51
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Knobel PA, Marti TM. Translesion DNA synthesis in the context of cancer research. Cancer Cell Int 2011; 11:39. [PMID: 22047021 PMCID: PMC3224763 DOI: 10.1186/1475-2867-11-39] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 11/02/2011] [Indexed: 11/17/2022] Open
Abstract
During cell division, replication of the genomic DNA is performed by high-fidelity DNA polymerases but these error-free enzymes can not synthesize across damaged DNA. Specialized DNA polymerases, so called DNA translesion synthesis polymerases (TLS polymerases), can replicate damaged DNA thereby avoiding replication fork breakdown and subsequent chromosomal instability. We focus on the involvement of mammalian TLS polymerases in DNA damage tolerance mechanisms. In detail, we review the discovery of TLS polymerases and describe the molecular features of all the mammalian TLS polymerases identified so far. We give a short overview of the mechanisms that regulate the selectivity and activity of TLS polymerases. In addition, we summarize the current knowledge how different types of DNA damage, relevant either for the induction or treatment of cancer, are bypassed by TLS polymerases. Finally, we elucidate the relevance of TLS polymerases in the context of cancer therapy.
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Affiliation(s)
- Philip A Knobel
- Laboratory of Molecular Oncology, Clinic and Polyclinic of Oncology, University Hospital Zürich, Häldeliweg 4, CH-8044 Zürich, Switzerland.
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52
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Li Y, Gao X, Wang JY. Comparison of two POLQ mutants reveals that a polymerase-inactive POLQ retains significant function in tolerance to etoposide and γ-irradiation in mouse B cells. Genes Cells 2011; 16:973-83. [PMID: 21883722 DOI: 10.1111/j.1365-2443.2011.01550.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
DNA polymerase θ (POLQ) is a family A polymerase that contains an intrinsic helicase domain. POLQ has been implicated in tolerance to DNA damage but whether this depends solely on its polymerase domain remains unknown. In this study, we generated POLQ-null CH12F3 B cells by gene targeting and compared their sensitivity to DNA-damaging agents with previously established POLQ-inactive CH12F3 cells in which only the polymerase core domain was deleted. Compared with WT cells, POLQ-null and POLQ-inactive cells exhibited similarly increased sensitivity to mitomycin C, cisplatin, and ultraviolet radiation, suggesting that tolerance to these DNA-damaging agents depends largely on POLQ polymerase activity. Intriguingly, POLQ-null cells exhibited higher sensitivity than did POLQ-inactive cells to etoposide and γ-irradiation, both of which induce double-strand breaks (DSBs). This observation indicates that the polymerase-deleted POLQ, expressed in POLQ-inactive cells, retains significant function in tolerance to these agents. Class switch recombination of immunoglobulin genes, which involves repair of activation-induced cytidine deaminase (AID)-triggered DSBs, however, was unaffected in both POLQ-null and POLQ-inactive cells. These results suggest that the polymerase and other functional domains of POLQ both play important roles in tolerance to etoposide and γ-irradiation but are dispensable for AID-mediated class switch recombination.
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Affiliation(s)
- Yingqian Li
- MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Medical School of Nanjing University, China
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53
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Mannuss A, Trapp O, Puchta H. Gene regulation in response to DNA damage. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1819:154-65. [PMID: 21867786 DOI: 10.1016/j.bbagrm.2011.08.003] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 07/25/2011] [Accepted: 08/04/2011] [Indexed: 11/17/2022]
Abstract
To deal with different kinds of DNA damages, there are a number of repair pathways that must be carefully orchestrated to guarantee genomic stability. Many proteins that play a role in DNA repair are involved in multiple pathways and need to be tightly regulated to conduct the functions required for efficient repair of different DNA damage types, such as double strand breaks or DNA crosslinks caused by radiation or genotoxins. While most of the factors involved in DNA repair are conserved throughout the different kingdoms, recent results have shown that the regulation of their expression is variable between different organisms. In the following paper, we give an overview of what is currently known about regulating factors and gene expression in response to DNA damage and put this knowledge in context with the different DNA repair pathways in plants. This article is part of a Special Issue entitled: Plant gene regulation in response to abiotic stress.
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Affiliation(s)
- Anja Mannuss
- Botanical Institute II, Karlsruhe Institute of Technology, Karlsruhe, Germany
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54
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Holloway JK, Mohan S, Balmus G, Sun X, Modzelewski A, Borst PL, Freire R, Weiss RS, Cohen PE. Mammalian BTBD12 (SLX4) protects against genomic instability during mammalian spermatogenesis. PLoS Genet 2011; 7:e1002094. [PMID: 21655083 PMCID: PMC3107204 DOI: 10.1371/journal.pgen.1002094] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 04/06/2011] [Indexed: 12/27/2022] Open
Abstract
The mammalian ortholog of yeast Slx4, BTBD12, is an ATM substrate that functions as a scaffold for various DNA repair activities. Mutations of human BTBD12 have been reported in a new sub-type of Fanconi anemia patients. Recent studies have implicated the fly and worm orthologs, MUS312 and HIM-18, in the regulation of meiotic crossovers arising from double-strand break (DSB) initiating events and also in genome stability prior to meiosis. Using a Btbd12 mutant mouse, we analyzed the role of BTBD12 in mammalian gametogenesis. BTBD12 localizes to pre-meiotic spermatogonia and to meiotic spermatocytes in wildtype males. Btbd12 mutant mice have less than 15% normal spermatozoa and are subfertile. Loss of BTBD12 during embryogenesis results in impaired primordial germ cell proliferation and increased apoptosis, which reduces the spermatogonial pool in the early postnatal testis. During prophase I, DSBs initiate normally in Btbd12 mutant animals. However, DSB repair is delayed or impeded, resulting in persistent γH2AX and RAD51, and the choice of repair pathway may be altered, resulting in elevated MLH1/MLH3 focus numbers at pachynema. The result is an increase in apoptosis through prophase I and beyond. Unlike yeast Slx4, therefore, BTBD12 appears to function in meiotic prophase I, possibly during the recombination events that lead to the production of crossovers. In line with its expected regulation by ATM kinase, BTBD12 protein is reduced in the testis of Atm−/− males, and Btbd12 mutant mice exhibit increased genomic instability in the form of elevated blood cell micronucleus formation similar to that seen in Atm−/− males. Taken together, these data indicate that BTBD12 functions throughout gametogenesis to maintain genome stability, possibly by co-ordinating repair processes and/or by linking DNA repair events to the cell cycle via ATM. Mutations in genes essential for genome maintenance during meiosis can result in severe disruptions to spermatogenesis and subsequent low fertility and/or birth defects in mammals. The mammalian homolog of yeast Slx4, BTBD12, plays a critical role in somatic cell repair in mice. Here, we show that this critical function extends to mammalian germ cells, by examining the effects of a Btbd12 gene disruption in mice. Btbd12 mutant mice show severely reduced fertility, as a result of both pre-meiotic spermatogonial proliferation defects and impairment of proper meiotic progression. BTBD12 appears to be required for normal progression of double-strand break repair events that result in the formation of crossovers between maternal and paternal homologous chromosomes, with Btbd12 mutants displaying an increase in unrepaired breaks, impaired homologous chromosome interactions, and a slight increase in the number of crossover intermediates. BTBD12 protein is also down-regulated in the testes of Atm null mice, supporting previous studies showing that BTBD12 is a target of ATM kinase. These data provide new evidence about the role of BTBD12 in mammalian gametogenesis and are critical to furthering the understanding of the molecular processes involved in meiotic DNA repair.
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Affiliation(s)
- J. Kim Holloway
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Swapna Mohan
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Gabriel Balmus
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Xianfei Sun
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Andrew Modzelewski
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Peter L. Borst
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Raimundo Freire
- Unidad de Investigacion, Hospital Universitario de Canarias, Tenerife, Spain
| | - Robert S. Weiss
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Paula E. Cohen
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
- * E-mail:
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55
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Xu B, Sun Z, Liu Z, Guo H, Liu Q, Jiang H, Zou Y, Gong Y, Tischfield JA, Shao C. Replication stress induces micronuclei comprising of aggregated DNA double-strand breaks. PLoS One 2011; 6:e18618. [PMID: 21525980 PMCID: PMC3078113 DOI: 10.1371/journal.pone.0018618] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2010] [Accepted: 03/07/2011] [Indexed: 11/30/2022] Open
Abstract
Background Micronuclei (MN) in mammalian cells serve as a reliable biomarker of genomic instability and genotoxic exposure. Elevation of MN is commonly observed in cells bearing intrinsic genomic instability and in normal cells exposed to genotoxic agents. DNA double-strand breaks are marked by phosphorylation of H2AX at serine 139 (γ-H2AX). One subclass of MN contains massive and uniform γ-H2AX signals. This study tested whether this subclass of MN can be induced by replication stress. Principal Findings We observed that a large proportion of MN, from 20% to nearly 50%, showed uniform staining by antibodies against γ-H2AX, a marker of DNA double-strand breaks (DSBs). Such micronuclei were designated as MN-γ–H2AX (+). We showed that such MN can be induced by chemicals that are known to cause DNA replication stress and S phase arrest. Hydroxyurea, aphidicolin and thymidine could all significantly induce MN-γ–H2AX (+), which were formed during S phase and appeared to be derived from aggregation of DSBs. MN-γ–H2AX (−), MN that were devoid of uniform γ-H2AX signals, were induced to a lesser extent in terms of fold change. Paclitaxel, which inhibits the disassembly of microtubules, only induced MN-γ–H2AX (−). The frequency of MN-γ–H2AX (+), but not that of MN-γ–H2AX (−), was also significantly increased in cells that experience S phase prolongation due to depletion of cell cycle regulator CUL4B. Depletion of replication protein A1 (RPA1) by RNA interference resulted in an elevation of both MN-γ–H2AX (+) and MN-γ–H2AX (−). Conclusions/Significance A subclass of MN, MN-γ–H2AX (+), can be preferentially induced by replication stress. Classification of MN according to their γ-H2AX status may provide a more refined evaluation of intrinsic genomic instabilities and the various environmental genotoxicants.
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Affiliation(s)
- Bing Xu
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Zhaoliang Sun
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Zhaojian Liu
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Haiyang Guo
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Qiao Liu
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Haiyan Jiang
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Yongxin Zou
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Yaoqin Gong
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Jay A. Tischfield
- Department of Genetics, Rutgers University, Piscataway, New Jersey, United States of America
| | - Changshun Shao
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
- Department of Genetics, Rutgers University, Piscataway, New Jersey, United States of America
- * E-mail:
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Abstract
There are 15 different DNA polymerases encoded in mammalian genomes, which are specialized for replication, repair or the tolerance of DNA damage. New evidence is emerging for lesion-specific and tissue-specific functions of DNA polymerases. Many point mutations that occur in cancer cells arise from the error-generating activities of DNA polymerases. However, the ability of some of these enzymes to bypass DNA damage may actually defend against chromosome instability in cells, and at least one DNA polymerase, Pol ζ, is a suppressor of spontaneous tumorigenesis. Because DNA polymerases can help cancer cells tolerate DNA damage, some of these enzymes might be viable targets for therapeutic strategies.
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Affiliation(s)
| | | | - Richard D. Wood
- Correspondence to: 1808 Park Road 1C, P.O. Box 389, Smithville, TX, USA, 78957 Tel: (512) 237-9431 Fax: (512) 237-6532
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57
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Hogg M, Seki M, Wood RD, Doublié S, Wallace SS. Lesion bypass activity of DNA polymerase θ (POLQ) is an intrinsic property of the pol domain and depends on unique sequence inserts. J Mol Biol 2011; 405:642-52. [PMID: 21050863 PMCID: PMC3025778 DOI: 10.1016/j.jmb.2010.10.041] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Revised: 10/12/2010] [Accepted: 10/22/2010] [Indexed: 11/18/2022]
Abstract
DNA polymerase θ (POLQ, polθ) is a large, multidomain DNA polymerase encoded in higher eukaryotic genomes. It is important for maintaining genetic stability in cells and helping protect cells from DNA damage caused by ionizing radiation. POLQ contains an N-terminal helicase-like domain, a large central domain of indeterminate function, and a C-terminal polymerase domain with sequence similarity to the A-family of DNA polymerases. The enzyme has several unique properties, including low fidelity and the ability to insert and extend past abasic sites and thymine glycol lesions. It is not known whether the abasic site bypass activity is an intrinsic property of the polymerase domain or whether helicase activity is also required. Three "insertion" sequence elements present in POLQ are not found in any other A-family DNA polymerase, and it has been proposed that they may lend some unique properties to POLQ. Here, we analyzed the activity of the DNA polymerase in the absence of each sequence insertion. We found that the pol domain is capable of highly efficient bypass of abasic sites in the absence of the helicase-like or central domains. Insertion 1 increases the processivity of the polymerase but has little, if any, bearing on the translesion synthesis properties of the enzyme. However, removal of insertions 2 and 3 reduces activity on undamaged DNA and completely abrogates the ability of the enzyme to bypass abasic sites or thymine glycol lesions.
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Affiliation(s)
- Matthew Hogg
- Department of Microbiology and Molecular Genetics, 95 Carrigan Drive, University of Vermont, Burlington, VT, 05405, USA
| | - Mineaki Seki
- Department of Carcinogenesis, The University of Texas Graduate School of Biomedical Sciences at Houston, The University of Texas MD Anderson Cancer Center, Science Park - Research Division, P.O. Box 389, Smithville, TX 78957, USA
| | - Richard D. Wood
- Department of Carcinogenesis, The University of Texas Graduate School of Biomedical Sciences at Houston, The University of Texas MD Anderson Cancer Center, Science Park - Research Division, P.O. Box 389, Smithville, TX 78957, USA
| | - Sylvie Doublié
- Department of Microbiology and Molecular Genetics, 95 Carrigan Drive, University of Vermont, Burlington, VT, 05405, USA
| | - Susan S. Wallace
- Department of Microbiology and Molecular Genetics, 95 Carrigan Drive, University of Vermont, Burlington, VT, 05405, USA
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58
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Ching YH, Munroe RJ, Moran JL, Barker AK, Mauceli E, Fennell T, Dipalma F, Lindblad-Toh K, Abcunas LM, Gilmour JF, Harris TP, Kloet SL, Luo Y, McElwee JL, Mu W, Park HK, Rogal DL, Schimenti KJ, Shen L, Shindo M, Shou JY, Stenson EK, Stover PJ, Schimenti JC. High resolution mapping and positional cloning of ENU-induced mutations in the Rw region of mouse chromosome 5. BMC Genet 2010; 11:106. [PMID: 21118569 PMCID: PMC3009607 DOI: 10.1186/1471-2156-11-106] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 11/30/2010] [Indexed: 01/02/2023] Open
Abstract
Background Forward genetic screens in mice provide an unbiased means to identify genes and other functional genetic elements in the genome. Previously, a large scale ENU mutagenesis screen was conducted to query the functional content of a ~50 Mb region of the mouse genome on proximal Chr 5. The majority of phenotypic mutants recovered were embryonic lethals. Results We report the high resolution genetic mapping, complementation analyses, and positional cloning of mutations in the target region. The collection of identified alleles include several with known or presumed functions for which no mutant models have been reported (Tbc1d14, Nol14, Tyms, Cad, Fbxl5, Haus3), and mutations in genes we or others previously reported (Tapt1, Rest, Ugdh, Paxip1, Hmx1, Otoe, Nsun7). We also confirmed the causative nature of a homeotic mutation with a targeted allele, mapped a lethal mutation to a large gene desert, and localized a spermiogenesis mutation to a region in which no annotated genes have coding mutations. The mutation in Tbc1d14 provides the first implication of a critical developmental role for RAB-GAP-mediated protein transport in early embryogenesis. Conclusion This collection of alleles contributes to the goal of assigning biological functions to all known genes, as well as identifying novel functional elements that would be missed by reverse genetic approaches.
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Affiliation(s)
- Yung-Hao Ching
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
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59
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Beier DR. New genetic resources for mammalian developmental biologists. F1000 BIOLOGY REPORTS 2010; 2:72. [PMID: 21173845 PMCID: PMC2989628 DOI: 10.3410/b2-72] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The utilization of homologous recombination in embryonic stem cells as a means to generate mice carrying pre-determined modifications of genomic sequences has revolutionized the study of developmental biology. Recognizing the potential efficiencies that can be obtained by high-throughput production at centralized technology centers, a number of large-scale efforts for generating mice with targeted mutations have been funded. These programs are reaching fruition, and a variety of libraries of embryonic stem cells with defined mutations are now available.
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Affiliation(s)
- David R Beier
- Genetics Division, Brigham and Women's Hospital, Harvard Medical School New Research Building 77 Avenue Louis Pasteur, Boston, MA 02115 USA
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60
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Díaz-Valdés N, Comendador MA, Sierra LM. Mus308 processes oxygen and nitrogen ethylation DNA damage in germ cells of Drosophila. J Nucleic Acids 2010; 2010. [PMID: 20936147 PMCID: PMC2948884 DOI: 10.4061/2010/416364] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Revised: 07/27/2010] [Accepted: 09/02/2010] [Indexed: 11/22/2022] Open
Abstract
The D. melanogaster mus308 gene, highly conserved among higher eukaryotes, is implicated in the repair of cross-links and of O-ethylpyrimidine DNA damage, working in a DNA damage tolerance mechanism. However, despite its relevance, its possible role on the processing of different DNA ethylation damages is not clear. To obtain data on mutation frequency and on mutation spectra in mus308 deficient (mus308−) conditions, the ethylating agent diethyl sulfate (DES) was analysed in postmeiotic male germ cells. These data were compared with those corresponding to mus308 efficient conditions. Our results indicate that Mus308 is necessary for the processing of oxygen and N-ethylation damage, for the survival of fertilized eggs depending on the level of induced DNA damage, and for an influence of the DNA damage neighbouring sequence. These results support the role of mus308 in a tolerance mechanism linked to a translesion synthesis pathway and also to the alternative end-joinig system.
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Affiliation(s)
- Nancy Díaz-Valdés
- Área de Genética, Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (IUOPA), University of Oviedo, 33006 Oviedo, Spain
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61
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Lemée F, Bergoglio V, Fernandez-Vidal A, Machado-Silva A, Pillaire MJ, Bieth A, Gentil C, Baker L, Martin AL, Leduc C, Lam E, Magdeleine E, Filleron T, Oumouhou N, Kaina B, Seki M, Grimal F, Lacroix-Triki M, Thompson A, Roché H, Bourdon JC, Wood RD, Hoffmann JS, Cazaux C. DNA polymerase theta up-regulation is associated with poor survival in breast cancer, perturbs DNA replication, and promotes genetic instability. Proc Natl Acad Sci U S A 2010; 107:13390-5. [PMID: 20624954 PMCID: PMC2922118 DOI: 10.1073/pnas.0910759107] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
"Replicative stress" is one of the main factors underlying neoplasia from its early stages. Genes involved in DNA synthesis may therefore represent an underexplored source of potential prognostic markers for cancer. To this aim, we generated gene expression profiles from two independent cohorts (France, n=206; United Kingdom, n=117) of patients with previously untreated primary breast cancers. We report here that among the 13 human nuclear DNA polymerase genes, DNA Polymerase (POLQ) is the only one significantly up-regulated in breast cancer compared with normal breast tissues. Importantly, POLQ up-regulation significantly correlates with poor clinical outcome (4.3-fold increased risk of death in patients with high POLQ expression), and this correlation is independent of Cyclin E expression or the number of positive nodes, which are currently considered as markers for poor outcome. POLQ expression provides thus an additional indicator for the survival outcome of patients with high Cyclin E tumor expression or high number of positive lymph nodes. Furthermore, to decipher the molecular consequences of POLQ up-regulation in breast cancer, we generated human MRC5-SV cell lines that stably overexpress POLQ. Strong POLQ expression was directly associated with defective DNA replication fork progression and chromosomal damage. Therefore, POLQ overexpression may be a promising genetic instability and prognostic marker for breast cancer.
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Affiliation(s)
- Fanny Lemée
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale and Université de Toulouse, Université Paul Sabatier, 31077 Toulouse, France
| | - Valérie Bergoglio
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale and Université de Toulouse, Université Paul Sabatier, 31077 Toulouse, France
| | - Anne Fernandez-Vidal
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale and Université de Toulouse, Université Paul Sabatier, 31077 Toulouse, France
| | - Alice Machado-Silva
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale and Université de Toulouse, Université Paul Sabatier, 31077 Toulouse, France
- European Associated Laboratory, University of Dundee, Institut National de la Santé et de la Recherche Médicale U858, Dundee DD1 9SY, United Kingdom
| | - Marie-Jeanne Pillaire
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale and Université de Toulouse, Université Paul Sabatier, 31077 Toulouse, France
| | - Anne Bieth
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale and Université de Toulouse, Université Paul Sabatier, 31077 Toulouse, France
| | - Catherine Gentil
- Service d’ Epidémiologie, Institut National de la Santé et de la Recherche Médicale U558, Centre Hospitalier Universitaire de Toulouse, Université de Toulouse, Université Paul Sabatier, 31073 Toulouse, France
| | - Lee Baker
- Department of Surgery and Molecular Oncology, Ninewells Hospital, Dundee DD1 9SY, United Kingdom
| | - Anne-Laure Martin
- Fédération des Centres de Lutte Contre le Cancer, 75654 Paris, France
| | - Claire Leduc
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale and Université de Toulouse, Université Paul Sabatier, 31077 Toulouse, France
| | - Elena Lam
- Department of Toxicology, University of Mainz, D-55131 Mainz, Germany
| | - Eddy Magdeleine
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale and Université de Toulouse, Université Paul Sabatier, 31077 Toulouse, France
| | - Thomas Filleron
- Institut Claudius Régaud, Université de Toulouse, Université Paul Sabatier, 31052 Toulouse, France
| | - Naïma Oumouhou
- Service d’ Epidémiologie, Institut National de la Santé et de la Recherche Médicale U558, Centre Hospitalier Universitaire de Toulouse, Université de Toulouse, Université Paul Sabatier, 31073 Toulouse, France
| | - Bernd Kaina
- Department of Toxicology, University of Mainz, D-55131 Mainz, Germany
| | - Mineaki Seki
- Laboratories for Organismal Biosystems, Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
| | - Fanny Grimal
- Département d’ Oncogenèse et de Signalisation des Cellules Hématopoïétiques, Institut National de la Santé et de la Recherche Médicale U563, Université de Toulouse, Université Paul Sabatier, 31059 Toulouse, France; and
| | - Magali Lacroix-Triki
- Institut Claudius Régaud, Université de Toulouse, Université Paul Sabatier, 31052 Toulouse, France
| | - Alastair Thompson
- Department of Surgery and Molecular Oncology, Ninewells Hospital, Dundee DD1 9SY, United Kingdom
| | - Henri Roché
- Institut Claudius Régaud, Université de Toulouse, Université Paul Sabatier, 31052 Toulouse, France
| | - Jean-Christophe Bourdon
- European Associated Laboratory, University of Dundee, Institut National de la Santé et de la Recherche Médicale U858, Dundee DD1 9SY, United Kingdom
| | - Richard D. Wood
- Science Park–Research Division, University of Texas Graduate School of Biomedical Sciences at Houston, M. D. Anderson Cancer Center, Smithville, TX 78957
| | - Jean-Sébastien Hoffmann
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale and Université de Toulouse, Université Paul Sabatier, 31077 Toulouse, France
| | - Christophe Cazaux
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale and Université de Toulouse, Université Paul Sabatier, 31077 Toulouse, France
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62
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Ho TV, Schärer OD. Translesion DNA synthesis polymerases in DNA interstrand crosslink repair. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2010; 51:552-566. [PMID: 20658647 DOI: 10.1002/em.20573] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
DNA interstrand crosslinks (ICLs) are induced by a number of bifunctional antitumor drugs such as cisplatin, mitomycin C, or the nitrogen mustards as well as endogenous agents formed by lipid peroxidation. The repair of ICLs requires the coordinated interplay of a number of genome maintenance pathways, leading to the removal of ICLs through at least two distinct mechanisms. The major pathway of ICL repair is dependent on replication, homologous recombination, and the Fanconi anemia (FA) pathway, whereas a minor, G0/G1-specific and recombination-independent pathway depends on nucleotide excision repair. A central step in both pathways in vertebrates is translesion synthesis (TLS) and mutants in the TLS polymerases Rev1 and Pol zeta are exquisitely sensitive to crosslinking agents. Here, we review the involvement of Rev1 and Pol zeta as well as additional TLS polymerases, in particular, Pol eta, Pol kappa, Pol iota, and Pol nu, in ICL repair. Biochemical studies suggest that multiple TLS polymerases have the ability to bypass ICLs and that the extent ofbypass depends upon the structure as well as the extent of endo- or exonucleolytic processing of the ICL. As has been observed for lesions that affect only one strand of DNA, TLS polymerases are recruited by ubiquitinated proliferating nuclear antigen (PCNA) to repair ICLs in the G0/G1 pathway. By contrast, this data suggest that a different mechanism involving the FA pathway is operative in coordinating TLS in the context of replication-dependent ICL repair.
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Affiliation(s)
- The Vinh Ho
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York 11794-3400, USA
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63
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McVey M. Strategies for DNA interstrand crosslink repair: insights from worms, flies, frogs, and slime molds. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2010; 51:646-658. [PMID: 20143343 DOI: 10.1002/em.20551] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
DNA interstrand crosslinks (ICLs) are complex lesions that covalently link both strands of the DNA double helix and impede essential cellular processes such as DNA replication and transcription. Recent studies suggest that multiple repair pathways are involved in their removal. Elegant genetic analysis has demonstrated that at least three distinct sets of pathways cooperate in the repair and/or bypass of ICLs in budding yeast. Although the mechanisms of ICL repair in mammals appear similar to those in yeast, important differences have been documented. In addition, mammalian crosslink repair requires other repair factors, such as the Fanconi anemia proteins, whose functions are poorly understood. Because many of these proteins are conserved in simpler metazoans, nonmammalian models have become attractive systems for studying the function(s) of key crosslink repair factors. This review discusses the contributions that various model organisms have made to the field of ICL repair. Specifically, it highlights how studies performed with C. elegans, Drosophila, Xenopus, and the social amoeba Dictyostelium serve to complement those from bacteria, yeast, and mammals. Together, these investigations have revealed that although the underlying themes of ICL repair are largely conserved, the complement of DNA repair proteins utilized and the ways in which each of the proteins is used can vary substantially between different organisms.
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Affiliation(s)
- Mitch McVey
- Department of Biology, Tufts University, Medford, Massachusetts 02155, USA.
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64
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Abstract
The use of mutagenesis in invertebrates to generate phenotypic variants has a long and productive history. Despite the conclusive demonstration by Russell and colleagues in the 1970s that the chemical N-ethyl-N-nitrosourea (ENU) is a highly effective mutagen in mice, the application of phenotypic-driven mutagenesis as a method to study mammalian biology proceeded slowly. With the development of tools for genomic analysis, the task of positional cloning ENU-induced mutations has become quite feasible, and this approach has recently been widely applied and highly productive. It has specifically lived up to its theoretical utility as means to provide insight into the biological roles of genes that is not biased by presumptions of their function. While the power of this approach is indisputable, the effort necessary for its success remains substantial, requiring careful attention to aspects including ENU treatment, mouse husbandry, screen assay design, genetic mapping, positional cloning, and mutation validation. In this chapter we discuss practical aspects of implementing a phenotype-driven analysis of an ENU-mutagenized mouse population.
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Abstract
DNA polymerases (Pols) act as key players in DNA metabolism. These enzymes are the only biological macromolecules able to duplicate the genetic information stored in the DNA and are absolutely required every time this information has to be copied, as during DNA replication or during DNA repair, when lost or damaged DNA sequences have to be replaced with "original" or "correct" copies. In each DNA repair pathway one or more specific Pols are required. A feature of mammalian DNA repair pathways is their redundancy. The failure of one of these pathways can be compensated by another one. However, several DNA lesions require a specific repair pathway for error free repair. In many tumors one or more DNA repair pathways are affected, leading to error prone repair of some kind of lesions by alternatives routes, thus leading to accumulation of mutations and contributing to genomic instability, a common feature of cancer cell. In this chapter, we present the role of each Pol in genome maintenance and highlight the connections between the malfunctioning of these enzymes and cancer progress.
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Affiliation(s)
- Emmanuele Crespan
- Istituto di Genetica Molecolare IGM-CNR, Consiglio Nazionale delle Ricerche, I-27100 Pavia, Italy
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66
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Inagaki S, Nakamura K, Morikami A. A link among DNA replication, recombination, and gene expression revealed by genetic and genomic analysis of TEBICHI gene of Arabidopsis thaliana. PLoS Genet 2009; 5:e1000613. [PMID: 19696887 PMCID: PMC2721414 DOI: 10.1371/journal.pgen.1000613] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Accepted: 07/24/2009] [Indexed: 12/28/2022] Open
Abstract
Spatio-temporal regulation of gene expression during development depends on many factors. Mutations in Arabidopsis thaliana TEBICHI (TEB) gene encoding putative helicase and DNA polymerase domains-containing protein result in defects in meristem maintenance and correct organ formation, as well as constitutive DNA damage response and a defect in cell cycle progression; but the molecular link between these phenotypes of teb mutants is unknown. Here, we show that mutations in the DNA replication checkpoint pathway gene, ATR, but not in ATM gene, enhance developmental phenotypes of teb mutants, although atr suppresses cell cycle defect of teb mutants. Developmental phenotypes of teb mutants are also enhanced by mutations in RAD51D and XRCC2 gene, which are involved in homologous recombination. teb and teb atr double mutants exhibit defects in adaxial-abaxial polarity of leaves, which is caused in part by the upregulation of ETTIN (ETT)/AUXIN RESPONSIVE FACTOR 3 (ARF3) and ARF4 genes. The Helitron transposon in the upstream of ETT/ARF3 gene is likely to be involved in the upregulation of ETT/ARF3 in teb. Microarray analysis indicated that teb and teb atr causes preferential upregulation of genes nearby the Helitron transposons. Furthermore, interestingly, duplicated genes, especially tandemly arrayed homologous genes, are highly upregulated in teb or teb atr. We conclude that TEB is required for normal progression of DNA replication and for correct expression of genes during development. Interplay between these two functions and possible mechanism leading to altered expression of specific genes will be discussed. DNA replication, repair, and recombination are interrelated processes. Chromatin structure, into which DNA is packaged, is important for regulation of DNA replication, repair, and recombination, as well as gene transcription. After DNA replication and repair, chromatin status including its structure and modification has to be reproduced, and defects in these processes can alter gene expression program because of change in chromatin regulation. Our series of genetic analysis of tebichi (teb) mutant of model plant Arabidopsis thaliana suggest that TEB gene is involved in DNA replication and recombination. We also show here that TEB gene is required for correct expression of many genes including genes regulating development. From these results we propose that TEB gene function is important for maintenance of gene expression pattern after DNA replication and recombination. Furthermore, preferential upregulation of genes near highly duplicated transposons and tandemly arrayed homologous genes are observed in teb mutants, suggesting the interrelationship between homologous recombination and gene transcription around the repetitive sequences.
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Affiliation(s)
- Soichi Inagaki
- Laboratory of Biochemistry, Graduate School of Bio-agricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan.
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Goff JP, Shields DS, Seki M, Choi S, Epperly MW, Dixon T, Wang H, Bakkenist CJ, Dertinger SD, Torous DK, Wittschieben J, Wood RD, Greenberger JS. Lack of DNA polymerase theta (POLQ) radiosensitizes bone marrow stromal cells in vitro and increases reticulocyte micronuclei after total-body irradiation. Radiat Res 2009; 172:165-74. [PMID: 19630521 PMCID: PMC2742993 DOI: 10.1667/rr1598.1] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Abstract Mammalian POLQ (pol theta) is a specialized DNA polymerase with an unknown function in vivo. Roles have been proposed in chromosome stability, as a backup enzyme in DNA base excision repair, and in somatic hypermutation of immunoglobulin genes. The purified enzyme can bypass AP sites and thymine glycol. Mice defective in POLQ are viable and have been reported to have elevated spontaneous and radiation-induced frequencies of micronuclei in circulating red blood cells. To examine the potential roles of POLQ in hematopoiesis and in responses to oxidative stress responses, including ionizing radiation, bone marrow cultures and marrow stromal cell lines were established from Polq(+/+) and Polq(-/-) mice. Aging of bone marrow cultures was not altered, but Polq(-/-) cells were more sensitive to gamma radiation than were Polq(+/+) cells. The D(0) was 1.38 +/- 0.06 Gy for Polq(+/+) cells compared to 1.27 +/- 0.16 and 0.98 +/- 0.10 Gy (P = 0.032) for two Polq(-/-) clones. Polq(-/-) cells were moderately more sensitive to bleomycin than Polq(+/+) cells and were not hypersensitive to paraquat or hydrogen peroxide. ATM kinase activation appeared to be normal in gamma-irradiated Polq(-/-) cells. Inhibition of ATM kinase activity increased the radiosensitivity of Polq(+/+) cells slightly but did not affect Polq(-/-) cells. Polq(-/-) mice had more spontaneous and radiation-induced micronucleated reticulocytes than Polq+/+ and (+/-) mice. The sensitivity of POLQ-defective bone marrow stromal cells to ionizing radiation and bleomycin and the increase in micronuclei in red blood cells support a role for this DNA polymerase in cellular tolerance of DNA damage that can lead to double-strand DNA breaks.
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Affiliation(s)
- Julie P. Goff
- Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
| | - Donna S. Shields
- Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
| | - Mineaki Seki
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
| | - Serah Choi
- Medical Scientist Training Program, Molecular Pharmacology Graduate Program, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
| | - Michael W. Epperly
- Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
| | - Tracy Dixon
- Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
| | - Hong Wang
- Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
| | - Christopher J. Bakkenist
- Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
| | | | | | - John Wittschieben
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
| | - Richard D. Wood
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
| | - Joel S. Greenberger
- Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
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68
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Prasad R, Longley MJ, Sharief FS, Hou EW, Copeland WC, Wilson SH. Human DNA polymerase theta possesses 5'-dRP lyase activity and functions in single-nucleotide base excision repair in vitro. Nucleic Acids Res 2009; 37:1868-77. [PMID: 19188258 PMCID: PMC2665223 DOI: 10.1093/nar/gkp035] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Revised: 12/26/2008] [Accepted: 01/11/2009] [Indexed: 12/18/2022] Open
Abstract
DNA polymerase theta (Pol theta) is a low-fidelity DNA polymerase that belongs to the family A polymerases and has been proposed to play a role in somatic hypermutation. Pol theta has the ability to conduct translesion DNA synthesis opposite an AP site or thymine glycol, and it was recently proposed to be involved in base excision repair (BER) of DNA damage. Here, we show that Pol theta has intrinsic 5'-deoxyribose phosphate (5'-dRP) lyase activity that is involved in single-nucleotide base excision DNA repair (SN-BER). Full-length human Pol theta is a approximately 300-kDa polypeptide, but we show here that the 98-kDa C-terminal region of Pol theta possesses both DNA polymerase activity and dRP lyase activity and is sufficient to carry out base excision repair in vitro. The 5'-dRP lyase activity is independent of the polymerase activity, in that a polymerase inactive mutant retained full 5'-dRP lyase activity. Domain mapping of the 98-kDa enzyme by limited proteolysis and NaBH(4) cross-linking with a BER intermediate revealed that the dRP lyase active site resides in a 24-kDa domain of Pol theta. These results are consistent with a role of Pol theta in BER.
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Affiliation(s)
- Rajendra Prasad
- Laboratory of Structural Biology and Laboratory of Molecular Genetics, NIEHS, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Matthew J. Longley
- Laboratory of Structural Biology and Laboratory of Molecular Genetics, NIEHS, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Farida S. Sharief
- Laboratory of Structural Biology and Laboratory of Molecular Genetics, NIEHS, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Esther W. Hou
- Laboratory of Structural Biology and Laboratory of Molecular Genetics, NIEHS, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - William C. Copeland
- Laboratory of Structural Biology and Laboratory of Molecular Genetics, NIEHS, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Samuel H. Wilson
- Laboratory of Structural Biology and Laboratory of Molecular Genetics, NIEHS, National Institutes of Health, Research Triangle Park, NC 27709, USA
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69
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Arana ME, Seki M, Wood RD, Rogozin IB, Kunkel TA. Low-fidelity DNA synthesis by human DNA polymerase theta. Nucleic Acids Res 2008; 36:3847-56. [PMID: 18503084 PMCID: PMC2441791 DOI: 10.1093/nar/gkn310] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 04/28/2008] [Accepted: 04/30/2008] [Indexed: 12/14/2022] Open
Abstract
Human DNA polymerase theta (pol or POLQ) is a proofreading-deficient family A enzyme implicated in translesion synthesis (TLS) and perhaps in somatic hypermutation (SHM) of immunoglobulin genes. These proposed functions and kinetic studies imply that pol may synthesize DNA with low fidelity. Here, we show that when copying undamaged DNA, pol generates single base errors at rates 10- to more than 100-fold higher than for other family A members. Pol adds single nucleotides to homopolymeric runs at particularly high rates, exceeding 1% in certain sequence contexts, and generates single base substitutions at an average rate of 2.4 x 10(-3), comparable to inaccurate family Y human pol kappa (5.8 x 10(-3)) also implicated in TLS. Like pol kappa, pol is processive, implying that it may be tightly regulated to avoid deleterious mutagenesis. Pol also generates certain base substitutions at high rates within sequence contexts similar to those inferred to be copied by pol during SHM of immunoglobulin genes in mice. Thus, pol is an exception among family A polymerases, and its low fidelity is consistent with its proposed roles in TLS and SHM.
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Affiliation(s)
- Mercedes E. Arana
- Laboratory of Molecular Genetics and Laboratory of Structural Biology, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, Department of Pharmacology, University of Pittsburgh Medical School, Hillman Cancer Center, Research Pavilion Suite 2.6, 5117 Centre Avenue, Pittsburgh, PA 15213-1863 and National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20894, USA
| | - Mineaki Seki
- Laboratory of Molecular Genetics and Laboratory of Structural Biology, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, Department of Pharmacology, University of Pittsburgh Medical School, Hillman Cancer Center, Research Pavilion Suite 2.6, 5117 Centre Avenue, Pittsburgh, PA 15213-1863 and National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20894, USA
| | - Richard D. Wood
- Laboratory of Molecular Genetics and Laboratory of Structural Biology, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, Department of Pharmacology, University of Pittsburgh Medical School, Hillman Cancer Center, Research Pavilion Suite 2.6, 5117 Centre Avenue, Pittsburgh, PA 15213-1863 and National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20894, USA
| | - Igor B. Rogozin
- Laboratory of Molecular Genetics and Laboratory of Structural Biology, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, Department of Pharmacology, University of Pittsburgh Medical School, Hillman Cancer Center, Research Pavilion Suite 2.6, 5117 Centre Avenue, Pittsburgh, PA 15213-1863 and National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20894, USA
| | - Thomas A. Kunkel
- Laboratory of Molecular Genetics and Laboratory of Structural Biology, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, Department of Pharmacology, University of Pittsburgh Medical School, Hillman Cancer Center, Research Pavilion Suite 2.6, 5117 Centre Avenue, Pittsburgh, PA 15213-1863 and National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20894, USA
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70
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Seki M, Wood RD. DNA polymerase theta (POLQ) can extend from mismatches and from bases opposite a (6-4) photoproduct. DNA Repair (Amst) 2008; 7:119-27. [PMID: 17920341 PMCID: PMC2185714 DOI: 10.1016/j.dnarep.2007.08.005] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 07/26/2007] [Accepted: 08/24/2007] [Indexed: 10/22/2022]
Abstract
DNA polymerase theta (pol theta) is a nuclear A-family DNA polymerase encoded by the POLQ gene in vertebrate cells. The biochemical properties of pol theta and of Polq-defective mice have suggested that pol theta participates in DNA damage tolerance. For example, pol theta was previously found to be proficient not only in incorporation of a nucleotide opposite a thymine glycol or an abasic site, but also extends a polynucleotide chain efficiently from the base opposite the lesion. We carried out experiments to determine whether this ability to extend from non-standard termini is a more general property of the enzyme. Pol theta extended relatively efficiently from matched termini as well as termini with A:G, A:T and A:C mismatches, with less descrimination than a well-studied A-family DNA polymerase, exonuclease-free pol I from E. coli. Although pol theta was unable to, by itself, bypass a cyclobutane pyrimidine dimer or a (6-4) photoproduct, it could perform some extension from primers with bases placed across from these lesions. When pol theta was combined with DNA polymerase iota, an enzyme that can insert a base opposite a UV-induced (6-4) photoproduct, complete bypass of a (6-4) photoproduct was possible. These data show that in addition to its ability to insert nucleotides opposite some DNA lesions, pol theta is proficient at extension of unpaired termini. These results show the potential of pol theta to act as an extender after incorporation of nucleotides by other DNA polymerases, and aid in understanding the role of pol theta in somatic mutagenesis and genome instability.
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Affiliation(s)
- Mineaki Seki
- Department of Pharmacology, University of Pittsburgh Medical School, Hillman Cancer Center, Research Pavilion, Suite 2.6, 5117 Centre Avenue, Pittsburgh, PA 15213-1863, USA
| | - Richard D. Wood
- Department of Pharmacology, University of Pittsburgh Medical School, Hillman Cancer Center, Research Pavilion, Suite 2.6, 5117 Centre Avenue, Pittsburgh, PA 15213-1863, USA
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71
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Barbaric I, Wells S, Russ A, Dear TN. Spectrum of ENU-induced mutations in phenotype-driven and gene-driven screens in the mouse. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2007; 48:124-42. [PMID: 17295309 DOI: 10.1002/em.20286] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
N-ethyl-N-nitrosourea (ENU) mutagenesis in mice has become a standard tool for (i) increasing the pool of mutants in many areas of biology, (ii) identifying novel genes involved in physiological processes and disease, and (iii) in assisting in assigning functions to genes. ENU is assumed to cause random mutations throughout the mouse genome, but this presumption has never been analyzed. This is a crucial point, especially for large-scale mutagenesis, as a bias would reflect a constraint on identifying possible genetic targets. There is a significant body of published data now available from both phenotype-driven and gene-driven ENU mutagenesis screens in the mouse that can be used to reveal the effectiveness and limitations of an ENU mutagenesis approach. Analysis of the published data is presented in this paper. As expected for a randomly acting mutagen, ENU-induced mutations identified in phenotype-driven screens were in genes that had higher coding sequence length and higher exon number than the average for the mouse genome. Unexpectedly, the data showed that ENU-induced mutations were more likely to be found in genes that had a higher G + C content and neighboring base analysis revealed that the identified ENU mutations were more often directly flanked by G or C nucleotides. ENU mutations from phenotype-driven and gene-driven screens were dominantly A:T to T:A transversions or A:T to G:C transitions. Knowledge of the spectrum of mutations that ENU elicits will assist in positional cloning of ENU-induced mutations by allowing prioritization of candidate genes based on some of their inherent features.
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Affiliation(s)
- Ivana Barbaric
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
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72
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Sweasy JB, Lauper JM, Eckert KA. DNA polymerases and human diseases. Radiat Res 2006; 166:693-714. [PMID: 17067213 DOI: 10.1667/rr0706.1] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Accepted: 07/12/2006] [Indexed: 11/03/2022]
Abstract
DNA polymerases function in DNA replication, repair, recombination and translesion synthesis. Currently, 15 DNA polymerase genes have been identified in human cells, belonging to four distinct families. In this review, we briefly describe the biochemical activities and known cellular roles of each DNA polymerase. Our major focus is on the phenotypic consequences of mutation or ablation of individual DNA polymerase genes. We discuss phenotypes of current mouse models and altered polymerase functions and the relationship of DNA polymerase gene mutations to human cell phenotypes. Interestingly, over 120 single nucleotide polymorphisms (SNPs) have been identified in human populations that are predicted to result in nonsynonymous amino acid substitutions of DNA polymerases. We discuss the putative functional consequences of these SNPs in relation to human disease.
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Affiliation(s)
- Joann B Sweasy
- Department of Therapeutic Radiology, Yale University School of Medicine, 15 York Street, HRT 313D, P.O. Box 208040, New Haven, CT 06520-8040, USA.
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73
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Shima N, Alcaraz A, Liachko I, Buske TR, Andrews CA, Munroe RJ, Hartford SA, Tye BK, Schimenti JC. A viable allele of Mcm4 causes chromosome instability and mammary adenocarcinomas in mice. Nat Genet 2006; 39:93-8. [PMID: 17143284 DOI: 10.1038/ng1936] [Citation(s) in RCA: 241] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2006] [Accepted: 11/03/2006] [Indexed: 12/30/2022]
Abstract
Mcm4 (minichromosome maintenance-deficient 4 homolog) encodes a subunit of the MCM2-7 complex (also known as MCM2-MCM7), the replication licensing factor and presumptive replicative helicase. Here, we report that the mouse chromosome instability mutation Chaos3 (chromosome aberrations occurring spontaneously 3), isolated in a forward genetic screen, is a viable allele of Mcm4. Mcm4(Chaos3) encodes a change in an evolutionarily invariant amino acid (F345I), producing an apparently destabilized MCM4. Saccharomyces cerevisiae strains that we engineered to contain a corresponding allele (resulting in an F391I change) showed a classical minichromosome loss phenotype. Whereas homozygosity for a disrupted Mcm4 allele (Mcm4(-)) caused preimplantation lethality, Mcm(Chaos3/-) embryos died late in gestation, indicating that Mcm4(Chaos3) is hypomorphic. Mutant embryonic fibroblasts were highly susceptible to chromosome breaks induced by the DNA replication inhibitor aphidicolin. Most notably, >80% of Mcm4(Chaos3/Chaos3) females succumbed to mammary adenocarcinomas with a mean latency of 12 months. These findings suggest that hypomorphic alleles of the genes encoding the subunits of the MCM2-7 complex may increase breast cancer risk.
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Affiliation(s)
- Naoko Shima
- Department of Genetics, Cell Biology and Development, College of Biological Sciences, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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74
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Yoshimura M, Kohzaki M, Nakamura J, Asagoshi K, Sonoda E, Hou E, Prasad R, Wilson SH, Tano K, Yasui A, Lan L, Seki M, Wood RD, Arakawa H, Buerstedde JM, Hochegger H, Okada T, Hiraoka M, Takeda S. Vertebrate POLQ and POLbeta cooperate in base excision repair of oxidative DNA damage. Mol Cell 2006; 24:115-25. [PMID: 17018297 PMCID: PMC1868411 DOI: 10.1016/j.molcel.2006.07.032] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2006] [Revised: 07/02/2006] [Accepted: 07/28/2006] [Indexed: 01/01/2023]
Abstract
Base excision repair (BER) plays an essential role in protecting cells from mutagenic base damage caused by oxidative stress, hydrolysis, and environmental factors. POLQ is a DNA polymerase, which appears to be involved in translesion DNA synthesis (TLS) past base damage. We disrupted POLQ, and its homologs HEL308 and POLN in chicken DT40 cells, and also created polq/hel308 and polq/poln double mutants. We found that POLQ-deficient mutants exhibit hypersensitivity to oxidative base damage induced by H(2)O(2), but not to UV or cisplatin. Surprisingly, this phenotype was synergistically increased by concomitant deletion of the major BER polymerase, POLbeta. Moreover, extracts from a polq null mutant cell line show reduced BER activity, and POLQ, like POLbeta, accumulated rapidly at sites of base damage. Accordingly, POLQ and POLbeta share an overlapping function in the repair of oxidative base damage. Taken together, these results suggest a role for vertebrate POLQ in BER.
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Affiliation(s)
- Michio Yoshimura
- Department of Radiation Genetics, CREST, Japan Science and Technology Laboratory, Graduate School of Medicine, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawaharacho, Sakyo-ku, Kyoto 606-8507
| | - Masaoki Kohzaki
- Department of Radiation Genetics, CREST, Japan Science and Technology Laboratory, Graduate School of Medicine, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501
- Research Reactor Institute, Kyoto University, 2 Asashironishi, Kumatoricho, Sennan-gun, Osaka 590-0494, Japan
| | - Jun Nakamura
- Department of Environmental Sciences and Engineering, The University of North Carolina, Chapel Hill, North Carolina 27599
| | - Kenjiro Asagoshi
- Laboratory of Structural Biology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Eiichiro Sonoda
- Department of Radiation Genetics, CREST, Japan Science and Technology Laboratory, Graduate School of Medicine, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501
| | - Esther Hou
- Laboratory of Structural Biology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Rajendra Prasad
- Laboratory of Structural Biology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Samuel H. Wilson
- Laboratory of Structural Biology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Keizo Tano
- Research Reactor Institute, Kyoto University, 2 Asashironishi, Kumatoricho, Sennan-gun, Osaka 590-0494, Japan
| | - Akira Yasui
- Department of Molecular Genetics, Institute of Development, Aging, and Cancer, Tohoku University, Seiryomachi 4-1, Sendai 980-8575, Japan
| | - Li Lan
- Department of Molecular Genetics, Institute of Development, Aging, and Cancer, Tohoku University, Seiryomachi 4-1, Sendai 980-8575, Japan
| | - Mineaki Seki
- University of Pittsburgh, Hillman Cancer Center, 5117 Centre Avenue, Research Pavilion Suite 2.6, Pittsburgh, Pennsylvania 15213
| | - Richard D. Wood
- University of Pittsburgh, Hillman Cancer Center, 5117 Centre Avenue, Research Pavilion Suite 2.6, Pittsburgh, Pennsylvania 15213
| | - Hiroshi Arakawa
- Institute of Molecular Radiobiology, GSF, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Munich, Germany
| | - Jean-Marie Buerstedde
- Institute of Molecular Radiobiology, GSF, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Munich, Germany
| | - Helfrid Hochegger
- Department of Radiation Genetics, CREST, Japan Science and Technology Laboratory, Graduate School of Medicine, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501
| | - Takashi Okada
- Department of Radiation Genetics, CREST, Japan Science and Technology Laboratory, Graduate School of Medicine, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501
- Department of Urology, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawaharacho, Sakyo-ku, Kyoto 606-8507, Japan
| | - Masahiro Hiraoka
- Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawaharacho, Sakyo-ku, Kyoto 606-8507
| | - Shunichi Takeda
- Department of Radiation Genetics, CREST, Japan Science and Technology Laboratory, Graduate School of Medicine, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501
- *Correspondence:
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75
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Masuda K, Ouchida R, Hikida M, Nakayama M, Ohara O, Kurosaki T, O-Wang J. Absence of DNA polymerase theta results in decreased somatic hypermutation frequency and altered mutation patterns in Ig genes. DNA Repair (Amst) 2006; 5:1384-91. [PMID: 16890500 DOI: 10.1016/j.dnarep.2006.06.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2006] [Revised: 06/09/2006] [Accepted: 06/13/2006] [Indexed: 11/27/2022]
Abstract
Multiple DNA polymerases participate in somatic hypermutation of immunoglobulin (Ig) genes. Mutations at A/T are largely dependent on DNA polymerase eta (POLH) whereas mutations at C/G appear to be generated by several DNA polymerases. We have previously shown that mice expressing a catalytically inactive POLQ (Polq-inactive) have a reduction in C/G mutations. Here we have generated mice that completely lack Polq expression (Polq-null). Polq-null mice have no obvious abnormality in B or T cell differentiation, and their splenic B cells responded normally to various activation signals and underwent normal Ig gene class switching. The mutant mice mounted relatively normal immune responses against a T-dependent antigen although there was a slight decrease in antigen specific antibodies. Polq-null mice exhibited a mild reduction in the overall mutation frequency, however, in contrast to Polq-inactive mice where the reduction mostly affected mutations at C/G, Polq-null mice showed a reduction of both C/G and A/T mutations and there was a significant increase of G to C transversions. These results confirm a role for POLQ in somatic hypermutation and suggest that in the complete absence of POLQ other polymerases may functionally substitute, resulting in a mutation pattern different from that found in Polq-inactive mice.
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Affiliation(s)
- Keiji Masuda
- Laboratory for Antigen Receptor Diversity, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Yokohama 230-0045, Japan
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76
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Moore JL, Rush LM, Breneman C, Mohideen MAPK, Cheng KC. Zebrafish genomic instability mutants and cancer susceptibility. Genetics 2006; 174:585-600. [PMID: 16888336 PMCID: PMC1602069 DOI: 10.1534/genetics.106.059386] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Somatic loss of tumor suppressor gene function comprising the second hit of Knudson's two-hit hypothesis is important in human cancer. A genetic screen was performed in zebrafish (Danio rerio) to find mutations that cause genomic instability (gin), as scored by Streisinger's mosaic-eye assay that models this second hit. The assay, based on a visible test for loss of wild-type gene function at a single locus, golden, is representative of genomewide events. Twelve ENU-induced genomic instability (gin) mutations were isolated. Most mutations showed weak dominance in heterozygotes and all showed a stronger phenotype in homozygotes. Trans-heterozygosity for 7 of these mutations showed greatly enhanced instability. A variety of spontaneous tumors were found in heterozygous adults from all gin lines, consistent with the expectation that genomic instability (mutator) mutations can accelerate carcinogenesis. The incidence of spontaneous cancer at 30-34 months was increased 9.6-fold in heterozygotes for the mutant with the strongest phenotype, gin-10. Tumors were seen in skin, colon, kidney, liver, pancreas, ovary, testis, and neuronal tissues, with multiple tumors in some fish. The study of these mutants will add to our understanding of the mechanisms of somatic loss of gene function and how those mechanisms contribute to cancer susceptibility.
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Affiliation(s)
- Jessica L Moore
- The Jake Gittlen Cancer Research Foundation, Department of Pathology, Pennsylvania State College of Medicine, Hershey, Pennsylvania 17033, USA
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77
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Inagaki S, Suzuki T, Ohto MA, Urawa H, Horiuchi T, Nakamura K, Morikami A. Arabidopsis TEBICHI, with helicase and DNA polymerase domains, is required for regulated cell division and differentiation in meristems. THE PLANT CELL 2006; 18:879-92. [PMID: 16517762 PMCID: PMC1425847 DOI: 10.1105/tpc.105.036798] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
In plant meristems, each cell divides and differentiates in a spatially and temporally regulated manner, and continuous organogenesis occurs using cells derived from the meristem. We report the identification of the Arabidopsis thaliana TEBICHI (TEB) gene, which is required for regulated cell division and differentiation in meristems. The teb mutants show morphological defects, such as short roots, serrated leaves, and fasciation, as well as defective patterns of cell division and differentiation in the meristem. The TEB gene encodes a homolog of Drosophila MUS308 and mammalian DNA polymerase theta, which prevent spontaneous or DNA damage-induced production of DNA double strand breaks. As expected from the function of animal homologs, teb mutants show constitutively activated DNA damage responses. Unlike other fasciation mutants with activated DNA damage responses, however, teb mutants do not activate transcriptionally silenced genes. teb shows an accumulation of cells expressing cyclinB1;1:GUS in meristems, suggesting that constitutively activated DNA damage responses in teb lead to a defect in G2/M cell cycle progression. Furthermore, other fasciation mutants, such as fasciata2 and tonsoku/mgoun3/brushy1, also show an accumulation of cells expressing cyclinB1;1:GUS in meristems. These results suggest that cell cycle progression at G2/M is important for the regulation of the pattern of cell division and of differentiation during plant development.
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Affiliation(s)
- Soichi Inagaki
- Laboratory of Biochemistry, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8601, Japan.
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78
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Seki M, Gearhart PJ, Wood RD. DNA polymerases and somatic hypermutation of immunoglobulin genes. EMBO Rep 2006; 6:1143-8. [PMID: 16319960 PMCID: PMC1369213 DOI: 10.1038/sj.embor.7400582] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Accepted: 10/17/2005] [Indexed: 11/08/2022] Open
Abstract
Somatic hypermutation of immunoglobulin variable genes, which increases antibody diversity, is initiated by the activation-induced cytosine deaminase (AID) protein. The current DNA-deamination model posits that AID deaminates cytosine to uracil in DNA, and that mutations are generated by DNA polymerases during replication or repair of the uracil residue. Mutations could arise as follows: by DNA replicating past the uracil; by removing the uracil with a uracil glycosylase and replicating past the resulting abasic site with a low-fidelity polymerase; or by repairing the uracil and synthesizing a DNA-repair patch downstream using a low-fidelity polymerase. In this review, we summarize the biochemical properties of specialized DNA polymerases in mammalian cells and discuss their participation in the mechanisms of hypermutation. Many recent studies have examined mice deficient in the genes that encode various DNA polymerases, and have shown that DNA polymerase H (POLH) contributes to hypermutation, whereas POLI, POLK and several other enzymes do not have major roles. The low-fidelity enzyme POLQ has been proposed as another candidate polymerase because it can efficiently bypass abasic sites and recent evidence indicates that it might participate in hypermutation.
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Affiliation(s)
- Mineaki Seki
- Suite 2.6, Research Pavilion, Hillman Cancer Center, University of Pittsburgh Cancer Institute, 5117 Centre Avenue, Pittsburgh, Pennsylvania 15213, USA
| | - Patricia J Gearhart
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, Maryland 21224, USA
| | - Richard D Wood
- Suite 2.6, Research Pavilion, Hillman Cancer Center, University of Pittsburgh Cancer Institute, 5117 Centre Avenue, Pittsburgh, Pennsylvania 15213, USA
- Tel: +1 412 623 7766; Fax: +1 412 623 7761; E-mail:
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79
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Ukai A, Maruyama T, Mochizuki S, Ouchida R, Masuda K, Kawamura K, Tagawa M, Kinoshita K, Sakamoto A, Tokuhisa T, O-Wang J. Role of DNA polymerase theta in tolerance of endogenous and exogenous DNA damage in mouse B cells. Genes Cells 2006; 11:111-21. [PMID: 16436048 DOI: 10.1111/j.1365-2443.2006.00922.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
DNA polymerase theta (Poltheta) is a family A polymerase that contains an intrinsic helicase domain. To investigate the function of Poltheta in mammalian cells, we have inactivated its polymerase activity in CH12 mouse B lymphoma cells by targeted deletion of the polymerase core domain that contains the catalytic aspartic acid residue. Compared to parental CH12 cells, mutant cells devoid of Poltheta polymerase activity exhibited a slightly reduced growth rate, accompanied by increased spontaneous cell death. In addition, mutant cells showed elevated sensitivity to mitomycin C, cisplatin, etoposide, gamma-irradiation and ultraviolet (UV) radiation. Interestingly, mutant cells were more sensitive to the alkylating agent methyl methanesulfonate (MMS) than parental cells. This elevated MMS sensitivity relative to WT cells persisted in the presence of methoxyamine, an inhibitor of the major base excision repair (BER) pathway, suggesting that Poltheta is involved in tolerance of MMS through a mechanism that appears to be different from BER. These results reveal an important role for Poltheta in preventing spontaneous cell death and in tolerance of not only DNA interstrand cross-links and double strand breaks but also UV adducts and alkylation damage in mammalian lymphocytes.
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Affiliation(s)
- Akiko Ukai
- Laboratory for Antigen Receptor Diversity, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Yokohama 230-0045, Japan
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80
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Kennedy CL, O'Bryan MK. N-ethyl-N-nitrosourea (ENU) mutagenesis and male fertility research. Hum Reprod Update 2006; 12:293-301. [PMID: 16436467 DOI: 10.1093/humupd/dmk004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Male infertility affects about 1 in 25 men in the western world. Conversely, there is an urgent requirement for additional male-based contraceptives, yet progress in both areas has been severely hampered by a lack of knowledge of the biochemistry and physiology of male reproductive function. It is only through a thorough knowledge of these processes that we can hope to insightfully regulate male reproductive function. Without doubt, mouse models will form an important foundation in any future process. In recent years, the chemical mutagen N-ethyl-N-nitrosourea (ENU) has been used widely to identify genes essential for a range of biological systems including male infertility. These studies have shown random mutagenesis is an attractive means of identifying key genes for male fertility. This technique has distinct, but complementary advantages compared to knockout technologies. Specifically, it allows the removal of researcher bias whereby only pre-conceived genes are tested for function; it produces mice with a guaranteed phenotype and allows for the production of allelic series of mice to dissect all aspects of gene function. ENU mouse mutagenesis programs will enable advances in the diagnosis and treatment of human male infertility and ultimately aid in the development of novel male-based contraceptives.
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Affiliation(s)
- C L Kennedy
- The Centre for Reproduction and Development, Monash Institute of Medical Research and the ARC Centre of Excellence in Biotechnology and Development, Monash University, Melbourne, Australia
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81
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82
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Fischhaber PL, McDaniel LD, Friedberg EC. DNA Polymerases for Translesion DNA Synthesis: Enzyme Purification and Mouse Models for Studying Their Function. Methods Enzymol 2006; 408:355-78. [PMID: 16793380 DOI: 10.1016/s0076-6879(06)08022-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
This chapter discusses experimental methods and protocols for the purification and preliminary characterization of DNA polymerases that are specialized for the replicative bypass (translesion DNA synthesis) of base or other types of DNA damage that typically arrest high-fidelity DNA synthesis, with particular emphasis on DNA polymerase kappa (Polkappa from mouse cells). It also describes some of the methods employed in the evaluation of mouse strains defective in genes that encode these enzymes.
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Affiliation(s)
- Paula L Fischhaber
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, USA
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83
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Abstract
In the mouse, random mutagenesis with N-ethyl-N-nitrosourea (ENU) has been used since the 1970s in forward mutagenesis screens. However, only in the last decade has ENU mutagenesis been harnessed to generate a myriad of new mouse mutations in large-scale genetic screens and focused, smaller efforts. The development of additional genetic tools, such as balancer chromosomes, refinements in genetic mapping strategies, and evolution of specialized assays, has allowed these screens to achieve new levels of sophistication. The impressive productivity of these screens has led to a deluge of mouse mutants that wait to be harnessed. Here the basic large- and small-scale strategies are described, as are the basics of screen design. Finally, and importantly, this review describes the mechanisms by which such mutants may be accessed now and in the future. Thus, this review should serve both as an overview of the power of forward mutagenesis in the mouse and as a resource for those interested in developing their own screens, adding onto existing efforts, or obtaining specific mouse mutants that have already been generated.
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Affiliation(s)
- Sabine P Cordes
- Samuel Lunenfeld Research Institute, Room 865, Mt. Sinai Hospital, Toronto, Ontario M5G 1X5, Canada.
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84
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Zan H, Shima N, Xu Z, Al-Qahtani A, Evinger III AJ, Zhong Y, Schimenti JC, Casali P. The translesion DNA polymerase theta plays a dominant role in immunoglobulin gene somatic hypermutation. EMBO J 2005; 24:3757-69. [PMID: 16222339 PMCID: PMC1276717 DOI: 10.1038/sj.emboj.7600833] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2005] [Accepted: 09/12/2005] [Indexed: 11/08/2022] Open
Abstract
Immunoglobulin (Ig) somatic hypermutation (SHM) critically underlies the generation of high-affinity antibodies. Mutations can be introduced by error-prone polymerases such as polymerase zeta (Rev3), a mispair extender, and polymerase eta, a mispair inserter with a preference for dA/dT, while repairing DNA lesions initiated by AID-mediated deamination of dC to yield dU:dG mismatches. The partial impairment of SHM observed in the absence of these polymerases led us to hypothesize a main role for another translesion DNA polymerase. Here, we show that deletion in C57BL/6J mice of the translesion polymerase theta, which possesses a dual nucleotide mispair inserter-extender function, results in greater than 60% decrease of mutations in antigen-selected V186.2DJ(H) transcripts and greater than 80% decrease in mutations in the Ig H chain intronic J(H)4-iEmu sequence, together with significant alterations in the spectrum of the residual mutations. Thus, polymerase theta plays a dominant role in SHM, possibly by introducing mismatches while bypassing abasic sites generated by UDG-mediated deglycosylation of AID-effected dU, by extending DNA past such abasic sites and by synthesizing DNA during dU:dG mismatch repair.
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Affiliation(s)
- Hong Zan
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA, USA
| | - Naoko Shima
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Zhenming Xu
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA, USA
| | - Ahmed Al-Qahtani
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA, USA
| | - Albert J Evinger III
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA, USA
| | - Yuan Zhong
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA, USA
| | - John C Schimenti
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Paolo Casali
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA, USA
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85
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van der Weyden L, Tachibana KK, Gonzalez MA, Adams DJ, Ng BL, Petty R, Venkitaraman AR, Arends MJ, Bradley A. The RASSF1A isoform of RASSF1 promotes microtubule stability and suppresses tumorigenesis. Mol Cell Biol 2005; 25:8356-67. [PMID: 16135822 PMCID: PMC1234312 DOI: 10.1128/mcb.25.18.8356-8367.2005] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The RASSF1A isoform of RASSF1 is frequently inactivated by epigenetic alterations in human cancers, but it remains unclear if and how it acts as a tumor suppressor. RASSF1A overexpression reduces in vitro colony formation and the tumorigenicity of cancer cell lines in vivo. Conversely, RASSF1A knockdown causes multiple mitotic defects that may promote genomic instability. Here, we have used a genetic approach to address the function of RASSF1A as a tumor suppressor in vivo by targeted deletion of Rassf1A in the mouse. Rassf1A null mice were viable and fertile and displayed no pathological abnormalities. Rassf1A null embryonic fibroblasts displayed an increased sensitivity to microtubule depolymerizing agents. No overtly altered cell cycle parameters or aberrations in centrosome number were detected in Rassf1A null fibroblasts. Rassf1A null fibroblasts did not show increased sensitivity to microtubule poisons or DNA-damaging agents and showed no evidence of gross genomic instability, suggesting that cellular responses to genotoxins were unaffected. Rassf1A null mice showed an increased incidence of spontaneous tumorigenesis and decreased survival rate compared with wild-type mice. Irradiated Rassf1A null mice also showed increased tumor susceptibility, particularly to tumors associated with the gastrointestinal tract, compared with wild-type mice. Thus, our results demonstrate that Rassf1A acts as a tumor suppressor gene.
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Affiliation(s)
- L van der Weyden
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, United Kingdom
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86
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Pang M, McConnell M, Fisher PA. The Drosophila mus 308 gene product, implicated in tolerance of DNA interstrand crosslinks, is a nuclear protein found in both ovaries and embryos. DNA Repair (Amst) 2005; 4:971-82. [PMID: 15961355 DOI: 10.1016/j.dnarep.2005.04.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2004] [Revised: 04/08/2005] [Accepted: 04/11/2005] [Indexed: 10/25/2022]
Abstract
mus 308 designates one of over 30 mutagen sensitivity loci found in Drosophila. It is predicted to code for a 229-kDa polypeptide. Published sequence analyses of others indicate that this polypeptide would have helicase motifs near its N-terminus, and similarities to bacterial DNA polymerase I-like enzymes near its C-terminus. In our studies, two different and highly specific antibodies were prepared and used for identification as well as characterization of the mus 308 gene product. Western blot analyses reveal a single reactive polypeptide in both ovaries and embryos as well as in two Drosophila embryo tissue culture cell lines; it is nearly absent in homozygous mus 308 mutants. This polypeptide is about 229 kDa in size, and indirect immunofluorescence shows that the mus 308 gene product localizes throughout nuclei in wild-type cells but appears to be absent in a mus 308 mutant. Immunoblot analyses throughout development suggest greatest abundance at the end of embryogenesis, immediately before hatching of first instar larvae. They also showed a smaller ( approximately 100 kDa) antigenically and genetically related polypeptide found only in adult males. Immunoprecipitation, a highly effective method of specific purification, suggests that the mus 308 protein has DNA polymerase activity that is NEM-sensitive but largely aphidicolin-resistant. In addition, the immunoprecipitated material has DNA-dependent ATPase but lacks detectable helicase.
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Affiliation(s)
- Maria Pang
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794-8651, USA
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87
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Masuda K, Ouchida R, Takeuchi A, Saito T, Koseki H, Kawamura K, Tagawa M, Tokuhisa T, Azuma T, O-Wang J. DNA polymerase theta contributes to the generation of C/G mutations during somatic hypermutation of Ig genes. Proc Natl Acad Sci U S A 2005; 102:13986-91. [PMID: 16172387 PMCID: PMC1236561 DOI: 10.1073/pnas.0505636102] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Accepted: 08/10/2005] [Indexed: 01/09/2023] Open
Abstract
Somatic hypermutation of Ig variable region genes is initiated by activation-induced cytidine deaminase; however, the activity of multiple DNA polymerases is required to ultimately introduce mutations. DNA polymerase eta (Poleta) has been implicated in mutations at A/T, but polymerases involved in C/G mutations have not been identified. We have generated mutant mice expressing DNA polymerase (Pol) specifically devoid of polymerase activity. Compared with WT mice, Polq-inactive (Polq, the gene encoding Pol) mice exhibited a reduced level of serum IgM and IgG1. The mutant mice mounted relatively normal primary and secondary immune responses to a T-dependent antigen, but the production of high-affinity specific antibodies was partially impaired. Analysis of the J(H)4 intronic sequences revealed a slight reduction in the overall mutation frequency in Polq-inactive mice. Remarkably, although mutations at A/T were unaffected, mutations at C/G were significantly decreased, indicating an important, albeit not exclusive, role for Pol activity. The reduction of C/G mutations was particularly focused on the intrinsic somatic hypermutation hotspots and both transitions and transversions were similarly reduced. These findings, together with the recent observation that Pol efficiently catalyzes the bypass of abasic sites, lead us to propose that Pol introduces mutations at C/G by replicating over abasic sites generated via uracil-DNA glycosylase.
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Affiliation(s)
- Keiji Masuda
- Laboratories for Antigen Receptor Diversity, Cell Signaling, and Developmental Genetics, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Yokohama, Kanagawa 230-0045, Japan
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88
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Abstract
Humans are mammals, not bacteria or plants, yeast or nematodes, insects or fish. Mice are also mammals, but unlike gorilla and goat, fox and ferret, giraffe and jackal, they are suited perfectly to the laboratory environment and genetic experimentation. In this review, we will summarize the tools, tricks and techniques for executing forward genetic screens in the mouse and argue that this approach is now accessible to most biologists, rather than being the sole domain of large national facilities and specialized genetics laboratories.
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Affiliation(s)
- Benjamin T Kile
- Division of Cancer and Hematology, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville 3050, Victoria, Australia.
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89
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Wilson L, Ching YH, Farias M, Hartford SA, Howell G, Shao H, Bucan M, Schimenti JC. Random mutagenesis of proximal mouse chromosome 5 uncovers predominantly embryonic lethal mutations. Genome Res 2005; 15:1095-105. [PMID: 16024820 PMCID: PMC1182222 DOI: 10.1101/gr.3826505] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A region-specific ENU mutagenesis screen was conducted to elucidate the functional content of proximal mouse Chr 5. We used the visibly marked, recessive, lethal inversion Rump White (Rw) as a balancer in a three-generation breeding scheme to identify recessive mutations within the approximately 50 megabases spanned by Rw. A total of 1003 pedigrees were produced, representing the largest inversion screen performed in mice. Test-class animals, homozygous for the ENU-mutagenized proximal Chr 5 and visibly distinguishable from nonhomozygous littermates, were screened for fertility, hearing, vestibular function, DNA repair, behavior, and dysmorphology. Lethals were identifiable by failure to derive test-class animals within a pedigree. Embryonic lethal mutations (total of 34) were overwhelmingly the largest class of mutants recovered. We characterized them with respect to the time of embryonic death, revealing that most act at midgestation (8.5-10.5) or sooner. To position the mutations within the Rw region and to guide allelism tests, we performed complementation analyses with a set of new and existing chromosomal deletions, as well as standard recombinational mapping on a subset of the mutations. By pooling the data from this and other region-specific mutagenesis projects, we calculate that the mouse genome contains approximately 3479-4825 embryonic lethal genes, or about 13.7%-19% of all genes.
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90
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Xu Z, Fulop Z, Zhong Y, Evinger AJ, Zan H, Casali P. DNA lesions and repair in immunoglobulin class switch recombination and somatic hypermutation. Ann N Y Acad Sci 2005; 1050:146-62. [PMID: 16014529 PMCID: PMC4621013 DOI: 10.1196/annals.1313.119] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Immunoglobulin (Ig) gene somatic hypermutation (SHM) and class switch DNA recombination (CSR) are critical for the maturation of the antibody response. These processes endow antibodies with increased antigen-binding affinity and acquisition of new biological effector functions, thereby underlying the generation of memory B cells and plasma cells. They are dependent on the generation of specific DNA lesions and the intervention of activation-induced cytidine deaminase as well as newly identified translesion DNA polymerases, which are expressed in germinal center B cells. DNA lesions include mismatches, abasic sites, nicks, single-strand breaks, and double-strand breaks (DSBs). DSBs in the switch (S) region DNA are critical for CSR, but they also occur in V(D)J regions and possibly contribute to the events that lead to SHM. The nature of the DSBs in the Ig locus, their generation, and the repair processes that they trigger and that are responsible for their regulation remain poorly understood. Aberrant regulation of these events can result in chromosomal breaks and translocations, which are significant steps in B-cell neoplastic transformation.
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Affiliation(s)
- Zhenming Xu
- Center for Immunology, 3028 Hewitt Hall, University of California, Irvine, CA 92697-4120, USA
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91
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Munroe RJ, Ackerman SL, Schimenti JC. Genomewide two-generation screens for recessive mutations by ES cell mutagenesis. Mamm Genome 2005; 15:960-5. [PMID: 15599554 DOI: 10.1007/s00335-004-2406-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Accepted: 08/24/2004] [Indexed: 10/24/2022]
Abstract
Forward genetic mutation screens in mice are typically begun by mutagenizing the germline of male mice with N-ethyl-N-nitrosourea (ENU). Genomewide recessive mutations transmitted by these males can be rendered homozygous after three generations of breeding, at which time phenotype screens can be performed. An alternative strategy for randomly mutagenizing the mouse genome is by chemical treatment of embryonic stem (ES) cells. Here we demonstrate the feasibility of performing genome-wide mutation screens with only two generations of breeding. Mice potentially homozygous for mutations were obtained by crossing chimeras derived from ethylmethane sulfonate (EMS)-mutagenized ES cells to their daughters, or by intercrossing offspring of chimeras. This strategy was possible because chimeras transmit variations of the same mutagenized diploid genome, whereas ENU-treated males transmit numerous unrelated genomes. This also results in a doubling of screenable mutations in a pedigree compared to germline ENU mutagenesis. Coupled with the flexibility to treat ES cells with a variety of potent mutagens and the ease of producing distributable, quality-controlled, long-term supplies of cells in a single experiment, this strategy offers a number of advantages for conducting forward genetic screens in mice.
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92
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Shima N, Munroe RJ, Schimenti JC. The mouse genomic instability mutation chaos1 is an allele of Polq that exhibits genetic interaction with Atm. Mol Cell Biol 2004; 24:10381-9. [PMID: 15542845 PMCID: PMC529050 DOI: 10.1128/mcb.24.23.10381-10389.2004] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2004] [Revised: 08/10/2004] [Accepted: 08/19/2004] [Indexed: 11/20/2022] Open
Abstract
chaos1 (for chromosome aberrations occurring spontaneously 1) is a recessive mutation that was originally identified in a phenotype-based screen for chromosome instability mutants in mice. Mutant animals exhibit significantly higher frequencies of spontaneous and radiation- or mitomycin C-induced micronucleated erythrocytes, indicating a potential defect in homologous recombination or interstrand cross-link repair. The chaos1 allele was genetically associated with a missense mutation in Polq, which encodes DNA polymerase theta;. We demonstrate here that chaos1 is a mutant allele of Polq by using two genetic approaches: chaos1 mutant phenotype correction by a bacterial artificial chromosome carrying wild-type Polq and a failed complementation test between chaos1 and a Polq-disrupted allele generated by gene targeting. To investigate the potential involvement of Polq in DNA double-strand break repair, we introduced chaos1 into an Atm (for ataxia telangiectasia mutated)-deficient background. The majority ( approximately 90%) of double-homozygous mice died during the neonatal period. Surviving double mutants exhibited synergistic phenotypes such as severe growth retardation and enhanced chromosome instability. However, remarkably, double mutants had delayed onset of thymic lymphoma, significantly increasing life span. These data suggest a unique role of Polq in maintaining genomic integrity, which is probably distinctive from the major homologous recombination pathway regulated by ATM.
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Affiliation(s)
- Naoko Shima
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, 9th Fl. Vet. Research Tower, Ithaca, NY 14853, USA
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93
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Seki M, Masutani C, Yang LW, Schuffert A, Iwai S, Bahar I, Wood RD. High-efficiency bypass of DNA damage by human DNA polymerase Q. EMBO J 2004; 23:4484-94. [PMID: 15496986 PMCID: PMC526458 DOI: 10.1038/sj.emboj.7600424] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2004] [Accepted: 08/27/2004] [Indexed: 01/03/2023] Open
Abstract
Endogenous DNA damage arises frequently, particularly apurinic (AP) sites. These must be dealt with by cells in order to avoid genotoxic effects. DNA polymerase theta; is a newly identified enzyme encoded by the human POLQ gene. We find that POLQ has an exceptional ability to bypass an AP site, inserting A with 22% of the efficiency of a normal template, and continuing extension as avidly as with a normally paired base. POLQ preferentially incorporates A opposite an AP site and strongly disfavors C. On nondamaged templates, POLQ makes frequent errors, incorporating G or T opposite T about 1% of the time. This very low fidelity distinguishes POLQ from other A-family polymerases. POLQ has three sequence insertions between conserved motifs in its catalytic site. One insert of approximately 22 residues into the tip of the polymerase thumb subdomain is predicted to confer considerable flexibility and additional DNA contacts to affect enzyme fidelity. POLQ is the only known enzyme that efficiently carries out both the insertion and extension steps for bypass of AP sites, commonly formed as endogenous genomic lesions.
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Affiliation(s)
- Mineaki Seki
- University of Pittsburgh Cancer Institute, Hillman Cancer Center, Research Pavilion, Pittsburgh, PA, USA
| | - Chikahide Masutani
- Graduate School of Frontier Biosciences, Osaka University and CREST, Japan Science and Technology Corporation, Suita, Osaka, Japan
| | - Lee Wei Yang
- Department of Molecular Genetics & Biochemistry, Center for Computational Biology and Bioinformatics, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Anthony Schuffert
- University of Pittsburgh Cancer Institute, Hillman Cancer Center, Research Pavilion, Pittsburgh, PA, USA
| | - Shigenori Iwai
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
| | - Ivet Bahar
- Department of Molecular Genetics & Biochemistry, Center for Computational Biology and Bioinformatics, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Richard D Wood
- University of Pittsburgh Cancer Institute, Hillman Cancer Center, Research Pavilion, Pittsburgh, PA, USA
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94
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Kawamura K, Bahar R, Seimiya M, Chiyo M, Wada A, Okada S, Hatano M, Tokuhisa T, Kimura H, Watanabe S, Honda I, Sakiyama S, Tagawa M, O-Wang J. DNA polymerase theta is preferentially expressed in lymphoid tissues and upregulated in human cancers. Int J Cancer 2004; 109:9-16. [PMID: 14735462 DOI: 10.1002/ijc.11666] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
DNA polymerase theta (Pol theta) is a recently identified family A polymerase that contains an intrinsic helicase domain. Drosophila Pol theta mutants are hypersensitive to bifunctional DNA crosslinking agents and exhibit an elevated frequency of spontaneous chromosomal aberrations, suggesting a role for Pol theta in repair of DNA interstrand crosslinks and in the general maintenance of genome stability. To investigate a possible involvement of Pol theta in tumorigenesis, we have examined its expression in various normal and malignant tissues. Paired tumor and adjacent nontumorous tissues from patients with lung (n = 27), stomach (n = 28) and colon (n = 26) cancer, as well as 26 normal human tissues, were examined for Pol theta expression by RT-PCR, Northern or Western blot analysis. Pol theta was predominantly expressed in primary lymphoid organs including the fetal liver, thymus and bone marrow where lymphocyte progenitors undergo V(D)J rearrangements of their antigen receptor genes. In addition, Pol theta expression was upregulated in germinal center B cells, in which class switch recombination of the immunoglobulin genes occurs. Examination of Pol theta expression in matched cancer specimens revealed that Pol theta was barely detectable in the nontumorous tissues but was upregulated in 17 of 27 (63%) lung, 11 of 28 (39%) stomach and 20 of 26 (77%) colon cancers. Moreover, patients with high levels of Pol theta expression had a significantly poorer clinical outcome compared with those expressing low levels of Pol theta. These results implicate that Pol theta may have a specialized function in lymphocytes and that its overexpression may contribute to tumor progression.
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Affiliation(s)
- Kiyoko Kawamura
- Division of Pathology, Chiba Cancer Center Research Institute, Chiba, Japan
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95
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Marini F, Kim N, Schuffert A, Wood RD. POLN, a nuclear PolA family DNA polymerase homologous to the DNA cross-link sensitivity protein Mus308. J Biol Chem 2003; 278:32014-9. [PMID: 12794064 DOI: 10.1074/jbc.m305646200] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Drosophila Mus308 gene is unusual in encoding both a family A DNA polymerase domain and a DNA/RNA helicase domain. A mus308 mutation was shown to result in increased sensitivity to DNA cross-linking agents, leading to the hypothesis that Mus308 functions in the repair of DNA interstrand cross-links. Recently a mammalian ortholog of Mus308, POLQ, has been identified. We report here the identification, cloning, and characterization of POLN and its gene product, a new mammalian DNA polymerase also related to Mus308. The human cDNA encodes a protein of 900 amino acid residues. The region starting from residue 419 shares 33% identity (48% similarity) with the equivalent region of Escherichia coli DNA polymerase I. POLN is expressed in human cell lines with numerous alternatively spliced transcripts, and a full-length human coding region that comprises 24 exons within 160 kilobases of genomic DNA. Expression analysis by northern blotting and in situ hybridization showed highest expression of full-length POLN in human and mouse testis. POLN localized to the nucleus when expressed as a enhanced green fluorescent protein (GFP)-tagged protein in human fibroblasts. GFP-tagged recombinant POLN had DNA polymerase activity on activated calf thymus DNA and on a singly primed template.
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Affiliation(s)
- Federica Marini
- University of Pittsburgh Cancer Institute, Hillman Cancer Center, Research Pavilion, Pittsburgh, Pennsylvania 15213, USA
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