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Mre11-Rad50: the DNA end game. Biochem Soc Trans 2023; 51:527-538. [PMID: 36892213 DOI: 10.1042/bst20220754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 02/09/2023] [Accepted: 02/17/2023] [Indexed: 03/10/2023]
Abstract
The Mre11-Rad50-(Nbs1/Xrs2) complex is an evolutionarily conserved factor for the repair of DNA double-strand breaks and other DNA termini in all kingdoms of life. It is an intricate DNA associated molecular machine that cuts, among other functions, a large variety of free and obstructed DNA termini for DNA repair by end joining or homologous recombination, yet leaves undamaged DNA intact. Recent years have brought progress in both the structural and functional analyses of Mre11-Rad50 orthologs, revealing mechanisms of DNA end recognition, endo/exonuclease activities, nuclease regulation and DNA scaffolding. Here, I review our current understanding and recent progress on the functional architecture Mre11-Rad50 and how this chromosome associated coiled-coil ABC ATPase acts as DNA topology specific endo-/exonuclease.
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Lund Johansen E, Fribert Thusgaard C, Thomassen M, Eriksen Boonen S, Marie Jochumsen K. Germline Pathogenic Variants Associated with Ovarian Cancer: A Historical Overview. Gynecol Oncol Rep 2022; 44:101105. [DOI: 10.1016/j.gore.2022.101105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 11/02/2022] [Accepted: 11/06/2022] [Indexed: 11/09/2022] Open
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Wang J, Xu WH, Wei Y, Zhu Y, Qin XJ, Zhang HL, Ye DW. Elevated MRE11 expression associated with progression and poor outcome in prostate cancer. J Cancer 2019; 10:4333-4340. [PMID: 31413753 PMCID: PMC6691708 DOI: 10.7150/jca.31454] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 05/06/2019] [Indexed: 01/14/2023] Open
Abstract
Objective: Growing evidence has proved that MRE11, a protein underpinned to be involved in DNA double-strand break (DSB) repair process, is correlated with cancer outcomes. However, its role in prostate cancer (PCa) remains unclear. This study aimed to investigate the expression of MRE11 in tumor tissue and defining its value in predicting prognosis of PCa patients. Methods: A total of 578 patients from two cohorts were enrolled in this study. Distribution of categorical clinical-pathological data together with levels of MRE11 expression was compared with χ2-test in a contingency table. Immunohistochemical (IHC) staining and evaluation was detected from 78 paired PCa and adjacent normal tissues. Partial likelihood test from univariate and multivariate Cox regression analysis was developed to address the influence of independent factors on disease-free survival (DFS) and overall survival (OS) in two cohorts. The Kaplan-Meier method and log-rank test were performed to assess the survival benefits between discrete levels. Set Enrichment Analysis (GSEA) was performed to select related genes and pathways from The Cancer Genome Atlas (TCGA) database. Results: In the current study, we demonstrated that MRE11 was highly expressed in PCa compared with normal tissues (P=0.011). In addition, in the TCGA cohort, the median DFS in patients with IHC positive and negative MRE11 expression levels was 24.5 and 30.6 months, and median OS was 28.7 and 33.0 months, respectively. In FUSCC cohort, median DFS in patients with IHC positive and negative MRE11 expression was 28.0 and 35.6 months. Furthermore, survival curves suggested that PCa patients with elevated MRE11 expression levels showed poorer OS (P=0.019) in TCGA cohort and poor DFS (P=0.047) in FUSCC cohort. Conclusion: In conclusion, our study reveals that elevated MRE11 expression is significantly correlated with cancer progression and poor survival in PCa patients. These data suggest that MRE11 may act as an oncoprotein and a promising prognostic marker for PCa patients.
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Affiliation(s)
- Jun Wang
- Department of Urology, Fudan University Shanghai Cancer Center, Shanghai 200032.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 20032, P.R. China
| | - Wen-Hao Xu
- Department of Urology, Fudan University Shanghai Cancer Center, Shanghai 200032.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 20032, P.R. China
| | - Yu Wei
- Department of Urology, Fudan University Shanghai Cancer Center, Shanghai 200032.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 20032, P.R. China
| | - Yao Zhu
- Department of Urology, Fudan University Shanghai Cancer Center, Shanghai 200032.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 20032, P.R. China
| | - Xiao-Jian Qin
- Department of Urology, Fudan University Shanghai Cancer Center, Shanghai 200032.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 20032, P.R. China
| | - Hai-Liang Zhang
- Department of Urology, Fudan University Shanghai Cancer Center, Shanghai 200032.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 20032, P.R. China
| | - Ding-Wei Ye
- Department of Urology, Fudan University Shanghai Cancer Center, Shanghai 200032.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 20032, P.R. China
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O'Hare EA, Antin PB, Delany ME. Two Proximally Close Priority Candidate Genes for diplopodia-1, an Autosomal Inherited Craniofacial-Limb Syndrome in the Chicken: MRE11 and GPR83. J Hered 2019; 110:194-210. [PMID: 30597046 PMCID: PMC6399517 DOI: 10.1093/jhered/esy071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 12/29/2018] [Indexed: 11/12/2022] Open
Abstract
Next-generation sequencing (NGS) and expression technologies were utilized to investigate the genes and sequence elements in a 586 kb region of chicken chromosome 1 associated with the autosomal recessive diplopodia-1 (dp-1) mutation. This mutation shows a syndromic phenotype similar to known human developmental abnormalities (e.g., cleft palate, polydactyly, omphalocele [exposed viscera]). Toward our goal to ascertain the variant responsible, the entire 586 kb region was sequenced following utilization of a specifically designed capture array and to confirm/validate fine-mapping results. Bioinformatic analyses identified a total of 6142 sequence variants, which included SNPs, indels, and gaps. Of these, 778 SNPs, 146 micro-indels, and 581 gaps were unique to the UCD-Dp-1.003 inbred congenic line; those found within exons and splice sites were studied for contribution to the mutant phenotype. Upon further validation with additional mutant samples, a smaller subset (of variants [51]) remains linked to the mutation. Additionally, utilization of specific samples in the NGS technology was advantageous in that fine-mapping methodologies eliminated an additional 326 kb of sequence information on chromosome 1. Predicted and confirmed protein-coding genes within the smaller 260 kb region were assessed for their developmental expression patterns over several stages of early embryogenesis in regions/tissues of interest (e.g., digits, craniofacial region). Based on these results and known function in other vertebrates, 2 genes within 5 kb of each other, MRE11 and GPR83, are proposed as high-priority candidates for the dp-1 mutation.
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Affiliation(s)
- Elizabeth A O'Hare
- Department of Animal Science, University of California, Davis, CA.,Elizabeth A. O'Hare is now at the Department of Biological Sciences, Towson University, Towson, MD
| | - Parker B Antin
- Department of Molecular and Cellular Medicine, University of Arizona, Tucson, AZ
| | - Mary E Delany
- Department of Animal Science, University of California, Davis, CA
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5
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Khan RT, Siddique A, Shahid N, Khokher S, Fatima W. Breast cancer risk associated with genes encoding DNA repair MRN complex: a study from Punjab, Pakistan. Breast Cancer 2018; 25:350-355. [PMID: 29368209 DOI: 10.1007/s12282-018-0837-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 01/18/2018] [Indexed: 02/01/2023]
Abstract
BACKGROUND Variants of DNA repair genes are extensively reported to cause genetic instability and increase the risk of breast cancer. In combination with NBS1, MRE11 and RAD50 constitute an MRN (MRE11-RAD50-NBS1) complex that repairs DNA damage. However, certain genetic alterations in MRE11 and RAD50 produce abnormal protein that affects the repairing process and may result in malignancy. We aimed to investigate the association of MRE11 and RAD50 polymorphisms with breast risk in the female population of Punjab, Pakistan. METHODS We collected blood samples of 100 breast cancer patients and 100 tumor-free females selected as controls. Extracted DNA was genotyped by tetra ARMS-PCR followed by gel electrophoresis. Results were analyzed by SPSS and SNPstats to analyze the association of different clinical factors and SNPs (single nucleotide polymorphisms) with the risk of breast cancer. RESULTS We found that the increased risk of breast cancer is associated with MRE11 variant rs684507 (odds ratio-OR 3.71, 95% confidence interval-CI 1.68-8.18, p value < 0.0001), whereas, RAD50 variant rs28903089 appeared to have protective effect (OR 0.55, CI 0.29-1.02, p value = 0.003). Additionally, clinical factors such as positive family history, life style, and marital status also play significant roles in breast cancer development. CONCLUSION In the present study, strong risk of breast cancer was associated with MRE11 gene. However, RAD50 showed protective effect. Additionally, clinical factors are also pivotal in risk assessment. We anticipate that targeting specific genetic variations confined to ethnic groups would be more effective in future therapeutic approaches for prevention and treatment of breast cancer.
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Affiliation(s)
- Rabbia Tariq Khan
- Department of Microbiology and Molecular Genetics, University of the Punjab, Lahore, Pakistan
| | - Ayesha Siddique
- Department of Microbiology and Molecular Genetics, University of the Punjab, Lahore, Pakistan.
| | - Naeem Shahid
- Department of Environmental Sciences, COMSATS Institute of Information Technology, Vehari, Pakistan
| | - Samina Khokher
- Services Institute of Medical Sciences, Lahore, Pakistan
| | - Warda Fatima
- Department of Microbiology and Molecular Genetics, University of the Punjab, Lahore, Pakistan
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Personalised Medicine: Genome Maintenance Lessons Learned from Studies in Yeast as a Model Organism. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1007:157-178. [PMID: 28840557 DOI: 10.1007/978-3-319-60733-7_9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Yeast research has been tremendously contributing to the understanding of a variety of molecular pathways due to the ease of its genetic manipulation, fast doubling time as well as being cost-effective. The understanding of these pathways did not only help scientists learn more about the cellular functions but also assisted in deciphering the genetic and cellular defects behind multiple diseases. Hence, yeast research not only opened the doors for transforming basic research into applied research, but also paved the roads for improving diagnosis and innovating personalized therapy of different diseases. In this chapter, we discuss how yeast research has contributed to understanding major genome maintenance pathways such as the S-phase checkpoint activation pathways, repair via homologous recombination and non-homologous end joining as well as topoisomerases-induced protein linked DNA breaks repair. Defects in these pathways lead to neurodegenerative diseases and cancer. Thus, the understanding of the exact genetic defects underlying these diseases allowed the development of personalized medicine, improving the diagnosis and treatment and overcoming the detriments of current conventional therapies such as the side effects, toxicity as well as drug resistance.
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Wang AT, Kim T, Wagner JE, Conti BA, Lach FP, Huang AL, Molina H, Sanborn EM, Zierhut H, Cornes BK, Abhyankar A, Sougnez C, Gabriel SB, Auerbach AD, Kowalczykowski SC, Smogorzewska A. A Dominant Mutation in Human RAD51 Reveals Its Function in DNA Interstrand Crosslink Repair Independent of Homologous Recombination. Mol Cell 2015; 59:478-90. [PMID: 26253028 DOI: 10.1016/j.molcel.2015.07.009] [Citation(s) in RCA: 195] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 05/26/2015] [Accepted: 07/07/2015] [Indexed: 12/17/2022]
Abstract
Repair of DNA interstrand crosslinks requires action of multiple DNA repair pathways, including homologous recombination. Here, we report a de novo heterozygous T131P mutation in RAD51/FANCR, the key recombinase essential for homologous recombination, in a patient with Fanconi anemia-like phenotype. In vitro, RAD51-T131P displays DNA-independent ATPase activity, no DNA pairing capacity, and a co-dominant-negative effect on RAD51 recombinase function. However, the patient cells are homologous recombination proficient due to the low ratio of mutant to wild-type RAD51 in cells. Instead, patient cells are sensitive to crosslinking agents and display hyperphosphorylation of Replication Protein A due to increased activity of DNA2 and WRN at the DNA interstrand crosslinks. Thus, proper RAD51 function is important during DNA interstrand crosslink repair outside of homologous recombination. Our study provides a molecular basis for how RAD51 and its associated factors may operate in a homologous recombination-independent manner to maintain genomic integrity.
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Affiliation(s)
- Anderson T Wang
- Laboratory of Genome Maintenance, The Rockefeller University, New York, NY 10065, USA
| | - Taeho Kim
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, CA 95616, USA
| | - John E Wagner
- Blood and Marrow Transplant Program, Department of Pediatrics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Brooke A Conti
- Laboratory of Genome Maintenance, The Rockefeller University, New York, NY 10065, USA
| | - Francis P Lach
- Laboratory of Genome Maintenance, The Rockefeller University, New York, NY 10065, USA
| | - Athena L Huang
- Laboratory of Genome Maintenance, The Rockefeller University, New York, NY 10065, USA
| | - Henrik Molina
- Proteomics Resource Center, The Rockefeller University, New York, NY 10065, USA
| | - Erica M Sanborn
- Laboratory of Genome Maintenance, The Rockefeller University, New York, NY 10065, USA
| | - Heather Zierhut
- Blood and Marrow Transplant Program, Department of Pediatrics, University of Minnesota, Minneapolis, MN 55455, USA
| | | | | | - Carrie Sougnez
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | | | - Arleen D Auerbach
- Human Genetics and Hematology, The Rockefeller University, New York, NY 10065, USA
| | - Stephen C Kowalczykowski
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, CA 95616, USA
| | - Agata Smogorzewska
- Laboratory of Genome Maintenance, The Rockefeller University, New York, NY 10065, USA.
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Cejka P. DNA End Resection: Nucleases Team Up with the Right Partners to Initiate Homologous Recombination. J Biol Chem 2015; 290:22931-8. [PMID: 26231213 DOI: 10.1074/jbc.r115.675942] [Citation(s) in RCA: 141] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The repair of DNA double-strand breaks by homologous recombination commences by nucleolytic degradation of the 5'-terminated strand of the DNA break. This leads to the formation of 3'-tailed DNA, which serves as a substrate for the strand exchange protein Rad51. The nucleoprotein filament then invades homologous DNA to drive template-directed repair. In this review, I discuss mainly the mechanisms of DNA end resection in Saccharomyces cerevisiae, which includes short-range resection by Mre11-Rad50-Xrs2 and Sae2, as well as processive long-range resection by Sgs1-Dna2 or Exo1 pathways. Resection mechanisms are highly conserved between yeast and humans, and analogous machineries are found in prokaryotes as well.
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Affiliation(s)
- Petr Cejka
- From the Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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9
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Yuan SSF, Hou MF, Hsieh YC, Huang CY, Lee YC, Chen YJ, Lo S. Role of MRE11 in cell proliferation, tumor invasion, and DNA repair in breast cancer. J Natl Cancer Inst 2012; 104:1485-502. [PMID: 22914783 DOI: 10.1093/jnci/djs355] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Previous studies have shown that altered forms of MRE11, a protein known to play a vital role in DNA double-strand break repair, DNA replication, and telomere maintenance are associated with cancer outcomes. We investigated the role of MRE11 in breast cancer in both clinical and in vitro settings. METHODS We examined MRE11 expression in tumor tissues from invasive ductal carcinoma breast cancer patients (n = 254) by immunohistochemistry, and associations with clinicopathological characteristics and overall survival were assessed using Cox proportional hazards regression models and Kaplan-Meier survival curves. Effect of MRE11 overexpression and knockdown on cell proliferation, invasion, and radioresistance was assessed in vitro using breast cancer cell lines (MCF-7 and MDA-MB-231). We also investigated the mechanisms involved. Effect of MRE11 overexpression on tumor growth was assessed in an orthotopic xenograft model (n = 8 mice per group). All statistical tests were two-sided. RESULTS Of the 254 tissue samples, 69.3% and 30.7% showed high and low MRE11 expression, respectively. High MRE11 expression was statistically significantly associated with malignant cancer behavior compared with low MRE11 expression (eg, stages III and IV vs stage I, P = .004; poor overall survival, P = .005). MRE11 overexpression in breast cancer cell lines promoted cell proliferation through STAT3, cell cycle entry, invasion and migration, and radioresistance via enhanced DNA repair activity and also inhibited apoptosis; knockdown of MRE11 had the opposite effect. In xenograft tumor-bearing mice (n = 8 per group), increased tumor growth was observed in the MRE11-overexpressing group compared with the control group (tumor volume at week 8, control vs MRE11-overexpressing tumor originating from MCF-7 cells, mean = 280.4 mm(3), 95% confidence interval [CI] = 62.4 to 498.4 mm(3) vs mean = 631.0 mm(3), 95% CI = 296.9 to 965.0 mm(3), P = .043). CONCLUSION High MRE11 expression was associated with a more malignant behavior in breast cancer. MRE11 may be a novel oncoprotein and may therefore serve as a new therapeutic intervention against breast cancer.
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Thompson EG, Fares H, Dixon K. BRCA1 requirement for the fidelity of plasmid DNA double-strand break repair in cultured breast epithelial cells. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2012; 53:32-43. [PMID: 22170030 DOI: 10.1002/em.21674] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 10/25/2011] [Accepted: 11/09/2011] [Indexed: 05/31/2023]
Abstract
The tumor suppressor breast cancer susceptibility protein 1 (BRCA1) protects our cells from genomic instability in part by facilitating the efficient repair of DNA double-strand breaks (DSBs). BRCA1 promotes the error-free repair of DSBs through homologous recombination and is also implicated in the regulation of nonhomologous end joining (NHEJ) repair fidelity. Here, we investigate the role of BRCA1 in NHEJ repair mutagenesis following a DSB. We examined the frequency of microhomology-mediated end joining (MMEJ) and the fidelity of DSB repair relative to BRCA1 protein levels in both control and tumorigenic breast epithelial cells. In addition to altered BRCA1 protein levels, we tested the effects of cellular exposure to mirin, an inhibitor of meiotic recombination enzyme 11 (Mre11) 3'-5'-exonuclease activity. Knockdown or loss of BRCA1 protein resulted in an increased frequency of overall plasmid DNA mutagenesis and MMEJ following a DSB. Inhibition of Mre11-exonuclease activity with mirin significantly decreased the occurrence of MMEJ, but did not considerably affect the overall mutagenic frequency of plasmid DSB repair. The results suggest that BRCA1 protects DNA from mutagenesis during nonhomologous DSB repair in plasmid-based assays. The increased frequency of DSB mutagenesis and MMEJ repair in the absence of BRCA1 suggests a potential mechanism for carcinogenesis.
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Affiliation(s)
- Eric G Thompson
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, USA.
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Two brothers with ataxia-telangiectasia-like disorder with lung adenocarcinoma. J Pediatr 2009; 155:435-8. [PMID: 19732584 DOI: 10.1016/j.jpeds.2009.02.037] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Revised: 01/15/2009] [Accepted: 02/17/2009] [Indexed: 11/21/2022]
Abstract
We report on 2 brothers with ataxia-telangiectasia-like disorder with lung adenocarcinoma. They both had ataxia with cerebellar atrophy and mental retardation. They had the same mutation of the MRE11 gene, which has not been reported previously (c.727T>C and g.24994G>A).
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Abstract
Double-strand breaks (DSBs) are deleterious DNA lesions and if left unrepaired result in severe genomic instability. Cells use two main pathways to repair DSBs: homologous recombination (HR) or non-homologous end joining (NHEJ) depending on the phase of the cell cycle and the nature of the DSB ends. A key step where pathway choice is exerted is in the 'licensing' of 5'-3' resection of the ends to produce recombinogenic 3' single-stranded tails. These tails are substrate for binding by Rad51 to initiate pairing and strand invasion with homologous duplex DNA. Moreover, the single-stranded DNA generated after end processing is important to activate the DNA damage response. The mechanism of end processing is the focus of this review and we will describe recent findings that shed light on this important initiating step for HR. The conserved MRX/MRN complex appears to be a major regulator of DNA end processing. Sae2/CtIP functions with the MRX complex, either to activate the Mre11 nuclease or via the intrinsic endonuclease, in an initial step to trim the DSB ends. In a second step, redundant systems remove long tracts of DNA to reveal extensive 3' single-stranded tails. One system is dependent on the helicase Sgs1 and the nuclease Dna2, and the other on the 5'-3' exonuclease Exo1.
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Affiliation(s)
- Eleni P Mimitou
- Department of Microbiology, Columbia University College of Physicians and Surgeons, New York, NY 10032, United States
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Meiotic localization of Mre11 and Rad50 in wild type, spo11-1, and MRN complex mutants of Coprinus cinereus. Chromosoma 2009; 118:471-86. [PMID: 19396455 DOI: 10.1007/s00412-009-0209-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Revised: 02/28/2009] [Accepted: 03/07/2009] [Indexed: 10/20/2022]
Abstract
The Mre11-Rad50-Nbs1 (MRN) complex is required for numerous cellular processes that involve interactions with DNA double-strand breaks. For the majority of these processes, the MRN complex is thought to act as a unit, with each protein aiding the activity of the others. We have examined the relationship between Mre11 and Rad50 during meiosis in the basidiomycete Coprinus cinereus (Coprinopsis cinerea), investigating to what extent activities of Mre11 and Rad50 are interdependent. We showed that mre11-1 is epistatic to rad50-1 with respect to the time of meiotic arrest, indicating that Mre11 activity facilitates the diffuse diplotene arrest of rad50 mutants. Anti-Mre11 and anti-Rad50 antibodies were used to examine MRN complex localization in a wild-type strain and in spo11, mre11, and rad50 mutants. In wild type, numbers of Mre11 and Rad50 foci peaked at time points corresponding to leptotene and early zygotene. In the spo11-1 mutant, which is defective in meiotic double-strand break formation, foci accumulated throughout prophase I. Of seven MRN mutants examined, only two rad50 strains exhibited Mre11 and Rad50 foci that localized to chromatin, although Mre11 protein was found in the cell for all of them. Analysis of predicted mutant structures showed that stable localization of Mre11 and Rad50 does not depend upon a wild-type hook-proximal coiled coil, but does require the presence of the Rad50 ATPase/adenylate cyclase domains. We found that Mre11 and Rad50 were interdependent for binding to meiotic chromosomes. However, the majority of foci observed apparently contained only one of the two proteins. Independent Mre11 and Rad50 foci might indicate disassociation of the complex during meiosis or could reflect independent structural roles for the two proteins in meiotic chromatin.
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Corley SM, Gready JE. Identification of the RGG box motif in Shadoo: RNA-binding and signaling roles? Bioinform Biol Insights 2008; 2:383-400. [PMID: 19812790 PMCID: PMC2735946 DOI: 10.4137/bbi.s1075] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Using comparative genomics and in-silico analyses, we previously identified a new member of the prion-protein (PrP) family, the gene SPRN, encoding the protein Shadoo (Sho), and suggested its functions might overlap with those of PrP. Extended bioinformatics and conceptual biology studies to elucidate Sho’s functions now reveal Sho has a conserved RGG-box motif, a well-known RNA-binding motif characterized in proteins such as FragileX Mental Retardation Protein. We report a systematic comparative analysis of RGG-box containing proteins which highlights the motif’s functional versatility and supports the suggestion that Sho plays a dual role in cell signaling and RNA binding in brain. These findings provide a further link to PrP, which has well-characterized RNA-binding properties.
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Affiliation(s)
- Susan M Corley
- Computational Proteomics and Therapy Design Group, Division of Molecular Bioscience, John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra ACT 2601, Australia
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Coprinus cinereus rad50 mutants reveal an essential structural role for Rad50 in axial element and synaptonemal complex formation, homolog pairing and meiotic recombination. Genetics 2008; 180:1889-907. [PMID: 18940790 DOI: 10.1534/genetics.108.092775] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Mre11/Rad50/Nbs1 (MRN) complex is required for eukaryotic DNA double-strand break (DSB) repair and meiotic recombination. We cloned the Coprinus cinereus rad50 gene and showed that it corresponds to the complementation group previously named rad12, identified mutations in 15 rad50 alleles, and mapped two of the mutations onto molecular models of Rad50 structure. We found that C. cinereus rad50 and mre11 mutants arrest in meiosis and that this arrest is Spo11 dependent. In addition, some rad50 alleles form inducible, Spo11-dependent Rad51 foci and therefore must be forming meiotic DSBs. Thus, we think it likely that arrest in both mre11-1 and the collection of rad50 mutants is the result of unrepaired or improperly processed DSBs in the genome and that Rad50 and Mre11 are dispensable in C. cinereus for DSB formation, but required for appropriate DSB processing. We found that the ability of rad50 mutant strains to form Rad51 foci correlates with their ability to promote synaptonemal complex formation and with levels of stable meiotic pairing and that partial pairing, recombination initiation, and synapsis occur in the absence of wild-type Rad50 catalytic domains. Examination of single- and double-mutant strains showed that a spo11 mutation that prevents DSB formation enhances axial element (AE) formation for rad50-4, an allele predicted to encode a protein with intact hook region and hook-proximal coiled coils, but not for rad50-1, an allele predicted to encode a severely truncated protein, or for rad50-5, which encodes a protein whose hook-proximal coiled-coil region is disrupted. Therefore, Rad50 has an essential structural role in the formation of AEs, separate from the DSB-processing activity of the MRN complex.
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Alsbeih G, Al-Hadyan K, Al-Harbi N. Assessment of Carriers' Frequency of a Novel MRE11 Mutation Responsible for the Rare Ataxia Telangiectasia-Like Disorder. ACTA ACUST UNITED AC 2008; 12:387-9. [DOI: 10.1089/gte.2008.0011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Ghazi Alsbeih
- Radiation Biology Laboratory, Biomedical Physics Department, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Khaled Al-Hadyan
- Radiation Biology Laboratory, Biomedical Physics Department, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Najla Al-Harbi
- Radiation Biology Laboratory, Biomedical Physics Department, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
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Mathew SS, Bridge E. Nbs1-dependent binding of Mre11 to adenovirus E4 mutant viral DNA is important for inhibiting DNA replication. Virology 2008; 374:11-22. [PMID: 18234271 DOI: 10.1016/j.virol.2007.12.034] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2007] [Revised: 08/30/2007] [Accepted: 12/14/2007] [Indexed: 11/24/2022]
Abstract
Adenovirus (Ad) infections stimulate the activation of cellular DNA damage response and repair pathways. Ad early regulatory proteins prevent activation of DNA damage responses by targeting the MRN complex, composed of the Mre11, Rad50 and Nbs1 proteins, for relocalization and degradation. In the absence of these viral proteins, Mre11 colocalizes with viral DNA replication foci. Mre11 foci formation at DNA damage induced by ionizing radiation depends on the Nbs1 component of the MRN complex and is stabilized by the mediator of DNA damage checkpoint protein 1 (Mdc1). We find that Nbs1 is required for Mre11 localization at DNA replication foci in Ad E4 mutant infections. Mre11 is important for Mdc1 foci formation in infected cells, consistent with its role as a sensor of DNA damage. Chromatin immunoprecipitation assays indicate that both Mre11 and Mdc1 are physically bound to viral DNA, which could account for their localization in viral DNA containing foci. Efficient binding of Mre11 to E4 mutant DNA depends on the presence of Nbs1, and is correlated with a significant E4 mutant DNA replication defect. Our results are consistent with a model in which physical interaction of Mre11 with viral DNA is mediated by Nbs1, and interferes with viral DNA replication.
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Affiliation(s)
- Shomita S Mathew
- Department of Microbiology, 32 Pearson Hall, Miami University, Oxford, OH 45056, USA
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18
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Donahue SL, Tabah AA, Schmitz K, Aaron A, Campbell C. Defective signal joint recombination in fanconi anemia fibroblasts reveals a role for Rad50 in V(D)J recombination. J Mol Biol 2007; 370:449-58. [PMID: 17524422 PMCID: PMC2727996 DOI: 10.1016/j.jmb.2007.03.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Revised: 03/02/2007] [Accepted: 03/05/2007] [Indexed: 10/23/2022]
Abstract
V(D)J recombination of immunoglobulin loci is dependent on the immune cell-specific Rag1 and Rag2 proteins as well as a number of ubiquitously expressed cellular DNA repair proteins that catalyze non-homologous end-joining of DNA double-strand breaks. The evolutionarily conserved Rad50/Mre11/Nibrin protein complex has a role in DNA double-strand break-repair, suggesting that these proteins, too, may participate in V(D)J recombination. Recent findings demonstrating that Rad50 function is defective in cells from patients afflicted with Fanconi anemia provide a possible mechanistic explanation for previous findings that lymphoblasts derived from these patients exhibit subtle defects in V(D)J recombination of extrachromosomal plasmid molecules. Here, we describe a series of findings that provide convincing evidence for a role of the Rad50 protein complex in V(D)J recombination. We found that the fidelity of V(D)J signal joint recombination in fibroblasts from patients afflicted with Fanconi anemia was reduced by nearly tenfold, compared to that observed in fibroblasts from normal donors. Second, we observed that antibody-mediated inhibition of the Rad50, Mre11, or Nibrin proteins reduced the fidelity of signal joint recombination significantly in wild-type cells. The latter finding was somewhat unexpected, because signal joint rejoining in cells from patients with Nijmegen breakage syndrome, which results from mutations in the Nibrin gene, occurs with normal fidelity. However, introduction of anti-Nibrin antibodies into these cells reduced the fidelity of signal joint recombination dramatically. These data reveal for the first time a role for the Rad50 complex in V(D)J recombination, and demonstrate that the protein product of the disease-causing allele responsible for Nijmegen breakage syndrome encodes a protein with residual DNA double-strand break repair activity.
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Affiliation(s)
| | | | - Kyle Schmitz
- From the Department of Pharmacology, University of Minnesota Medical School, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis MN 55455
| | - Ashley Aaron
- From the Department of Pharmacology, University of Minnesota Medical School, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis MN 55455
| | - Colin Campbell
- From the Department of Pharmacology, University of Minnesota Medical School, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis MN 55455
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19
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de Bustos A, Pérez R, Jouve N. Characterization of the gene Mre11 and evidence of silencing after polyploidization in Triticum. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2007; 114:985-99. [PMID: 17262197 DOI: 10.1007/s00122-006-0493-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Accepted: 12/21/2006] [Indexed: 05/13/2023]
Abstract
The MRE11 protein is a component of the highly conserved MRN complex, along with RAD50 and NBS1. This complex is crucial in the repair of breaks in double stranded DNA, and is involved in many other cell processes. The present paper reports the molecular characterization of Mre11 gene in all three genomes of wheat, making use of the diploid species Triticum monococcum (genome A) and Aegilops Tauschii (genome D), the tetraploid T. turgidum (genomes A and B), and the hexaploid T. aestivum (genomes A, B and D). The genomic sequences characterized ranged from 4,662 to 4,766 bp in length; the cDNA corresponding to the processed mRNA was 2,440-2,510 bp long. In all cases, Mre11 coded for a highly conserved protein of 699 amino acids with a structure involving 22 exons. Mre11 expression was determined by real-time PCR in all the species analysed. The tetraploid species showed an expression similar to that of the diploid Ae. tauschii and lower than that of T. monococcum. Stronger expression was detected in the hexaploid T. aestivum. The SSCP technique was modified by introducing fluorescent labelling to the procedure in order to analyse the expression of the different Mre11 genes (i.e., those belonging to the different genomes) in the polyploid species. In both polyploids, the Mre11 gene belonging to the B genome was the least expressed. This probably reflects a first step in the process of silencing duplicate genes after polyploidization.
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MESH Headings
- Amino Acid Sequence
- Base Pairing
- Base Sequence
- Blotting, Southern
- DNA, Complementary
- DNA, Plant/genetics
- DNA, Plant/isolation & purification
- Exons
- Gene Expression Regulation, Plant
- Gene Silencing
- Genes, Plant
- Genetic Variation
- Genome, Plant
- Molecular Sequence Data
- Phylogeny
- Plant Proteins/analysis
- Plant Proteins/chemistry
- Plant Proteins/genetics
- Polymerase Chain Reaction
- Polymorphism, Single-Stranded Conformational
- Polyploidy
- RNA, Messenger/chemistry
- RNA, Plant/chemistry
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Species Specificity
- Triticum/classification
- Triticum/genetics
- Triticum/metabolism
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Affiliation(s)
- Alfredo de Bustos
- Department of Cell Biology and Genetics, University of Alcalá, Campus Universidad de Alcalá, 28871 Alcalá de Henares (Madrid), Spain
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20
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Moore SR, Papworth D, Grosovsky AJ. Non-random distribution of instability-associated chromosomal rearrangement breakpoints in human lymphoblastoid cells. Mutat Res 2006; 600:113-24. [PMID: 16716366 DOI: 10.1016/j.mrfmmm.2006.03.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2005] [Revised: 03/15/2006] [Accepted: 03/24/2006] [Indexed: 11/25/2022]
Abstract
Genomic instability is observed in tumors and in a large fraction of the progeny surviving irradiation. One of the best-characterized phenotypic manifestations of genomic instability is delayed chromosome aberrations. Our working hypothesis for the current study was that if genomic instability is in part attributable to cis mechanisms, we should observe a non-random distribution of chromosomes or sites involved in instability-associated rearrangements, regardless of radiation quality, dose, or trans factor expression. We report here the karyotypic examination of 296 instability-associated chromosomal rearrangement breaksites (IACRB) from 118 unstable TK6 human B lymphoblast, and isogenic derivative, clones. When we tested whether IACRB were distributed across the chromosomes based on target size, a significant non-random distribution was evident (p<0.00001), and three IACRB hotspots (chromosomes 11, 12, and 22) and one IACRB coldspot (chromosome 2) were identified. Statistical analysis at the chromosomal band-level identified four IACRB hotspots accounting for 20% of all instability-associated breaks, two of which account for over 14% of all IACRB. Further, analysis of independent clones provided evidence within 14 individual clones of IACRB clustering at the chromosomal band level, suggesting a predisposition for further breaks after an initial break at some chromosomal bands. All of these events, independently, or when taken together, were highly unlikely to have occurred by chance (p<0.000001). These IACRB band-level cluster hotspots were observed independent of radiation quality, dose, or cellular p53 status. The non-random distribution of instability-associated chromosomal rearrangements described here significantly differs from the distribution that was observed in a first-division post-irradiation metaphase analysis (p=0.0004). Taken together, these results suggest that genomic instability may be in part driven by chromosomal cis mechanisms.
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Affiliation(s)
- Stephen R Moore
- Environmental Toxicology Graduate Program, Department of Cell Biology and Neuroscience, University of California, Riverside, CA, USA
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21
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Trenz K, Smith E, Smith S, Costanzo V. ATM and ATR promote Mre11 dependent restart of collapsed replication forks and prevent accumulation of DNA breaks. EMBO J 2006; 25:1764-74. [PMID: 16601701 PMCID: PMC1440833 DOI: 10.1038/sj.emboj.7601045] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2005] [Accepted: 02/22/2006] [Indexed: 01/14/2023] Open
Abstract
Ataxia-telangiectasia mutated (ATM), ataxia-telangiectasia Rad3-related (ATR) and the Mre11/Rad50/Nbs1 complex ensure genome stability in response to DNA damage. However, their essential role in DNA metabolism remains unknown. Here we show that ATM and ATR prevent accumulation of DNA double-strand breaks (DSBs) during chromosomal replication. Replicating chromosomes accumulate DSBs in Xenopus laevis egg extracts depleted of ATM and ATR. Addition of ATM and ATR proteins to depleted extracts prevents DSB accumulation by promoting restart of collapsed replication forks that arise during DNA replication. We show that collapsed forks maintain MCM complex but lose Pol epsilon, and that Pol epsilon reloading requires ATM and ATR. Replication fork restart is abolished in Mre11 depleted extracts and is restored by supplementation with recombinant human Mre11/Rad50/Nbs1 complex. Using a novel fluorescence resonance energy transfer-based technique, we demonstrate that ATM and ATR induce Mre11/Rad50/Nbs1 complex redistribution to restarting forks. This study provides direct biochemical evidence that ATM and ATR prevent accumulation of chromosomal abnormalities by promoting Mre11/Rad50/Nbs1 dependent recovery of collapsed replication forks.
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Affiliation(s)
- Kristina Trenz
- Genome Stability Unit, London Research Institute, Clare Hall Laboratories, South Mimms, London, UK
| | - Eloise Smith
- Genome Stability Unit, London Research Institute, Clare Hall Laboratories, South Mimms, London, UK
| | - Sarah Smith
- Genome Stability Unit, London Research Institute, Clare Hall Laboratories, South Mimms, London, UK
| | - Vincenzo Costanzo
- Genome Stability Unit, London Research Institute, Clare Hall Laboratories, South Mimms, London, UK
- Genome Stability Unit, London Research Institute, Clare Hall Laboratories, Blanch Lane, South Mimms, EN6 3LD London, UK. Tel.: +44 1707 625548; Fax: +44 1707 625546; E-mail:
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22
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Zhou J, Lim CUK, Li JJ, Cai L, Zhang Y. The role of NBS1 in the modulation of PIKK family proteins ATM and ATR in the cellular response to DNA damage. Cancer Lett 2006; 243:9-15. [PMID: 16530324 PMCID: PMC3658610 DOI: 10.1016/j.canlet.2006.01.026] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Revised: 01/23/2006] [Accepted: 01/24/2006] [Indexed: 01/10/2023]
Abstract
Ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR) kinases have been considered the primary activators of the cellular response to DNA damage. They belong to the protein kinase family, phosphoinositide 3-kinase-related kinase (PIKKs). In human beings, deficiency of these kinases leads to hereditary diseases, namely ataxia telangiectasia (AT) with ATM deficiency and ATR-Seckel with ATR deficiency. NBS1, a component of MRE11/RAD50/NBS1 (MRN) complex, is another important player in DNA damage response (DDR). Mutations of NBS1 are responsible for Nijmegen breakage syndrome (NBS), a human hereditary disease with the characteristics that almost encompassed those of AT and ATR-Seckel. NBS1 has been conventionally thought to be a downstream substrate of ATM and ATR in DDR; however, recent studies suggest that NBS1/MRN functions upstream of both ATM and ATR by recruiting them to the proximity of DNA damage sites and activating their functions. In this mini-review, we would emphasize the requirement of NBS1 as an upstream mediator for the modulation of PIKK family proteins ATM and ATR.
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Affiliation(s)
- Junqing Zhou
- Department of Environmental and Radiological Health Science, Colorado State University, Fort Collins, CO 80521, USA
| | - Chang UK Lim
- Cancer Center, Ordway Research Institute, 150 New Scotland Avenue Rm 4133, Albany, NY 12208, USA
| | - Jian Jian Li
- Division of Molecular Radiobiology, Purdue University School of Health Sciences, West Lafayette, IN 47907, USA
| | - Lu Cai
- Department of Medicine and Radiation Oncology, University of Louisville, School of Medicine, Louisville, KT 40202, USA
- Corresponding authors. Tel.: +1 970 491 0574; fax: +1 970 491 0623. (Y. Zhang). * Tel.: +1 502 852 5215; fax: +1 502 852 6904 (L. Cai). (Y. Zhang), (L. Cai)
| | - Ying Zhang
- Department of Environmental and Radiological Health Science, Colorado State University, Fort Collins, CO 80521, USA
- Corresponding authors. Tel.: +1 970 491 0574; fax: +1 970 491 0623. (Y. Zhang). * Tel.: +1 502 852 5215; fax: +1 502 852 6904 (L. Cai). (Y. Zhang), (L. Cai)
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23
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Cerosaletti K, Wright J, Concannon P. Active role for nibrin in the kinetics of atm activation. Mol Cell Biol 2006; 26:1691-9. [PMID: 16478990 PMCID: PMC1430256 DOI: 10.1128/mcb.26.5.1691-1699.2006] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2005] [Revised: 09/27/2005] [Accepted: 12/06/2005] [Indexed: 01/02/2023] Open
Abstract
The Atm protein kinase is central to the DNA double-strand break response in mammalian cells. After irradiation, dimeric Atm undergoes autophosphorylation at Ser 1981 and dissociates into active monomers. Atm activation is stimulated by expression of the Mre11/Rad50/nibrin complex. Previously, we showed that a C-terminal fragment of nibrin, containing binding sites for both Mre11 and Atm, was sufficient to provide this stimulatory effect in Nijmegen breakage syndrome (NBS) cells. To discriminate whether nibrin's role in Atm activation is to bind and translocate Mre11/Rad50 to the nucleus or to interact directly with Atm, we expressed an Mre11 transgene with a C-terminal NLS sequence in NBS fibroblasts. The Mre11-NLS protein complexed with Rad50, localized to the nucleus in NBS fibroblasts, and associated with chromatin. However, Atm autophosphorylation was not stimulated in cells expressing Mre11-NLS, nor were downstream Atm targets phosphorylated. To determine whether nibrin-Atm interaction is necessary to stimulate Atm activation, we expressed nibrin transgenes lacking the Atm binding domain in NBS fibroblasts. The nibrin DeltaAtm protein interacted with Mre11/Rad50; however, Atm autophosphorylation was dramatically reduced after irradiation in NBS cells expressing the nibrin DeltaAtm transgenes relative to wild-type nibrin. These results indicate that nibrin plays an active role in Atm activation beyond translocating Mre11/Rad50 to the nucleus and that this function requires nibrin-Atm interaction.
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Affiliation(s)
- Karen Cerosaletti
- Molecular Genetics Program, Benaroya Research Institute, Seattle, WA 98101, USA
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24
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Bleuyard JY, Gallego ME, White CI. Recent advances in understanding of the DNA double-strand break repair machinery of plants. DNA Repair (Amst) 2005; 5:1-12. [PMID: 16202663 DOI: 10.1016/j.dnarep.2005.08.017] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2005] [Revised: 08/22/2005] [Accepted: 08/22/2005] [Indexed: 11/21/2022]
Abstract
Living cells suffer numerous and varied alterations of their genetic material. Of these, the DNA double-strand break (DSB) is both particularly threatening and common. Double-strand breaks arise from exposure to DNA damaging agents, but also from cell metabolism-in a fortuitous manner during DNA replication or repair of other kinds of lesions and in a programmed manner, for example during meiosis or V(D)J gene rearrangement. Cells possess several overlapping repair pathways to deal with these breaks, generally designated as genetic recombination. Genetic and biochemical studies have provided considerable amounts of data about the proteins involved in recombination processes and their functions within these processes. Although they have long played a key role in building understanding of genetics, relatively little is known at the molecular level of the genetic recombination processes in plants. The use of reverse genetic approaches and the public availability of sequence tagged mutants in Arabidopsis thaliana have led to increasingly rapid progress in this field over recent years. The rapid progress of studies of recombination in plants is obviously not limited to the DSB repair machinery as such and we ask readers to understand that in order to maintain the focus and to rest within a reasonable length, we present only limited discussion of the exciting advances in the of plant meiosis field, which require a full review in their own right . We thus present here an update on recent advances in understanding of the DSB repair machinery of plants, focussing on Arabidopsis and making a particular effort to place these in the context of more general of understanding of these processes.
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Affiliation(s)
- Jean-Yves Bleuyard
- Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, UK.
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25
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Abstract
Ataxia telangiectasia (AT) is a rare human disease characterized by extreme cellular sensitivity to radiation and a predisposition to cancer, with a hallmark of onset in early childhood. Several human diseases also share similar symptoms with AT albeit with different degrees of severity and different associated disorders. While all AT patients contain mutations in the AT-mutated gene (ATM), most other AT-like disorders are defective in genes encoding an MRN protein complex consisting of Mre11, Rad50 and Nbs1. Both ATM and MRN function as cellular sensors to DNA double-strand breaks, which lead to the recruitment and phosphorylation of an array of substrate proteins involved in DNA repair, apoptosis and cell-cycle checkpoints, as well as gene regulation, translation initiation and telomere maintenance. ATM is a member of the family of phosphatidylinositol 3-kinase-like protein kinases (PIKK), and the discovery of many ATM substrates provides the underlying mechanisms of heterologous symptoms among AT patients. This review article focuses on recent findings related to the initial recognition of double-strand breaks by ATM and MRN, as well as a DNA-dependent protein kinase complex consisting of the heterodimer Ku70/Ku80 and its catalytic subunit DNA-PKcs, another member of PIKK. This possible interaction suggests that a much greater complex is involved in sensing, transducing and co-ordinating cellular events in response to genome instability.
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Affiliation(s)
- Lindsay G Ball
- Department of Microbiology and Immunology, University of Saskatchewan, Saskatoon, SK Canada, S7N 5E5
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26
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Dudásová Z, Dudás A, Chovanec M. Non-homologous end-joining factors of Saccharomyces cerevisiae. FEMS Microbiol Rev 2005; 28:581-601. [PMID: 15539075 DOI: 10.1016/j.femsre.2004.06.001] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2004] [Revised: 06/02/2004] [Accepted: 06/02/2004] [Indexed: 01/09/2023] Open
Abstract
DNA double-strand breaks (DSB) are considered to be a severe form of DNA damage, because if left unrepaired, they can cause a cell death and, if misrepaired, they can lead to genomic instability and, ultimately, the development of cancer in multicellular organisms. The budding yeast Saccharomyces cerevisiae repairs DSB primarily by homologous recombination (HR), despite the presence of the KU70, KU80, DNA ligase IV and XRCC4 homologues, essential factors of the mammalian non-homologous end-joining (NHEJ) machinery. S. cerevisiae, however, lacks clear DNA-PKcs and ARTEMIS homologues, two important additional components of mammalian NHEJ. On the other hand, S. cerevisiae is endowed with a regulatory NHEJ component, Nej1, which has not yet been found in other organisms. Furthermore, there is evidence in budding yeast for a requirement for the Mre11/Rad50/Xrs2 complex for NHEJ, which does not appear to be the case either in Schizosaccharomyces pombe or in mammals. Here, we comprehensively describe the functions of all the S. cerevisiae NHEJ components identified so far and present current knowledge about the NHEJ process in this organism. In addition, this review depicts S. cerevisiae as a powerful model system for investigating the utilization of either NHEJ or HR in DSB repair.
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Affiliation(s)
- Zuzana Dudásová
- Laboratory of Molecular Genetics, Cancer Research Institute, Slovak Academy of Sciences, Vlárska 7, 833 91 Bratislava 37, Slovak Republic
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27
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Tran HM, Shi G, Li G, Carney JP, O'Malley B, Li D. Mutant Nbs1 enhances cisplatin-induced DNA damage and cytotoxicity in head and neck cancer. Otolaryngol Head Neck Surg 2004; 131:477-84. [PMID: 15467621 DOI: 10.1016/j.otohns.2004.04.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Enhanced DNA double-strand break (DSB) repair could be a primary cause for development of resistance in tumor cells to cisplatin, which induces crosslinks and DNA DSBs. A protein complex consisting of hMre11, hRad50, and Nbs1 (MRN) has been identified as a critical component in repair of DNA DSBs. The present study investigates whether the expression of a truncated form of Nbs1 interrupts the function of the MRN complex and therefore enhances cisplatin-induced DNA damage and cytotoxicity in human head and neck squamous cell carcinoma (HNSCC). METHODS AND MEASURES Two human HNSCC cell lines, JHU006 and JHU029, were used. A dominant negative recombinant adenovirus expressing domains of Nbs1 was constructed. Adenovirus-mediated mutant Nbs1 (Ad-Nbs1) gene transfer was performed with replication-defective virus (DL312) and no treatment as controls. Transgene expression and cell viability were evaluated in transfected cells. Neutral comet assay was performed and the "tail moment," the product of the amount of DNA in the tail and the distance of tail migration, was analyzed for evaluating DNA DSB damage at 24, 48, and 72 hours. RESULTS Transgene expression of mutant Nbs1 was confirmed by Western blotting. Ad-Nbs1 gene transfer significantly increased cisplatin-induced cytotoxicity as shown by stunting of 6-day growth curves. Neutral comet analysis revealed that the mean tail moment, indicative of DNA damage, was significantly elevated in cells treated with combined cisplatin and Ad-Nbs1 compared to cisplatin alone in both cell lines. CONCLUSIONS Expression of mutant Nbs1 significantly increases cisplatin-induced DNA DSBs and cytotoxicity. The increase in double-strand DNA damage corresponds to the level of cytotoxicity in the different treatment groups and suggests that tumor chemosensitization occurs through augmentation of DNA DSBs. CLINICAL SIGNIFICANCE Alteration of DNA repair may provide a novel approach to enhancing sensitivity of HNSCC to chemotherapy. Our study supports the potential application of Ad-Nbs1 in combination with cisplatin for treatment of advanced and metastatic HNSCC.
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Affiliation(s)
- Hao Mimi Tran
- Department of Otolarygology-Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, USA
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28
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Dudás A, Chovanec M. DNA double-strand break repair by homologous recombination. Mutat Res 2004; 566:131-67. [PMID: 15164978 DOI: 10.1016/j.mrrev.2003.07.001] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2003] [Revised: 07/29/2003] [Accepted: 07/30/2003] [Indexed: 01/06/2023]
Abstract
DNA double-strand breaks (DSB) are presumed to be the most deleterious DNA lesions as they disrupt both DNA strands. Homologous recombination (HR), single-strand annealing, and non-homologous end-joining are considered to be the pathways for repairing DSB. In this review, we focus on DSB repair by HR. The proteins involved in this process as well as the interactions among them are summarized and characterized. The main emphasis is on eukaryotic cells, particularly the budding yeast Saccharomyces cerevisiae and mammals. Only the RAD52 epistasis group proteins are included.
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Affiliation(s)
- Andrej Dudás
- Laboratory of Molecular Genetics, Cancer Research Institute, Slovak Academy of Sciences, Vlárska 7, 833 91 Bratislava 37, Slovak Republic
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29
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de Lange T, Petrini JH. A new connection at human telomeres: association of the Mre11 complex with TRF2. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2003; 65:265-73. [PMID: 12760040 DOI: 10.1101/sqb.2000.65.265] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- T de Lange
- Laboratory for Cell Biology and Genetics, Rockefeller University, New York, New York 10021, USA
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30
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Semighini CP, von Zeska Kress Fagundes MR, Ferreira JC, Pascon RC, de Souza Goldman MH, Goldman GH. Different roles of the Mre11 complex in the DNA damage response in Aspergillus nidulans. Mol Microbiol 2003; 48:1693-709. [PMID: 12791148 DOI: 10.1046/j.1365-2958.2003.03539.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Mre11-Rad50-Nbs1 protein complex has emerged as a central player in the cellular DNA damage response. Mutations in scaANBS1, which encodes the apparent homologue of human Nbs1 in Aspergillus nidulans, inhibit growth in the presence of the anti-topoisomerase I drug camptothecin. We have used the scaANBS1 cDNA as a bait in a yeast two-hybrid screening and report the identification of the A. nidulans Mre11 homologue (mreA). The inactivated mreA strain was more sensitive to several DNA damaging and oxidative stress agents. Septation in A. nidulans is dependent not only on the uvsBATR gene, but also on the mre11 complex. scaANBS1 and mreA genes are both involved in the DNA replication checkpoint whereas mreA is specifically involved in the intra-S-phase checkpoint. ScaANBS1 also participates in G2-M checkpoint control upon DNA damage caused by MMS. In addition, the scaANBS1 gene is also important for ascospore viability, whereas mreA is required for successful meiosis in A. nidulans. Consistent with this view, the Mre11 complex and the uvsCRAD51 gene are highly expressed at the mRNA level during the sexual development.
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Affiliation(s)
- Camile P Semighini
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Brazil
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31
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Limoli CL, Laposa R, Cleaver JE. DNA replication arrest in XP variant cells after UV exposure is diverted into an Mre11-dependent recombination pathway by the kinase inhibitor wortmannin. Mutat Res 2002; 510:121-9. [PMID: 12459448 DOI: 10.1016/s0027-5107(02)00257-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Ultraviolet (UV) irradiation produces DNA photoproducts that are blocks to DNA replication by normal replicative polymerases. A specialized, damage-specific, distributive polymerase, Pol H or Pol h, that is the product of the hRad30A gene, is required for replication past these photoproducts. This polymerase is absent from XP variant (XP-V) cells that must employ other mechanisms to negotiate blocks to DNA replication. These mechanisms include the use of alternative polymerases or recombination between sister chromatids. Replication forks arrested by UV damage in virus transformed XP-V cells degrade into DNA double strand breaks that are sites for recombination, but in normal cells arrested forks may be protected from degradation by p53 protein. These breaks are sites for binding a protein complex, hMre11/hRad50/Nbs1, that colocalizes with H2AX and PCNA, and can be visualized as immunofluorescent foci. The protein complexes need phosphorylation to activate their DNA binding capacity. Incubation of UV irradiated XP-V cells with the irreversible kinase inhibitor wortmannin, however, increased the yield of Mre11 focus-positive cells. One interpretation of this observation is that two classes of kinases are involved after UV irradiation. One would be a wortmannin-resistant kinase that phosphorylates the Mre11 complex. The other would be a wortmannin-sensitive kinase that phosphorylates and activates the p53/large T in SV40 transformed XP-V cells. The sensitive class corresponds to the PI3-kinases of ATM, ATR, and DNA-PK, but the resistant class remains to be identified. Alternatively, the elevated yield of Mre11 foci positive cells following wortmannin treatment may reflect an overall perturbation to the signaling cascades regulated by wortmannin-sensitive PI3 related kinases. In this scenario, wortmannin could compromise damage inducible-signaling pathways that maintain the stability of stalled forks, resulting in a further destabilization of stalled forks that then degrade, with the formation of DNA double strand breaks.
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Affiliation(s)
- C L Limoli
- Department of Radiation Oncology, University of California, San Francisco, CA 94103-0806, USA
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Symington LS. Role of RAD52 epistasis group genes in homologous recombination and double-strand break repair. Microbiol Mol Biol Rev 2002; 66:630-70, table of contents. [PMID: 12456786 PMCID: PMC134659 DOI: 10.1128/mmbr.66.4.630-670.2002] [Citation(s) in RCA: 787] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The process of homologous recombination is a major DNA repair pathway that operates on DNA double-strand breaks, and possibly other kinds of DNA lesions, to promote error-free repair. Central to the process of homologous recombination are the RAD52 group genes (RAD50, RAD51, RAD52, RAD54, RDH54/TID1, RAD55, RAD57, RAD59, MRE11, and XRS2), most of which were identified by their requirement for the repair of ionizing-radiation-induced DNA damage in Saccharomyces cerevisiae. The Rad52 group proteins are highly conserved among eukaryotes, and Rad51, Mre11, and Rad50 are also conserved in prokaryotes and archaea. Recent studies showing defects in homologous recombination and double-strand break repair in several human cancer-prone syndromes have emphasized the importance of this repair pathway in maintaining genome integrity. Although sensitivity to ionizing radiation is a universal feature of rad52 group mutants, the mutants show considerable heterogeneity in different assays for recombinational repair of double-strand breaks and spontaneous mitotic recombination. Herein, I provide an overview of recent biochemical and structural analyses of the Rad52 group proteins and discuss how this information can be incorporated into genetic studies of recombination.
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Affiliation(s)
- Lorraine S Symington
- Department of Microbiology and Institute of Cancer Research, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
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Tauchi H, Kobayashi J, Morishima KI, van Gent DC, Shiraishi T, Verkaik NS, vanHeems D, Ito E, Nakamura A, Sonoda E, Takata M, Takeda S, Matsuura S, Komatsu K. Nbs1 is essential for DNA repair by homologous recombination in higher vertebrate cells. Nature 2002; 420:93-8. [PMID: 12422221 DOI: 10.1038/nature01125] [Citation(s) in RCA: 217] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2002] [Accepted: 08/13/2002] [Indexed: 11/08/2022]
Abstract
Double-strand breaks occur during DNA replication and are also induced by ionizing radiation. There are at least two pathways which can repair such breaks: non-homologous end joining and homologous recombination (HR). Although these pathways are essentially independent of one another, it is possible that the proteins Mre11, Rad50 and Xrs2 are involved in both pathways in Saccharomyces cerevisiae. In vertebrate cells, little is known about the exact function of the Mre11-Rad50-Nbs1 complex in the repair of double-strand breaks because Mre11- and Rad50-null mutations are lethal. Here we show that Nbs1 is essential for HR-mediated repair in higher vertebrate cells. The disruption of Nbs1 reduces gene conversion and sister chromatid exchanges, similar to other HR-deficient mutants. In fact, a site-specific double-strand break repair assay showed a notable reduction of HR events following generation of such breaks in Nbs1-disrupted cells. The rare recombinants observed in the Nbs1-disrupted cells were frequently found to have aberrant structures, which possibly arise from unusual crossover events, suggesting that the Nbs1 complex might be required to process recombination intermediates.
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Affiliation(s)
- Hiroshi Tauchi
- Department of Environmental Sciences, Faculty of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512 Japan.
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Allinen M, Peri L, Kujala S, Lahti-Domenici J, Outila K, Karppinen SM, Launonen V, Winqvist R. Analysis of 11q21-24 loss of heterozygosity candidate target genes in breast cancer: indications of TSLC1 promoter hypermethylation. Genes Chromosomes Cancer 2002; 34:384-9. [PMID: 12112527 DOI: 10.1002/gcc.10079] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Loss of heterozygosity (LOH) at the distal half of chromosome arm 11q is frequent in a variety of human tumors, including breast cancer, and is often associated with poor prognosis. In an ongoing attempt to locate and characterize the main target genes within this chromosome region, we first looked for aberrations in known genes either suggested to be involved in tumorigenesis or shown to suppress tumor formation. We examined 31 primary breast tumors showing LOH in 11q21-24 for mutations in the MRE11A, CHK1, PPP2R1B, and TSLC1 genes. The absence of intragenic alterations related to cancer led us next to evaluate possible gene silencing resulting from promoter region CpG hypermethylation, using the bisulfite sequencing technique. In addition to the four genes mentioned above, we also analyzed the ATM gene, which had been investigated for certain germline mutations in an earlier study. Only the TSLC1 promoter region exhibited aberrant methylation patterns, and altogether 33% (10/30) of the successfully analyzed tumors showed evidence of elevated levels of TSLC1 CpG methylation. Ten percent (3/30) of the tumors showed significantly increased methylation. Thus, as has been shown in lung and some other forms of cancer, hypermethylation of the TSLC1 promoter region is also frequently a second hit along with LOH in breast cancer.
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Affiliation(s)
- Minna Allinen
- Department of Clinical Genetics, University Hospital, University of Oulu, FIN-90029 OYS, Oulu, Finland
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Limoli CL, Giedzinski E, Bonner WM, Cleaver JE. UV-induced replication arrest in the xeroderma pigmentosum variant leads to DNA double-strand breaks, gamma -H2AX formation, and Mre11 relocalization. Proc Natl Acad Sci U S A 2002; 99:233-8. [PMID: 11756691 PMCID: PMC117544 DOI: 10.1073/pnas.231611798] [Citation(s) in RCA: 172] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/15/2001] [Indexed: 01/08/2023] Open
Abstract
UV-induced replication arrest in the xeroderma pigmentosum variant (XPV) but not in normal cells leads to an accumulation of the Mre11/Rad50/Nbs1 complex and phosphorylated histone H2AX (gamma-H2AX) in large nuclear foci at sites of stalled replication forks. These complexes have been shown to signal the presence of DNA damage, in particular, double-strand breaks (DSBs). This finding suggests that UV damage leads to the formation of DSBs during the course of replication arrest. After UV irradiation, XPV cells showed a fluence-dependent increase in the yield of gamma-H2AX foci that paralleled the production of Mre11 foci. The percentage of foci-positive cells increased rapidly (10-15%) up to fluences of 10 J.(-2) before saturating at higher fluences. Frequencies of gamma-H2AX and Mre11 foci both reached maxima at 4 h after UV irradiation. This pattern contrasts sharply to the situation observed after x-irradiation, where peak levels of gamma-H2AX foci were found to precede the formation of Mre11 foci by several hours. The nuclear distributions of gamma-H2AX and Mre11 were found to colocalize spatially after UV- but not x-irradiation. UV-irradiated XPV cells showed a one-to-one correspondence between Mre11 and gamma-H2AX foci-positive cells. These results show that XPV cells develop DNA DSBs during the course of UV-induced replication arrest. These UV-induced foci occur in cells that are unable to carry out efficient bypass replication of UV damage and may contribute to further genetic variation.
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Affiliation(s)
- Charles L Limoli
- Department of Radiation Oncology, University of California, San Francisco, CA 94103-0806,USA.
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36
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Abstract
The induction of double-strand breaks (DSBs) in DNA by exposure to DNA damaging agents or as intermediates in normal cellular processes, creates a severe threat for the integrity of the genome. Unrepaired or incorrectly repaired DSBs lead to broken chromosomes and/or gross chromosomal rearrangements which are frequently associated with tumor formation in mammals. To maintain the integrity of the genome and to prevent the formation of chromosomal aberrations, several pathways exist in eukaryotes: homologous recombination (HR), non-homologous end joining (NHEJ) and single-strand annealing (SSA). These mechanisms are conserved in evolution, but the relative contribution depends on the organism, cell type and stage of the cell cycle. In yeast, DSBs are primarily repaired via HR while in higher eukaryotes, both HR and NHEJ are important. In mammals, defects in both HR or NHEJ lead to a predisposition to cancer and at the cellular level, the frequency of chromosomal aberrations is increased. This review summarizes our current knowledge about DSB-repair with emphasis on recent progress in understanding the precise biochemical activities of individual proteins involved.
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Affiliation(s)
- A Pastink
- Sylvius Laboratory, Department of Radiation Genetics and Chemical Mutagenesis, Wassenaarseweg 72, 2333 AL Leiden, The Netherlands.
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Costanzo V, Robertson K, Bibikova M, Kim E, Grieco D, Gottesman M, Carroll D, Gautier J. Mre11 protein complex prevents double-strand break accumulation during chromosomal DNA replication. Mol Cell 2001; 8:137-47. [PMID: 11511367 DOI: 10.1016/s1097-2765(01)00294-5] [Citation(s) in RCA: 186] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mre11 complex promotes repair of DNA double-strand breaks (DSBs). Xenopus Mre11 (X-Mre11) has been cloned, and its role in DNA replication and DNA damage checkpoint studied in cell-free extracts. DSBs stimulate the phosphorylation and 3'-5' exonuclease activity of X-Mre11 complex. This induced phosphorylation is ATM independent. Phosphorylated X-Mre11 is found associated with replicating nuclei. X-Mre11 complex is required to yield normal DNA replication products. Genomic DNA replicated in extracts immunodepleted of X-Mre11 complex accumulates DSBs as demonstrated by TUNEL assay and reactivity to phosphorylated histone H2AX antibodies. In contrast, the ATM-dependent DNA damage checkpoint that blocks DNA replication initiation is X-Mre11 independent. These results strongly suggest that the function of X-Mre11 complex is to repair DSBs that arise during normal DNA replication, thus unraveling a critical link between recombination-dependent repair and DNA replication.
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Affiliation(s)
- V Costanzo
- Department of Genetics and Development, Columbia University, New York, NY 10032, USA
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38
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Tong WM, Hande MP, Lansdorp PM, Wang ZQ. DNA strand break-sensing molecule poly(ADP-Ribose) polymerase cooperates with p53 in telomere function, chromosome stability, and tumor suppression. Mol Cell Biol 2001; 21:4046-54. [PMID: 11359911 PMCID: PMC87066 DOI: 10.1128/mcb.21.12.4046-4054.2001] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Genomic instability is often caused by mutations in genes that are involved in DNA repair and/or cell cycle checkpoints, and it plays an important role in tumorigenesis. Poly(ADP-ribose) polymerase (PARP) is a DNA strand break-sensing molecule that is involved in the response to DNA damage and the maintenance of telomere function and genomic stability. We report here that, compared to single-mutant cells, PARP and p53 double-mutant cells exhibit many severe chromosome aberrations, including a high degree of aneuploidy, fragmentations, and end-to-end fusions, which may be attributable to telomere dysfunction. While PARP(-/-) cells showed telomere shortening and p53(-/-) cells showed normal telomere length, inactivation of PARP in p53(-/-) cells surprisingly resulted in very long and heterogeneous telomeres, suggesting a functional interplay between PARP and p53 at the telomeres. Strikingly, PARP deficiency widens the tumor spectrum in mice deficient in p53, resulting in a high frequency of carcinomas in the mammary gland, lung, prostate, and skin, as well as brain tumors, reminiscent of Li-Fraumeni syndrome in humans. The enhanced tumorigenesis is likely to be caused by PARP deficiency, which facilitates the loss of function of tumor suppressor genes as demonstrated by a high rate of loss of heterozygosity at the p53 locus in these tumors. These results indicate that PARP and p53 interact to maintain genome integrity and identify PARP as a cofactor for suppressing tumorigenesis.
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Affiliation(s)
- W M Tong
- International Agency for Research on Cancer (IARC), F-69008 Lyon, France
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Mazur DJ, Perrino FW. Excision of 3' termini by the Trex1 and TREX2 3'-->5' exonucleases. Characterization of the recombinant proteins. J Biol Chem 2001; 276:17022-9. [PMID: 11279105 DOI: 10.1074/jbc.m100623200] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The excision of nucleotides from DNA 3' termini is an important step in DNA replication, repair, and recombination pathways to generate correctly base paired termini for subsequent processing. The mammalian TREX1 and TREX2 proteins contain potent 3'-->5' exonucleases capable of functioning in this capacity. To study the activities of these exonucleases we have developed strategies to express and purify the recombinant mouse Trex1 and human TREX2 proteins in Escherichia coli in quantities sufficient for biochemical characterization. The Trex1 and TREX2 proteins are homodimers that exhibit robust 3' excision activities with very similar preferred reaction conditions and preferences for specific DNA substrates. In a steady-state kinetic analysis, oligonucleotide substrates were used to measure 3' nucleotide excision by Trex1 and TREX2. The Michaelis constants derived from these data indicate similar apparent kcat values of 22 s(-1) for Trex1 and 16 s(-1) for TREX2 using single-stranded oligonucleotides. The apparent KM values of 19 nm for Trex1 and 190 nm for TREX2 suggest relatively high affinities for DNA for both Trex1 and TREX2. An exonuclease competition assay was designed using heparin as a nonsubstrate inhibitor with a series of partial duplex DNAs to delineate the substrate structure preferences for 3' nucleotide excision by Trex1 and TREX2. The catalytic properties of the TREX proteins suggest roles for these enzymes in the 3' end-trimming processes necessary for producing correctly base paired 3' termini.
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Affiliation(s)
- D J Mazur
- Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
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40
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Mazur DJ, Perrino FW. Structure and expression of the TREX1 and TREX2 3' --> 5' exonuclease genes. J Biol Chem 2001; 276:14718-27. [PMID: 11278605 DOI: 10.1074/jbc.m010051200] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The TREX1 and TREX2 genes encode mammalian 3'-->5' exonucleases. Expression of the TREX genes in human cells was investigated using a reverse transcription-polymerase chain reaction strategy. Our results show that TREX1 and TREX2 are expressed in all tissues tested, providing direct evidence for the expression of these genes in human cells. Potential transcription start sites are identified for the TREX genes using rapid amplification of cDNA ends to recover the 5'-flanking regions of the TREX transcripts. The 5'-flanking sequences indicate transcription initiation from consensus putative promoters identified -140 and -650 base pairs upstream of the TREX1 open reading frame (ORF) and -623 and -753 base pairs upstream of the TREX2 ORF. Novel TREX1 and TREX2 cDNAs are identified that contain protein-coding sequences generated from exons positioned in genomic DNA up to 18 kilobases 5' to the TREX1 ORF and up to 25 kilobases 5' to the TREX2 ORF. These novel cDNAs and sequences in the GenBank data base indicate that transcripts containing the TREX1 and TREX2 ORFs are produced using a variety of mechanisms that include alternate promoter usage, alternative splicing, and varied sites for 3' cleavage and polyadenylation. These initial studies have revealed previously unrecognized complexities in the structure and expression of the TREX1 and TREX2 genes.
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Affiliation(s)
- D J Mazur
- Wake Forest University School of Medicine, Department of Biochemistry, Winston-Salem, North Carolina 27157, USA
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41
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de Jager M, Dronkert ML, Modesti M, Beerens CE, Kanaar R, van Gent DC. DNA-binding and strand-annealing activities of human Mre11: implications for its roles in DNA double-strand break repair pathways. Nucleic Acids Res 2001; 29:1317-25. [PMID: 11238998 PMCID: PMC29748 DOI: 10.1093/nar/29.6.1317] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
DNA double-strand breaks (DSBs) in eukaryotic cells can be repaired by non-homologous end-joining or homologous recombination. The complex containing the Mre11, Rad50 and Nbs1 proteins has been implicated in both DSB repair pathways, even though they are mechanistically different. To get a better understanding of the properties of the human Mre11 (hMre11) protein, we investigated some of its biochemical activities. We found that hMre11 binds both double- and single-stranded (ss)DNA, with a preference for ssDNA. hMre11 does not require DNA ends for efficient binding. Interestingly, hMre11 mediates the annealing of complementary ssDNA molecules. In contrast to the annealing activity of the homologous recombination protein hRad52, the activity of hMre11 is abrogated by the ssDNA binding protein hRPA. We discuss the possible implications of the results for the role(s) of hMre11 in both DSB repair pathways.
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Affiliation(s)
- M de Jager
- Department of Cell Biology and Genetics, Erasmus University Rotterdam, Dr Molewaterplein 50, PO Box 1738, 3000 DR Rotterdam, The Netherlands
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42
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Ronen A, Glickman BW. Human DNA repair genes. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2001; 37:241-283. [PMID: 11317342 DOI: 10.1002/em.1033] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
DNA repair systems are essential for the maintenance of genome integrity. Consequently, the disregulation of repair genes can be expected to be associated with significant, detrimental health effects, which can include an increased prevalence of birth defects, an enhancement of cancer risk, and an accelerated rate of aging. Although original insights into DNA repair and the genes responsible were largely derived from studies in bacteria and yeast, well over 125 genes directly involved in DNA repair have now been identified in humans, and their cDNA sequence established. These genes function in a diverse set of pathways that involve the recognition and removal of DNA lesions, tolerance to DNA damage, and protection from errors of incorporation made during DNA replication or DNA repair. Additional genes indirectly affect DNA repair, by regulating the cell cycle, ostensibly to provide an opportunity for repair or to direct the cell to apoptosis. For about 70 of the DNA repair genes listed in Table I, both the genomic DNA sequence and the cDNA sequence and chromosomal location have been elucidated. In 45 cases single-nucleotide polymorphisms have been identified and, in some cases, genetic variants have been associated with specific disorders. With the accelerating rate of gene discovery, the number of identified DNA repair genes and sequence variants is quickly rising. This report tabulates the current status of what is known about these genes. The report is limited to genes whose function is directly related to DNA repair.
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Affiliation(s)
- A Ronen
- Centre for Environmental Health, University of Victoria, Victoria, British Columbia, Canada.
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43
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de Vries H, Rüegsegger U, Hübner W, Friedlein A, Langen H, Keller W. Human pre-mRNA cleavage factor II(m) contains homologs of yeast proteins and bridges two other cleavage factors. EMBO J 2000; 19:5895-904. [PMID: 11060040 PMCID: PMC305781 DOI: 10.1093/emboj/19.21.5895] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Six different protein factors are required in vitro for 3' end formation of mammalian pre-mRNAs by endonucleolytic cleavage and polyadenylation. Five of the factors have been purified and most of their components cloned, but cleavage factor II(m) (CF II(m)) remained uncharacterized. We have purified CF II(m) from HeLa cell nuclear extract by several chromatographic steps. During purification, CF II(m) activity separated into two components, one essential (CF IIA(m)) and one stimulatory (CF IIB(m)) for the cleavage reaction. CF IIA(m) fractions contain the human homologs of two yeast 3' end processing factors, Pcf11p and Clp1p, as well as cleavage factor I(m) (CF I(m)) and several splicing and transcription factors. We report the cloning of hClp1 and show that it is a genuine subunit of CF IIA(m). Antibodies directed against hClp1 deplete cleavage activity, but not polyadenylation activity from HeLa cell nuclear extract. hClp1 interacts with CF I(m) and the cleavage and polyadenylation specificity factor CPSF, suggesting that it bridges these two 3' end processing factors within the cleavage complex.
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Affiliation(s)
- H de Vries
- Department of Cell Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Germany
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44
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Lanson NA, Egeland DB, Royals BA, Claycomb WC. The MRE11-NBS1-RAD50 pathway is perturbed in SV40 large T antigen-immortalized AT-1, AT-2 and HL-1 cardiomyocytes. Nucleic Acids Res 2000; 28:2882-92. [PMID: 10908350 PMCID: PMC102680 DOI: 10.1093/nar/28.15.2882] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2000] [Revised: 06/14/2000] [Accepted: 06/14/2000] [Indexed: 01/19/2023] Open
Abstract
To investigate molecular controls of cardiomyocyte proliferation, we utilized cardiomyocytes induced to proliferate indefinitely by SV40 large T antigen (T-ag). In the T-ag-immortalized AT-1, AT-2 and HL-1 cardiomyocytes, normal cellular proteins associating with T-ag and p53 were identified, isolated and micro-sequenced. Peptide sequencing revealed that proteins of 90, 100 and 160 kDa were homologs of MRE11, NBS1 and RAD50, respectively. These three proteins play critical roles in the detection and repair of DNA double-strand breaks, activation of cell cycle checkpoints and telomere maintenance. In this report, we describe the cDNA cloning and double-strand sequencing of the rat homologs of MRE11, NBS1 and RAD50. We also determined the mRNA and protein levels of MRE11, NBS1 and RAD50 at different stages of heart development and in different tissues. MRE11 mRNA was only detected in the immortalized cardiomyocytes and in the testes. Although the 90 kDa MRE11 protein was seen in most samples examined, it was only detected at extremely low levels in proliferating cardiomyocytes (normal and immortalized). The 6.0 kb MRE11-related mRNA transcript (MRT) was seen in all samples examined. Levels of both NBS1 and RAD50 mRNA transcripts peaked in the heart at postnatal day 10. NBS1 mRNA levels were at very low levels in the T-ag-immortalized AT-1, AT-2 and HL-1 cells but NBS1 protein was observed at extremely high levels. We propose that SV40 large T antigen's interaction with the MRE11-NBS1-RAD50 pathway and with p53 ablates critical cell cycle checkpoints and that this is one of the major factors involved in the ability of this oncoprotein to immortalize cardiomyocytes.
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Affiliation(s)
- N A Lanson
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
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45
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Fouladi B, Waldren CA, Rydberg B, Cooper PK. Comparison of repair of DNA double-strand breaks in identical sequences in primary human fibroblast and immortal hamster-human hybrid cells harboring a single copy of human chromosome 11. Radiat Res 2000; 153:795-804. [PMID: 10825755 DOI: 10.1667/0033-7587(2000)153[0795:corodd]2.0.co;2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We have optimized a pulsed-field gel electrophoresis assay that measures induction and repair of double-strand breaks (DSBs) in specific regions of the genome (Löbrich et al., Proc. Natl. Acad. Sci. USA 92, 12050-12054, 1995). The increased sensitivity resulting from these improvements makes it possible to analyze the size distribution of broken DNA molecules immediately after the introduction of DSBs and after repair incubation. This analysis shows that the distribution of broken DNA pieces after exposure to sparsely ionizing radiation is consistent with the distribution expected from randomly induced DSBs. It is apparent from the distribution of rejoined DNA pieces after repair incubation that DNA ends continue to rejoin between 3 and 24 h postirradiation and that some of these rejoining events are in fact misrejoining events, since novel restriction fragments both larger and smaller than the original fragment are generated after repair. This improved assay was also used to study the kinetics of DSB rejoining and the extent of misrejoining in identical DNA sequences in human GM38 cells and human-hamster hybrid A(L) cells containing a single human chromosome 11. Despite the numerous differences between these cells, which include species and tissue of origin, levels of TP53, expression of telomerase, and the presence or absence of a homologous chromosome for the restriction fragments examined, the kinetics of rejoining of radiation-induced DSBs and the extent of misrejoining were similar in the two cell lines when studied in the G(1) phase of the cell cycle. Furthermore, DSBs were removed from the single-copy human chromosome in the hamster A(L) cells with similar kinetics and misrejoining frequency as at a locus on this hybrid's CHO chromosomes.
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Affiliation(s)
- B Fouladi
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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46
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Gerecke EE, Zolan ME. An mre11 mutant of Coprinus cinereus has defects in meiotic chromosome pairing, condensation and synapsis. Genetics 2000; 154:1125-39. [PMID: 10757758 PMCID: PMC1460984 DOI: 10.1093/genetics/154.3.1125] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The rad11 gene of the basidiomycete Coprinus cinereus is required for the completion of meiosis and for survival after gamma irradiation. We have cloned the rad11 gene and shown that it is a homolog of MRE11, a gene required for meiosis and DNA repair in numerous organisms. The expression of C. cinereus mre11 is induced during prophase I of meiosis and following gamma irradiation. The gene encodes a predicted polypeptide of 731 amino acids, and the mre11-1 (rad11-1) mutation is a single base pair change that results in a stop codon after amino acid 315. The mre11-1 mutant shows enhanced sensitivity to ionizing radiation, but no enhanced sensitivity to UV radiation. It shows a delay in fruitbody formation and a reduction in the number of mushrooms formed per dikaryon. The mre11-1 mutant also has several meiotic defects. Pachytene chromatin condensation is disrupted, and although some meiotic cells appear to achieve metaphase I condensation, no further meiotic progression is observed. The mre11-1 mutant also fails to undergo proper chromosome synapsis; neither axial elements nor mature synaptonemal complexes are complete. Finally, meiotic homolog pairing is reduced in the mre11-1 mutant. Thus, in C. cinereus, Mre11 is required for meiotic DNA metabolism.
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Affiliation(s)
- E E Gerecke
- Department of Biology, Indiana University, Bloomington, Indiana 47405, USA
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47
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Dasika GK, Lin SC, Zhao S, Sung P, Tomkinson A, Lee EY. DNA damage-induced cell cycle checkpoints and DNA strand break repair in development and tumorigenesis. Oncogene 1999; 18:7883-99. [PMID: 10630641 DOI: 10.1038/sj.onc.1203283] [Citation(s) in RCA: 320] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Several newly identified tumor suppressor genes including ATM, NBS1, BRCA1 and BRCA2 are involved in DNA double-strand break repair (DSBR) and DNA damage-induced checkpoint activation. Many of the gene products involved in checkpoint control and DSBR have been studied in great detail in yeast. In addition to evolutionarily conserved proteins such as Chk1 and Chk2, studies in mammalian cells have identified novel proteins such as p53 in executing checkpoint control. DSBR proteins including Mre11, Rad50, Rad51, Rad54, and Ku are present in yeast and in mammals. Many of the tumor suppressor gene products interact with these repair proteins as well as checkpoint regulators, thus providing a biochemical explanation for the pleiotropic phenotypes of mutant cells. This review focuses on the proteins mediating G1/S, S, and G2/M checkpoint control in mammalian cells. In addition, mammalian DSBR proteins and their activities are discussed. An intricate network among DNA damage signal transducers, cell cycle regulators and the DSBR pathways is illustrated. Mouse knockout models for genes involved in these processes have provided valuable insights into their function, establishing genomic instability as a major contributing factor in tumorigenesis.
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Affiliation(s)
- G K Dasika
- Department of Molecular Medicine, Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 78245, USA
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48
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Stewart GS, Maser RS, Stankovic T, Bressan DA, Kaplan MI, Jaspers NG, Raams A, Byrd PJ, Petrini JH, Taylor AM. The DNA double-strand break repair gene hMRE11 is mutated in individuals with an ataxia-telangiectasia-like disorder. Cell 1999; 99:577-87. [PMID: 10612394 DOI: 10.1016/s0092-8674(00)81547-0] [Citation(s) in RCA: 880] [Impact Index Per Article: 35.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We show that hypomorphic mutations in hMRE11, but not in ATM, are present in certain individuals with an ataxia-telangiectasia-like disorder (ATLD). The cellular features resulting from these hMRE11 mutations are similar to those seen in A-T as well as NBS and include hypersensitivity to ionizing radiation, radioresistant DNA synthesis, and abrogation of ATM-dependent events, such as the activation of Jun kinase following exposure to gamma irradiation. Although the mutant hMre11 proteins retain some ability to interact with hRad50 and Nbs1, formation of ionizing radiation-induced hMre11 and Nbs1 foci was absent in hMRE11 mutant cells. These data demonstrate that ATM and the hMre11/hRad50/Nbs1 protein complex act in the same DNA damage response pathway and link hMre11 to the complex pathology of A-T.
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Affiliation(s)
- G S Stewart
- The University of Birmingham CRC Institute for Cancer Studies, The Medical School Edgbaston, United Kingdom
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49
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Abstract
The ability to recognize and repair abnormal DNA structures is common to all forms of life. Studies in a variety of species have identified an incredible diversity of DNA repair pathways. Documenting and characterizing the similarities and differences in repair between species has important value for understanding the origin and evolution of repair pathways as well as for improving our understanding of phenotypes affected by repair (e.g., mutation rates, lifespan, tumorigenesis, survival in extreme environments). Unfortunately, while repair processes have been studied in quite a few species, the ecological and evolutionary diversity of such studies has been limited. Complete genome sequences can provide potential sources of new information about repair in different species. In this paper, we present a global comparative analysis of DNA repair proteins and processes based upon the analysis of available complete genome sequences. We use a new form of analysis that combines genome sequence information and phylogenetic studies into a composite analysis we refer to as phylogenomics. We use this phylogenomic analysis to study the evolution of repair proteins and processes and to predict the repair phenotypes of those species for which we now know the complete genome sequence.
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Affiliation(s)
- J A Eisen
- Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA.
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Moll U, Lau R, Sypes MA, Gupta MM, Anderson CW. DNA-PK, the DNA-activated protein kinase, is differentially expressed in normal and malignant human tissues. Oncogene 1999; 18:3114-26. [PMID: 10340383 DOI: 10.1038/sj.onc.1202640] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
DNA-PK is a nuclear, serine/threonine protein kinase required for repairing DNA double-strand breaks and for V(D)J recombination. To determine the distribution of DNA-PK in human tissues, we assayed paraffin-embedded sections of normal and cancerous tissues for DNA-PKcs and Ku80 by immunohistochemistry. We also assayed for Brca2, a human tumor suppressor gene that is implicated in the repair of DNA strand-breaks. Brca2 was strongly expressed in epithelial cells of the breast, endometrium, and thymus, in tingible body macrophages of follicular germinal centers of lymphoid tissue, and in reticuloendothelial cells in the spleen. DNA-PKcs and Ku80 expression was usually parallel, but both were expressed in a highly cell- and tissue-specific manner. The highest levels were observed in spermatogenic cells (but not in spermatozoa), and in neurons and glial cells of the central and autonomic nervous system. Neither protein was consistently expressed in liver nor in resting mammary epithelium, but lactating breast epithelium was strongly positive for DNA-PKcs and Ku80. In contrast to established human cell cultures, expression between cells in the same tissue was highly selective in the epidermis, exocrine pancreas, renal glomeruli, the red pulp of the spleen, and within cellular compartments of tonsils, lymph nodes, and thymus. Most cancerous tissues were consistently positive for DNA-PKcs and Ku80, except invasive carcinoma of the breast. DNA-PKcs, Ku80, and Ku70 mRNAs were expressed in all normal tissues with relatively little variation in levels. Our results suggest that the apparent absence of DNA-PKcs and Ku80 from some cells or tissues is a consequence of post-transcriptional mechanisms that regulate protein levels.
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Affiliation(s)
- U Moll
- Department of Pathology, State University of New York at Stony Brook, 11794, USA
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