101
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Mladenov E, Tsaneva I, Anachkova B. Activation of the S phase DNA damage checkpoint by mitomycin C. J Cell Physiol 2007; 211:468-76. [PMID: 17167777 DOI: 10.1002/jcp.20957] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We have studied the rate of DNA synthesis, cell cycle distribution, formation of gamma-H2AX, and Rad51 nuclear foci and association of Rad51 with the nuclear matrix after treatment of HeLa cells with the interstrand crosslinking agent mitomycin C (MMC) in the presence of the kinase inhibitors caffeine and wortmannin. The results showed that MMC treatment arrested the cells in S-phase and induced the appearance of gamma-H2AX and Rad51 nuclear foci, accompanied with a sequestering of Rad51 to the nuclear matrix. These effects were abrogated by caffeine, which inhibits the Ataxia-telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR) kinases. However, wortmannin at a concentration that inhibits ATM, but not ATR did not affect cell cycle progression, damage-induced phosphorylation of H2AX and Rad51 foci formation, and association with the nuclear matrix, suggesting that the S-phase arrest induced by MMC is ATR-dependent. These findings were confirmed by experiments with ATR-deficient and AT cells. They indicate that the DNA damage ATR-dependent S-phase checkpoint pathway may regulate the spatiotemporal organization of the process of repair of interstrand crosslinks.
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Affiliation(s)
- Emil Mladenov
- Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia, Bulgaria
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102
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Kalb R, Neveling K, Hoehn H, Schneider H, Linka Y, Batish SD, Hunt C, Berwick M, Callen E, Surralles J, Casado JA, Bueren J, Dasi A, Soulier J, Gluckman E, Zwaan CM, van Spaendonk R, Pals G, de Winter JP, Joenje H, Grompe M, Auerbach AD, Hanenberg H, Schindler D. Hypomorphic mutations in the gene encoding a key Fanconi anemia protein, FANCD2, sustain a significant group of FA-D2 patients with severe phenotype. Am J Hum Genet 2007; 80:895-910. [PMID: 17436244 PMCID: PMC1852747 DOI: 10.1086/517616] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Accepted: 02/26/2007] [Indexed: 01/06/2023] Open
Abstract
FANCD2 is an evolutionarily conserved Fanconi anemia (FA) gene that plays a key role in DNA double-strand-type damage responses. Using complementation assays and immunoblotting, a consortium of American and European groups assigned 29 patients with FA from 23 families and 4 additional unrelated patients to complementation group FA-D2. This amounts to 3%-6% of FA-affected patients registered in various data sets. Malformations are frequent in FA-D2 patients, and hematological manifestations appear earlier and progress more rapidly when compared with all other patients combined (FA-non-D2) in the International Fanconi Anemia Registry. FANCD2 is flanked by two pseudogenes. Mutation analysis revealed the expected total of 66 mutated alleles, 34 of which result in aberrant splicing patterns. Many mutations are recurrent and have ethnic associations and shared allelic haplotypes. There were no biallelic null mutations; residual FANCD2 protein of both isotypes was observed in all available patient cell lines. These analyses suggest that, unlike the knockout mouse model, total absence of FANCD2 does not exist in FA-D2 patients, because of constraints on viable combinations of FANCD2 mutations. Although hypomorphic mutations arie involved, clinically, these patients have a relatively severe form of FA.
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Affiliation(s)
- Reinhard Kalb
- Department of Human Genetics, University of Wurzburg, Wurzburg, Germany
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103
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Gallmeier E, Kern SE. Targeting Fanconi anemia/BRCA2 pathway defects in cancer: the significance of preclinical pharmacogenomic models. Clin Cancer Res 2007; 13:4-10. [PMID: 17200332 DOI: 10.1158/1078-0432.ccr-06-1637] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Defects in the Fanconi anemia (FA) pathway occur in subsets of diverse human cancers. The hypersensitivity of FA pathway-deficient cells to DNA interstrand cross-linking and possibly other agents renders these genes attractive targets for a genotype-based, individualized anticancer therapy. A prerequisite before clinical trials is the validation and quantification of this hypersensitivity in suitable preclinical pharmacogenomic models. In addition, the effects of combinational therapy need to be evaluated and novel agents sought. We discuss here the pitfalls and limitations in the interpretation of common FA models when applied to the validation of FA gene defects as therapeutic targets. In general, all preclinical models are prone to certain artifacts and, thus, promising results in a single or few models rarely translate into clinical success. Nevertheless, the extraordinary robustness of FA pathway-deficient cells to interstrand cross-linking agents, which are observable in virtually any model independent of species, cell type, or technique used to engineer the gene defect, in various in vitro and in vivo settings, renders these gene defects particularly attractive for targeted therapy. Clinical trials are now under way.
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Affiliation(s)
- Eike Gallmeier
- The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University, Baltimore, Maryland 21231, USA
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104
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Phelps RA, Gingras H, Hockenbery DM. Loss of FANCC function is associated with failure to inhibit late firing replication origins after DNA cross-linking. Exp Cell Res 2007; 313:2283-92. [PMID: 17490643 DOI: 10.1016/j.yexcr.2007.03.034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2006] [Revised: 03/29/2007] [Accepted: 03/29/2007] [Indexed: 01/06/2023]
Abstract
Fanconi anemia (FA) cells are abnormally sensitive to DNA cross-linking agents with increased levels of apoptosis and chromosomal instability. Defects in eight FA complementation groups inhibit monoubiquitination of FANCD2, and subsequent recruitment of FANCD2 to DNA damage and S-phase-associated nuclear foci. The specific functional defect in repair or response to DNA damage in FA cells remains unknown. Damage-resistant DNA synthesis is present 2.5-5 h after cross-linker treatment of FANCC, FANCA and FANCD2-deficient cells. Analysis of the size distribution of labeled DNA replication strands revealed that diepoxybutane treatment suppressed labeling of early but not late-firing replicons in FANCC-deficient cells. In contrast, normal responses to ionizing radiation were observed in FANCC-deficient cells. Absence of this late S-phase response in FANCC-deficient cells leads to activation of secondary checkpoint responses.
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Affiliation(s)
- Randall A Phelps
- Molecular and Cellular Biology Program, Fred Hutchinson Cancer Research Center and University of Washington, Seattle, WA, USA
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105
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Ciccia A, Ling C, Coulthard R, Yan Z, Xue Y, Meetei AR, Laghmani EH, Joenje H, McDonald N, de Winter JP, Wang W, West SC. Identification of FAAP24, a Fanconi anemia core complex protein that interacts with FANCM. Mol Cell 2007; 25:331-43. [PMID: 17289582 DOI: 10.1016/j.molcel.2007.01.003] [Citation(s) in RCA: 232] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2006] [Revised: 11/28/2006] [Accepted: 01/02/2007] [Indexed: 11/26/2022]
Abstract
The Fanconi anemia (FA) core complex plays a crucial role in a DNA damage response network with BRCA1 and BRCA2. How this complex interacts with damaged DNA is unknown, as only the FA core protein FANCM (the homolog of an archaeal helicase/nuclease known as HEF) exhibits DNA binding activity. Here, we describe the identification of FAAP24, a protein that targets FANCM to structures that mimic intermediates formed during the replication/repair of damaged DNA. FAAP24 shares homology with the XPF family of flap/fork endonucleases, associates with the C-terminal region of FANCM, and is a component of the FA core complex. FAAP24 is required for normal levels of FANCD2 monoubiquitylation following DNA damage. Depletion of FAAP24 by siRNA results in cellular hypersensitivity to DNA crosslinking agents and chromosomal instability. Our data indicate that the FANCM/FAAP24 complex may play a key role in recruitment of the FA core complex to damaged DNA.
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Affiliation(s)
- Alberto Ciccia
- Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Herts, UK
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106
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Bogliolo M, Lyakhovich A, Callén E, Castellà M, Cappelli E, Ramírez MJ, Creus A, Marcos R, Kalb R, Neveling K, Schindler D, Surrallés J. Histone H2AX and Fanconi anemia FANCD2 function in the same pathway to maintain chromosome stability. EMBO J 2007; 26:1340-51. [PMID: 17304220 PMCID: PMC1817623 DOI: 10.1038/sj.emboj.7601574] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Accepted: 01/03/2007] [Indexed: 01/01/2023] Open
Abstract
Fanconi anemia (FA) is a chromosome fragility syndrome characterized by bone marrow failure and cancer susceptibility. The central FA protein FANCD2 is known to relocate to chromatin upon DNA damage in a poorly understood process. Here, we have induced subnuclear accumulation of DNA damage to prove that histone H2AX is a novel component of the FA/BRCA pathway in response to stalled replication forks. Analyses of cells from H2AX knockout mice or expressing a nonphosphorylable H2AX (H2AX(S136A/S139A)) indicate that phosphorylated H2AX (gammaH2AX) is required for recruiting FANCD2 to chromatin at stalled replication forks. FANCD2 binding to gammaH2AX is BRCA1-dependent and cells deficient or depleted of H2AX show an FA-like phenotype, including an excess of chromatid-type chromosomal aberrations and hypersensitivity to MMC. This MMC hypersensitivity of H2AX-deficient cells is not further increased by depleting FANCD2, indicating that H2AX and FANCD2 function in the same pathway in response to DNA damage-induced replication blockage. Consequently, histone H2AX is functionally connected to the FA/BRCA pathway to resolve stalled replication forks and prevent chromosome instability.
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Affiliation(s)
- Massimo Bogliolo
- Group of Mutagenesis, Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Alex Lyakhovich
- Group of Mutagenesis, Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Elsa Callén
- Group of Mutagenesis, Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Maria Castellà
- Group of Mutagenesis, Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Enrico Cappelli
- Group of Mutagenesis, Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - María J Ramírez
- Group of Mutagenesis, Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Amadeu Creus
- Group of Mutagenesis, Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Ricard Marcos
- Group of Mutagenesis, Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Reinhard Kalb
- Department of Human Genetics, University of Wurzburg, Wurzburg, Germany
| | - Kornelia Neveling
- Department of Human Genetics, University of Wurzburg, Wurzburg, Germany
| | - Detlev Schindler
- Department of Human Genetics, University of Wurzburg, Wurzburg, Germany
| | - Jordi Surrallés
- Group of Mutagenesis, Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
- Centre for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Bellaterra, Barcelona, Spain
- Department of Genetics and Microbiology, Universitat Autonoma de Barcelona, Campus de Bellaterra, Bellaterra, Barcelona 08193, Spain. Tel.: + 34 93 581 18 30; Fax: + 34 93 581 23 87; E-mail:
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107
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Dimitrova N, de Lange T. MDC1 accelerates nonhomologous end-joining of dysfunctional telomeres. Genes Dev 2007; 20:3238-43. [PMID: 17158742 PMCID: PMC1686600 DOI: 10.1101/gad.1496606] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Here we document the role of MDC1 (mediator of DNA damage checkpoint 1) in the detection and repair of human and mouse telomeres rendered dysfunctional through inhibition of TRF2. Consistent with its role in promoting DNA damage foci, MDC1 knockdown affected the formation of telomere dysfunction-induced foci (TIFs), diminishing the accumulation of phosphorylated ATM, 53BP1, Nbs1, and to a lesser extent, gamma-H2AX. In addition to this effect on TIFs, the rate of nonhomologous end-joining (NHEJ) of dysfunctional telomeres was significantly decreased when MDC1 itself or its recruitment to chromatin was inhibited. MDC1 appeared to promote a step in the NHEJ pathway after the removal of the 3' telomeric overhang. The acceleration of NHEJ was unlikely to be due to increased presence of 53BP1 and Mre11 in TIFs, since knockdown of neither factor affected telomere fusions. Furthermore, relevant cell cycle effectors (Chk2, p53, and p21) of the ATM kinase pathway were unaffected and there was no change in the rate of cell cycle progression. We propose that the binding of MDC1 to gamma-H2AX directly affects NHEJ in a manner that is independent of the ATM-dependent cell cycle arrest pathway.
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Affiliation(s)
- Nadya Dimitrova
- Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, New York 10021, USA
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108
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Mladenov E, Tsaneva I, Anachkova B. Cell Cycle–Dependent Association of Rad51 with the Nuclear Matrix. DNA Cell Biol 2007; 26:36-43. [PMID: 17263595 DOI: 10.1089/dna.2006.0503] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Progression of the cells through the S phase of the cell cycle is connected with accumulation of stalled and collapsed replication forks that are repaired by homologous recombination. To investigate the temporal order of homologous recombination events during the S phase, HeLa cells synchronized at the G1/S phase boundary with mimosine were released to progress into the S phase and the phosphorylation of the histone variant H2AX, the appearance of Rad51 nuclear foci and the subcellular redistribution of Rad51 were followed. The results showed that there was gradual accumulation of double-strand breaks as judged by the increase in the phosphorylation of H2AX during the S phase. Rad51 nuclear foci did not appear until middle S phase, and this was accompanied by an increase in the chromatin- and nuclear matrix-bound Rad51 in the middle to late S phase. To determine the role of the intra S phase checkpoint in the S phase-dependent redistribution of Rad51 the cells were released in the S phase in the presence of the protein kinase inhibitors caffeine and wortmannin. The results suggest that the association of Rad51 with the nuclear matrix is regulated by activation of the intra S phase ATR-dependent checkpoint pathway.
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Affiliation(s)
- Emil Mladenov
- Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia, Bulgaria
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109
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Otterlei M, Bruheim P, Ahn B, Bussen W, Karmakar P, Baynton K, Bohr VA. Werner syndrome protein participates in a complex with RAD51, RAD54, RAD54B and ATR in response to ICL-induced replication arrest. J Cell Sci 2006; 119:5137-46. [PMID: 17118963 DOI: 10.1242/jcs.03291] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Werner syndrome (WS) is a rare genetic disorder characterized by genomic instability caused by defects in the WRN gene encoding a member of the human RecQ helicase family. RecQ helicases are involved in several DNA metabolic pathways including homologous recombination (HR) processes during repair of stalled replication forks. Following introduction of interstrand DNA crosslinks (ICL), WRN relocated from nucleoli to arrested replication forks in the nucleoplasm where it interacted with the HR protein RAD52. In this study, we use fluorescence resonance energy transfer (FRET) and immune-precipitation experiments to demonstrate that WRN participates in a multiprotein complex including RAD51, RAD54, RAD54B and ATR in cells where replication has been arrested by ICL. We verify the WRN-RAD51 and WRN-RAD54B direct interaction in vitro. Our data support a role for WRN also in the recombination step of ICL repair.
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Affiliation(s)
- Marit Otterlei
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Dr., Baltimore, MD 21224, USA.
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110
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Lee KY, Yang I, Park JE, Baek OR, Chung KY, Koo HS. Developmental stage- and DNA damage-specific functions of C. elegans FANCD2. Biochem Biophys Res Commun 2006; 352:479-85. [PMID: 17126808 DOI: 10.1016/j.bbrc.2006.11.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Accepted: 11/09/2006] [Indexed: 02/04/2023]
Abstract
In this study, we set out to investigate the role of Fanconi anemia complementation group D2 protein (FANCD2) in developmental stage-specific DNA damage responses in Caenorhabditis elegans. A mutant C. elegans strain containing a deletion in the gene encoding the FANCD2 homolog, FCD-2, exhibited egg-laying defects, precocious oogenesis, and partial defects in fertilization. The mutant strain also had a lower hatching rate than the wild-type after gamma-irradiation of embryos, but not after the irradiation of pachytene stage germ cells. This mutation sensitized pachytene stage germ cells to the genotoxic effects of photoactivated psoralen, as seen by a greatly reduced hatching rate and increased chromosomal aberrations. This mutation also enhanced physiological M-phase arrest and apoptosis. Taken together, our data reveal that the C. elegans FANCD2 homolog participates in the repair of spontaneous DNA damage and DNA crosslinks, not only in proliferating cells but also in pachytene stage cells, and it may have an additional role in double-stranded DNA break repair during embryogenesis.
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Affiliation(s)
- Kyong Yun Lee
- Department of Biochemistry, College of Science, Yonsei University, 134 Sinchon-dong, Seodaemun-ku, Seoul 120-749, Republic of Korea
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111
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Eller MS, Liao X, Liu S, Hanna K, Bäckvall H, Opresko PL, Bohr VA, Gilchrest BA. A role for WRN in telomere-based DNA damage responses. Proc Natl Acad Sci U S A 2006; 103:15073-8. [PMID: 17015833 PMCID: PMC1586178 DOI: 10.1073/pnas.0607332103] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Indexed: 12/26/2022] Open
Abstract
Telomeres cap the ends of eukaryotic chromosomes and prevent them from being recognized as DNA breaks. We have shown that certain DNA damage responses induced during senescence and, at times of telomere uncapping, also can be induced by treatment of cells with small DNA oligonucleotides homologous to the telomere 3' single-strand overhang (T-oligos), implicating this overhang in generation of these telomere-based damage responses. Here, we show that T-oligo-treated fibroblasts contain gammaH2AX foci and that these foci colocalize with telomeres. T-oligos with nuclease-resistant 3' ends are inactive, suggesting that a nuclease initiates T-oligo responses. We therefore examined WRN, a 3'-->5' exonuclease and helicase mutated in Werner syndrome, a disorder characterized by aberrant telomere maintenance, premature aging, chromosomal rearrangements, and predisposition to malignancy. Normal fibroblasts and U20S osteosarcoma cells rendered deficient in WRN showed reduced phosphorylation of p53 and histone H2AX in response to T-oligo treatment. Together, these data demonstrate a role for WRN in processing of telomeric DNA and subsequent activation of DNA damage responses. The T-oligo model helps define the role of WRN in telomere maintenance and initiation of DNA damage responses after telomere disruption.
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Affiliation(s)
- Mark S. Eller
- *Department of Dermatology, Boston University School of Medicine, 609 Albany Street, Boston, MA 02118
| | - Xiaodong Liao
- *Department of Dermatology, Boston University School of Medicine, 609 Albany Street, Boston, MA 02118
| | - SuiYang Liu
- *Department of Dermatology, Boston University School of Medicine, 609 Albany Street, Boston, MA 02118
| | - Kendra Hanna
- *Department of Dermatology, Boston University School of Medicine, 609 Albany Street, Boston, MA 02118
| | - Helena Bäckvall
- *Department of Dermatology, Boston University School of Medicine, 609 Albany Street, Boston, MA 02118
| | - Patricia L. Opresko
- Department of Environmental and Occupational Health, University of Pittsburgh, 100 Technology Drive, Cellomics Building, Suite 350, Pittsburgh, PA 15219; and
| | - Vilhelm A. Bohr
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224-6825
| | - Barbara A. Gilchrest
- *Department of Dermatology, Boston University School of Medicine, 609 Albany Street, Boston, MA 02118
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112
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Durocher F, Labrie Y, Soucy P, Sinilnikova O, Labuda D, Bessette P, Chiquette J, Laframboise R, Lépine J, Lespérance B, Ouellette G, Pichette R, Plante M, Tavtigian SV, Simard J. Mutation analysis and characterization of ATR sequence variants in breast cancer cases from high-risk French Canadian breast/ovarian cancer families. BMC Cancer 2006; 6:230. [PMID: 17010193 PMCID: PMC1599749 DOI: 10.1186/1471-2407-6-230] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2006] [Accepted: 09/29/2006] [Indexed: 02/08/2023] Open
Abstract
Background Ataxia telangiectasia-mutated and Rad3-related (ATR) is a member of the PIK-related family which plays, along with ATM, a central role in cell-cycle regulation. ATR has been shown to phosphorylate several tumor suppressors like BRCA1, CHEK1 and TP53. ATR appears as a good candidate breast cancer susceptibility gene and the current study was designed to screen for ATR germline mutations potentially involved in breast cancer predisposition. Methods ATR direct sequencing was performed using a fluorescent method while widely available programs were used for linkage disequilibrium (LD), haplotype analyses, and tagging SNP (tSNP) identification. Expression analyses were carried out using real-time PCR. Results The complete sequence of all exons and flanking intronic sequences were analyzed in DNA samples from 54 individuals affected with breast cancer from non-BRCA1/2 high-risk French Canadian breast/ovarian families. Although no germline mutation has been identified in the coding region, we identified 41 sequence variants, including 16 coding variants, 3 of which are not reported in public databases. SNP haplotypes were established and tSNPs were identified in 73 healthy unrelated French Canadians, providing a valuable tool for further association studies involving the ATR gene, using large cohorts. Our analyses led to the identification of two novel alternative splice transcripts. In contrast to the transcript generated by an alternative splicing site in the intron 41, the one resulting from a deletion of 121 nucleotides in exon 33 is widely expressed, at significant but relatively low levels, in both normal and tumoral cells including normal breast and ovarian tissue. Conclusion Although no deleterious mutations were identified in the ATR gene, the current study provides an haplotype analysis of the ATR gene polymorphisms, which allowed the identification of a set of SNPs that could be used as tSNPs for large-scale association studies. In addition, our study led to the characterization of a novel Δ33 splice form, which could generate a putative truncated protein lacking several functional domains. Additional studies in large cohorts and other populations will be needed to further evaluate if common and/or rare ATR sequence variants can be associated with a modest or intermediate breast cancer risk.
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Affiliation(s)
- Francine Durocher
- Cancer Genomics Laboratory, Oncology and Molecular Endocrinology Research Centre, Centre Hospitalier Universitaire de Québec and Laval University, Québec, G1V 4G2, Canada
| | - Yvan Labrie
- Cancer Genomics Laboratory, Oncology and Molecular Endocrinology Research Centre, Centre Hospitalier Universitaire de Québec and Laval University, Québec, G1V 4G2, Canada
| | - Penny Soucy
- Cancer Genomics Laboratory, Oncology and Molecular Endocrinology Research Centre, Centre Hospitalier Universitaire de Québec and Laval University, Québec, G1V 4G2, Canada
| | - Olga Sinilnikova
- Unité Mixte de Génétique Constitutionnelle des Cancers Fréquents, Hospices Civils de Lyon/Centre Léon Bérard, Lyon, France
| | - Damian Labuda
- Centre de cancérologie Charles Bruneau, Ste-Justine Hospital, Montréal, Canada
| | - Paul Bessette
- Service de gynécologie, Centre Hospitalier Universitaire de Sherbrooke, Fleurimont, Canada
| | - Jocelyne Chiquette
- Clinique des maladies du sein Deschênes-Fabia, Hôpital du Saint-Sacrement, Québec, G1S 4L8, Canada
| | - Rachel Laframboise
- Service de médecine génétique, CHUQ, Pavillon CHUL, Québec, G1V 4G2, Canada
| | - Jean Lépine
- Centre hospitalier régional de Rimouski, Rimouski, G5L 5T1, Canada
| | | | - Geneviève Ouellette
- Cancer Genomics Laboratory, Oncology and Molecular Endocrinology Research Centre, Centre Hospitalier Universitaire de Québec and Laval University, Québec, G1V 4G2, Canada
| | - Roxane Pichette
- Service d'hémato-oncologie, Hôpital du Sacré-Cœur, Montréal, Canada
| | - Marie Plante
- Service de gynécologie, CHUQ, L'Hôtel-Dieu de Québec, Québec, G1R 2J6, Canada
| | - Sean V Tavtigian
- Unit of Genetic Cancer Susceptibility, International Agency for Research on Cancer, World Health Organization, Lyon, France
| | - Jacques Simard
- Cancer Genomics Laboratory, Oncology and Molecular Endocrinology Research Centre, Centre Hospitalier Universitaire de Québec and Laval University, Québec, G1V 4G2, Canada
- Canada Research Chair in Oncogenetics, Department of Anatomy and Physiology, Laval University, Québec, Canada
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113
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Godthelp BC, van Buul PPW, Jaspers NGJ, Elghalbzouri-Maghrani E, van Duijn-Goedhart A, Arwert F, Joenje H, Zdzienicka MZ. Cellular characterization of cells from the Fanconi anemia complementation group, FA-D1/BRCA2. Mutat Res 2006; 601:191-201. [PMID: 16920162 DOI: 10.1016/j.mrfmmm.2006.07.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 07/04/2006] [Accepted: 07/11/2006] [Indexed: 01/07/2023]
Abstract
Fanconi anemia (FA) is an inherited cancer-susceptibility disorder, characterized by genomic instability and hypersensitivity to DNA cross-linking agents. The discovery of biallelic BRCA2 mutations in the FA-D1 complementation group allows for the first time to study the characteristics of primary BRCA2-deficient human cells. FANCD1/BRCA2-deficient fibroblasts appeared hypersensitive to mitomycin C (MMC), slightly sensitive to methyl methane sulfonate (MMS), and like cells derived from other FA complementation groups, not sensitive to X-ray irradiation. However, unlike other FA cells, FA-D1 cells were slightly sensitive to UV irradiation. Despite the observed lack of X-ray sensitivity in cell survival, significant radioresistant DNA synthesis (RDS) was observed in the BRCA2-deficient fibroblasts but also in the FANCA-deficient fibroblasts, suggesting an impaired S-phase checkpoint. FA-D1/BRCA2 cells displayed greatly enhanced levels of spontaneous as well as MMC-induced chromosomal aberrations (CA), similar to cells deficient in homologous recombination (HR) and non-D1 FA cells. In contrast to Brca2-deficient rodent cells, FA-D1/BRCA2 cells showed normal sister chromatid exchange (SCE) levels, both spontaneous as well as after MMC treatment. Hence, these data indicate that human cells with biallelic BRCA2 mutations display typical features of both FA- and HR-deficient cells, which suggests that FANCD1/BRCA2 is part of the integrated FA/BRCA DNA damage response pathway but also controls other functions outside the FA pathway.
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Affiliation(s)
- Barbara C Godthelp
- Department of Toxicogenetics, Leiden University Medical Center, Building 2, Postzone S-6-P, 2300 RC, Leiden, The Netherlands
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114
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Takemura H, Rao VA, Sordet O, Furuta T, Miao ZH, Meng L, Zhang H, Pommier Y. Defective Mre11-dependent activation of Chk2 by ataxia telangiectasia mutated in colorectal carcinoma cells in response to replication-dependent DNA double strand breaks. J Biol Chem 2006; 281:30814-23. [PMID: 16905549 DOI: 10.1074/jbc.m603747200] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The Mre11.Rad50.Nbs1 (MRN) complex binds DNA double strand breaks to repair DNA and activate checkpoints. We report MRN deficiency in three of seven colon carcinoma cell lines of the NCI Anticancer Drug Screen. To study the involvement of MRN in replication-mediated DNA double strand breaks, we examined checkpoint responses to camptothecin, which induces replication-mediated DNA double strand breaks after replication forks collide with topoisomerase I cleavage complexes. MRN-deficient cells were deficient for Chk2 activation, whereas Chk1 activation was independent of MRN. Chk2 activation was ataxia telangiectasia mutated (ATM)-dependent and associated with phosphorylation of Mre11 and Nbs1. Mre11 complementation in MRN-deficient HCT116 cells restored Chk2 activation as well as Rad50 and Nbs1 levels. Conversely, Mre11 down-regulation by small interference RNA (siRNA) in HT29 cells inhibited Chk2 activation and down-regulated Nbs1 and Rad50. Proteasome inhibition also restored Rad50 and Nbs1 levels in HCT116 cells suggesting that Mre11 stabilizes Rad50 and Nbs1. Chk2 activation was also defective in three of four MRN-proficient colorectal cell lines because of low Chk2 levels. Thus, six of seven colon carcinoma cell lines from the NCI Anticancer Drug Screen are functionally Chk2-deficient in response to replication-mediated DNA double strand breaks. We propose that Mre11 stabilizes Nbs1 and Rad50 and that MRN activates Chk2 downstream from ATM in response to replication-mediated DNA double strand breaks. Chk2 deficiency in HCT116 is associated with defective S-phase checkpoint, prolonged G2 arrest, and hypersensitivity to camptothecin. The high frequency of MRN and Chk2 deficiencies may contribute to genomic instability and therapeutic response to camptothecins in colorectal cancers.
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Affiliation(s)
- Haruyuki Takemura
- Laboratory of Molecular Pharmacology, Center for Cancer Research, NCI, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892-4255, USA
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115
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Colton SL, Xu XS, Wang YA, Wang G. The involvement of ataxia-telangiectasia mutated protein activation in nucleotide excision repair-facilitated cell survival with cisplatin treatment. J Biol Chem 2006; 281:27117-25. [PMID: 16849332 DOI: 10.1074/jbc.m602826200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
DNA damage can lead to either DNA repair with cell survival or to apoptotic cell death. Although the biochemical processes underlying DNA repair and apoptosis have been extensively studied, the mechanisms by which cells determine whether the damage will be repaired or the apoptotic pathway will be activated is largely unknown. We have studied the role of nucleotide excision repair (NER) in cisplatin DNA damage-induced apoptotic cell death using both normal human fibroblasts and NER-defective xeroderma pigmentosum (XP) XPA and XPG cells. The caspase-3 activation experiment demonstrated a greatly increased casapse-3 activation in the NER-defective cells following cisplatin treatment. The flow cytometry experiment revealed an altered cell cycle arrest pattern of the NER-defective cells following cisplatin treatment. The results obtained from the Western blot experiment showed that NER defects resulted in enhanced CHK1 phosphorylation and p21 induction after cisplatin treatment. The cisplatin treatment-induced ATM phosphorylation, however, was attenuated in NER-defective cells. The results obtained from our immunoprecipitation experiment further demonstrated that the ATM protein interacted with the TFIIH basal transcription factor and the XPG protein of the NER pathway. It also showed that a functional XPC protein was required for the association of the ATM protein to genomic DNA. These results suggest that the NER process may prevent the cisplatin treatment-induced apoptosis by activating the ATM protein, and that the presence of the XPC protein is essential for recruiting the ATM protein to the DNA template.
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Affiliation(s)
- Stephanie L Colton
- Institute of Environmental Health Sciences, Karmanos Cancer Research Institute, Wayne State University, Detroit, Michigan 48201, USA
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116
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Hinz JM, Nham PB, Salazar EP, Thompson LH. The Fanconi anemia pathway limits the severity of mutagenesis. DNA Repair (Amst) 2006; 5:875-84. [PMID: 16815103 DOI: 10.1016/j.dnarep.2006.05.039] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Accepted: 05/17/2006] [Indexed: 12/13/2022]
Abstract
Fanconi anemia (FA) is a developmental and cancer predisposition disorder in which key, yet unknown, physiological events promoting chromosome stability are compromised. FA cells exhibit excess metaphase chromatid breaks and are universally hypersensitive to DNA interstrand crosslinking agents. Published mutagenesis data from single-gene mutation assays show both increased and decreased mutation frequencies in FA cells. In this review we discuss the data from the literature and from our isogenic fancg knockout hamster CHO cells, and interpret these data within the framework of a molecular model that accommodates these seemingly divergent observations. In FA cells, reduced rates of recovery of viable X-linked hypoxanthine phosphoribosyltransferase (hprt) mutants are characteristically observed for diverse mutagenic agents, but also in untreated cultures, indicating the relevance of the FA pathway for processing assorted DNA lesions. We ascribe these reductions to: (1) impaired mutagenic translesion synthesis within hprt during DNA replication and (2) lethality of mutant cells following replication fork breakage on the X chromosome, caused by unrepaired double-strand breaks or large deletions/translocations encompassing essential genes flanking hprt. These findings, along with studies showing increased spontaneous mutability of FA cells at two autosomal loci, support a model in which FA proteins promote both translesion synthesis at replication-blocking lesions and repair of broken replication forks by homologous recombination and DNA end joining. The essence of this model is that the FANC protein pathway serves to restrict the severity of mutational outcome by favoring base substitutions and small deletions over larger deletions and chromosomal rearrangements.
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Affiliation(s)
- John M Hinz
- Biosciences Directorate, L441, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551-0808, USA
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117
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Liu G, Chen X. DNA polymerase eta, the product of the xeroderma pigmentosum variant gene and a target of p53, modulates the DNA damage checkpoint and p53 activation. Mol Cell Biol 2006; 26:1398-413. [PMID: 16449651 PMCID: PMC1367184 DOI: 10.1128/mcb.26.4.1398-1413.2006] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
DNA polymerase eta (PolH) is the product of the xeroderma pigmentosum variant (XPV) gene and a well-characterized Y-family DNA polymerase for translesion synthesis. Cells derived from XPV patients are unable to faithfully bypass UV photoproducts and DNA adducts and thus acquire genetic mutations. Here, we found that PolH can be up-regulated by DNA breaks induced by ionizing radiation or chemotherapeutic agents, and knockdown of PolH gives cells resistance to apoptosis induced by DNA breaks in multiple cell lines and cell types in a p53-dependent manner. To explore the underlying mechanism, we examined p53 activation upon DNA breaks and found that p53 activation is impaired in PolH knockdown cells and PolH-null primary fibroblasts. Importantly, reconstitution of PolH into PolH knockdown cells restores p53 activation. Moreover, we provide evidence that, upon DNA breaks, PolH is partially colocalized with phosphorylated ATM at gamma-H2AX foci and knockdown of PolH impairs ATM to phosphorylate Chk2 and p53. However, upon DNA damage by UV, PolH knockdown cells exhibit two opposing temporal responses: at the early stage, knockdown of PolH suppresses p53 activation and gives cells resistance to UV-induced apoptosis in a p53-dependent manner; at the late stage, knockdown of PolH suppresses DNA repair, leading to sustained activation of p53 and increased susceptibility to apoptosis in both a p53-dependent and a p53-independent manner. Taken together, we found that PolH has a novel role in the DNA damage checkpoint and that a p53 target can modulate the DNA damage response and subsequently regulate p53 activation.
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Affiliation(s)
- Gang Liu
- Department of Cell Biology, The University of Alabama at Birmingham, AL 35294-0005, USA
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118
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Hovest MG, Brüggenolte N, Hosseini KS, Krieg T, Herrmann G. Senescence of human fibroblasts after psoralen photoactivation is mediated by ATR kinase and persistent DNA damage foci at telomeres. Mol Biol Cell 2006. [PMID: 16436511 DOI: 10.1091/mbc.e05] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2023] Open
Abstract
Cellular senescence is a phenotype that is likely linked with aging. Recent concepts view different forms of senescence as permanently maintained DNA damage responses partially characterized by the presence of senescence-associated DNA damage foci at dysfunctional telomeres. Irradiation of primary human dermal fibroblasts with the photosensitizer 8-methoxypsoralen and ultraviolet A radiation (PUVA) induces senescence. In the present study, we demonstrate that senescence after PUVA depends on DNA interstrand cross-link (ICL) formation that activates ATR kinase. ATR is necessary for the manifestation and maintenance of the senescent phenotype, because depletion of ATR expression before PUVA prevents induction of senescence, and reduction of ATR expression in PUVA-senesced fibroblasts releases cells from growth arrest. We find an ATR-dependent phosphorylation of the histone H2AX (gamma-H2AX). After PUVA, ATR and gamma-H2AX colocalize in multiple nuclear foci. After several days, only few predominantly telomere-localized foci persist and telomeric DNA can be coimmunoprecipitated with ATR from PUVA-senesced fibroblasts. We thus identify ATR as a novel mediator of telomere-dependent senescence in response to ICL induced by photoactivated psoralens.
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119
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Abstract
A rare genetic disease, Fanconi anemia (FA), now attracts broader attention from cancer biologists and basic researchers in the DNA repair and ubiquitin biology fields as well as from hematologists. FA is a chromosome instability syndrome characterized by childhood-onset aplastic anemia, cancer or leukemia susceptibility, and cellular hypersensitivity to DNA crosslinking agents. Identification of 11 genes for FA has led to progress in the molecular understanding of this disease. FA proteins, including a ubiquitin ligase (FANCL), a monoubiquitinated protein (FANCD2), a helicase (FANCJ/BACH1/BRIP1), and a breast/ovarian cancer susceptibility protein (FANCD1/BRCA2), appear to cooperate in a pathway leading to the recognition and repair of damaged DNA. Molecular interactions among FA proteins and responsible proteins for other chromosome instability syndromes (BLM, NBS1, MRE11, ATM, and ATR) have also been found. Furthermore, inactivation of FA genes has been observed in a wide variety of human cancers in the general population. These findings have broad implications for predicting the sensitivity and resistance of tumors to widely used anticancer DNA crosslinking agents (cisplatin, mitomycin C, and melphalan). Here, we summarize recent progress in the molecular biology of FA and discuss roles of the FA proteins in DNA repair and cancer biology.
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Affiliation(s)
- Toshiyasu Taniguchi
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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120
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Ouyang Y, Kwon YT, An JY, Eller D, Tsai SC, Diaz-Perez S, Troke JJ, Teitell MA, Marahrens Y. Loss of Ubr2, an E3 ubiquitin ligase, leads to chromosome fragility and impaired homologous recombinational repair. Mutat Res 2006; 596:64-75. [PMID: 16488448 DOI: 10.1016/j.mrfmmm.2005.12.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Revised: 12/05/2005] [Accepted: 12/21/2005] [Indexed: 01/08/2023]
Abstract
The N-end rule pathway of protein degradation targets proteins with destabilizing N-terminal residues. Ubr2 is one of the E3 ubiquitin ligases of the mouse N-end rule pathway. We have previously shown that Ubr2-/- male mice are infertile, owing to the arrest of spermatocytes between the leptotene/zygotene and pachytene of meiosis I, the failure of chromosome pairing, and subsequent apoptosis. Here, we report that mouse fibroblast cells derived from Ubr2-/- embryos display genome instability. The frequency of chromosomal bridges and micronuclei were much higher in Ubr2-/- fibroblasts than in +/+ controls. Metaphase chromosome spreads from Ubr2-/- cells revealed a high incidence of spontaneous chromosomal gaps, indicating chromosomal fragility. These fragile sites were generally replicated late in S phase. Ubr2-/- cells were hypersensitive to mitomycin C, a DNA cross-linking agent, but displayed normal sensitivity to gamma-irradiation. A reporter assay showed that Ubr2-/- cells are significantly impaired in the homologous recombination repair of a double strand break. In contrast, Ubr2-/- cells appeared normal in an assay for non-homologous end joining. Our results therefore unveil the role of the ubiquitin ligase Ubr2 in maintaining genome integrity and in homologous recombination repair.
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Affiliation(s)
- Yan Ouyang
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
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121
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Abstract
Over the past few years, study of the rare inherited chromosome instability disorder, Fanconi Anemia (FA), has uncovered a novel DNA damage response pathway. Through the cooperation of multiple proteins, this pathway regulates a complicated cellular response to DNA cross-linking agents and other genotoxic stresses. In this article we review recent data identifying new components of the FA pathway that implicate it in several aspects of the DNA damage response, including the direct processing of DNA, translesion synthesis, homologous recombination, and cell cycle regulation. We also discuss new findings that explain how the FA pathway is regulated through the processes of ubiquitination and deubiquitination. We then consider the clinical implications of our current understanding of the FA pathway, particularly in the development and treatment of malignancy in heterozygous carriers of FA mutations or in patients with sporadic cancers. We consider how recent studies of p53-mediated apoptosis and loss of p53 function in models of FA may help explain the clinical features of the disease and finally present a hypothesis to account for the specificity of the FA pathway in the response to DNA cross-links.
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Affiliation(s)
- Richard D Kennedy
- Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
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122
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Digweed M. Genomic Instability in Fanconi Anaemia and Nijmegen Breakage Syndrome. Genome Integr 2006. [DOI: 10.1007/7050_013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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123
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O'Driscoll M, Jeggo PA. The role of double-strand break repair - insights from human genetics. Nat Rev Genet 2006; 7:45-54. [PMID: 16369571 DOI: 10.1038/nrg1746] [Citation(s) in RCA: 394] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The efficient repair of DNA double-strand breaks is crucial in safeguarding the genomic integrity of organisms. Responses to double-strand breaks include complex signal-transduction, cell-cycle-checkpoint and repair pathways. Defects in these pathways lead to several human disorders with pleiotropic clinical features. Dissection of the molecular basis that underlies the diverse clinical features is enhancing our understanding of the damage-response mechanisms and their role in development, and might ultimately facilitate treatment.
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Affiliation(s)
- Mark O'Driscoll
- Genome Damage and Stability Centre, University of Sussex, East Sussex BN1 9RQ, UK.
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124
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Hovest MG, Brüggenolte N, Hosseini KS, Krieg T, Herrmann G. Senescence of human fibroblasts after psoralen photoactivation is mediated by ATR kinase and persistent DNA damage foci at telomeres. Mol Biol Cell 2006; 17:1758-67. [PMID: 16436511 PMCID: PMC1415309 DOI: 10.1091/mbc.e05-08-0701] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cellular senescence is a phenotype that is likely linked with aging. Recent concepts view different forms of senescence as permanently maintained DNA damage responses partially characterized by the presence of senescence-associated DNA damage foci at dysfunctional telomeres. Irradiation of primary human dermal fibroblasts with the photosensitizer 8-methoxypsoralen and ultraviolet A radiation (PUVA) induces senescence. In the present study, we demonstrate that senescence after PUVA depends on DNA interstrand cross-link (ICL) formation that activates ATR kinase. ATR is necessary for the manifestation and maintenance of the senescent phenotype, because depletion of ATR expression before PUVA prevents induction of senescence, and reduction of ATR expression in PUVA-senesced fibroblasts releases cells from growth arrest. We find an ATR-dependent phosphorylation of the histone H2AX (gamma-H2AX). After PUVA, ATR and gamma-H2AX colocalize in multiple nuclear foci. After several days, only few predominantly telomere-localized foci persist and telomeric DNA can be coimmunoprecipitated with ATR from PUVA-senesced fibroblasts. We thus identify ATR as a novel mediator of telomere-dependent senescence in response to ICL induced by photoactivated psoralens.
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125
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Myers JS, Cortez D. Rapid activation of ATR by ionizing radiation requires ATM and Mre11. J Biol Chem 2006; 281:9346-50. [PMID: 16431910 PMCID: PMC1821075 DOI: 10.1074/jbc.m513265200] [Citation(s) in RCA: 226] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ataxia-telangiectasia-mutated (ATM) and ATM- and Rad3-related (ATR) protein kinases are crucial regulatory proteins in genotoxic stress response pathways that pause the cell cycle to permit DNA repair. Here we show that Chk1 phosphorylation in response to hydroxyurea and ultraviolet radiation is ATR-dependent and ATM- and Mre11-independent. In contrast, Chk1 phosphorylation in response to ionizing radiation (IR) is dependent on ATR, ATM, and Mre11. The ATR and ATM/Mre11 pathways are generally thought to be separate with ATM activation occurring early and ATR activation occurring as a late response to double strand breaks. However, we demonstrate that ATR is activated rapidly by IR, and ATM and Mre11 enhance ATR signaling. ATR-ATR-interacting protein recruitment to double strand breaks is less efficient in the absence of ATM and Mre11. Furthermore, IR-induced replication protein A foci formation is defective in ATM- and Mre11-deficient cells. Thus, ATM and Mre11 may stimulate the ATR signaling pathway by converting DNA damage generated by IR into structures that recruit and activate ATR.
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Affiliation(s)
- Jeremy S Myers
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee 37232, USA
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126
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Lyakhovich A, Surralles J. Disruption of the Fanconi anemia/BRCA pathway in sporadic cancer. Cancer Lett 2006; 232:99-106. [PMID: 16246487 DOI: 10.1016/j.canlet.2005.07.038] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2005] [Accepted: 07/10/2005] [Indexed: 11/18/2022]
Abstract
An increasing number of studies provide evidences linking disruption of Fanconi anemia/BRCA cascade with sporadic cancers. Given that this pathway plays essential roles in response to the DNA interstrand cross-links, these cancers are expected to be chemosensitive to cross-link based therapy. In the present mini-review we expand the spectrum of possibilities for FA/BRCA disruption and review some works describing functional upstream and downstream events linking disruption of the FA/BRCA pathway to sporadic cancer. This may involve but not limited to epigenetic silencing of the FA-core complex or BRCA1/2, mutations of one or several FA-BRCA genes or modification of encoded products. All this may serve as a platform for occurrence, development and treatment of sporadic cancers and therefore deserves to be in the focus of new research directions.
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Affiliation(s)
- Alex Lyakhovich
- Group of Mutagenesis, Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
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127
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Sobeck A, Stone S, Costanzo V, de Graaf B, Reuter T, de Winter J, Wallisch M, Akkari Y, Olson S, Wang W, Joenje H, Christian JL, Lupardus PJ, Cimprich KA, Gautier J, Hoatlin ME. Fanconi anemia proteins are required to prevent accumulation of replication-associated DNA double-strand breaks. Mol Cell Biol 2006; 26:425-37. [PMID: 16382135 PMCID: PMC1346898 DOI: 10.1128/mcb.26.2.425-437.2006] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2005] [Revised: 07/20/2005] [Accepted: 10/13/2005] [Indexed: 12/19/2022] Open
Abstract
Fanconi anemia (FA) is a multigene cancer susceptibility disorder characterized by cellular hypersensitivity to DNA interstrand cross-linking agents such as mitomycin C (MMC). FA proteins are suspected to function at the interface between cell cycle checkpoints, DNA repair, and DNA replication. Using replicating extracts from Xenopus eggs, we developed cell-free assays for FA proteins (xFA). Recruitment of the xFA core complex and xFANCD2 to chromatin is strictly dependent on replication initiation, even in the presence of MMC indicating specific recruitment to DNA lesions encountered by the replication machinery. The increase in xFA chromatin binding following treatment with MMC is part of a caffeine-sensitive S-phase checkpoint that is controlled by xATR. Recruitment of xFANCD2, but not xFANCA, is dependent on the xATR-xATR-interacting protein (xATRIP) complex. Immunodepletion of either xFANCA or xFANCD2 from egg extracts results in accumulation of chromosomal DNA breaks during replicative synthesis. Our results suggest coordinated chromatin recruitment of xFA proteins in response to replication-associated DNA lesions and indicate that xFA proteins function to prevent the accumulation of DNA breaks that arise during unperturbed replication.
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Affiliation(s)
- Alexandra Sobeck
- Division of Biochemistry and Molecular Biology, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, Oregon 97239, USA
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128
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Abstract
Fanconi anemia is characterized by hypersensitivity to DNA interstrand crosslinks (ICLs) and susceptibility to tumor formation. Despite the identification of numerous Fanconi anemia (FANC) genes, the mechanism by which proteins encoded by these genes protect a cell from DNA interstrand crosslinks remains unclear. The recent discovery of two DNA helicases that, when defective, cause Fanconi anemia tips the balance in favor of the direct involvement of the FANC proteins in DNA repair and the bypass of DNA lesions.
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Affiliation(s)
- Laura J Niedernhofer
- Center for Biomedical Genetics, Medical Genetic Center, Department of Cell Biology and Genetics, Erasmus Medical Center, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
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129
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Lee YJ, Park SJ, Ciccone SLM, Kim CR, Lee SH. An
in vivo
analysis of MMC-induced DNA damage and its repair. Carcinogenesis 2005; 27:446-53. [PMID: 16258176 DOI: 10.1093/carcin/bgi254] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mitomycin C (MMC) induces various types of DNA damages that cause significant cytotoxicity to cells. Accordingly, repair of MMC-induced damages involves multiple repair pathways such as nucleotide excision repair, homologous recombination repair and translesion bypass repair pathways. Nonetheless, repair of the MMC-induced DNA damages in mammals have not been fully delineated. In this study, we investigated potential roles for Xeroderma pigmentosum (XP) proteins in the repair of MMC-induced DNA damages using an assay that detects the ssDNA patches generated following treatment with MMC or 8'-methoxy-psoralen (8-MOP) + UVA (ultraviolet light A). Human wild-type cells formed distinctive ssDNA foci following treatment with MMC or 8-MOP + UVA, but not with those inducing alkylation damage, oxidative damage or strand-break damage, suggesting that the foci represent ssDNA patches formed during the crosslink repair. In contrast to wild-type cells, mutant defective in XPE orXPG did not form the ssDNA foci following MMC treatment, while XPF mutant cells showed a significantly delayed response in forming the foci. A positive role for XPG in the repair of MMC-induced DNA damages was further supported by observations that cells treated with MMC induced a tight association of XPG with chromatin, and a targeted inhibition of XPG abolished MMC-induced ssDNA foci formation, rendering cells hypersensitive to MMC. Together, our results suggest that XPG along with XPE and XPF play unique role(s) in the repair of MMC-induced DNA damages.
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Affiliation(s)
- Young-Ju Lee
- Department of Biochemistry and Molecular Biology, Microbiology and Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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130
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Zhou C, Huang P, Liu J. The carboxyl-terminal of BRCA1 is required for subnuclear assembly of RAD51 after treatment with cisplatin but not ionizing radiation in human breast and ovarian cancer cells. Biochem Biophys Res Commun 2005; 336:952-60. [PMID: 16165098 DOI: 10.1016/j.bbrc.2005.08.197] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2005] [Accepted: 08/24/2005] [Indexed: 11/23/2022]
Abstract
BRCA1 plays an important role in maintaining genomic stability through its involvement in DNA repair. Although it is known that BRCA1 and RAD51 form distinct DNA repair subnuclear complexes, or foci, following environmental insults to the DNA, the role of BRCA1 in this process remains to be characterized. The purpose of the study was therefore to determine the role of BRCA1 in the formation of RAD51 foci following treatment with cisplatin and ionizing radiation. We found that although a functional BRCA1 is required for the subnuclear assembly of BRCA1 foci following treatment with either ionizing radiation or cisplatin, a functional BRCA1 is required for RAD51 foci to form following treatment with cisplatin but not with ionizing radiation. Similar results were obtained in SKOV-3 cells when the level of BRCA1 expression was knocked down by stable expression of a retrovirus-mediated small-interfering RNA against BRCA1. We also found that the carboxyl-terminal of BRCA1 contains uncharacterized phosphorylation sites that are responsive to cisplatin. The functional BRCA1 is also required for breast and ovarian cancer cells to mount resistance to cisplatin. These results suggest that the carboxyl-terminal of BRCA1 is required for the cisplatin-induced recruitment of RAD51 to the DNA-damage site, which may contribute to cisplatin resistance.
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Affiliation(s)
- Chenyi Zhou
- Department of Pathology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030-4095, USA
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131
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Abstract
Fanconi anemia (FA) is a rare inherited disorder characterized clinically by aplastic anemia, developmental defects, and a susceptibility to cancer. Eleven complementation groups have been identified (FA-A, -B, -C, -D1, -D2, -E, -F, -G, -I, -J, and -L), and the genes responsible for 9 groups (FANCA, B, C, D1, D2, E, F, G, and L) have been cloned. The proteins involved in FA act coordinately in the cellular response to DNA cross-links in a pathway that has been shown to interact physically or functionally with a variety of other proteins involved in DNA repair or cell cycle control, notably BRCA1, Rad51,ATM,ATR, and Nbs1. Considerable advances in the identification and description of proteins involved in FA have been recorded, but the precise biochemical function of the FA pathway remains elusive. As research continues to improve our understanding of FA, insight will be gained into what is a pivotal process in cancer biology.
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Affiliation(s)
- Natalie Collins
- Department of Microbiology, University of Virginia Health System, University of Virginia, Charlottesville, Virginia 22908, USA
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132
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Macé G, Bogliolo M, Guervilly JH, Dugas du Villard JA, Rosselli F. 3R coordination by Fanconi anemia proteins. Biochimie 2005; 87:647-58. [PMID: 15935541 DOI: 10.1016/j.biochi.2005.05.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Fanconi anemia (FA) is a recessive cancer prone syndrome featuring bone marrow failure and hypersensitivity to DNA crosslinks. Nine FA genes have been isolated so far. The biochemical function(s) of the FA proteins remain(s) poorly determined. However, a large consensus exists on the evidence that, to cope with DNA cross-links, a cell needs a functional FA pathway. In this review, we resume current understanding of how the FA pathway works in response to DNA damage and how it is integrated in a complex network of proteins involved in the maintenance of the genetic stability.
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Affiliation(s)
- Gaëtane Macé
- Institut Gustave-Roussy PR2, UPR2169 du CNRS, 39, rue Camille-Desmoulins, 94805 Villejuif cedex, France
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133
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Ljungman M. Activation of DNA damage signaling. Mutat Res 2005; 577:203-16. [PMID: 15922368 DOI: 10.1016/j.mrfmmm.2005.02.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2005] [Revised: 02/18/2005] [Accepted: 02/18/2005] [Indexed: 05/02/2023]
Abstract
Cells respond to DNA damage by activating DNA repair and DNA damage signaling pathways. While DNA repair proteins directly interact with DNA lesions, activation of DNA damage signaling pathways may be triggered by the effect the DNA lesions have on replication, transcription or chromatin topology. This review will focus on the potential mechanisms of the activation of DNA damage-induced signal transduction pathways.
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Affiliation(s)
- Mats Ljungman
- Department of Radiation Oncology, Division of Radiation & Cancer Biology, University of Michigan Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109-0936, USA.
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134
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Meetei AR, Medhurst AL, Ling C, Xue Y, Singh TR, Bier P, Steltenpool J, Stone S, Dokal I, Mathew CG, Hoatlin M, Joenje H, de Winter JP, Wang W. A human ortholog of archaeal DNA repair protein Hef is defective in Fanconi anemia complementation group M. Nat Genet 2005; 37:958-63. [PMID: 16116422 PMCID: PMC2704909 DOI: 10.1038/ng1626] [Citation(s) in RCA: 329] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Accepted: 07/26/2005] [Indexed: 11/09/2022]
Abstract
Fanconi anemia is a genetic disease characterized by genomic instability and cancer predisposition. Nine genes involved in Fanconi anemia have been identified; their products participate in a DNA damage-response network involving BRCA1 and BRCA2 (refs. 2,3). We previously purified a Fanconi anemia core complex containing the FANCL ubiquitin ligase and six other Fanconi anemia-associated proteins. Each protein in this complex is essential for monoubiquitination of FANCD2, a key reaction in the Fanconi anemia DNA damage-response pathway. Here we show that another component of this complex, FAAP250, is mutant in individuals with Fanconi anemia of a new complementation group (FA-M). FAAP250 or FANCM has sequence similarity to known DNA-repair proteins, including archaeal Hef, yeast MPH1 and human ERCC4 or XPF. FANCM can dissociate DNA triplex, possibly owing to its ability to translocate on duplex DNA. FANCM is essential for monoubiquitination of FANCD2 and becomes hyperphosphorylated in response to DNA damage. Our data suggest an evolutionary link between Fanconi anemia-associated proteins and DNA repair; FANCM may act as an engine that translocates the Fanconi anemia core complex along DNA.
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Affiliation(s)
- Amom Ruhikanta Meetei
- Division of Experimental Hematology, Cincinnati Children’s Hospital Research Foundation and University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, Ohio 45229
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, 333 Cassell Drive, TRIAD Center Room 3000, Baltimore, Maryland 21224
| | - Annette L. Medhurst
- Department of Clinical Genetics and Human Genetics, VU University Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - Chen Ling
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, 333 Cassell Drive, TRIAD Center Room 3000, Baltimore, Maryland 21224
| | - Yutong Xue
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, 333 Cassell Drive, TRIAD Center Room 3000, Baltimore, Maryland 21224
| | - Thiyam Ramsing Singh
- Division of Experimental Hematology, Cincinnati Children’s Hospital Research Foundation and University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, Ohio 45229
| | - Patrick Bier
- Department of Clinical Genetics and Human Genetics, VU University Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - Jurgen Steltenpool
- Department of Clinical Genetics and Human Genetics, VU University Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - Stacie Stone
- Division of Molecular Medicine & Molecular and Medical Genetics/NRC3, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, U.S.A
| | - Inderjeet Dokal
- Department of Haematology, Imperial College London, Hammersmith Hospital, London, United Kingdom
| | - Christopher G. Mathew
- Department of Medical and Molecular Genetics, Guy’s, King’s and St Thomas’ School of Medicine, London, United Kingdom
| | - Maureen Hoatlin
- Division of Molecular Medicine & Molecular and Medical Genetics/NRC3, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, U.S.A
| | - Hans Joenje
- Department of Clinical Genetics and Human Genetics, VU University Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - Johan P. de Winter
- Department of Clinical Genetics and Human Genetics, VU University Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
- #: Correspondence should be addressed to JPW and WW. Telephone: 410-558-8334 (WW); 31-020-444-8283 (JPW), Fax: 410-558-8331 (WW); 31-020-444-8285 (JPW), (WW); (JPW)
| | - Weidong Wang
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, 333 Cassell Drive, TRIAD Center Room 3000, Baltimore, Maryland 21224
- #: Correspondence should be addressed to JPW and WW. Telephone: 410-558-8334 (WW); 31-020-444-8283 (JPW), Fax: 410-558-8331 (WW); 31-020-444-8285 (JPW), (WW); (JPW)
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135
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Abstract
Fanconi anemia (FA), a rare inherited disorder, exhibits a complex phenotype including progressive bone marrow failure, congenital malformations and increased risk of cancers, mainly acute myeloid leukaemia. At the cellular level, FA is characterized by hypersensitivity to DNA cross-linking agents and by high frequencies of induced chromosomal aberrations, a property used for diagnosis. FA results from mutations in one of the eleven FANC (FANCA to FANCJ) genes. Nine of them have been identified. In addition, FANCD1 gene has been shown to be identical to BRCA2, one of the two breast cancer susceptibility genes. Seven of the FANC proteins form a complex, which exists in four different forms depending of its subcellular localisation. Four FANC proteins (D1(BRCA2), D2, I and J) are not associated to the complex. The presence of the nuclear form of the FA core complex is necessary for the mono-ubiquitinylation of FANCD2 protein, a modification required for its re-localization to nuclear foci, likely to be sites of DNA repair. A clue towards understanding the molecular function of the FANC genes comes from the recently identified connection of FANC to the BRCA1, ATM, NBS1 and ATR genes. Two of the FANC proteins (A and D2) directly interact with BRCA1, which in turn interacts with the MRE11/RAD50/NBS1 complex, which is one of the key components in the mechanisms involved in the cellular response to DNA double strand breaks (DSB). Moreover, ATM, a protein kinase that plays a central role in the network of DSB signalling, phosphorylates in vitro and in vivo FANCD2 in response to ionising radiations. Moreover, the NBS1 protein and the monoubiquitinated form of FANCD2 seem to act together in response to DNA crosslinking agents. Taken together with the previously reported impaired DSB and DNA interstrand crosslinks repair in FA cells, the connection of FANC genes to the ATM, ATR, NBS1 and BRCA1 links the FANC genes function to the finely orchestrated network involved in the sensing, signalling and repair of DNA replication-blocking lesions.
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Affiliation(s)
- Dora Papadopoulo
- Institut Curie, Section de recherche, UMR 218 CNRS, 26 rue d'Ulm, 75248 Paris Cedex 05, France.
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136
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Pagano G, Degan P, d'Ischia M, Kelly FJ, Nobili B, Pallardó FV, Youssoufian H, Zatterale A. Oxidative stress as a multiple effector in Fanconi anaemia clinical phenotype. Eur J Haematol 2005; 75:93-100. [PMID: 16000125 DOI: 10.1111/j.1600-0609.2005.00507.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Fanconi anaemia (FA) is a genetic disease characterised by bone marrow failure with excess risk of myelogenous leukaemia and solid tumours. A widely accepted notion in FA research invokes a deficiency of response to DNA damage as the fundamental basis of the 'crosslinker sensitivity' observed in this disorder. However, such an isolated defect cannot readily account for the full cellular and clinical phenotype, which includes a number of other abnormalities, such as malformations, endocrinopathies, and typical skin spots. An extensive body of evidence pointing toward an involvement of oxidative stress in the FA phenotype includes the following: (i) In vitro and ex vivo abnormalities in a number of redox status endpoints; (ii) the functions of several FA proteins in protecting cells from oxidative stress; (iii) redox-related toxicity mechanisms of the xenobiotics evoking excess toxicity in FA cells. The clinical features in FA and the in vivo abnormalities of redox parameters are here reconsidered in view of the pleiotropic clinical phenotype and known biochemical and molecular links to an in vivo prooxidant state, which causes oxidative damage to biomolecules, resulting in an excessive number of acquired abnormalities that may overwhelm the cellular repair capacity rather than a primary deficiency in DNA repair. FA may thus represent a unique model disease in testing the integration between the acquisition of macromolecular damage as a result of oxidative stress and the ability of the mammalian cell to respond effectively to such damage.
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Affiliation(s)
- Giovanni Pagano
- Centre for Research, Innovation and Technological Transfer in Oncology and Life Sciences, Mercogliano (AV), Italy.
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137
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Affiliation(s)
- David Cortez
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37232, USA.
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138
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Chen Q, Van der Sluis PC, Boulware D, Hazlehurst LA, Dalton WS. The FA/BRCA pathway is involved in melphalan-induced DNA interstrand cross-link repair and accounts for melphalan resistance in multiple myeloma cells. Blood 2005; 106:698-705. [PMID: 15802532 PMCID: PMC1895179 DOI: 10.1182/blood-2004-11-4286] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Melphalan, a DNA cross-linker, is one of the most widely used and effective drugs in the treatment of multiple myeloma (MM). In this report, we demonstrate that enhanced interstrand cross-link (ICL) repair via the Fanconi anemia (FA)/BRCA pathway contributes to acquired drug resistance in melphalan-resistant myeloma cell lines, and disruption of this pathway reverses drug resistance. Using the alkaline comet assay (single-cell gel electrophoresis), we observed that melphalan-resistant cells have reduced ICL formation and enhanced ICL repair compared with melphalan-sensitive cells. Cell-cycle studies demonstrated that enhanced ICL repair released cells from melphalan-induced cell-cycle delay. Using siRNA to knock down FANCF in 8226/LR5 and U266/LR6 drug-resistant cells demonstrated a direct relationship between ICL repair capacity and drug sensitivity. Overexpression of FANCF in 8226/S and U266/S drug-sensitive cells partially reproduced the drug-resistant phenotype. These data show that enhanced DNA repair via the Fanconi anemia/BRCA pathway is involved in acquired melphalan resistance. Our findings provide for a new target to enhance response to DNA cross-linking agents in cancer treatment.
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Affiliation(s)
- Qing Chen
- Department of Interdisciplinary Oncology and Experimental Therapeutics Program, Biostatistics Core Facility, H. Lee Moffitt Cancer Center & Research Institute at University of South Florida, 12902 Magnolia Dr, Tampa, FL 33612, USA
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139
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Friesner JD, Liu B, Culligan K, Britt AB. Ionizing radiation-dependent gamma-H2AX focus formation requires ataxia telangiectasia mutated and ataxia telangiectasia mutated and Rad3-related. Mol Biol Cell 2005; 16:2566-76. [PMID: 15772150 PMCID: PMC1087258 DOI: 10.1091/mbc.e04-10-0890] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The histone variant H2AX is rapidly phosphorylated at the sites of DNA double-strand breaks (DSBs). This phosphorylated H2AX (gamma-H2AX) is involved in the retention of repair and signaling factor complexes at sites of DNA damage. The dependency of this phosphorylation on the various PI3K-related protein kinases (in mammals, ataxia telangiectasia mutated and Rad3-related [ATR], ataxia telangiectasia mutated [ATM], and DNA-PKCs) has been a subject of debate; it has been suggested that ATM is required for the induction of foci at DSBs, whereas ATR is involved in the recognition of stalled replication forks. In this study, using Arabidopsis as a model system, we investigated the ATR and ATM dependency of the formation of gamma-H2AX foci in M-phase cells exposed to ionizing radiation (IR). We find that although the majority of these foci are ATM-dependent, approximately 10% of IR-induced gamma-H2AX foci require, instead, functional ATR. This indicates that even in the absence of DNA replication, a distinct subset of IR-induced damage is recognized by ATR. In addition, we find that in plants, gamma-H2AX foci are induced at only one-third the rate observed in yeasts and mammals. This result may partly account for the relatively high radioresistance of plants versus yeast and mammals.
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Affiliation(s)
- Joanna D Friesner
- Genetics Graduate Group, University of California, Davis, Davis, CA 95616, USA
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140
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Thompson LH, Hinz JM, Yamada NA, Jones NJ. How Fanconi anemia proteins promote the four Rs: replication, recombination, repair, and recovery. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2005; 45:128-142. [PMID: 15668941 DOI: 10.1002/em.20109] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The genetically complex disease Fanconi anemia (FA) comprises cancer predisposition, developmental defects, and bone marrow failure due to elevated apoptosis. The FA cellular phenotype includes universal sensitivity to DNA crosslinking damage, symptoms of oxidative stress, and reduced mutability at the X-linked HPRT gene. In this review article, we present a new heuristic molecular model that accommodates these varied features of FA cells. In our view, the FANCA, -C, and -G proteins, which are both cytoplasmic and nuclear, have an integrated dual role in which they sense and convey information about cytoplasmic oxidative stress to the nucleus, where they participate in the further assembly and functionality of the nuclear core complex (NCCFA= FANCA/B/C/E/F/G/L). In turn, NCCFA facilitates DNA replication at sites of base damage and strand breaks by performing the critical monoubiquitination of FANCD2, an event that somehow helps stabilize blocked and broken replication forks. This stabilization facilitates two kinds of processes: translesion synthesis at sites of blocking lesions (e.g., oxidative base damage), which produces point mutations by error-prone polymerases, and homologous recombination-mediated restart of broken forks, which arise spontaneously and when crosslinks are unhooked by the ERCC1-XPF endonuclease. In the absence of the critical FANCD2 monoubiquitination step, broken replication forks further lose chromatid continuity by collapsing into a configuration that is more difficult to restart through recombination and prone to aberrant repair through nonhomologous end joining. Thus, the FA regulatory pathway promotes chromosome integrity by monitoring oxidative stress and coping efficiently with the accompanying oxidative DNA damage during DNA replication.
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Affiliation(s)
- Larry H Thompson
- Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, Livermore, California 94551, USA.
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141
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Nahas SA, Lai CH, Gatti RA. Post-irradiation phosphorylation of structural maintenance chromosome 1 (SMC1) is independent of the Fanconi protein pathway. Int J Radiat Oncol Biol Phys 2005; 61:1167-72. [PMID: 15752898 DOI: 10.1016/j.ijrobp.2004.11.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2004] [Revised: 11/04/2004] [Accepted: 11/09/2004] [Indexed: 10/25/2022]
Abstract
PURPOSE To confirm the sensitivity of cells from patients with Fanconi anemia (FA) to ionizing radiation, and to determine whether the phosphorylation of structural maintenance chromosome 1 (SMC1) was associated with radiosensitivity, as it is in other DNA repair disorders. METHODS AND MATERIALS Using lymphoblastoid cell lines from FA patients before and after exposure to ionizing radiation, the colony survival assay, radioresistant DNA synthesis, and SMC1 phosphorylation were measured. FA lymphoblastoid cell lines that had been transfected with the wild-type FANC gene were used as controls. RESULTS Cells from FA patients of six complementation groups were radiosensitive. Despite this, SMC1 phosphorylation was normal in each case; radioresistant DNA synthesis, a measure of S phase checkpoint integrity, was defective in FANCD2 lymphoblastoid cell lines and was corrected in FANCD2 + D2 cells. CONCLUSIONS The data indicate that the FANC pathway proteins play a major role in the cellular responses to ionizing radiation, but not in SMC1 phosphorylation or in the S phase checkpoint of FANCD2-deficient cells. Thus, SMC1 activation is not a common denominator of radiosensitivity, as has been suggested by radiation responses of cells from ataxia-telangiectasia, Nijmegen breakage syndrome, or Mre11 deficiency patients.
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Affiliation(s)
- Shareef A Nahas
- Department of Pathology, University of California, Los Angeles, David Geffen School of Medicine, Los Angeles, CA 90095-1732, USA
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142
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Revy P, Buck D, le Deist F, de Villartay JP. The Repair of DNA Damages/Modifications During the Maturation of the Immune System: Lessons from Human Primary Immunodeficiency Disorders and Animal Models. Adv Immunol 2005; 87:237-95. [PMID: 16102576 DOI: 10.1016/s0065-2776(05)87007-5] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The immune system is the site of various genotoxic stresses that occur during its maturation as well as during immune responses. These DNA lesions/modifications are primarily the consequences of specific physiological processes such as the V(D)J recombination, the immunoglobulin class switch recombination (CSR), and the generation of somatic hypermutations (SHMs) within Ig variable domains. The DNA lesions can be introduced either by specific factors (RAG1 and RAG2 in the case of V(D)J recombination and AID in the case of CSR and SHM) or during the various phases of cellular proliferation and cellular activation. All these DNA lesions are taken care of by the diverse DNA repair machineries of the cell. Several animal models as well as human conditions have established the critical importance of these DNA lesions/modifications and their repair in the physiology of the immune system. Indeed their defects have consequences ranging from immune deficiency to development of immune malignancy. The survey of human pathology has been highly instrumental in the past in identifying key factors involved in the generation of DNA modifications (AID for the Ig CSR and generation of SHM) or the repair of specific DNA damages (Artemis for V(D)J recombination). Defects in factors involved in the cell cycle checkpoints following DNA damage also have deleterious consequences on the immune system. The continuous survey of human diseases characterized by primary immunodeficiency associated with increased sensitivity to ionizing radiation should help identify other important DNA repair factors essential for the development and maintenance of the immune system.
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Affiliation(s)
- Patrick Revy
- Développement Normal et Pathologique du Système Immunitaire, INSERM U429, Hôpital Necker, Paris, France
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143
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Abstract
All life on earth must cope with constant exposure to DNA-damaging agents such as the Sun's radiation. Highly conserved DNA-repair and cell-cycle checkpoint pathways allow cells to deal with both endogenous and exogenous sources of DNA damage. How much an individual is exposed to these agents and how their cells respond to DNA damage are critical determinants of whether that individual will develop cancer. These cellular responses are also important for determining toxicities and responses to current cancer therapies, most of which target the DNA.
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Affiliation(s)
- Michael B Kastan
- Department of Hematology-Oncology, St Jude Children's Research Hospital, 332 North Lauderdale Street, Memphis, Tennessee 38105, USA.
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144
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Stiff T, Reis C, Alderton GK, Woodbine L, O'Driscoll M, Jeggo PA. Nbs1 is required for ATR-dependent phosphorylation events. EMBO J 2004; 24:199-208. [PMID: 15616588 PMCID: PMC544916 DOI: 10.1038/sj.emboj.7600504] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Accepted: 11/12/2004] [Indexed: 01/11/2023] Open
Abstract
Nijmegen breakage syndrome (NBS) is characterised by microcephaly, developmental delay, characteristic facial features, immunodeficiency and radiosensitivity. Nbs1, the protein defective in NBS, functions in ataxia telangiectasia mutated protein (ATM)-dependent signalling likely facilitating ATM phosphorylation events. While NBS shares overlapping characteristics with ataxia telangiectasia, it also has features overlapping with ATR-Seckel (ATR: ataxia-telangiectasia and Rad3-related protein) syndrome, a subclass of Seckel syndrome mutated in ATR. We show that Nbs1 also facilitates ATR-dependent phosphorylation. NBS cell lines show a similar defect in ATR phosphorylation of Chk1, c-jun and p-53 in response to UV irradiation- and hydroxyurea (HU)-induced replication stalling. They are also impaired in ubiquitination of FANCD2 after HU treatment, which is ATR dependent. Following HU-induced replication arrest, NBS and ATR-Seckel cells show similarly impaired G2/M checkpoint arrest and an impaired ability to restart DNA synthesis at stalled replication forks. Moreover, NBS cells fail to retain ATR in the nucleus following HU treatment and extraction. Our findings suggest that Nbs1 functions in both ATR- and ATM-dependent signalling. We propose that the NBS clinical features represent the result of these combined defects.
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Affiliation(s)
- Tom Stiff
- Genome Damage and Stability Centre, University of Sussex, East Sussex, UK
| | - Caroline Reis
- Genome Damage and Stability Centre, University of Sussex, East Sussex, UK
| | - Gemma K Alderton
- Genome Damage and Stability Centre, University of Sussex, East Sussex, UK
| | - Lisa Woodbine
- Genome Damage and Stability Centre, University of Sussex, East Sussex, UK
| | - Mark O'Driscoll
- Genome Damage and Stability Centre, University of Sussex, East Sussex, UK
| | - Penny A Jeggo
- Genome Damage and Stability Centre, University of Sussex, East Sussex, UK
- Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton, East Sussex BN1 9RQ, UK. Tel.: +44 1273 678482; Fax: +44 1273 678121; E-mail:
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145
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Kennedy RD, Quinn JE, Mullan PB, Johnston PG, Harkin DP. The role of BRCA1 in the cellular response to chemotherapy. J Natl Cancer Inst 2004; 96:1659-68. [PMID: 15547178 DOI: 10.1093/jnci/djh312] [Citation(s) in RCA: 323] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Germline mutations of the BRCA1 gene account for approximately 5% of breast and ovarian cancer cases, and lower than normal BRCA1 expression or function may be an important contributing factor in sporadic cancers. The major role of BRCA1 is to respond to DNA damage by participating in cellular pathways for DNA repair, mRNA transcription, cell cycle regulation, and protein ubiquitination. Because most chemotherapeutic agents function by directly or indirectly damaging DNA, the role of BRCA1 as a regulator of chemotherapy-induced DNA damage has been the subject of an increasing number of investigations. We review published preclinical and clinical evidence that the level of BRCA1 function in an individual patient's tumor can guide the choice of chemotherapeutic agents for breast and ovarian cancer. We conclude that a loss of BRCA1 function is associated with sensitivity to DNA-damaging chemotherapy and may also be associated with resistance to spindle poisons. We recommend that prospective clinical studies investigating the role of BRCA1 in the response to chemotherapy be conducted.
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Affiliation(s)
- Richard D Kennedy
- Department of Oncology, Cancer Research Centre, The Queen's University of Belfast, Northern Ireland
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146
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Abstract
A subset of human cancer syndromes result from inherited defects in genes responsible for DNA repair. During the past few years, discoveries concerning the intersection of certain DNA repair processes have increased our understanding of how the disruption of specific DNA repair mechanisms leads to genomic instability and tumorigenesis. This review focuses on the human genes MUTYH, BRCA2/FANCD1, and BLM.
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Affiliation(s)
- Mary A Risinger
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267, USA
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147
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Abstract
The precise replication of the genome and the continuous surveillance of its integrity are essential for survival and the avoidance of various diseases. Cells respond to DNA damage by activating a complex network of the so-called checkpoint pathways to delay their cell-cycle progression and repair the defects. In this review we integrate findings on the emerging mechanisms of activation, the signalling pathways and the spatio-temporal organization of the intra-S-phase DNA-damage checkpoint and its impact on the cell-cycle machinery, and discuss its biological significance.
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Affiliation(s)
- Jiri Bartek
- Danish Cancer Society, Institute of Cancer Biology, Strandboulevarden 49, DK-2100 Copenhagen, Denmark.
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149
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150
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