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Human RECQ helicases: roles in DNA metabolism, mutagenesis and cancer biology. Semin Cancer Biol 2010; 20:329-39. [PMID: 20934517 DOI: 10.1016/j.semcancer.2010.10.002] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 10/01/2010] [Indexed: 12/13/2022]
Abstract
Helicases use the energy of ATP hydrolysis to separate double-stranded nucleic acids to facilitate essential processes such as replication, recombination, transcription and repair. This article focuses on the human RECQ helicase gene and protein family. Loss of function of three different members has been shown to cause Bloom syndrome (BS), Werner syndrome (WS) and Rothmund-Thomson syndrome (RTS). This article outlines clinical and cellular features of these cancer predisposition syndromes, and discusses their pathogenesis in light of our understanding of RECQ helicase biochemical activities and in vivo functions. I also discuss the emerging role for RECQ helicases as predictors of disease risk and the response to therapy.
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Zhang J, Zhao D, Park HK, Wang H, Dyer RB, Liu W, Klee GG, McNiven MA, Tindall DJ, Molina JR, Fei P. FAVL elevation in human tumors disrupts Fanconi anemia pathway signaling and promotes genomic instability and tumor growth. J Clin Invest 2010; 120:1524-34. [PMID: 20407210 DOI: 10.1172/jci40908] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Accepted: 02/17/2010] [Indexed: 12/22/2022] Open
Abstract
Fanconi anemia (FA) is a rare human genetic disease caused by mutations in any one of 13 known genes that encode proteins functioning in one common signaling pathway, the FA pathway, or in unknown genes. One characteristic of FA is an extremely high incidence of cancer, indicating the importance of the FA pathway in tumor suppression. However, the role of this pathway in the development and progression of human cancers in individuals who do not have FA has not been clearly determined. Here, we report that elevated expression of what we believe to be a novel splice variant of FA complementation group L (FANCL), which we identified and named FAVL, can impair the FA pathway in non-FA human tumor cells and act as a tumor promoting factor. FAVL expression was elevated in half of the human carcinoma cell lines and carcinoma tissue samples tested. Expression of FAVL resulted in decreased FANCL expression by sequestering FANCL to the cytoplasm and enhancing its degradation. Importantly, this impairment of the FA pathway by FAVL elevation provided human cancer cells with a growth advantage, caused chromosomal instability in vitro, and promoted tumor development in a xenograft mouse model. These data indicate that FAVL impairment of the FA pathway likely contributes to the development of non-FA human cancers and therefore add a challenging layer of complexity to the pathogenesis of human cancer. We further believe that these data will prove useful for developing additional tools for fighting human cancer.
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Affiliation(s)
- Jun Zhang
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota 55905, USA
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3
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Saintigny Y, Makienko K, Swanson C, Emond MJ, Monnat RJ. Homologous recombination resolution defect in werner syndrome. Mol Cell Biol 2002; 22:6971-8. [PMID: 12242278 PMCID: PMC139822 DOI: 10.1128/mcb.22.20.6971-6978.2002] [Citation(s) in RCA: 209] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2002] [Revised: 07/05/2002] [Accepted: 07/12/2002] [Indexed: 11/20/2022] Open
Abstract
Werner syndrome (WRN) is an uncommon autosomal recessive disease whose phenotype includes features of premature aging, genetic instability, and an elevated risk of cancer. We used three different experimental strategies to show that WRN cellular phenotypes of limited cell division potential, DNA damage hypersensitivity, and defective homologous recombination (HR) are interrelated. WRN cell survival and the generation of viable mitotic recombinant progeny could be rescued by expressing wild-type WRN protein or by expressing the bacterial resolvase protein RusA. The dependence of WRN cellular phenotypes on RAD51-dependent HR pathways was demonstrated by using a dominant-negative RAD51 protein to suppress mitotic recombination in WRN and control cells: the suppression of RAD51-dependent recombination led to significantly improved survival of WRN cells following DNA damage. These results define a physiological role for the WRN RecQ helicase protein in RAD51-dependent HR and identify a mechanistic link between defective recombination resolution and limited cell division potential, DNA damage hypersensitivity, and genetic instability in human somatic cells.
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Affiliation(s)
- Yannick Saintigny
- Departments of Pathology. Biostatistics. Genome Sciences, University of Washington, Seattle, Washington 98195-7705, USA
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Abstract
Werner syndrome (WS) is one of a group of human genetic diseases that have recently been linked to deficits in cellular helicase function. We review the spectrum of WS-associated WRN mutations, the organization and potential functions of the WRN protein, and potential mechanistic links between the loss of WRN function and pathogenesis of the WS clinical and cellular phenotypes.
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Affiliation(s)
- M J Moser
- Department of Pathology, University of Washington, Seattle 98195-7705, USA
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5
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Lin CW, Darzynkiewicz Z, Li X, Traganos F, Bedner E, Tse-Dinh YC. Differential expression of human topoisomerase IIIalpha during the cell cycle progression in HL-60 leukemia cells and human peripheral blood lymphocytes. Exp Cell Res 2000; 256:225-36. [PMID: 10739669 DOI: 10.1006/excr.1999.4778] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Human topoisomerase IIIalpha (huTop IIIalpha) has been demonstrated to belong to type IA subfamily. In this study, we found that huTop IIIalpha expressed constitutively and remained at high levels throughout the cell cycle in HL-60 cells when compared to the cell-cycle-dependent expression of huTop IIIalpha in phytohemagglutinin-activated peripheral blood lymphocytes. During the cell cycle progression, this protein remained accentuated in the nucleolus without significant translocation from the nucleolus to the nucleoplasm. In addition, during the course of granulocytic maturation in DMSO-treated HL-60 cells, huTop IIIalpha levels decreased when cells stopped proliferation and nucleoli diminished in size. However, its level remained unchanged during the course of monocytic maturation of vitamin D(3)-treated HL-60 cells which still retained its proliferative capacity and did not change the size of the nucleolus. The data suggested that huTop IIIalpha is involved in rDNA metabolism, such as rDNA transcription. Its cellular level appeared to be under control during the cell cycle progression of normal lymphocytes, but was found to be deregulated in HL-60 cells which may be associated with the tumor transformed cell phenotypes.
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Affiliation(s)
- C W Lin
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, New York 10595, USA
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6
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Moser MJ, Kamath-Loeb AS, Jacob JE, Bennett SE, Oshima J, Monnat RJ. WRN helicase expression in Werner syndrome cell lines. Nucleic Acids Res 2000; 28:648-54. [PMID: 10606667 PMCID: PMC102521 DOI: 10.1093/nar/28.2.648] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Mutations in the chromosome 8p WRN gene cause Werner syndrome (WRN), a human autosomal recessive disease that mimics premature aging and is associated with genetic instability and an increased risk of cancer. All of the WRN mutations identified in WRN patients are predicted to truncate the WRN protein with loss of a C-terminal nuclear localization signal. However, many of these truncated proteins would retain WRN helicase and/or nuclease functional domains. We have used a combination of immune blot and immune precipitation assays to quantify WRN protein and its associated 3'-->5' helicase activity in genetically characterized WRN patient cell lines. None of the cell lines from patients harboring four different WRN mutations contained detectable WRN protein or immune-precipitable WRN helicase activity. Cell lines from WRN heterozygous individuals contained reduced amounts of both WRN protein and helicase activity. Quantitative immune blot analyses indicate that both lymphoblastoid cell lines and fibroblasts contain approximately 6 x 10(4)WRN molecules/cell. Our results indicate that most WRN mutations result in functionally equivalent null alleles, that WRN heterozygote effects may result from haploinsufficiency and that successful modeling of WRN pathogenesis in the mouse or in other model systems will require the use of WRN mutations that eliminate WRN protein expression.
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Affiliation(s)
- M J Moser
- Department of Pathology, University of Washington, Seattle, WA 98195, USA
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7
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Hirsch-Kauffmann M, Schweiger M. Aging and chromosomal instability. Rev Physiol Biochem Pharmacol 1999; 139:141-74. [PMID: 10453695 DOI: 10.1007/bfb0033651] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Affiliation(s)
- M Hirsch-Kauffmann
- Institut für Medizinische Biologie und Humangenetik, Universität Innsbruck, Austria
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8
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Smith J, Rothstein R. An allele of RFA1 suppresses RAD52-dependent double-strand break repair in Saccharomyces cerevisiae. Genetics 1999; 151:447-58. [PMID: 9927442 PMCID: PMC1460496 DOI: 10.1093/genetics/151.2.447] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
An allele of RFA1, the largest subunit of the single-stranded DNA-binding complex RP-A, was identified as a suppressor of decreased direct-repeat recombination in rad1 rad52 double mutants. In this study, we used two LEU2 direct-repeat assays to investigate the mechanism by which the rfa1-D228Y allele increases recombination. We found that both intrachromatid and sister chromatid recombination are stimulated in rfa1-D228Y strains. In a rad1 rad52 background, however, the majority of the increased recombination is caused by stimulation of deletion events by an intrachromatid recombination mechanism that is likely to be single-strand annealing. Studies in which an HO endonuclease cut was introduced between the two leu2 copies indicate that the rfa1-D228Y mutation partially suppresses the rad52 defect in recovering recombination products. Furthermore, molecular analysis of processing and product formation kinetics reveals that, in a rad52 background, the rfa1-D228Y mutation results in increased levels of recombinant products and the disappearance of large single-stranded intermediates characteristic of rad52 strains. On the basis of these results, we propose that in the absence of wild-type Rad52, the interaction of RP-A with single-stranded DNA inhibits strand annealing, and that this inhibition is overcome by the rfa1-D228Y mutation.
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Affiliation(s)
- J Smith
- Department of Genetics and Development, Columbia University College of Physician and Surgeons, New York, New York 10032-2704, USA
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Yamabe Y, Shimamoto A, Goto M, Yokota J, Sugawara M, Furuichi Y. Sp1-mediated transcription of the Werner helicase gene is modulated by Rb and p53. Mol Cell Biol 1998; 18:6191-200. [PMID: 9774636 PMCID: PMC109206 DOI: 10.1128/mcb.18.11.6191] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The regulation of Werner's syndrome gene (WRN) expression was studied by characterizing the cis-regulatory elements in the promoter region and the trans-activating factors that bind to them. First, we defined the transcription initiation sites and the sequence of the 5' upstream region (2.8 kb) of WRN that contains a number of cis-regulatory elements, including 7 Sp1, 9 retinoblastoma control element (RCE), and 14 AP2 motifs. A region consisting of nucleotides -67 to +160 was identified as the principal promoter of WRN by reporter gene assays in HeLa cells, using a series of WRN promoter-luciferase reporter (WRN-Luc) plasmids that contained the 5'-truncated or mutated WRN upstream regions. In particular, two Sp1 elements proximal to the transcription initiation site are indispensable for WRN promoter activity and bind specifically to Sp1 proteins. The RCE enhances WRN promoter activity. Coexpression of the WRN-Luc plasmids with various dosages of plasmids expressing Rb or p53 in Saos2 cells lacking active Rb and p53 proteins showed that the introduced Rb upregulates WRN promoter activity a maximum of 2. 5-fold, while p53 downregulates it a maximum of 7-fold, both dose dependently. Consistently, the overexpressed Rb and p53 proteins also affected the endogenous WRN mRNA levels in Saos2 cells, resulting in an increase with Rb and a decrease with p53. These findings suggest that WRN expression, like that of other housekeeping genes, is directed mainly by the Sp1 transcriptional control system but is also further modulated by transcription factors, including Rb and p53, that are implicated in the cell cycle, cell senescence, and genomic instability.
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Affiliation(s)
- Y Yamabe
- AGENE Research Institute, Kamakura, Kanagawa 247, Japan
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Fritz E, Elsea SH, Patel PI, Meyn MS. Overexpression of a truncated human topoisomerase III partially corrects multiple aspects of the ataxia-telangiectasia phenotype. Proc Natl Acad Sci U S A 1997; 94:4538-42. [PMID: 9114025 PMCID: PMC20758 DOI: 10.1073/pnas.94.9.4538] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Ataxia-telangiectasia (A-T) is a recessive human disease characterized by radiation sensitivity, genetic instability, immunodeficiency, and high cancer risk. We previously used expression cloning to identify CAT4.5, a human cDNA that partially suppresses multiple aspects of the A-T phenotype upon transfection into cultured cells. Sequencing CAT4.5 revealed a 1.1-kb intronic fragment followed by a related ORF of 2.5 kb that encodes the near full-length ORF for hTOP3, the first mammalian topoisomerase III to be identified. Endogenous expression of hTOP3 was found in all human tissues tested. Both pCAT4.5 and an antisense hTOP3 construct were able to inhibit spontaneous and radiation-induced apoptosis in A-T fibroblasts, whereas overexpression of a full-length hTOP3 cDNA did not. We postulate that topoisomerase III may be deregulated in A-T cells and that CAT4.5 complements the A-T phenotype via a dominant-negative mechanism. Furthermore, functional correction of hyper-recombination in A-T cells by CAT4.5 supports the hypothesis that the hTOP3 topoisomerase is involved in the control of genomic stability, perhaps in concert with the Bloom or Werner syndrome DNA helicases.
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Affiliation(s)
- E Fritz
- Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
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Brooks-Wilson AR, Emond MJ, Monnat RJ. Unexpectedly low loss of heterozygosity in genetically unstable Werner syndrome cell lines. Genes Chromosomes Cancer 1997. [DOI: 10.1002/(sici)1098-2264(199702)18:2<133::aid-gcc8>3.0.co;2-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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12
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Affiliation(s)
- M S Meyn
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
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Weirich HG, Weirich-Schwaiger H, Kofler H, Sidoroff A, Fritsch P, Schachtschabel DO, Schweiger M, Hirsch-Kauffmann M. Werner syndrome: studies in an affected family reveal a cellular phenotype of unaffected siblings. Mech Ageing Dev 1996; 88:1-15. [PMID: 8803918 DOI: 10.1016/0047-6374(96)01709-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Werner syndrome is an inherited disease with symptoms of presenescence. The primary defect site either on the protein or at the DNA level is not known, nor is it possible to identify a heterozygous phenotype. On the basis of cellular peculiarities expressed in the homozygotes-lifespan reduction of cells in culture, length of population doubling time and chromosomal instability-we searched for a 'Werner-like' phenotype in otherwise phenotypically unaffected siblings. We established primary fibroblasts from eight members of a Tyrolean family, two of whom had been diagnosed as typical Werner syndrome, as well as from unrelated healthy young and old volunteers. Determination of the lifespan of each strain and studies on population doubling time and chromosomal instability revealed similar cellular characteristics in all family members, albeit to a lesser extent with the siblings than with the homozygotes when compared to age-matched controls. These features, also apparent in cultivated fibroblasts from old but healthy controls, appear to be indicative of Werner syndrome when expressed in young or middle aged persons. The possible identification of otherwise clinically healthy gene carriers of Werner syndrome is of utmost importance for genetic counselling and medical surveillance for this disorder.
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Affiliation(s)
- H G Weirich
- Institut für Medizinische Biologie und Humangenetik, Universität Innsbruck, Austria
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Elli R, Chessa L, Antonelli A, Petrinelli P, Ambra R, Marcucci L. Effects of topoisomerase II inhibition in lymphoblasts from patients with progeroid and "chromosome instability" syndromes. CANCER GENETICS AND CYTOGENETICS 1996; 87:112-6. [PMID: 8625255 DOI: 10.1016/0165-4608(95)00294-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
DNA topoisomerase II is involved in DNA topologic changes through the formation of a cleavable complex. This is stabilized by the antitumor drug VP16, which results in DNA breakage, aberrant recombination, and cell death. In this work, we compare the chromosomal damage induced by VP16 with that induced by bleomycin (BLM) in lymphoblasts from patients affected by the chromosome breakage syndromes ataxia telangiectasia (AT), xeroderma pigmentosum (XP), and Bloom syndrome (BS), and by the progeroid syndromes Werner (WS) and Cockayne (CS). Patients affected by AT, XP, BS, and WS have a greatly enhanced risk of developing cancer. The results show that AF and WS cells are hypersensitive to VP16, as revealed in the higher proportion of metaphases showing exchange figures and more than two breaks. All lines except AT and one CS line showed normal sensitivity to BLM. Our data on the sensitivity to VP16 of all these mutant cells underline the fact that VP16 damage is amplified only in cells that have abnormal illegitimate recombination (i.e., AT and WS).
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Affiliation(s)
- R Elli
- Dipartimento di Biopatologia Umana, Università La Sapienza, Rome, Italy
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Rothstein R, Gangloff S. Hyper-recombination and Bloom's syndrome: microbes again provide clues about cancer. Genome Res 1995; 5:421-6. [PMID: 8808463 DOI: 10.1101/gr.5.5.421] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- R Rothstein
- Department of Genetics and Development, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA. rothstein/cuccfa.ccc.col
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Abstract
Intrachromosomal recombination between direct repeats can occur either as gene conversion events, which maintain exactly the number of repeat units, or as deletions, which reduce the number of repeat units. Gene conversions are classical recombination events that utilize the standard chromosome recombination machinery. Spontaneous deletions between direct repeats are generally recA-independent in E. coli and RAD52-independent in S. cerevisiae. This independence from the major recombination genes does not mean that deletions form through a nonrecombinational process. Deletions have been suggested to result from sister chromatid exchange at the replication fork in a recA-independent process. The same type of exchange is proposed to be RAD52-independent in Saccharomyces cerevisiae. RAD52-dependent events encompass all events that involve the initial steps of a recombination reaction, which include strand invasion to form a heteroduplex intermediate.
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Affiliation(s)
- H L Klein
- Department of Biochemistry, New York University Medical Center, NY 10016
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