteomics, and metabolomics is highlighted. These are anticipated to lead to new hypotheses to understand IR effects on biological systems and improve IR-based therapies.
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Affiliation(s)
- Julie A Reisz
- Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine , Winston-Salem, North Carolina
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7
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Akilzhanova AR, Nyshanbekkyzy B, Nurkina ZM, Shtephanov II, Makishev AK, Adylkhanov TA, Rakhypbekov TK, Ramanculov EM, Momynaliev KT. BRCA1 and BRCA2 Gene Mutations Screening In Sporadic Breast Cancer Patients In Kazakhstan. Cent Asian J Glob Health 2013; 2:29. [PMID: 29755871 PMCID: PMC5927761 DOI: 10.5195/cajgh.2013.29] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND A large number of distinct mutations in the BRCA1 and BRCA2 genes have been reported worldwide, but little is known regarding the role of these inherited susceptibility genes in breast cancer risk among Kazakhstan women. AIM To evaluate the role of BRCA1/2 mutations in Kazakhstan women presenting with sporadic breast cancer. METHODS We investigated the distribution and nature of polymorphisms in BRCA1 and BRCA2 entire coding regions in 156 Kazakhstan sporadic breast cancer cases and 112 age-matched controls using automatic direct sequencing. RESULTS We identified 22 distinct variants, including 16 missense mutations and 6 polymorphisms in BRCA1/2 genes. In BRCA1, 9 missense mutations and 3 synonymous polymorphisms were observed. In BRCA2, 7 missense mutations and 3 polymorphisms were detected. There was a higher prevalence of observed mutations in Caucasian breast cancer cases compared to Asian cases (p<0.05); higher frequencies of sequence variants were observed in Asian controls. No recurrent or founder mutations were observed in BRCA1/2 genes. There were no statistically significant differences in age at diagnosis, tumor histology, size of tumor, and lymph node involvement between women with breast cancer with or without the BRCA sequence alterations. CONCLUSIONS Considering the majority of breast cancer cases are sporadic, the present study will be helpful in the evaluation of the need for the genetic screening of BRCA1/2 mutations and reliable genetic counseling for Kazakhstan sporadic breast cancer patients. Evaluation of common polymorphisms and mutations and breast cancer risk in families with genetic predisposition to breast cancer is ongoing in another current investigation.
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Affiliation(s)
- Ainur R Akilzhanova
- Center for Life sciences, Nazarbayev University, Astana, Kazakhstan.,National Center for Biotechnology, Astana, Kazakhstan
| | | | - Zhannur M Nurkina
- Center for Life sciences, Nazarbayev University, Astana, Kazakhstan.,National Center for Biotechnology, Astana, Kazakhstan
| | - Ivan I Shtephanov
- State Medical University Astana, Astana Oncological Center, Astana, Kazakhstan
| | - Abay K Makishev
- State Medical University Astana, Astana Oncological Center, Astana, Kazakhstan
| | - Tasbolat A Adylkhanov
- Semey Oncological Center, Semey, Kazakhstan.,Semey State Medical University, Semey, Kazakhstan
| | - Tolebay K Rakhypbekov
- Semey Oncological Center, Semey, Kazakhstan.,Semey State Medical University, Semey, Kazakhstan
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8
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Smolle E, Taucher V, Pichler M, Petru E, Lax S, Haybaeck J. Targeting signaling pathways in epithelial ovarian cancer. Int J Mol Sci 2013; 14:9536-55. [PMID: 23644885 PMCID: PMC3676798 DOI: 10.3390/ijms14059536] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 04/13/2013] [Accepted: 04/22/2013] [Indexed: 12/16/2022] Open
Abstract
Ovarian carcinoma (OC) is the most lethal gynecological malignancy. Response to platinum-based chemotherapy is poor in some patients and, thus, current research is focusing on new therapy options. The various histological types of OC are characterized by distinctive molecular genetic alterations that are relevant for ovarian tumorigenesis. The understanding of these molecular pathways is essential for the development of novel therapeutic strategies.
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Affiliation(s)
- Elisabeth Smolle
- Institute of Pathology, Medical University Graz, Auenbruggerplatz 25, A-8036 Graz, Austria; E-Mails: (E.S.); (V.T.)
| | - Valentin Taucher
- Institute of Pathology, Medical University Graz, Auenbruggerplatz 25, A-8036 Graz, Austria; E-Mails: (E.S.); (V.T.)
| | - Martin Pichler
- Department of Internal Medicine, Division of Clinical Oncology, Medical University Graz, A-8036 Graz, Austria; E-Mail:
| | - Edgar Petru
- Department of Obstetrics and Gynecology, Medical University Graz, A-8036 Graz, Austria; E-Mail:
| | - Sigurd Lax
- Department of Pathology, General Hospital Graz West, Goestinger Straße 22, A-8020 Graz, Austria
- Authors to whom correspondence should be addressed; E-Mails: (S.L.); (J.H.); Tel.: +43-316-5466-4652 (S.L.); +43-316-385-80594 (J.H.); Fax: +43-316-5466-74652 (S.L.); +43-316-384-329 (J.H.)
| | - Johannes Haybaeck
- Institute of Pathology, Medical University Graz, Auenbruggerplatz 25, A-8036 Graz, Austria; E-Mails: (E.S.); (V.T.)
- Authors to whom correspondence should be addressed; E-Mails: (S.L.); (J.H.); Tel.: +43-316-5466-4652 (S.L.); +43-316-385-80594 (J.H.); Fax: +43-316-5466-74652 (S.L.); +43-316-384-329 (J.H.)
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9
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Jadav RS, Chanduri MVL, Sengupta S, Bhandari R. Inositol pyrophosphate synthesis by inositol hexakisphosphate kinase 1 is required for homologous recombination repair. J Biol Chem 2013; 288:3312-21. [PMID: 23255604 PMCID: PMC3561551 DOI: 10.1074/jbc.m112.396556] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 12/12/2012] [Indexed: 01/08/2023] Open
Abstract
Inositol pyrophosphates, such as diphosphoinositol pentakisphosphate (IP(7)), are water-soluble inositol phosphates that contain high energy diphosphate moieties on the inositol ring. Inositol hexakisphosphate kinase 1 (IP6K1) participates in inositol pyrophosphate synthesis, converting inositol hexakisphosphate (IP(6)) to IP(7). In the present study, we show that mouse embryonic fibroblasts (MEFs) lacking IP6K1 exhibit impaired DNA damage repair via homologous recombination (HR). IP6K1 knock-out MEFs show decreased viability and reduced recovery after induction of DNA damage by the replication stress inducer, hydroxyurea, or the radiomimetic antibiotic, neocarzinostatin. Cells lacking IP6K1 arrest after genotoxic stress, and markers associated with DNA repair are recruited to DNA damage sites, indicating that HR repair is initiated in these cells. However, repair does not proceed to completion because these markers persist as nuclear foci long after drug removal. A fraction of IP6K1-deficient MEFs continues to proliferate despite the persistence of DNA damage, rendering the cells more susceptible to chromosomal aberrations. Expression of catalytically active but not inactive IP6K1 can restore the repair process in knock-out MEFs, implying that inositol pyrophosphates are required for HR-mediated repair. Our study therefore highlights inositol pyrophosphates as novel small molecule regulators of HR signaling in mammals.
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Affiliation(s)
- Rathan S. Jadav
- From the Laboratory of Cell Signalling, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500001 and
| | - Manasa V. L. Chanduri
- From the Laboratory of Cell Signalling, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500001 and
| | - Sagar Sengupta
- the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Rashna Bhandari
- From the Laboratory of Cell Signalling, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500001 and
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10
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Schlacher K, Christ N, Siaud N, Egashira A, Wu H, Jasin M. Double-strand break repair-independent role for BRCA2 in blocking stalled replication fork degradation by MRE11. Cell 2011; 145:529-42. [PMID: 21565612 DOI: 10.1016/j.cell.2011.03.041] [Citation(s) in RCA: 945] [Impact Index Per Article: 72.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 01/27/2011] [Accepted: 03/22/2011] [Indexed: 01/11/2023]
Abstract
Breast cancer suppressor BRCA2 is critical for maintenance of genomic integrity and resistance to agents that damage DNA or collapse replication forks, presumably through homology-directed repair of double-strand breaks (HDR). Using single-molecule DNA fiber analysis, we show here that nascent replication tracts created before fork stalling with hydroxyurea are degraded in the absence of BRCA2 but are stable in wild-type cells. BRCA2 mutational analysis reveals that a conserved C-terminal site involved in stabilizing RAD51 filaments, but not in loading RAD51 onto DNA, is essential for this fork protection but dispensable for HDR. RAD51 filament disruption in wild-type cells phenocopies BRCA2 deficiency. BRCA2 prevents chromosomal aberrations on replication stalling, which are alleviated by inhibition of MRE11, the nuclease responsible for this form of fork instability. Thus, BRCA2 prevents rather than repairs nucleolytic lesions at stalled replication forks to maintain genomic integrity and hence likely suppresses tumorigenesis through this replication-specific function.
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Affiliation(s)
- Katharina Schlacher
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
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11
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Abstract
Deficiencies in DNA damage response and repair not only can result in genome instability and cancer predisposition, but also can render the cancer cells intrinsically more vulnerable to certain types of DNA damage insults. Particularly, replication stress is both a hallmark of human cancers and a common instigator for genome instability and cell death. Here, we review our work based on the genetic knockout studies on Blm and Recql5, two members of the mammalian RecQ helicase family. These studies have uncovered a unique partnership between these two helicases in the implementation of proper mitigation strategies under different circumstances to promote DNA replication and cell survival and suppress genome instability and cancer. In particular, current studies have revealed the presence of a novel Recql5/RECQL5-dependent mechanism for suppressing replication fork collapse in response to global replication fork stalling following exposure to camptothecin (CPT), a topoisomerase I inhibitor, and a potent inhibitor of DNA replication. The unique partnership between Blm and Recql5 in coping with the challenge imposed by replication stress is discussed. In addition, given that irinotecan and topotecan, two CPT derivatives, are currently used in clinic for treating human cancer patients with very promising results, the potential implication of the new findings from these studies in anticancer treatments is also discussed.
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Affiliation(s)
- Xincheng Lu
- Institute of Genomic Medicine, Wenzhou Medical College, Wenzhou 325027, China
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12
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Hu Y, Scully R, Sobhian B, Xie A, Shestakova E, Livingston DM. RAP80-directed tuning of BRCA1 homologous recombination function at ionizing radiation-induced nuclear foci. Genes Dev 2011; 25:685-700. [PMID: 21406551 PMCID: PMC3070932 DOI: 10.1101/gad.2011011] [Citation(s) in RCA: 187] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Accepted: 02/07/2011] [Indexed: 01/12/2023]
Abstract
In response to DNA double-strand breaks (DSBs), BRCA1 forms biochemically distinct complexes with certain other DNA damage response proteins. These structures, some of which are required for homologous recombination (HR)-type DSB repair, concentrate at distinct nuclear foci that demarcate sites of genome breakage. Polyubiquitin binding by one of these structures, the RAP80/BRCA1 complex, is required for efficient BRCA1 focal recruitment, but the relationship of this process to the execution of HR has been unclear. We found that this complex actively suppresses otherwise exaggerated, BRCA1-driven HR. By controlling the kinetics by which other BRCA1-interacting proteins that promote HR concentrate together with BRCA1 in nuclear foci, RAP80/BRCA1 complexes suppress excessive DSB end processing, HR-type DSB repair, and overt chromosomal instability. Since chromosomal instability emerges when BRCA1 HR function is either unbridled or absent, active tuning of BRCA1 activity, executed in nuclear foci, is important to genome integrity maintenance.
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Affiliation(s)
- Yiduo Hu
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
| | - Ralph Scully
- Department of Medicine, Harvard Medical School, Boston Massachusetts 02215, USA
- Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA
| | - Bijan Sobhian
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
| | - Anyong Xie
- Department of Medicine, Harvard Medical School, Boston Massachusetts 02215, USA
- Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA
| | - Elena Shestakova
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
| | - David M. Livingston
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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13
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Abstract
Structural changes to DNA severely affect its functions, such as replication and transcription, and play a major role in age-related diseases and cancer. A complicated and entangled network of DNA damage response (DDR) mechanisms, including multiple DNA repair pathways, damage tolerance processes, and cell-cycle checkpoints safeguard genomic integrity. Like transcription and replication, DDR is a chromatin-associated process that is generally tightly controlled in time and space. As DNA damage can occur at any time on any genomic location, a specialized spatio-temporal orchestration of this defense apparatus is required.
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14
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Abstract
The tumor suppressor, breast cancer susceptibility gene 1 (BRCA1), plays an integral role in the maintenance of genome stability and, in particular, the cellular response to DNA damage. Here, the emerging role of BRCA1 in nonhomologous end-joining-mediated DNA repair following DNA damage will be reviewed, as well as the activation of apoptotic pathways. The control of these functions via DNA damage-induced BRCA1 shuttling will also be discussed, in particular BRCA1 shuttling induced by erlotinib and irradiation. Finally, the potential targeting of BRCA1 shuttling as a novel strategy to sensitize cells to DNA damage will be entertained.
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Affiliation(s)
- Eddy S Yang
- Department of Radiation Oncology, Vanderbilt Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232-5671, USA
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15
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Hinz JM. Role of homologous recombination in DNA interstrand crosslink repair. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2010; 51:582-603. [PMID: 20658649 DOI: 10.1002/em.20577] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Homologous recombination repair (HRR) encompasses mechanisms that employ homologous DNA sequences as templates for repair or tolerance of a wide range of DNA lesions that inhibit DNA replication in S phase. Arguably the most imposing of these DNA lesions is that of the interstrand crosslink (ICL), consisting of a covalently attached chemical bridge between opposing DNA strands. ICL repair requires the coordinated activities of HRR and a number of proteins from other DNA repair and damage response systems, including nucleotide excision repair, base excision repair, mismatch repair, and translesion DNA synthesis (TLS). Interestingly, different organisms favor alternative methods of HRR in the ICL repair process. E. coli perform ICL repair using a homology-driven damage bypass mechanism analogous to daughter strand gap repair. Eukaryotes from yeast to humans initiate ICL repair primarily during DNA replication, relying on HRR activity to restart broken replication forks associated with double-strand break intermediates induced by nucleolytic activities of other excision repair factors. Higher eukaryotes also employ several additional factors, including members of the Fanconi anemia damage-response network, which further promote replication-associated ICL repair through the activation and coordination of various DNA excision repair, TLS, and HRR proteins. This review focuses on the proteins and general mechanisms of HRR associated with ICL repair in different model organisms.
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Affiliation(s)
- John M Hinz
- School of Molecular Biosciences, Washington State University, Pullman, Washington, USA.
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16
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Abstract
DNA chromosomal DSBs (double-strand breaks) are potentially hazardous DNA lesions, and their accurate repair is essential for the successful maintenance and propagation of genetic information. Two major pathways have evolved to repair DSBs: HR (homologous recombination) and NHEJ (non-homologous end-joining). Depending on the context in which the break is encountered, HR and NHEJ may either compete or co-operate to fix DSBs in eukaryotic cells. Defects in either pathway are strongly associated with human disease, including immunodeficiency and cancer predisposition. Here we review the current knowledge of how NHEJ and HR are controlled in somatic mammalian cells, and discuss the role of the chromatin context in regulating each pathway. We also review evidence for both co-operation and competition between the two pathways.
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17
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Ghafari F, Pelengaris S, Walters E, Hartshorne G. Influence of p53 and genetic background on prenatal oogenesis and oocyte attrition in mice. Hum Reprod 2009; 24:1460-72. [DOI: 10.1093/humrep/dep022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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Mohamad HB, Apffelstaedt JP. Counseling for male BRCA mutation carriers: a review. Breast 2008; 17:441-50. [PMID: 18657973 DOI: 10.1016/j.breast.2008.05.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2008] [Accepted: 05/01/2008] [Indexed: 12/24/2022] Open
Abstract
BRCA mutations in women confer a high risk for breast and ovarian cancers. The risks to male carriers are poorly understood and risk management strategies undescribed. This review summarizes current evidence and gives recommendations for counseling male BRCA mutation carriers. Reported risks for breast, prostate, pancreatic, gastric and hematologic cancers are higher in male BRCA mutation carriers vs non-carriers. Especially in male BRCA2 mutation carriers under age 65 prostate and pancreatic cancer risks are increased. The risk increase for primary cancers of organs like the liver, bone and brain is difficult to assess as these organs are common sites for metastases. Reports on colorectal cancer and melanoma risks are inconclusive. On the current limited evidence available, male BRCA mutation carriers should be regarded as at high risk for breast, prostate, gastric, pancreatic and colorectal cancers; surveillance by appropriate investigations should start at age 40 years.
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Affiliation(s)
- Hussain B Mohamad
- Breast Clinic, Department of Surgery, University of Stellenbosch, Tygerberg, Cape Town, South Africa.
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19
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Mojas N, Lopes M, Jiricny J. Mismatch repair-dependent processing of methylation damage gives rise to persistent single-stranded gaps in newly replicated DNA. Genes Dev 2008; 21:3342-55. [PMID: 18079180 DOI: 10.1101/gad.455407] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
O(6)-Methylguanine ((Me)G) is a highly cytotoxic DNA modification generated by S(N)1-type methylating agents. Despite numerous studies implicating DNA replication, mismatch repair (MMR), and homologous recombination (HR) in (Me)G toxicity, its mode of action has remained elusive. We studied the molecular transactions in the DNA of yeast and mammalian cells treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Although replication fork progression was unaffected in the first cell cycle after treatment, electron microscopic analysis revealed an accumulation of (Me)G- and MMR-dependent single-stranded DNA (ssDNA) gaps in newly replicated DNA. Progression into the second cell cycle required HR, while the following G(2) arrest required the continued presence of (Me)G. Yeast cells overcame this block, while mammalian cells generally failed to recover, and those that did contained multiple sister chromatid exchanges. Notably, the arrest could be abolished by removal of (Me)G after the first S phase. These new data provide compelling support for the hypothesis that MMR attempts to correct (Me)G/C or (Me)G/T mispairs arising during replication. Due to the persistence of (Me)G in the exposed template strand, repair synthesis cannot take place, which leaves single-stranded gaps behind the replication fork. During the subsequent S phase, these gaps cause replication fork collapse and elicit recombination and cell cycle arrest.
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Affiliation(s)
- Nina Mojas
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
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20
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Martin RW, Orelli BJ, Yamazoe M, Minn AJ, Takeda S, Bishop DK. RAD51 up-regulation bypasses BRCA1 function and is a common feature of BRCA1-deficient breast tumors. Cancer Res 2007; 67:9658-65. [PMID: 17942895 DOI: 10.1158/0008-5472.can-07-0290] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The breast cancer susceptibility gene BRCA1 encodes a large protein thought to contribute to a variety of cellular processes, although the critical determinants of BRCA1-deficient tumorigenesis remain unclear. Given that BRCA1 is required for cell proliferation, suppressor mutations are believed to modify BRCA1 phenotypes and contribute to the etiology of BRCA1-deficient tumors. Here, we show that overexpression of the homologous recombinase RAD51 in a DT40 BRCA1Delta/Delta mutant rescues defects in proliferation, DNA damage survival, and homologous recombination (HR). In addition, epistasis analysis with BRCA1 and the DNA end-joining factor KU70 indicates that these factors operate independently of one another to repair double-strand breaks. Consistent with this genetic finding, cell synchronization studies show that the ability of BRCA1 to promote radioresistance is restricted to the late S and G2 phases of the cell cycle, as predicted for genes whose function is specific to homology-mediated repair rather than nonhomologous end-joining. Notably, retrospective analyses of microarray expression data reveal elevated expression of RAD51 and two of its late-acting cofactors, RAD54 and RAD51AP1, in BRCA1-deficient versus sporadic breast tumors. Taken together, our results indicate that up-regulation of HR provides a permissive genetic context for cells lacking BRCA1 function by circumventing its requirement in RAD51 subnuclear assembly. Furthermore, the data support a model in which enhanced HR activity contributes to the etiology of BRCA1-deficient tumors.
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Affiliation(s)
- Richard W Martin
- Department of Radiation, Ludwig Center for Metastasis Research, University of Chicago, Chicago, Illinois 60637, USA
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21
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Nagaraju G, Scully R. Minding the gap: the underground functions of BRCA1 and BRCA2 at stalled replication forks. DNA Repair (Amst) 2007; 6:1018-31. [PMID: 17379580 PMCID: PMC2989184 DOI: 10.1016/j.dnarep.2007.02.020] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The hereditary breast and ovarian cancer predisposition genes, BRCA1 and BRCA2, participate in the repair of DNA double strand breaks by homologous recombination. Circumstantial evidence implicates these genes in recombinational responses to DNA polymerase stalling during the S phase of the cell cycle. These responses play a key role in preventing genomic instability and cancer. Here, we review the current literature implicating the BRCA pathway in HR at stalled replication forks and explore the hypothesis that BRCA1 and BRCA2 participate in the recombinational resolution of single stranded DNA lesions termed "daughter strand gaps", generated during replication across a damaged DNA template.
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Affiliation(s)
| | - Ralph Scully
- Corresponding author. Tel.: +1 617 667 4252; fax: +1 617 667 0980. (R. Scully)
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22
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23
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Cefle K, Ucur A, Guney N, Ozturk S, Palanduz S, Tas F, Asoglu O, Bayrak A, Muslumanoglu M, Aydiner A. Increased sister chromatid exchange frequency in young women with breast cancer and in their first-degree relatives. ACTA ACUST UNITED AC 2006; 171:65-7. [PMID: 17074593 DOI: 10.1016/j.cancergencyto.2006.06.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2006] [Revised: 06/05/2006] [Accepted: 06/14/2006] [Indexed: 11/27/2022]
Abstract
The well-known increased risk of breast cancer (BC) in first-degree relatives of patients with BC has been related to shared genetic factors including defective DNA repair, with loss of genomic integrity. On the other hand, it can be hypothesized that early-onset breast cancer is also associated with overburden of heritable factors leading to increased DNA injury. In this respect, we analyzed sister chromatid exchange frequency (SCE) in 20 women with breast cancer (all < or =40 years old), in their first-degree female relatives, and in 20 age-matched healthy females without a personal or family history of cancer. SCE was significantly increased (P < 0.05) in patients (7.17 +/- 1.81 per metaphase) and in their first-degree relatives (6.44 +/- 0.98), compared with controls (5.85 +/- 0.72). There was no difference in SCE frequency between patients and their first-degree relatives. We suggest that the increased SCE in patients reflects a genomic instability that may be operative in carcinogenesis. Further, genomic instability is shared also by first-degree relatives, although none of them had a history of breast cancer at the time of the study.
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Affiliation(s)
- Kivanc Cefle
- Division of Medical Genetics, Department of Internal Medicine, Istanbul Medical Faculty, Istanbul University, Istanbul, Turkey.
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24
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Saxena S, Chakraborty A, Kaushal M, Kotwal S, Bhatanager D, Mohil RS, Chintamani C, Aggarwal AK, Sharma VK, Sharma PC, Lenoir G, Goldgar DE, Szabo CI. Contribution of germline BRCA1 and BRCA2 sequence alterations to breast cancer in Northern India. BMC MEDICAL GENETICS 2006; 7:75. [PMID: 17018160 PMCID: PMC1617095 DOI: 10.1186/1471-2350-7-75] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Accepted: 10/04/2006] [Indexed: 12/24/2022]
Abstract
Background A large number of distinct mutations in the BRCA1 and BRCA2 genes have been reported worldwide, but little is known regarding the role of these inherited susceptibility genes in breast cancer risk among Indian women. We investigated the distribution and the nature of BRCA1 and BRCA2 germline mutations and polymorphisms in a cohort of 204 Indian breast cancer patients and 140 age-matched controls. Method Cases were selected with regard to early onset disease (≤40 years) and family history of breast and ovarian cancer. Two hundred four breast cancer cases along with 140 age-matched controls were analyzed for mutations. All coding regions and exon-intron boundaries of the BRCA1 and BRCA2 genes were screened by heteroduplex analysis followed by direct sequencing of detected variants. Results In total, 18 genetic alterations were identified. Three deleterious frame-shift mutations (185delAG in exon 2; 4184del4 and 3596del4 in exon 11) were identified in BRCA1, along with one missense mutation (K1667R), one 5'UTR alteration (22C>G), three intronic variants (IVS10-12delG, IVS13+2T>C, IVS7+38T>C) and one silent substitution (5154C>T). Similarly three pathogenic protein-truncating mutations (6376insAA in exon 11, 8576insC in exon19, and 9999delA in exon 27) along with one missense mutation (A2951T), four intronic alterations (IVS2+90T>A, IVS7+75A>T, IVS8+56C>T, IVS25+58insG) and one silent substitution (1593A>G) were identified in BRCA2. Four previously reported polymorphisms (K1183R, S1613G, and M1652I in BRCA1, and 7470A>G in BRCA2) were detected in both controls and breast cancer patients. Rare BRCA1/2 sequence alterations were observed in 15 out of 105 (14.2%) early-onset cases without family history and 11.7% (4/34) breast cancer cases with family history. Of these, six were pathogenic protein truncating mutations. In addition, several variants of uncertain clinical significance were identified. Among these are two missense variants, one alteration of a consensus splice donor sequence, and a variant that potentially disrupts translational initiation. Conclusion BRCA1 and BRCA2 mutations appear to account for a lower proportion of breast cancer patients at increased risk of harboring such mutations in Northern India (6/204, 2.9%) than has been reported in other populations. However, given the limited extent of reported family history among these patients, the observed mutation frequency is not dissimilar from that reported in other cohorts of early onset breast cancer patients. Several of the identified mutations are unique and novel to Indian patients.
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Affiliation(s)
- Sunita Saxena
- Institute of Pathology, Safdarjang Hospital Campus, New Delhi, India
| | | | - Mishi Kaushal
- Institute of Pathology, Safdarjang Hospital Campus, New Delhi, India
| | | | | | | | | | - Anil K Aggarwal
- Department Of Pathology, L.L.R.M. Medical College, Meerut, India
| | - Veena K Sharma
- Department Of Pathology, L.L.R.M. Medical College, Meerut, India
| | - Prakash C Sharma
- Guru Govind Singh Indraprastha University, Kashmiri Gate, Delhi, India
| | | | - David E Goldgar
- Unit of Genetic Epidemiology, International Agency for Research on Cancer, Lyon, France
| | - Csilla I Szabo
- Unit of Genetic Epidemiology, International Agency for Research on Cancer, Lyon, France
- Laboratory Medicine and Experimental Pathology, MayoClinic, Rochester, MN, USA
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25
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Youds JL, O'Neil NJ, Rose AM. Homologous recombination is required for genome stability in the absence of DOG-1 in Caenorhabditis elegans. Genetics 2006; 173:697-708. [PMID: 16547095 PMCID: PMC1526509 DOI: 10.1534/genetics.106.056879] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In C. elegans, DOG-1 prevents deletions that initiate in polyG/polyC tracts (G/C tracts), most likely by unwinding secondary structures that can form in G/C tracts during lagging-strand DNA synthesis. We have used the dog-1 mutant to assay the in vivo contribution of various repair genes to the maintenance of G/C tracts. Here we show that DOG-1 and the BLM ortholog, HIM-6, act synergistically during replication; simultaneous loss of function of both genes results in replicative stress and an increase in the formation of small deletions that initiate in G/C tracts. Similarly, we demonstrate that the C. elegans orthologs of the homologous recombination repair genes BARD1, RAD51, and XPF and the trans-lesion synthesis polymerases poleta and polkappa contribute to the prevention of deletions in dog-1 mutants. Finally, we provide evidence that the small deletions generated in the dog-1 background are not formed through homologous recombination, nucleotide excision repair, or nonhomologous end-joining mechanisms, but appear to result from a mutagenic repair mechanism acting at G/C tracts. Our data support the hypothesis that absence of DOG-1 leads to replication fork stalling that can be repaired by deletion-free or deletion-prone mechanisms.
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Affiliation(s)
- Jillian L Youds
- Department of Medical Genetics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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26
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Chen JH, Ozanne SE, Hales CN. Heterogeneity in premature senescence by oxidative stress correlates with differential DNA damage during the cell cycle. DNA Repair (Amst) 2006; 4:1140-8. [PMID: 16006199 DOI: 10.1016/j.dnarep.2005.06.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2005] [Revised: 05/31/2005] [Accepted: 06/02/2005] [Indexed: 11/23/2022]
Abstract
The development of cellular senescence both by replication and by oxidative stress is not homogenous in cultured primary human fibroblasts. To investigate whether this is due to the heterogeneity in the susceptibility of DNA in different phases of the cell cycle, we subjected synchronised cells to oxidative stress and examined the extent of DNA damage and its long-term effects on the induction of cellular senescence. Here, we first show marked heterogeneity in DNA damage as detected by markers of double strand breaks caused by oxidative stress in an asynchronous human fibroblast culture. Cell cycle synchronization followed by oxidative stress demonstrated that DNA in S-phase is most susceptible to oxidative stress whereas DNA in the quiescent phase is most resistant. DNA repair is an ongoing process after sensing DNA damage; reparable DNA damage is repaired even in cells that contain persistent DNA damage. The extent of persistent DNA damage is tightly correlated with permanent cessation of DNA replication and SA-beta-gal activity. Oxidative stress encountered by cells in S-phase resulted in more persistent DNA damage, more permanent cell cycle arrest and the induction of premature senescence.
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Affiliation(s)
- Jian-Hua Chen
- Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital Level 4, Hills Road, Cambridge CB2 2QR, UK.
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27
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Zinkel SS, Hurov KE, Ong C, Abtahi FM, Gross A, Korsmeyer SJ. A Role for Proapoptotic BID in the DNA-Damage Response. Cell 2005; 122:579-91. [PMID: 16122425 DOI: 10.1016/j.cell.2005.06.022] [Citation(s) in RCA: 181] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2004] [Revised: 05/12/2005] [Accepted: 06/13/2005] [Indexed: 01/26/2023]
Abstract
The BCL-2 family of apoptotic proteins encompasses key regulators proximal to irreversible cell damage. The BH3-only members of this family act as sentinels, interconnecting specific death signals to the core apoptotic pathway. Our previous data demonstrated a role for BH3-only BID in maintaining myeloid homeostasis and suppressing leukemogenesis. In the absence of Bid, mice accumulate chromosomal aberrations and develop a fatal myeloproliferative disorder resembling chronic myelomonocytic leukemia. Here, we describe a role for BID in preserving genomic integrity that places BID at an early point in the path to determine the fate of a cell. We show that BID plays an unexpected role in the intra-S phase checkpoint downstream of DNA damage distinct from its proapoptotic function. We further demonstrate that this role is mediated through BID phosphorylation by the DNA-damage kinase ATM. These results establish a link between proapoptotic Bid and the DNA-damage response.
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MESH Headings
- Animals
- Apoptosis/drug effects
- Apoptosis/genetics
- Ataxia Telangiectasia Mutated Proteins
- BH3 Interacting Domain Death Agonist Protein
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cell Cycle Proteins/genetics
- Cell Cycle Proteins/metabolism
- Cell Line, Transformed
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Neoplastic/metabolism
- DNA Damage/drug effects
- DNA Damage/genetics
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Female
- Genes, cdc/drug effects
- Genes, cdc/physiology
- Genomic Instability/genetics
- Leukemia, Myelomonocytic, Chronic/genetics
- Leukemia, Myelomonocytic, Chronic/metabolism
- Male
- Mice
- Mice, Knockout
- Mutagens/pharmacology
- Myeloid Progenitor Cells/metabolism
- NIH 3T3 Cells
- Phosphorylation
- Protein Serine-Threonine Kinases/genetics
- Protein Serine-Threonine Kinases/metabolism
- Protein Structure, Tertiary/genetics
- S Phase/genetics
- Tumor Suppressor Proteins/genetics
- Tumor Suppressor Proteins/metabolism
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Affiliation(s)
- Sandra S Zinkel
- Howard Hughes Medical Institute, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
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28
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Abaji C, Cousineau I, Belmaaza A. BRCA2 regulates homologous recombination in response to DNA damage: implications for genome stability and carcinogenesis. Cancer Res 2005; 65:4117-25. [PMID: 15899802 DOI: 10.1158/0008-5472.can-04-3071] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BRCA2 has been implicated in the maintenance of genome stability and RAD51-mediated homologous recombination repair of chromosomal double-strand breaks (DSBs), but its role in these processes is unclear. To gain more insight into its role in homologous recombination, we expressed wild-type BRCA2 in the well-characterized BRCA2-deficient human cell line CAPAN-1 containing, as homologous recombination substrates, either direct or inverted repeats of two inactive marker genes. Whereas direct repeats monitor a mixture of RAD51-dependent and RAD51-independent homologous recombination events, inverted repeats distinguish between these events by reporting RAD51-dependent homologous recombination, gene conversion, and crossover events only. At either repeats, BRCA2 decreases the rate and frequency of spontaneous homologous recombination, but following chromosomal DSBs, BRCA2 increases the frequency of homologous recombination. At direct repeats, BRCA2 suppresses both spontaneous gene conversion and deletions, which can arise either from crossover or RAD51-independent sister chromatid replication slippage (SCRS), but following chromosomal DSBs, BRCA2 highly promotes gene conversion with little effect on deletions. At inverted repeats, spontaneous or DSB-induced crossover events were scarce and BRCA2 does not suppress their formation. From these results, we conclude that (i) BRCA2 regulates RAD51 recombination in response to the type of DNA damage and (ii) BRCA2 suppresses SCRS, suggesting a role for BRCA2 in sister chromatids cohesion and/or alignment. Loss of such control in response to estrogen-induced DNA damage after BRCA2 inactivation may be a key initial event triggering genome instability and carcinogenesis.
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Affiliation(s)
- Christine Abaji
- Department of Biochemistry, Centre de recherche, Centre hospitalier de l'université de Montréal-Hôpital Notre-Dame, Institut du Cancer de Montréal, Université de Montréal, Montréal, Québec, Canada
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29
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Choudhury AD, Xu H, Modi AP, Zhang W, Ludwig T, Baer R. Hyperphosphorylation of the BARD1 Tumor Suppressor in Mitotic Cells. J Biol Chem 2005; 280:24669-79. [PMID: 15855157 DOI: 10.1074/jbc.m502446200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Although the BRCA1 tumor suppressor has been implicated in a number of cellular processes, it plays an especially important role in the DNA damage response as a regulator of cell cycle checkpoints and DNA repair pathways. In vivo, BRCA1 exists as a heterodimer with the BARD1 protein, and many of its biological functions are mediated by the BRCA1-BARD1 complex. Here, we show that BARD1 is phosphorylated in a cell cycle-dependent manner and that the hyperphosphorylated forms of BARD1 predominate during M phase. By mobility shift analysis and mass spectrometry, we have identified seven sites of mitotic phosphorylation within BARD1. All sites exist within either an SP or TP sequence, and two sites resemble the consensus motif recognized by cyclin-dependent kinases. To examine the functional consequences of BARD1 phosphorylation, we used a gene targeting knock-in approach to generate isogenic cell lines that express either wild-type or mutant forms of the BARD1 polypeptide. Analysis of these lines in clonogenic survival assays revealed that cells bearing phosphorylation site mutations are hypersensitive to mitomycin C, a genotoxic agent that induces interstrand DNA cross-links. These results implicate BARD1 phosphorylation in the cellular response to DNA damage.
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Affiliation(s)
- Atish D Choudhury
- Institute for Cancer Genetics and the Departments of Pathology and Anatomy and Cell Biology, Columbia University Medical Center, New York, New York 10032, USA
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30
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Limoli CL, Giedzinski E, Cleaver JE. Alternative recombination pathways in UV-irradiated XP variant cells. Oncogene 2005; 24:3708-14. [PMID: 15750628 DOI: 10.1038/sj.onc.1208515] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2004] [Revised: 01/06/2005] [Accepted: 01/06/2005] [Indexed: 01/11/2023]
Abstract
XP variant (XP-V) cells lack the damage-specific polymerase eta and exhibit prolonged replication arrest after UV irradiation due to impaired bypass of UV photoproducts. To analyse the outcome of the arrested replication forks, homologous recombination (HR, Rad51 events) and fork breakage (Rad50 events) were assayed by immunofluorescent detection of foci-positive cells. Within 1 h of irradiation, XP-V cells showed more Rad51-positive cells than normal cells, while neither cell type showed an increase in Rad50 foci. Beyond 1 h, the frequency of Rad51-positive cells reached similar levels in both cell types, then declined at higher UV doses. At these later times, Rad50-positive cells increased with dose and to a greater extent in XP-V cells. Few cells were simultaneously positive for both sets of foci, suggesting a mutually exclusive recruitment of recombination proteins, or that these pathways operate at different stages during S phase. Analysis of cells containing a vector of tandemly arranged enhanced green fluorescent protein genes also showed that UV-induced HR was higher in XP-V cells. These results suggest that cells make an early commitment to HR, and that at later times a subset of arrested forks degrade into double-strand breaks, two alternative pathways that are greater in XP-V cells.
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Affiliation(s)
- Charles L Limoli
- 1Radiation Oncology Research Laboratory, Department of Radiation Oncology, University of California, 1855 Folsom St., MCB-200, San Francisco, CA 94103-0806, USA
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31
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Puget N, Knowlton M, Scully R. Molecular analysis of sister chromatid recombination in mammalian cells. DNA Repair (Amst) 2005; 4:149-61. [PMID: 15590323 PMCID: PMC2967438 DOI: 10.1016/j.dnarep.2004.08.010] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2004] [Indexed: 01/19/2023]
Abstract
Sister chromatid recombination (SCR) is a potentially error-free pathway for the repair of double-strand breaks arising during replication and is thought to be important for the prevention of genomic instability and cancer. Analysis of sister chromatid recombination at a molecular level has been limited by the difficulty of selecting specifically for these events. To overcome this, we have developed a novel "nested intron" reporter that allows the positive selection in mammalian cells of "long tract" gene conversion events arising between sister chromatids. We show that these events arise spontaneously in cycling cells and are strongly induced by a site-specific double-strand break (DSB) caused by the restriction endonuclease, I-SceI. Notably, some I-SceI-induced sister chromatid recombination events entailed multiple rounds of gene amplification within the reporter, with the generation of a concatemer of amplified gene segments. Thus, there is an intimate relationship between sister chromatid recombination control and certain types of gene amplification. Dysregulated sister chromatid recombination may contribute to cancer progression, in part, by promoting gene amplification.
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Affiliation(s)
| | | | - Ralph Scully
- Corresponding author. Tel.: +1 617 667 4252; fax: +1 617 667 0980. (R. Scully)
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Abstract
DNA base excision repair (BER) is the main pathway for repair of endogenous damage in human cells. It was expected that a number of degenerative diseases could derive from BER defects. On the contrary, the link between BER defects and human pathology is elusive and the literature is full of conflicting results. The fact that most studies have investigated DNA variations but not their functional consequences has probably contributed to this confusing picture. From a functional point of view, it is likely that gross BER defects are simply not compatible with life and only limited reductions can be observed. Notwithstanding those limits, the pathological consequences of partial BER defects might be widespread and significant at the population level. This starts to emerge in particular for colorectal and lung cancer.
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Affiliation(s)
- Guido Frosina
- Department of Aetiology and Epidemiology, Mutagenesis Laboratory, Istituto Nazionale Ricerca Cancro, Largo Rosanna Benzi n. 10, 16132 Genova, Italy.
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33
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Kim MK, Zitzmann S, Westermann F, Arnold K, Brouwers S, Schwab M, Savelyeva L. Increased rates of spontaneous sister chromatid exchange in lymphocytes of BRCA2+/- carriers of familial breast cancer clusters. Cancer Lett 2004; 210:85-94. [PMID: 15172125 DOI: 10.1016/j.canlet.2004.01.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2004] [Accepted: 01/15/2004] [Indexed: 12/20/2022]
Abstract
Heterozygous carriers of germ-line mutations of the BRCA2 breast cancer susceptibility gene are predisposed to breast, ovarian, pancreatic and other cancers. The BRCA2 protein is implicated in the maintenance of chromosome stability through its essential function in double-strand DNA repair and recombination. Our previous studies had revealed multiple intrachromosomal rearrangements, duplications, inversions and deletions on 9p23-24 in lymphocytes and fibroblasts of BRCA2+/- members from independently ascertained familial breast cancer clusters. In pursuit of evaluating if there is a subtle genomic instability in BRCA2+/- individuals, we have determined frequencies of spontaneous sister chromatid exchanges (SCEs) in BRCA2 wild-types and BRCA2 mutation carriers of two familial breast cancer clusters. Here, we demonstrate an average increase of 65% of spontaneous SCEs in BRCA2+/- versus BRCA2+/+ family members. In one cluster, the number of metaphases with multiple SCEs was 5-times higher in BRCA2+/- compared to wild-type members, while in the second cluster BRCA2+/- members had 8.9% of metaphases with multiple SCEs compared to a level below detection in BRCA2 wild types. To investigate the correlation between SCE and genomic instability in 9p, we performed fluorescence detection of SCEs and FISH analysis with 9p probes. The frequency of SCE in 9p of BRCA2 mutation carriers was 3-4 fold (P = 0.005) higher compared to BRCA2 wild-types. Collectively, the increased rates of SCE in BRCA2 heterozygous mutation carriers indicate a BRCA2 haploinsufficiency, which might be an important factor for the accumulation of structural chromosomal alterations with the consequence of damage in as yet unidentified genes.
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Affiliation(s)
- Min-Kyoung Kim
- Deutsches Krebsforschungszentrum, Abteilung Tumorgenetik B030, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
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34
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Herbig U, Jobling WA, Chen BPC, Chen DJ, Sedivy JM. Telomere shortening triggers senescence of human cells through a pathway involving ATM, p53, and p21(CIP1), but not p16(INK4a). Mol Cell 2004; 14:501-13. [PMID: 15149599 DOI: 10.1016/s1097-2765(04)00256-4] [Citation(s) in RCA: 916] [Impact Index Per Article: 45.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Revised: 03/29/2004] [Accepted: 03/30/2004] [Indexed: 11/16/2022]
Abstract
Cellular senescence can be triggered by telomere shortening as well as a variety of stresses and signaling imbalances. We used multiparameter single-cell detection methods to investigate upstream signaling pathways and ensuing cell cycle checkpoint responses in human fibroblasts. Telomeric foci containing multiple DNA damage response factors were assembled in a subset of senescent cells and signaled through ATM to p53, upregulating p21 and causing G1 phase arrest. Inhibition of ATM expression or activity resulted in cell cycle reentry, indicating that stable arrest requires continuous signaling. ATR kinase appears to play a minor role in normal cells but in the absence of ATM elicited a delayed G2 phase arrest. These pathways do not affect expression of p16, which was upregulated in a telomere- and DNA damage-independent manner in a subset of cells. Distinct senescence programs can thus progress in parallel, resulting in mosaic cultures as well as individual cells responding to multiple signals.
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Affiliation(s)
- Utz Herbig
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
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35
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Feng Z, Kachnic L, Zhang J, Powell SN, Xia F. DNA damage induces p53-dependent BRCA1 nuclear export. J Biol Chem 2004; 279:28574-84. [PMID: 15087457 DOI: 10.1074/jbc.m404137200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The tumor suppressor gene BRCA1 plays an important role in the response to DNA damage. BRCA1 function is regulated by a variety of mechanisms including transcriptional control, phosphorylation, and protein-protein interactions. Recent studies have shown that BRCA1 is a nuclear-cytoplasmic shuttle protein. Its subcellular localization is controlled by a nuclear localization signal-mediated nuclear import via the importin receptor pathway and a nuclear export signal-facilitated nuclear export through a CRM1-dependent pathway. Using the human breast cancer cell line, MCF7, the subcellular distribution of BRCA1 was assessed by immunohistochemical staining and Western blotting analyses of fractionated subcellullar extracts. Ionizing radiation stimulated BRCA1 nuclear export in a dose-dependent manner. This DNA damage-induced BRCA1 nuclear export utilized a CRM1-dependent mechanism and also required wild-type p53, whose function was abrogated by the E6 protein in MCF7 cells. In addition, the dependence on p53 was confirmed using a second cell type operating a tetracycline-inducible system. The effect of ionizing radiation on BRCA1 export was observed in every phase of the cell cycle, although BRCA1 localization did vary between the G(1), S, and G(2)/M phases. These results imply that, in addition to ATM-, ATR-, and Chk2-dependent phosphorylations, cytoplasmic relocalization of BRCA1 protein is a mechanism whereby BRCA1 function is regulated in response to DNA damage.
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Affiliation(s)
- Zhihui Feng
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
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36
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Abstract
Hereditary predisposition to breast and ovarian cancer is determined in large part by loss-of-function mutations in one of two genes, BRCA1 and BRCA2 . Early discoveries that the two genes function in the control of homologous recombination and the prevention of genomic instability have been strongly supported by subsequent work. Our aim here is to highlight new advances in the study of BRCA1 and BRCA2 , and to place these advances in the context of existing knowledge.
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Affiliation(s)
- Ralph Scully
- Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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37
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Rothfuss A, Grompe M. Repair kinetics of genomic interstrand DNA cross-links: evidence for DNA double-strand break-dependent activation of the Fanconi anemia/BRCA pathway. Mol Cell Biol 2004; 24:123-34. [PMID: 14673148 PMCID: PMC303365 DOI: 10.1128/mcb.24.1.123-134.2004] [Citation(s) in RCA: 177] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Revised: 09/04/2003] [Accepted: 10/23/2003] [Indexed: 11/20/2022] Open
Abstract
The detailed mechanisms of DNA interstrand cross-link (ICL) repair and the involvement of the Fanconi anemia (FA)/BRCA pathway in this process are not known. Present models suggest that recognition and repair of ICL in human cells occur primarily during the S phase. Here we provide evidence for a refined model in which ICLs are recognized and are rapidly incised by ERCC1/XPF independent of DNA replication. However, the incised ICLs are then processed further and DNA double-strand breaks (DSB) form exclusively in the S phase. FA cells are fully proficient in the sensing and incision of ICL as well as in the subsequent formation of DSB, suggesting a role of the FA/BRCA pathway downstream in ICL repair. In fact, activation of FANCD2 occurs slowly after ICL treatment and correlates with the appearance of DSB in the S phase. In contrast, activation is rapid after ionizing radiation, indicating that the FA/BRCA pathway is specifically activated upon DSB formation. Furthermore, the formation of FANCD2 foci is restricted to a subpopulation of cells, which can be labeled by bromodeoxyuridine incorporation. We therefore conclude that the FA/BRCA pathway, while being dispensable for the early events in ICL repair, is activated in S-phase cells after DSB have formed.
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Affiliation(s)
- Andreas Rothfuss
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, Oregon 97239, USA.
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38
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Abrahams PJ, Houweling A, Schouten R, van der Eb AJ, Terleth C. Abnormal kinetics of induction of UV-stimulated recombination in human DNA repair disorders. DNA Repair (Amst) 2003; 2:1211-25. [PMID: 14599743 DOI: 10.1016/s1568-7864(03)00141-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Recombination can result in genetic instability, and thus constitutes an important factor in the carcinogenic conversion of mammalian cells. Here we describe the occurrence of UV-stimulated recombination called enhanced recombination (EREC), measured with the use of Herpes Simplex Viruses type 1 mutants. In normal diploid human cells, EREC is induced by UV-C, mitomycin C and ENU, but not by X-ray or MMS. The kinetics of induction of EREC is similar to that of other SOS-like responses such as enhanced reactivation (ER) and enhanced mutagenesis (EM). In contrast to the latter responses, EREC is induced to higher levels and persists for longer periods in DNA repair deficient fibroblasts derived from xeroderma pigmentosum (XP), Cockayne syndrome (CS) and Trichothiodystrophy (TTD) patients. This observation indicates that EREC is a distinct SOS-like response. Apparently, the presence of unrepaired DNA lesions in the host genome is a strongly inducing signal for EREC. On the other hand, in cells derived from patients suffering from Bloom, Werner or Rothmund-Thomson syndrome (RTS) the EREC response is absent. These data indicate that determining EREC is a useful assay to investigate diploid human fibroblasts for abnormalities in UV-stimulated recombination.
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Affiliation(s)
- Peter J Abrahams
- Department of Toxicogenetics, Leiden University Medical Center, Wassenaarseweg 72, 2333 Al Leiden, The Netherlands.
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39
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Pichierri P, Rosselli F, Franchitto A. Werner's syndrome protein is phosphorylated in an ATR/ATM-dependent manner following replication arrest and DNA damage induced during the S phase of the cell cycle. Oncogene 2003; 22:1491-500. [PMID: 12629512 DOI: 10.1038/sj.onc.1206169] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Werner's syndrome (WS) is an autosomal recessive disorder, characterized at the cellular level by genomic instability in the form of variegated translocation mosaicism and extensive deletions. Individuals with WS prematurely develop multiple age-related pathologies and exhibit increased incidence of cancer. WRN, the gene defective in WS, encodes a 160-kDa protein (WRN), which has 3'-5'exonuclease, DNA helicase and DNA-dependent ATPase activities. WRN-defective cells are hypersensitive to certain genotoxic agents that cause replication arrest and/or double-strand breaks at the replication fork, suggesting a pivotal role for WRN in the protection of the integrity of the genoma during the DNA replication process. Here, we show that WRN is phosphorylated through an ATR/ATM dependent pathway in response to replication blockage. However, we provide evidence that WRN phosphorylation is not essential for its subnuclear relocalization after replication arrest. Finally, we show that WRN and ATR colocalize after replication fork arrest, suggesting that WRN and the ATR kinase collaborate to prevent genome instability during the S phase.
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Affiliation(s)
- Pietro Pichierri
- CNRS, UPR2169 'Genetic Instability and Cancer', Institut Gustave Roussy, France
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40
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Abstract
Fanconi anaemia (FA) is a rare genetic cancer-susceptibility syndrome that is characterized by congenital abnormalities, bone-marrow failure and cellular sensitivity to DNA crosslinking agents. Seven FA-associated genes have recently been cloned, and their products were found to interact with well-known DNA-damage-response proteins, including BRCA1, ATM and NBS1. The FA proteins could therefore be involved in the cell-cycle checkpoint and DNA-repair pathways. Recent studies implicate the FA proteins in the process of repairing chromosome defects that occur during homologous recombination, and disruption of the FA genes results in chromosome instability--a common feature of many human cancers.
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Affiliation(s)
- Alan D D'Andrea
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston, Massachusetts 02115, USA.
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41
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Abstract
Heterozygous carriers of loss-of-function germline mutations in the BRCA1 or BRCA2 breast cancer susceptibility genes have a predisposition to breast and ovarian cancer. Multiple functions have been ascribed to the products of these genes, linking them to pathways that inhibit progression to neoplasia. Various investigators have assigned roles for these tumor suppressor gene products in the cell functions of genome repair, transcription, and growth control. There is emerging evidence that BRCA1 may participate in ubiquitin E3 ligase activity. BRCA1 and BRCA2 have each been implicated in chromatin remodeling dynamics via protein partnering. Ubiquitin ligase and chromatin remodeling activities need not be mutually exclusive and both may function in DNA repair, transcriptional regulation, or cell cycle control. Here we highlight certain recent findings and currently unanswered questions regarding BRCA1 and BRCA2 in breast cancer.
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Affiliation(s)
- Dianne C Daniel
- Mount Sinai School of Medicine, Department of Pathology, New York, New York 10029, USA.
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42
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Segurado M, Gómez M, Antequera F. Increased recombination intermediates and homologous integration hot spots at DNA replication origins. Mol Cell 2002; 10:907-16. [PMID: 12419233 DOI: 10.1016/s1097-2765(02)00684-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
We have studied the relationship between DNA replication and recombination in Schizosaccharomyces pombe using two-dimensional gel electrophoresis and functional analysis. Our results indicate that the activation of replication origins (ORIs) during the mitotic cell cycle is associated with the generation of joint DNA molecules between sister chromatids. The frequency of integration by homologous recombination was up to 50-fold higher than the genomic average within a narrow window overlapping the ars1 replication initiation site. The S. pombe rad22Delta, rhp51Delta, and rhp54Delta mutants, deficient in mitotic recombination, activate ORIs very inefficiently and accumulate abnormal replication intermediates. These results focus on the general link between replication and recombination previously found in several systems and suggest a role for recombination in the initiation of eukaryotic DNA replication.
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Affiliation(s)
- Mónica Segurado
- Instituto de Microbiología Bioquímica, CSIC/Universidad de Salamanca, Edificio Departamental, Campus Miguel de Unamuno, 37007, Salamanca, Spain
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43
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Muto M, Kanari Y, Kubo E, Takabe T, Kurihara T, Fujimori A, Tatsumi K. Targeted disruption of Np95 gene renders murine embryonic stem cells hypersensitive to DNA damaging agents and DNA replication blocks. J Biol Chem 2002; 277:34549-55. [PMID: 12084726 DOI: 10.1074/jbc.m205189200] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
NP95, which contains a ubiquitin-like domain, a cyclin A/E-Cdk2 phosphorylation site, a retinoblastoma (Rb) binding motif, and a ring finger domain, has been shown to be colocalized as foci with proliferating cell nuclear antigen in early and mid-S phase nuclei. We established Np95 nulligous embryonic stem cells by replacing the exons 2-7 of the Np95 gene with a neo cassette and by selecting out a spontaneously occurring homologous chromosome crossing over with a higher concentration of neomycin. Np95-null cells were more sensitive to x-rays, UV light, N-methyl-N"-nitro-N-nitrosoguanidine (MNNG), and hydroxyurea than embryonic stem wild type (Np95(+/+)) or heterozygously inactivated (Np95(+/-)) cells. Expression of transfected Np95 cDNA in Np95-null cells restored the resistance to x-rays, UV, MNNG, or hydroxyurea concurrently to a level similar to that of Np95(+/-) cells, although slightly below that of wild type (Np95(+/+)) cells. These findings suggest that NP95 plays a role in the repair of DNA damage incurred by these agents. The frequency of spontaneous sister chromatid exchange was significantly higher for Np95-null cells than for Np95(+/+) cells or Np95(+/-) cells (p < 0.001). We conclude that NP95 functions as a common component in the multiple response pathways against DNA damage and replication arrest and thereby contributes to genomic stability.
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Affiliation(s)
- Masahiro Muto
- Research Center for Radiation Safety, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba-shi, Chiba 263-8555, Japan
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44
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Abstract
Large proportions of hereditary breast cancers are due to mutations in the two breast cancer susceptibility genes BRCA1 and BRCA2. Considerable effort has gone into studying the function(s) of these tumor suppressor genes, both in attempts to better understand why individuals with these inherited mutations acquire breast (and ovarian) cancer and to potentially develop better treatment strategies. The advent of tools such as cDNA microarrays has enabled researchers to study global gene expression patterns in, for example, primary tumors, thus providing more comprehensive overviews of tumor development and progression. Our recent study (Hedenfalk et al., 2001) strongly supports the principle that genomic approaches to classification of hereditary breast cancers are possible, and that further studies will likely identify the most significant genes that discriminate between subgroups and may influence prognosis and treatment. A large number of hereditary breast cancer cases cannot be accounted for by mutations in these two genes and are believed to be due to as yet unidentified breast cancer predisposition genes (BRCAx). Subclassification of these non-BRCA1/2 breast cancers using cDNA microarray-based gene expression profiling, followed by linkage analysis and/or investigation of genomic alterations, may help in the recognition of novel breast cancer predisposition loci. To summarize, gene expression-based analysis of hereditary breast cancer can potentially be used for classification purposes, as well as to expand upon our knowledge of differences between different forms of hereditary breast cancer. Initial studies indicate that a patient's genotype does in fact leave an identifiable trace on her/his cancer's gene expression profile.
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Affiliation(s)
- Ingrid A Hedenfalk
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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45
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Herzig M, Christofori G. Recent advances in cancer research: mouse models of tumorigenesis. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1602:97-113. [PMID: 12020798 DOI: 10.1016/s0304-419x(02)00039-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Over the past 20 years, cancer research has gained major insights into the complexity of tumor development, in particular into the molecular mechanisms that underlie the progressive transformation of normal cells into highly malignant derivatives. It is estimated that the transformation of a normal cell to a malignant tumor cell is dependent upon a small number of genetic alterations, estimated to be within the range of four to seven rate-limiting events. Critical events in the evolution of neoplastic disease include the loss of proliferative control, the failure to undergo programmed cell death (apoptosis), the onset of neoangiogenesis, tissue remodeling, invasion of tumor cells into surrounding tissue and, finally, metastatic dissemination of tumor cells to distant organs. In patients, the molecular analysis of these multiple steps is hampered by the unavailability of tumor biopsies from all tumor stages. In contrast, mouse models of tumorigenesis allow the reproducible isolation of all tumor stages, including normal tissue, which are then amenable to pathological, genetic and biochemical analyses and, hence, have been instrumental in investigating cancer-related genes and their role in carcinogenesis. In this review, we discuss mouse tumor models that have contributed substantially to the identification and characterization of novel tumor pathways. In particular, we focus on transgenic and knockout mouse models that closely mimic human cancer and thus can be used as model systems for cancer research.
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46
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Abstract
The hereditary breast and ovarian cancer susceptibility genes, BRCA1 and BRCA2, have established roles in genome integrity maintenance and in the control of homologous recombination. Recent work has produced valuable insights into the mechanisms of action of the gene products. This review summarizes some of these advances, and attempts to place them in the context of known functions of the genes.
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Affiliation(s)
- Ralph Scully
- Department of Hematology/Oncology, Cancer Biology Program, Beth Israel Deaconess Medical Center and Harvard Medical School, 77 Avenue Louis Pasteur, HIM 925, Boston, MA 02215, USA.
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47
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Tutt A, Bertwistle D, Valentine J, Gabriel A, Swift S, Ross G, Griffin C, Thacker J, Ashworth A. Mutation in Brca2 stimulates error-prone homology-directed repair of DNA double-strand breaks occurring between repeated sequences. EMBO J 2001; 20:4704-16. [PMID: 11532935 PMCID: PMC125603 DOI: 10.1093/emboj/20.17.4704] [Citation(s) in RCA: 331] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2001] [Revised: 07/13/2001] [Accepted: 07/13/2001] [Indexed: 01/17/2023] Open
Abstract
Mutation of BRCA2 causes familial early onset breast and ovarian cancer. BRCA2 has been suggested to be important for the maintenance of genome integrity and to have a role in DNA repair by homology- directed double-strand break (DSB) repair. By studying the repair of a specific induced chromosomal DSB we show that loss of Brca2 leads to a substantial increase in error-prone repair by homology-directed single-strand annealing and a reduction in DSB repair by conservative gene conversion. These data demonstrate that loss of Brca2 causes misrepair of chromosomal DSBs occurring between repeated sequences by stimulating use of an error-prone homologous recombination pathway. Furthermore, loss of Brca2 causes a large increase in genome-wide error-prone repair of both spontaneous DNA damage and mitomycin C-induced DNA cross-links at the expense of error-free repair by sister chromatid recombination. This provides insight into the mechanisms that induce genome instability in tumour cells lacking BRCA2.
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Affiliation(s)
- A Tutt
- The Breakthrough Toby Robins, Breast Cancer Research Centre, Institute of Cancer Research, Fulham Road, London SW3 6JB, UK
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48
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Affiliation(s)
- R T Abraham
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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49
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Saintigny Y, Delacôte F, Varès G, Petitot F, Lambert S, Averbeck D, Lopez BS. Characterization of homologous recombination induced by replication inhibition in mammalian cells. EMBO J 2001; 20:3861-70. [PMID: 11447127 PMCID: PMC125539 DOI: 10.1093/emboj/20.14.3861] [Citation(s) in RCA: 244] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
To analyze relationships between replication and homologous recombination in mammalian cells, we used replication inhibitors to treat mouse and hamster cell lines containing tandem repeat recombination substrates. In the first step, few double-strand breaks (DSBs) are produced, recombination is slightly increased, but cell lines defective in non-homologous end-joining (NHEJ) affected in ku86 (xrs6) or xrcc4 (XR-1) genes show enhanced sensitivity to replication inhibitors. In the second step, replication inhibition leads to coordinated kinetics of DSB accumulation, Rad51 foci formation and RAD51-dependent gene conversion stimulation. In xrs6 as well as XR-1 cell lines, Rad51 foci accumulate more rapidly compared with their respective controls. We propose that replication inhibition produces DSBs, which are first processed by the NHEJ; then, following DSB accumulation, RAD51 recombination can act.
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Affiliation(s)
- Yannick Saintigny
- UMR217 CNRS-CEA and CEA, Direction des Sciences du Vivant, Département de Radiobiologie et Radiopathologie, 60–68 avenue du Général Leclerc, 92 265 Fontenay aux Roses cedex, and UMR 2027 CNRS-Institut Curie, Section de recherche, Centre Universitaire Bat. 110, 91 405, Orsay cedex, France Corresponding author e-mail:
| | - Fabien Delacôte
- UMR217 CNRS-CEA and CEA, Direction des Sciences du Vivant, Département de Radiobiologie et Radiopathologie, 60–68 avenue du Général Leclerc, 92 265 Fontenay aux Roses cedex, and UMR 2027 CNRS-Institut Curie, Section de recherche, Centre Universitaire Bat. 110, 91 405, Orsay cedex, France Corresponding author e-mail:
| | - Guillaume Varès
- UMR217 CNRS-CEA and CEA, Direction des Sciences du Vivant, Département de Radiobiologie et Radiopathologie, 60–68 avenue du Général Leclerc, 92 265 Fontenay aux Roses cedex, and UMR 2027 CNRS-Institut Curie, Section de recherche, Centre Universitaire Bat. 110, 91 405, Orsay cedex, France Corresponding author e-mail:
| | - Fabrice Petitot
- UMR217 CNRS-CEA and CEA, Direction des Sciences du Vivant, Département de Radiobiologie et Radiopathologie, 60–68 avenue du Général Leclerc, 92 265 Fontenay aux Roses cedex, and UMR 2027 CNRS-Institut Curie, Section de recherche, Centre Universitaire Bat. 110, 91 405, Orsay cedex, France Corresponding author e-mail:
| | - Sarah Lambert
- UMR217 CNRS-CEA and CEA, Direction des Sciences du Vivant, Département de Radiobiologie et Radiopathologie, 60–68 avenue du Général Leclerc, 92 265 Fontenay aux Roses cedex, and UMR 2027 CNRS-Institut Curie, Section de recherche, Centre Universitaire Bat. 110, 91 405, Orsay cedex, France Corresponding author e-mail:
| | - Dietrich Averbeck
- UMR217 CNRS-CEA and CEA, Direction des Sciences du Vivant, Département de Radiobiologie et Radiopathologie, 60–68 avenue du Général Leclerc, 92 265 Fontenay aux Roses cedex, and UMR 2027 CNRS-Institut Curie, Section de recherche, Centre Universitaire Bat. 110, 91 405, Orsay cedex, France Corresponding author e-mail:
| | - Bernard S. Lopez
- UMR217 CNRS-CEA and CEA, Direction des Sciences du Vivant, Département de Radiobiologie et Radiopathologie, 60–68 avenue du Général Leclerc, 92 265 Fontenay aux Roses cedex, and UMR 2027 CNRS-Institut Curie, Section de recherche, Centre Universitaire Bat. 110, 91 405, Orsay cedex, France Corresponding author e-mail:
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50
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Costanzo V, Robertson K, Bibikova M, Kim E, Grieco D, Gottesman M, Carroll D, Gautier J. Mre11 protein complex prevents double-strand break accumulation during chromosomal DNA replication. Mol Cell 2001; 8:137-47. [PMID: 11511367 DOI: 10.1016/s1097-2765(01)00294-5] [Citation(s) in RCA: 186] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mre11 complex promotes repair of DNA double-strand breaks (DSBs). Xenopus Mre11 (X-Mre11) has been cloned, and its role in DNA replication and DNA damage checkpoint studied in cell-free extracts. DSBs stimulate the phosphorylation and 3'-5' exonuclease activity of X-Mre11 complex. This induced phosphorylation is ATM independent. Phosphorylated X-Mre11 is found associated with replicating nuclei. X-Mre11 complex is required to yield normal DNA replication products. Genomic DNA replicated in extracts immunodepleted of X-Mre11 complex accumulates DSBs as demonstrated by TUNEL assay and reactivity to phosphorylated histone H2AX antibodies. In contrast, the ATM-dependent DNA damage checkpoint that blocks DNA replication initiation is X-Mre11 independent. These results strongly suggest that the function of X-Mre11 complex is to repair DSBs that arise during normal DNA replication, thus unraveling a critical link between recombination-dependent repair and DNA replication.
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Affiliation(s)
- V Costanzo
- Department of Genetics and Development, Columbia University, New York, NY 10032, USA
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