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Yoon JH, Sellamuthu K, Prakash L, Prakash S. WRN exonuclease imparts high fidelity on translesion synthesis by Y family DNA polymerases. Genes Dev 2024; 38:213-232. [PMID: 38503516 PMCID: PMC11065173 DOI: 10.1101/gad.351410.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Accepted: 02/26/2024] [Indexed: 03/21/2024]
Abstract
Purified translesion synthesis (TLS) DNA polymerases (Pols) replicate through DNA lesions with a low fidelity; however, TLS operates in a predominantly error-free manner in normal human cells. To explain this incongruity, here we determine whether Y family Pols, which play an eminent role in replication through a diversity of DNA lesions, are incorporated into a multiprotein ensemble and whether the intrinsically high error rate of the TLS Pol is ameliorated by the components in the ensemble. To this end, we provide evidence for an indispensable role of Werner syndrome protein (WRN) and WRN-interacting protein 1 (WRNIP1) in Rev1-dependent TLS by Y family Polη, Polι, or Polκ and show that WRN, WRNIP1, and Rev1 assemble together with Y family Pols in response to DNA damage. Importantly, we identify a crucial role of WRN's 3' → 5' exonuclease activity in imparting high fidelity on TLS by Y family Pols in human cells, as the Y family Pols that accomplish TLS in an error-free manner manifest high mutagenicity in the absence of WRN's exonuclease function. Thus, by enforcing high fidelity on TLS Pols, TLS mechanisms have been adapted to safeguard against genome instability and tumorigenesis.
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Affiliation(s)
- Jung-Hoon Yoon
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch at Galveston, Galveston, Texas 77555, USA
| | - Karthi Sellamuthu
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch at Galveston, Galveston, Texas 77555, USA
| | - Louise Prakash
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch at Galveston, Galveston, Texas 77555, USA
| | - Satya Prakash
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch at Galveston, Galveston, Texas 77555, USA
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Yao S, Yuan Y, Zhang J, Yu Y, Luo GH. Gene polymorphisms associated with sudden decreases in heart rate during extensive peritoneal lavage with distilled water after gastrectomy. World J Gastrointest Surg 2023; 15:2154-2170. [PMID: 37969699 PMCID: PMC10642470 DOI: 10.4240/wjgs.v15.i10.2154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 08/04/2023] [Accepted: 08/17/2023] [Indexed: 10/27/2023] Open
Abstract
BACKGROUND Our previous study found that the telomerase-associated protein 1 (TEP1, rs938886 and rs1713449) and homo sapiens RecQ like helicase 5 (RECQL5, rs820196) single nucleotide polymorphisms (SNPs) were associated with changes in heart rate (HR) ≥ 30% during peritoneal lavage with distilled water after gastrectomy. This study established a single tube method for detecting these three SNPs using two-dimensional (2D) polymerase chain reaction (PCR), and investigated whether SNP-SNP and SNP-environment interactions increase the risk of high HR variability (HRV). AIM To investigate whether genotypes, genetic patterns, SNP-SNP and SNP-environment interactions were associated with HRV. METHODS 2D PCR was used to establish a single-tube method to detect TEP1 rs938886 and rs1713449 and RECQL5 rs820196, and the results were compared with those of sanger sequencing. After adjusting for confounders such as age, sex, smoking, hypertension, and thyroid dysfunction, a nonconditional logistic regression model was used to assess the associations between the genotypes and the genetic patterns (codominant, dominant, overdominant, recessive, and additive) of the three SNPs and a risk ≥ 15% or ≥ 30% of a sudden drop in HR during postoperative peritoneal lavage in patients with gastric cancer. Gene-gene and gene-environment interactions were analyzed using generalized multifactor dimensionality reduction. RESULTS The coincidence rate between the 2D PCR and sequencing was 100%. When the HRV cutoff value was 15%, the patients with the RECQL5 (rs820196) TC genotype had a higher risk of high HRV than those who had the TT genotype (odds ratio = 1.97; 95%CI: 1.05-3.70; P = 0.045). Under the codominant and overdominant models, the TC genotype of RECQL5 (rs820196) was associated with a higher risk of HR decrease relative to the TT and TT + CC genotypes (P = 0.031 and 0.016, respectively). When the HRV cutoff value was 30%, patients carrying the GC-TC genotypes of rs938886 and rs820196 showed a higher HRV risk when compared with the GG-TT genotype carriers (P = 0.01). In the three-factor model of rs938886, rs820196, and rs1713449, patients carrying the GC-TC-CT genotype had a higher risk of HRV compared with the wild-type GG-TT-CC carriers (P = 0.01). For rs820196, nonsmokers with the TC genotype had a higher HRV risk compared with nonsmokers carrying the TT genotype (P = 0.04). When the HRV cutoff value was 15%, patients carrying the TT-TT and the TC-CT genotypes of rs820196 and rs1713449 showed a higher HRV risk when compared with TT-CC genotype carriers (P = 0.04 and 0.01, respectively). Patients carrying the GC-CT-TC genotypes of rs938886, rs1713449, and rs820196 showed a higher HRV risk compared with GG-CC-TT genotype carriers (P = 0.02). When the HRV cutoff value was 15%, the best-fitting models for the interactions between the SNPs and the environment were the rs820196-smoking (P = 0.022) and rs820196-hypertension (P = 0.043) models. Consistent with the results of the previous grouping, for rs820196, the TC genotype nonsmokers had a higher HRV risk compared with nonsmokers carrying the TT genotype (P = 0.01). CONCLUSION The polymorphism of the RECQL5 and TEP1 genes were associated with HRV during peritoneal lavage with distilled water after gastrectomy.
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Affiliation(s)
- Shuang Yao
- Clinical Medical Research Center, The Third Affiliated Hospital of Soochow University, Changzhou 213000, Jiangsu Province, China
| | - Yan Yuan
- Department of Anesthesiology, The Third Affiliated Hospital of Soochow University, Changzhou 213000, Jiangsu Province, China
| | - Jun Zhang
- Clinical Medical Research Center, The Third Affiliated Hospital of Soochow University, Changzhou 213000, Jiangsu Province, China
| | - Yang Yu
- Clinical Medical Research Center, The Third Affiliated Hospital of Soochow University, Changzhou 213000, Jiangsu Province, China
| | - Guang-Hua Luo
- Clinical Medical Research Center, The Third Affiliated Hospital of Soochow University, Changzhou 213000, Jiangsu Province, China
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Poot M, Hochstenbach R. Prevalence and Phenotypic Impact of Robertsonian Translocations. Mol Syndromol 2021; 12:1-11. [PMID: 33776621 PMCID: PMC7983559 DOI: 10.1159/000512676] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 10/26/2020] [Indexed: 12/11/2022] Open
Abstract
Robertsonian translocations (RTs) result from fusion of 2 acrocentric chromosomes (e.g., 13, 14, 15, 21, 22) and consequential losses of segments of the p arms containing 47S rDNA clusters and transcription factor binding sites. Depending on the position of the breakpoints, the size of these losses vary considerably between types of RTs. The prevalence of RTs in the general population is estimated to be around 1 per 800 individuals, making RTs the most common chromosomal rearrangement in healthy individuals. Based on their prevalence, RTs are classified as "common," rob(13;14) and rob(14;21), or "rare" (the 8 remaining nonhomologous combinations). Carriers of RTs are at an increased risk for offspring with chromosomal imbalances or with uniparental disomy. RTs are generally regarded as phenotypically neutral, although, due to RTs formation, 2 of the 10 ribosomal rDNA gene clusters, several long noncoding RNAs, and in the case of RTs involving chromosome 21, several mRNA encoding genes are lost. Nevertheless, recent evidence indicates that RTs may have a significant phenotypic impact. In particular, rob(13;14) carriers have a significantly elevated risk for breast cancer. While RTs are easily spotted by routine karyotyping, they may go unnoticed if only array-CGH and NextGen sequencing methods are applied. This review first discusses possible molecular mechanisms underlying the particularly high rates of RT formation and their incidence in the general population, and second, likely causes for the elevated cancer risk of some RTs will be examined.
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Affiliation(s)
- Martin Poot
- Department of Human Genetics, University of Würzburg, Würzburg, Germany
| | - Ron Hochstenbach
- Department of Clinical Genetics, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
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D'Amico AM, Vasquez KM. The multifaceted roles of DNA repair and replication proteins in aging and obesity. DNA Repair (Amst) 2021; 99:103049. [PMID: 33529944 DOI: 10.1016/j.dnarep.2021.103049] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 01/12/2021] [Accepted: 01/14/2021] [Indexed: 12/14/2022]
Abstract
Efficient mechanisms for genomic maintenance (i.e., DNA repair and DNA replication) are crucial for cell survival. Aging and obesity can lead to the dysregulation of genomic maintenance proteins/pathways and are significant risk factors for the development of cancer, metabolic disorders, and other genetic diseases. Mutations in genes that code for proteins involved in DNA repair and DNA replication can also exacerbate aging- and obesity-related disorders and lead to the development of progeroid diseases. In this review, we will discuss the roles of various DNA repair and replication proteins in aging and obesity as well as investigate the possible mechanisms by which aging and obesity can lead to the dysregulation of these proteins and pathways.
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Affiliation(s)
- Alexandra M D'Amico
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Pediatric Research Institute, 1400 Barbara Jordan Boulevard, Austin, TX, 78723, USA
| | - Karen M Vasquez
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Pediatric Research Institute, 1400 Barbara Jordan Boulevard, Austin, TX, 78723, USA.
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Brosh RM, Matson SW. History of DNA Helicases. Genes (Basel) 2020; 11:genes11030255. [PMID: 32120966 PMCID: PMC7140857 DOI: 10.3390/genes11030255] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 02/18/2020] [Accepted: 02/20/2020] [Indexed: 12/13/2022] Open
Abstract
Since the discovery of the DNA double helix, there has been a fascination in understanding the molecular mechanisms and cellular processes that account for: (i) the transmission of genetic information from one generation to the next and (ii) the remarkable stability of the genome. Nucleic acid biologists have endeavored to unravel the mysteries of DNA not only to understand the processes of DNA replication, repair, recombination, and transcription but to also characterize the underlying basis of genetic diseases characterized by chromosomal instability. Perhaps unexpectedly at first, DNA helicases have arisen as a key class of enzymes to study in this latter capacity. From the first discovery of ATP-dependent DNA unwinding enzymes in the mid 1970's to the burgeoning of helicase-dependent pathways found to be prevalent in all kingdoms of life, the story of scientific discovery in helicase research is rich and informative. Over four decades after their discovery, we take this opportunity to provide a history of DNA helicases. No doubt, many chapters are left to be written. Nonetheless, at this juncture we are privileged to share our perspective on the DNA helicase field - where it has been, its current state, and where it is headed.
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Affiliation(s)
- Robert M. Brosh
- Section on DNA Helicases, Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
- Correspondence: (R.M.B.J.); (S.W.M.); Tel.: +1-410-558-8578 (R.M.B.J.); +1-919-962-0005 (S.W.M.)
| | - Steven W. Matson
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Correspondence: (R.M.B.J.); (S.W.M.); Tel.: +1-410-558-8578 (R.M.B.J.); +1-919-962-0005 (S.W.M.)
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Maierhofer A, Flunkert J, Oshima J, Martin GM, Poot M, Nanda I, Dittrich M, Müller T, Haaf T. Epigenetic signatures of Werner syndrome occur early in life and are distinct from normal epigenetic aging processes. Aging Cell 2019; 18:e12995. [PMID: 31259468 PMCID: PMC6718529 DOI: 10.1111/acel.12995] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 05/24/2019] [Accepted: 06/05/2019] [Indexed: 12/11/2022] Open
Abstract
Werner Syndrome (WS) is an adult-onset segmental progeroid syndrome. Bisulfite pyrosequencing of repetitive DNA families revealed comparable blood DNA methylation levels between classical (18 WRN-mutant) or atypical WS (3 LMNA-mutant and 3 POLD1-mutant) patients and age- and sex-matched controls. WS was not associated with either age-related accelerated global losses of ALU, LINE1, and α-satellite DNA methylations or gains of rDNA methylation. Single CpG methylation was analyzed with Infinium MethylationEPIC arrays. In a correspondence analysis, atypical WS samples clustered together with the controls and were clearly separated from classical WS, consistent with distinct epigenetic pathologies. In classical WS, we identified 659 differentially methylated regions (DMRs) comprising 3,656 CpG sites and 613 RefSeq genes. The top DMR was located in the HOXA4 promoter. Additional DMR genes included LMNA, POLD1, and 132 genes which have been reported to be differentially expressed in WRN-mutant/depleted cells. DMRs were enriched in genes with molecular functions linked to transcription factor activity and sequence-specific DNA binding to promoters transcribed by RNA polymerase II. We propose that transcriptional misregulation of downstream genes by the absence of WRN protein contributes to the variable premature aging phenotypes of WS. There were no CpG sites showing significant differences in DNA methylation changes with age between WS patients and controls. Genes with both WS- and age-related methylation changes exhibited a constant offset of methylation between WRN-mutant patients and controls across the entire analyzed age range. WS-specific epigenetic signatures occur early in life and do not simply reflect an acceleration of normal epigenetic aging processes.
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Affiliation(s)
- Anna Maierhofer
- Institute of Human Genetics Julius Maximilians University Würzburg Germany
| | - Julia Flunkert
- Institute of Human Genetics Julius Maximilians University Würzburg Germany
| | - Junko Oshima
- Department of Pathology University of Washington Seattle Washington USA
- Department of Clinical Cell Biology and Medicine, Graduate School of Medicine Chiba University Chiba Japan
| | - George M. Martin
- Department of Pathology University of Washington Seattle Washington USA
| | - Martin Poot
- Institute of Human Genetics Julius Maximilians University Würzburg Germany
| | - Indrajit Nanda
- Institute of Human Genetics Julius Maximilians University Würzburg Germany
| | - Marcus Dittrich
- Institute of Human Genetics Julius Maximilians University Würzburg Germany
- Department of Bioinformatics Julius Maximilians University Würzburg Germany
| | - Tobias Müller
- Department of Bioinformatics Julius Maximilians University Würzburg Germany
| | - Thomas Haaf
- Institute of Human Genetics Julius Maximilians University Würzburg Germany
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7
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Mukherjee S, Sinha D, Bhattacharya S, Srinivasan K, Abdisalaam S, Asaithamby A. Werner Syndrome Protein and DNA Replication. Int J Mol Sci 2018; 19:ijms19113442. [PMID: 30400178 PMCID: PMC6274846 DOI: 10.3390/ijms19113442] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 10/22/2018] [Accepted: 10/25/2018] [Indexed: 01/07/2023] Open
Abstract
Werner Syndrome (WS) is an autosomal recessive disorder characterized by the premature development of aging features. Individuals with WS also have a greater predisposition to rare cancers that are mesenchymal in origin. Werner Syndrome Protein (WRN), the protein mutated in WS, is unique among RecQ family proteins in that it possesses exonuclease and 3' to 5' helicase activities. WRN forms dynamic sub-complexes with different factors involved in DNA replication, recombination and repair. WRN binding partners either facilitate its DNA metabolic activities or utilize it to execute their specific functions. Furthermore, WRN is phosphorylated by multiple kinases, including Ataxia telangiectasia mutated, Ataxia telangiectasia and Rad3 related, c-Abl, Cyclin-dependent kinase 1 and DNA-dependent protein kinase catalytic subunit, in response to genotoxic stress. These post-translational modifications are critical for WRN to function properly in DNA repair, replication and recombination. Accumulating evidence suggests that WRN plays a crucial role in one or more genome stability maintenance pathways, through which it suppresses cancer and premature aging. Among its many functions, WRN helps in replication fork progression, facilitates the repair of stalled replication forks and DNA double-strand breaks associated with replication forks, and blocks nuclease-mediated excessive processing of replication forks. In this review, we specifically focus on human WRN's contribution to replication fork processing for maintaining genome stability and suppressing premature aging. Understanding WRN's molecular role in timely and faithful DNA replication will further advance our understanding of the pathophysiology of WS.
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Affiliation(s)
- Shibani Mukherjee
- Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Debapriya Sinha
- Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Souparno Bhattacharya
- Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Kalayarasan Srinivasan
- Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Salim Abdisalaam
- Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Aroumougame Asaithamby
- Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Abstract
The highly complex structural genome variations chromothripsis, chromoanasynthesis, and chromoplexy are subsumed under the term chromoanagenesis, which means chromosome rebirth. Precipitated by numerous DNA double-strand breaks, they differ in number of and distances between breakpoints, associated copy number variations, order and orientation of segments, and flanking sequences at joining points. Results from patients with the autosomal dominant cancer susceptibility disorder Li-Fraumeni syndrome implicated somatic TP53 mutations in chromothripsis. TP53 participates in the G2/M phase checkpoint, halting cell cycling after premature chromosome compaction during the second half of the S phase, thus preventing chromosome shattering. By experimental TP53 ablation and micronucleus induction, one or a few isolated chromosomes underwent desynchronized replication and chromothripsis. Secondly, chromothripsis occurred after experimental induction of telomere crisis after which dicentric chromosomes sustained TREX1-mediated resolution of chromosome bridges and kataegis. Third, DNA polymerase Polθ-dependent chromothripsis has been documented. Finally, a family with chromothripsis after L1 element-dependent retrotransposition and Alu/Alu homologous recombination has been reported. Human chromosomal instability syndromes share defects in responses to DNA double-strand breaks, characteristic cell cycle perturbations, elevated rates of micronucleus formation, premature chromosome compaction, and apoptosis. They are also associated with elevated susceptibility to malignant disease, such as medulloblastomas and gliomas in ataxia-telangiectasia, leukemia and lymphoma in Bloom syndrome, and osteosarcoma and soft tissue sarcoma in Werner syndrome. The latter syndrome is characterized by a premature aging-like progressive decline of mesenchymal tissues. In all thus far studied cases, constitutional chromothripsis occurred in the male germline and male patients with defects in the double-strand break response genes ATM, MRE11, BLM, LIG4, WRN, and Ku70 show impaired fertility. Conceivably, chromothripsis may, in a stochastic rather than deterministic way, be implicated in germline structural variation, malignant disease, premature aging, genome mosaicism in somatic tissues, and male infertility.
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Affiliation(s)
- Martin Poot
- Department of Human Genetics, University of Würzburg, Würzburg, Germany.
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Wu PF, Jin JY, Li JJ, He JQ, Fan LL, Jin M, Huang H, Xia K, Tang JY, Xiang R. A novel splice-site mutation of WRN (c.IVS28+2T>C) identified in a consanguineous family with Werner Syndrome. Mol Med Rep 2017; 15:3735-3738. [DOI: 10.3892/mmr.2017.6465] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 01/16/2017] [Indexed: 11/06/2022] Open
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10
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Poot M. Recombine and Associate to Prevent Genomic Instability and Premature Aging. Mol Syndromol 2017; 8:1-3. [PMID: 28232777 DOI: 10.1159/000452784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/12/2016] [Indexed: 11/19/2022] Open
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Tokita M, Kennedy SR, Risques RA, Chun SG, Pritchard C, Oshima J, Liu Y, Bryant-Greenwood PK, Welcsh P, Monnat RJ. Werner syndrome through the lens of tissue and tumour genomics. Sci Rep 2016; 6:32038. [PMID: 27559010 PMCID: PMC4997333 DOI: 10.1038/srep32038] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 08/01/2016] [Indexed: 12/11/2022] Open
Abstract
Werner syndrome (WS) is the canonical adult human progeroid ('premature aging') syndrome. Patients with this autosomal recessive Mendelian disorder display constitutional genomic instability and an elevated risk of important age-associated diseases including cancer. Remarkably few analyses of WS patient tissue and tumors have been performed to provide insight into WS disease pathogenesis or the high risk of neoplasia. We used autopsy tissue from four mutation-typed WS patients to characterize pathologic and genomic features of WS, and to determine genomic features of three neoplasms arising in two of these patients. The results of these analyses provide new information on WS pathology and genomics; provide a first genomic characterization of neoplasms arising in WS; and provide new histopathologic and genomic data to test several popular models of WS disease pathogenesis.
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Affiliation(s)
- Mari Tokita
- Department of Medicine Division of Medical Genetics, University of Washington, Seattle, WA USA
| | - Scott R. Kennedy
- Department of Pathology, University of Washington, Seattle, WA USA
| | - Rosa Ana Risques
- Department of Pathology, University of Washington, Seattle, WA USA
| | - Stephen G. Chun
- Department of Radiation Oncology, MD Anderson Cancer Center, Houston, TX USA
| | - Colin Pritchard
- Department of Laboratory Medicine, University of Washington, Seattle, WA USA
| | - Junko Oshima
- Department of Pathology, University of Washington, Seattle, WA USA
- Department of Medicine, Chiba University, Chiba, Japan
| | - Yan Liu
- Department of Pathology, University of Washington, Seattle, WA USA
| | - Peter K. Bryant-Greenwood
- Department of Pathology, John Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI USA
| | - Piri Welcsh
- Department of Pathology, University of Washington, Seattle, WA USA
| | - Raymond J. Monnat
- Department of Pathology, University of Washington, Seattle, WA USA
- Department of Genome Sciences, University of Washington, Seattle, WA USA
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Poot M. Chromothripsis after Stumbling through DNA Replication. Mol Syndromol 2016; 6:207-9. [PMID: 26997940 DOI: 10.1159/000441081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/02/2015] [Indexed: 11/19/2022] Open
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Chang TC, Tang W, Koh WJH, Rettie AJE, Emond MJ, Monnat RJ, Folch A. Microwell arrays reveal cellular heterogeneity during the clonal expansion of transformed human cells. TECHNOLOGY 2015; 3:163-171. [PMID: 27158641 PMCID: PMC4854201 DOI: 10.1142/s2339547815200046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We developed micromolded microwell arrays to study the proliferation and senescence of single cells. Microwell arrays were designed to be compatible with conventional cell culture protocols to simplify cell loading, cell culture, and imaging. We demonstrated the utility of these arrays by measuring the proliferation and senescence of isogenic cells which expressed or had been depleted of the human Werner syndrome protein. Our results allowed us to reveal cell-to-cell heterogeneity in proliferation in WRN+ and WRN-depleted fibroblasts during clonal growth.
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Affiliation(s)
- Tim C Chang
- Departments of Bioengineering, University of Washington, Seattle, WA 98195, USA
| | - Weiliang Tang
- Departments of Pathology, University of Washington, Seattle, WA 98195, USA
| | - William Jen Hoe Koh
- Departments of Biostatistics, University of Washington, Seattle, WA 98195, USA
| | | | - Mary J Emond
- Departments of Biostatistics, University of Washington, Seattle, WA 98195, USA
| | - Raymond J Monnat
- Departments of Pathology, University of Washington, Seattle, WA 98195, USA; Departments of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Albert Folch
- Departments of Bioengineering, University of Washington, Seattle, WA 98195, USA
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Poot M. Gene Fusion due to Chromosome Misconnection May Seriously Affect Your Health. Mol Syndromol 2015; 6:55-7. [PMID: 26279648 DOI: 10.1159/000381081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/09/2015] [Indexed: 11/19/2022] Open
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Poot M, Haaf T. Mechanisms of Origin, Phenotypic Effects and Diagnostic Implications of Complex Chromosome Rearrangements. Mol Syndromol 2015; 6:110-34. [PMID: 26732513 DOI: 10.1159/000438812] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/23/2015] [Indexed: 01/08/2023] Open
Abstract
Complex chromosome rearrangements (CCRs) are currently defined as structural genome variations that involve more than 2 chromosome breaks and result in exchanges of chromosomal segments. They are thought to be extremely rare, but their detection rate is rising because of improvements in molecular cytogenetic technology. Their population frequency is also underestimated, since many CCRs may not elicit a phenotypic effect. CCRs may be the result of fork stalling and template switching, microhomology-mediated break-induced repair, breakage-fusion-bridge cycles, or chromothripsis. Patients with chromosomal instability syndromes show elevated rates of CCRs due to impaired DNA double-strand break responses during meiosis. Therefore, the putative functions of the proteins encoded by ATM, BLM, WRN, ATR, MRE11, NBS1, and RAD51 in preventing CCRs are discussed. CCRs may exert a pathogenic effect by either (1) gene dosage-dependent mechanisms, e.g. haploinsufficiency, (2) mechanisms based on disruption of the genomic architecture, such that genes, parts of genes or regulatory elements are truncated, fused or relocated and thus their interactions disturbed - these mechanisms will predominantly affect gene expression - or (3) mixed mutation mechanisms in which a CCR on one chromosome is combined with a different type of mutation on the other chromosome. Such inferred mechanisms of pathogenicity need corroboration by mRNA sequencing. Also, future studies with in vitro models, such as inducible pluripotent stem cells from patients with CCRs, and transgenic model organisms should substantiate current inferences regarding putative pathogenic effects of CCRs. The ramifications of the growing body of information on CCRs for clinical and experimental genetics and future treatment modalities are briefly illustrated with 2 cases, one of which suggests KDM4C (JMJD2C) as a novel candidate gene for mental retardation.
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Affiliation(s)
- Martin Poot
- Department of Human Genetics, University of Würzburg, Würzburg, Germany
| | - Thomas Haaf
- Department of Human Genetics, University of Würzburg, Würzburg, Germany
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Monnat RJ. "...Rewritten in the skin": clues to skin biology and aging from inherited disease. J Invest Dermatol 2015; 135:1484-1490. [PMID: 25810110 PMCID: PMC4526269 DOI: 10.1038/jid.2015.88] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 02/07/2015] [Accepted: 02/24/2015] [Indexed: 12/11/2022]
Abstract
The growing diversity of heritable skin diseases, a practical challenge to clinicians and dermato-nosologists alike, has nonetheless served as a rich source of insight into skin biology and disease mechanisms. I summarize below some key insights from the recent gene-driven phase of research on Werner syndrome, a heritable adult progeroid syndrome with prominent dermatologic features, constitutional genomic instability, and an elevated risk of cancer. I also indicate how new insights into skin biology, disease, and aging may come from unexpected sources.
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Affiliation(s)
- Raymond J Monnat
- Department of Pathology and Genome Sciences, University of Washington, Seattle, Washington, USA.
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17
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Poot M. What a Difference an ERCC1 or ERCC4 (XPF) Mutation Makes! Mol Syndromol 2014; 5:199-200. [PMID: 25337066 DOI: 10.1159/000358893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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18
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Oshitari T, Kitahashi M, Mizuno S, Baba T, Kubota-Taniai M, Takemoto M, Yokote K, Yamamoto S, Roy S. Werner syndrome with refractory cystoid macular edema and immunohistochemical analysis of WRN proteins in human retinas. BMC Ophthalmol 2014; 14:31. [PMID: 24620826 PMCID: PMC3995689 DOI: 10.1186/1471-2415-14-31] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 03/07/2014] [Indexed: 11/19/2022] Open
Abstract
Background To present our findings in a case of Werner syndrome with refractory cystoid macular edema (CME) and to determine the expression and the distribution of WRN proteins in human retinas. Case presentation A 35-year-old man with Werner syndrome who developed CME after YAG laser treatment was studied. Optical coherence tomographic (OCT) scans were used to examine the CME in the right eye. The patient received topical eye drops (0.1% bromfenac sodium hydrate twice daily and 1% dorzolamide hydrochloride thrice daily), sub-Tenon triamcinolone injection thrice, intravitreal bevacizumab injection twice, and pars plana vitrectomy of the right eye. Genetic analyses were performed to diagnose the disease. To examine the expression and distribution of WRN proteins in the retinas, immunohistochemistry for WRN proteins was performed in human retinas. The CME in the right eye was not improved by any of the treatments. During the follow-up period, CME developed in the left eye. Genetic analyses detected compound heterozygosity, Mut4 and Mut11, in the WRN gene and the individual was diagnosed with Werner syndrome. Immunohistochemical analysis of WRN proteins expression in human retinas showed that WRN proteins were expressed in the parts of the Müller cells in the inner nuclear layer and outer nuclear layer. Conclusion Patients with Werner syndrome can develop severe CME after laser treatment. A pathological link may exist between mutations in the WRN gene and the development of CME in patients with Werner syndrome.
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Affiliation(s)
- Toshiyuki Oshitari
- Department of Ophthalmology and Visual Science, Chiba University Graduate School of Medicine, Inohana 1-8-1, Chuo-ku, Chiba 260-8670, Chiba, Japan.
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Popuri V, Tadokoro T, Croteau DL, Bohr VA. Human RECQL5: guarding the crossroads of DNA replication and transcription and providing backup capability. Crit Rev Biochem Mol Biol 2013; 48:289-99. [PMID: 23627586 DOI: 10.3109/10409238.2013.792770] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
DNA helicases are ubiquitous enzymes that catalyze unwinding of duplex DNA and function in all metabolic processes in which access to single-stranded DNA is required, including DNA replication, repair, recombination and RNA transcription. RecQ helicases are a conserved family of DNA helicases that display highly specialized and vital roles in the maintenance of genome stability. Mutations in three of the five human RecQ helicases, BLM, WRN and RECQL4 are associated with the genetic disorders Bloom syndrome, Werner syndrome and Rothmund-Thomson syndrome that are characterized by chromosomal instability, premature aging and predisposition to cancer. The biological role of human RECQL5 is only partially understood and RECQL5 has not yet been associated with any human disease. Illegitimate recombination and replication stress are hallmarks of human cancers and common instigators for genomic instability and cell death. Recql5 knockout mice are cancer prone and show increased chromosomal instability. Recql5-deficient mouse embryonic fibroblasts are sensitive to camptothecin and display elevated levels of sister chromatid exchanges. Unlike other human RecQ helicases, RECQL5 is recruited to single-stranded DNA breaks and is also proposed to play an essential role in RNA transcription. Here, we review the established roles of RECQL5 at the cross roads of DNA replication, recombination and transcription, and propose that human RECQL5 provides important backup functions in the absence of other DNA helicases.
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Affiliation(s)
- Venkateswarlu Popuri
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, Baltimore, MD 21224, USA
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20
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Unwinding and rewinding: double faces of helicase? J Nucleic Acids 2012; 2012:140601. [PMID: 22888405 PMCID: PMC3409536 DOI: 10.1155/2012/140601] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 05/28/2012] [Indexed: 12/29/2022] Open
Abstract
Helicases are enzymes that use ATP-driven motor force to unwind double-stranded DNA or RNA. Recently, increasing evidence demonstrates that some helicases also possess rewinding activity—in other words, they can anneal two complementary single-stranded nucleic acids. All five members of the human RecQ helicase family, helicase PIF1, mitochondrial helicase TWINKLE, and helicase/nuclease Dna2 have been shown to possess strand-annealing activity. Moreover, two recently identified helicases—HARP and AH2 have only ATP-dependent rewinding activity. These findings not only enhance our understanding of helicase enzymes but also establish the presence of a new type of protein: annealing helicases. This paper discusses what is known about these helicases, focusing on their biochemical activity to zip and unzip double-stranded DNA and/or RNA, their possible regulation mechanisms, and biological functions.
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21
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Patro BS, Frøhlich R, Bohr VA, Stevnsner T. WRN helicase regulates the ATR-CHK1-induced S-phase checkpoint pathway in response to topoisomerase-I-DNA covalent complexes. J Cell Sci 2011; 124:3967-79. [PMID: 22159421 DOI: 10.1242/jcs.081372] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Checkpoints are cellular surveillance and signaling pathways that coordinate the response to DNA damage and replicative stress. Consequently, failure of cellular checkpoints increases susceptibility to DNA damage and can lead to profound genome instability. This study examines the role of a human RECQ helicase, WRN, in checkpoint activation in response to DNA damage. Mutations in WRN lead to genomic instability and the premature aging condition Werner syndrome. Here, the role of WRN in a DNA-damage-induced checkpoint was analyzed in U-2 OS (WRN wild type) and isogenic cells stably expressing WRN-targeted shRNA (WRN knockdown). The results of our studies suggest that WRN has a crucial role in inducing an S-phase checkpoint in cells exposed to the topoisomerase I inhibitor campthothecin (CPT), but not in cells exposed to hydroxyurea. Intriguingly, WRN decreases the rate of replication fork elongation, increases the accumulation of ssDNA and stimulates phosphorylation of CHK1, which releases CHK1 from chromatin in CPT-treated cells. Importantly, knockdown of WRN expression abolished or delayed all these processes in response to CPT. Together, our results strongly suggest an essential regulatory role for WRN in controlling the ATR-CHK1-mediated S-phase checkpoint in CPT-treated cells.
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Affiliation(s)
- Birija Sankar Patro
- Department of Molecular Biology, University of Aarhus, C. F. Mollers Alle 3, DK-8000 Aarhus C, Denmark
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22
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Arai A, Chano T, Futami K, Furuichi Y, Ikebuchi K, Inui T, Tameno H, Ochi Y, Shimada T, Hisa Y, Okabe H. RECQL1 and WRN proteins are potential therapeutic targets in head and neck squamous cell carcinoma. Cancer Res 2011; 71:4598-607. [PMID: 21571861 DOI: 10.1158/0008-5472.can-11-0320] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RECQL1 and WRN proteins are RecQ DNA helicases that participate in suppression of DNA hyper-recombination and repair. In this study, we report evidence supporting their candidacy as cancer therapeutic targets. In hypopharyngeal carcinomas, which have the worst prognosis among head and neck squamous cell carcinomas (HNSCC) that are rapidly rising in incidence, we found that RECQL1 and WRN proteins are highly expressed and that siRNA-mediated silencing of either gene suppressed carcinoma cell growth in vitro. Similarly, siRNA administration in a murine xenograft model of hypopharyngeal carcinoma markedly inhibited tumor growth. Moreover, combining either siRNA with cis-platinum (II) diammine dichloride significantly augmented the in vivo anticancer effects of this drug that is used commonly in HNSCC treatment. Notably, we observed no recurrence of some tumors following siRNA treatment in this model. Our findings offer a preclinical proof of concept for RECQL1 and WRN proteins as novel therapeutic targets to treat aggressive HNSCC and perhaps other cancers.
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Affiliation(s)
- Akihito Arai
- Department of Clinical Laboratory Medicine, Shiga University of Medical Science, Shiga, Japan
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23
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Bacolla A, Wang G, Jain A, Chuzhanova NA, Cer RZ, Collins JR, Cooper DN, Bohr VA, Vasquez KM. Non-B DNA-forming sequences and WRN deficiency independently increase the frequency of base substitution in human cells. J Biol Chem 2011; 286:10017-26. [PMID: 21285356 PMCID: PMC3060453 DOI: 10.1074/jbc.m110.176636] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Revised: 01/31/2011] [Indexed: 01/01/2023] Open
Abstract
Although alternative DNA secondary structures (non-B DNA) can induce genomic rearrangements, their associated mutational spectra remain largely unknown. The helicase activity of WRN, which is absent in the human progeroid Werner syndrome, is thought to counteract this genomic instability. We determined non-B DNA-induced mutation frequencies and spectra in human U2OS osteosarcoma cells and assessed the role of WRN in isogenic knockdown (WRN-KD) cells using a supF gene mutation reporter system flanked by triplex- or Z-DNA-forming sequences. Although both non-B DNA and WRN-KD served to increase the mutation frequency, the increase afforded by WRN-KD was independent of DNA structure despite the fact that purified WRN helicase was found to resolve these structures in vitro. In U2OS cells, ∼70% of mutations comprised single-base substitutions, mostly at G·C base-pairs, with the remaining ∼30% being microdeletions. The number of mutations at G·C base-pairs in the context of NGNN/NNCN sequences correlated well with predicted free energies of base stacking and ionization potentials, suggesting a possible origin via oxidation reactions involving electron loss and subsequent electron transfer (hole migration) between neighboring bases. A set of ∼40,000 somatic mutations at G·C base pairs identified in a lung cancer genome exhibited similar correlations, implying that hole migration may also be involved. We conclude that alternative DNA conformations, WRN deficiency and lung tumorigenesis may all serve to increase the mutation rate by promoting, through diverse pathways, oxidation reactions that perturb the electron orbitals of neighboring bases. It follows that such "hole migration" is likely to play a much more widespread role in mutagenesis than previously anticipated.
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Affiliation(s)
- Albino Bacolla
- From the Department of Molecular Carcinogenesis, Science Park-Research Division, The University of Texas, M. D. Anderson Cancer Center, Smithville, Texas 78957
| | - Guliang Wang
- From the Department of Molecular Carcinogenesis, Science Park-Research Division, The University of Texas, M. D. Anderson Cancer Center, Smithville, Texas 78957
| | - Aklank Jain
- From the Department of Molecular Carcinogenesis, Science Park-Research Division, The University of Texas, M. D. Anderson Cancer Center, Smithville, Texas 78957
| | - Nadia A. Chuzhanova
- the School of Science and Technology, Nottingham Trent University, Nottingham, NG11 8NS, United Kingdom
| | - Regina Z. Cer
- the Advanced Biomedical Computing Center, SAIC-Frederick, Inc., NCI-Frederick, Frederick, Maryland 21702
| | - Jack R. Collins
- the Advanced Biomedical Computing Center, SAIC-Frederick, Inc., NCI-Frederick, Frederick, Maryland 21702
| | - David N. Cooper
- the Institute of Medical Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, United Kingdom, and
| | - Vilhelm A. Bohr
- the Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224
| | - Karen M. Vasquez
- From the Department of Molecular Carcinogenesis, Science Park-Research Division, The University of Texas, M. D. Anderson Cancer Center, Smithville, Texas 78957
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24
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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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25
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Rahn JJ, Lowery MP, Della-Coletta L, Adair GM, Nairn RS. Depletion of Werner helicase results in mitotic hyperrecombination and pleiotropic homologous and nonhomologous recombination phenotypes. Mech Ageing Dev 2010; 131:562-73. [PMID: 20708636 DOI: 10.1016/j.mad.2010.08.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 07/22/2010] [Accepted: 08/03/2010] [Indexed: 11/30/2022]
Abstract
Werner syndrome (WS) is a rare, segmental progeroid syndrome caused by defects in the WRN gene, which encodes a RecQ helicase. WRN has roles in many aspects of DNA metabolism including DNA repair and recombination. In this study, we exploited two different recombination assays previously used to describe a role for the structure-specific endonuclease ERCC1-XPF in mitotic and targeted homologous recombination. We constructed Chinese hamster ovary (CHO) cell lines isogenic with the cell lines used in these previous studies by depleting WRN using shRNA vectors. When intrachromosomal, mitotic recombination was assayed in WRN-depleted CHO cells, a hyperrecombination phenotype was observed, and a small number of aberrant recombinants were generated. Targeted homologous recombination was also examined in WRN-depleted CHO cells using a plasmid-chromosome targeting assay. In these experiments, loss of WRN resulted in a significant decrease in nonhomologous integration events and ablation of recombinants that required random integration of the corrected targeting vector. Aberrant recombinants were also recovered, but only from WRN-depleted cells. The pleiotropic recombination phenotypes conferred by WRN depletion, reflected in distinct homologous and nonhomologous recombination pathways, suggest a role for WRN in processing specific types of homologous recombination intermediates as well as an important function in nonhomologous recombination.
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Affiliation(s)
- Jennifer J Rahn
- University of Texas M.D. Anderson Cancer Center, Department of Carcinogenesis, Science Park Research Division, P.O. Box 389, Smithville, TX 78597, United States
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26
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Phillips LG, Sale JE. The Werner's Syndrome protein collaborates with REV1 to promote replication fork progression on damaged DNA. DNA Repair (Amst) 2010; 9:1064-72. [PMID: 20691646 PMCID: PMC2956782 DOI: 10.1016/j.dnarep.2010.07.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 06/23/2010] [Accepted: 07/09/2010] [Indexed: 11/26/2022]
Abstract
DNA damage tolerance pathways facilitate the bypass of DNA lesions encountered during replication. These pathways can be mechanistically divided into recombinational damage avoidance and translesion synthesis, in which the lesion is directly bypassed by specialised DNA polymerases. We have recently shown distinct genetic dependencies for lesion bypass at and behind the replication fork in the avian cell line DT40, bypass at the fork requiring REV1 and bypass at post-replicative gaps requiring PCNA ubiquitination by RAD18. The WRN helicase/exonuclease, which is mutated in the progeroid and cancer predisposition disorder Werner's Syndrome, has previously been implicated in a RAD18-dependent DNA damage tolerance pathway. However, WRN has also been shown to be required to maintain normal replication fork progression on a damaged DNA template, a defect reminiscent of REV1-deficient cells. Here we use the avian cell line DT40 to demonstrate that WRN assists REV1-dependent translesion synthesis at the replication fork and that PCNA ubiquitination-dependent post-replicative lesion bypass provides an important backup mechanism for damage tolerance in the absence of WRN protein.
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Affiliation(s)
- Lara G Phillips
- Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
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27
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Mao FJ, Sidorova JM, Lauper JM, Emond MJ, Monnat RJ. The human WRN and BLM RecQ helicases differentially regulate cell proliferation and survival after chemotherapeutic DNA damage. Cancer Res 2010; 70:6548-55. [PMID: 20663905 DOI: 10.1158/0008-5472.can-10-0475] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Loss-of-function mutations in the human RecQ helicase genes WRN and BLM respectively cause the genetic instability/cancer predisposition syndromes Werner syndrome and Bloom syndrome. To identify common and unique functions of WRN and BLM, we systematically analyzed cell proliferation, cell survival, and genomic damage in isogenic cell lines depleted of WRN, BLM, or both proteins. Cell proliferation and survival were assessed before and after treatment with camptothecin, cis-diamminedichloroplatinum(II), hydroxyurea, or 5-fluorouracil. Genomic damage was assessed, before and after replication arrest, by gamma-H2AX staining, which was quantified at the single-cell level by flow cytometry. Cell proliferation was affected strongly by the extent of WRN and/or BLM depletion, and more strongly by BLM than by WRN depletion (P = 0.005). The proliferation of WRN/BLM-codepleted cells, in contrast, did not differ from BLM-depleted cells (P = 0.34). BLM-depleted and WRN/BLM-codepleted cells had comparably impaired survival after DNA damage, whereas WRN-depleted cells displayed a distinct pattern of sensitivity to DNA damage. BLM-depleted and WRN/BLM-codepleted cells had similar, significantly higher gamma-H2AX induction levels than did WRN-depleted cells. Our results provide new information on the role of WRN and BLM in determining cell proliferation, cell survival, and genomic damage after chemotherapeutic DNA damage or replication arrest. We also provide new information on functional redundancy between WRN and BLM. These results provide a strong rationale for further developing WRN and BLM as biomarkers of tumor chemotherapeutic responsiveness.
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Affiliation(s)
- Frances J Mao
- Department of Pathology, University of Washington, Seattle, Washington 98195-7705, USA
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28
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The Werner syndrome protein suppresses telomeric instability caused by chromium (VI) induced DNA replication stress. PLoS One 2010; 5:e11152. [PMID: 20585393 PMCID: PMC2886837 DOI: 10.1371/journal.pone.0011152] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Accepted: 05/20/2010] [Indexed: 01/08/2023] Open
Abstract
Telomeres protect the chromosome ends and consist of guanine-rich repeats coated by specialized proteins. Critically short telomeres are associated with disease, aging and cancer. Defects in telomere replication can lead to telomere loss, which can be prevented by telomerase-mediated telomere elongation or activities of the Werner syndrome helicase/exonuclease protein (WRN). Both telomerase and WRN attenuate cytotoxicity induced by the environmental carcinogen hexavalent chromium (Cr(VI)), which promotes replication stress and DNA polymerase arrest. However, it is not known whether Cr(VI)-induced replication stress impacts telomere integrity. Here we report that Cr(VI) exposure of human fibroblasts induced telomeric damage as indicated by phosphorylated H2AX (γH2AX) at telomeric foci. The induced γH2AX foci occurred in S-phase cells, which is indicative of replication fork stalling or collapse. Telomere fluorescence in situ hybridization (FISH) of metaphase chromosomes revealed that Cr(VI) exposure induced an increase in telomere loss and sister chromatid fusions that were rescued by telomerase activity. Human cells depleted for WRN protein exhibited a delayed reduction in telomeric and non-telomeric damage, indicated by γH2AX foci, during recovery from Cr(VI) exposure, consistent with WRN roles in repairing damaged replication forks. Telomere FISH of chromosome spreads revealed that WRN protects against Cr(VI)-induced telomere loss and downstream chromosome fusions, but does not prevent chromosome fusions that retain telomere sequence at the fusion point. Our studies indicate that environmentally induced replication stress leads to telomere loss and aberrations that are suppressed by telomerase-mediated telomere elongation or WRN functions in replication fork restoration.
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29
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Saharia A, Teasley DC, Duxin JP, Dao B, Chiappinelli KB, Stewart SA. FEN1 ensures telomere stability by facilitating replication fork re-initiation. J Biol Chem 2010; 285:27057-27066. [PMID: 20551483 DOI: 10.1074/jbc.m110.112276] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Telomeres are terminal repetitive DNA sequences whose stability requires the coordinated actions of telomere-binding proteins and the DNA replication and repair machinery. Recently, we demonstrated that the DNA replication and repair protein Flap endonuclease 1 (FEN1) is required for replication of lagging strand telomeres. Here, we demonstrate for the first time that FEN1 is required for efficient re-initiation of stalled replication forks. At the telomere, we find that FEN1 depletion results in replicative stress as evidenced by fragile telomere expression and sister telomere loss. We show that FEN1 participation in Okazaki fragment processing is not required for efficient telomere replication. Instead we find that FEN1 gap endonuclease activity, which processes DNA structures resembling stalled replication forks, and the FEN1 interaction with the RecQ helicases are vital for telomere stability. Finally, we find that FEN1 depletion neither impacts cell cycle progression nor in vitro DNA replication through non-telomeric sequences. Our finding that FEN1 is required for efficient replication fork re-initiation strongly suggests that the fragile telomere expression and sister telomere losses observed upon FEN1 depletion are the direct result of replication fork collapse. Together, these findings suggest that other nucleases compensate for FEN1 loss throughout the genome during DNA replication but fail to do so at the telomere. We propose that FEN1 maintains stable telomeres by facilitating replication through the G-rich lagging strand telomere, thereby ensuring high fidelity telomere replication.
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Affiliation(s)
- Abhishek Saharia
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Daniel C Teasley
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Julien P Duxin
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Benjamin Dao
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Katherine B Chiappinelli
- Division of Endocrine and Oncologic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Sheila A Stewart
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110; Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
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30
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Thangavel S, Mendoza-Maldonado R, Tissino E, Sidorova JM, Yin J, Wang W, Monnat RJ, Falaschi A, Vindigni A. Human RECQ1 and RECQ4 helicases play distinct roles in DNA replication initiation. Mol Cell Biol 2010; 30:1382-96. [PMID: 20065033 PMCID: PMC2832491 DOI: 10.1128/mcb.01290-09] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Revised: 10/26/2009] [Accepted: 12/29/2009] [Indexed: 11/20/2022] Open
Abstract
Cellular and biochemical studies support a role for all five human RecQ helicases in DNA replication; however, their specific functions during this process are unclear. Here we investigate the in vivo association of the five human RecQ helicases with three well-characterized human replication origins. We show that only RECQ1 (also called RECQL or RECQL1) and RECQ4 (also called RECQL4) associate with replication origins in a cell cycle-regulated fashion in unperturbed cells. RECQ4 is recruited to origins at late G(1), after ORC and MCM complex assembly, while RECQ1 and additional RECQ4 are loaded at origins at the onset of S phase, when licensed origins begin firing. Both proteins are lost from origins after DNA replication initiation, indicating either disassembly or tracking with the newly formed replisome. Nascent-origin DNA synthesis and the frequency of origin firing are reduced after RECQ1 depletion and, to a greater extent, after RECQ4 depletion. Depletion of RECQ1, though not that of RECQ4, also suppresses replication fork rates in otherwise unperturbed cells. These results indicate that RECQ1 and RECQ4 are integral components of the human replication complex and play distinct roles in DNA replication initiation and replication fork progression in vivo.
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Affiliation(s)
- Saravanabhavan Thangavel
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy, Laboratorio di Biologia Molecolare, Scuola Normale Superiore, Via Moruzzi 1, Pisa I-56124, Italy, Departments of Pathology, Genome Sciences, University of Washington, Seattle, Washington 98195-7705, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224, Istituto di Fisiologia Clinica, CNR, Via Moruzzi 1, I-56124 Pisa, Italy
| | - Ramiro Mendoza-Maldonado
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy, Laboratorio di Biologia Molecolare, Scuola Normale Superiore, Via Moruzzi 1, Pisa I-56124, Italy, Departments of Pathology, Genome Sciences, University of Washington, Seattle, Washington 98195-7705, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224, Istituto di Fisiologia Clinica, CNR, Via Moruzzi 1, I-56124 Pisa, Italy
| | - Erika Tissino
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy, Laboratorio di Biologia Molecolare, Scuola Normale Superiore, Via Moruzzi 1, Pisa I-56124, Italy, Departments of Pathology, Genome Sciences, University of Washington, Seattle, Washington 98195-7705, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224, Istituto di Fisiologia Clinica, CNR, Via Moruzzi 1, I-56124 Pisa, Italy
| | - Julia M. Sidorova
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy, Laboratorio di Biologia Molecolare, Scuola Normale Superiore, Via Moruzzi 1, Pisa I-56124, Italy, Departments of Pathology, Genome Sciences, University of Washington, Seattle, Washington 98195-7705, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224, Istituto di Fisiologia Clinica, CNR, Via Moruzzi 1, I-56124 Pisa, Italy
| | - Jinhu Yin
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy, Laboratorio di Biologia Molecolare, Scuola Normale Superiore, Via Moruzzi 1, Pisa I-56124, Italy, Departments of Pathology, Genome Sciences, University of Washington, Seattle, Washington 98195-7705, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224, Istituto di Fisiologia Clinica, CNR, Via Moruzzi 1, I-56124 Pisa, Italy
| | - Weidong Wang
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy, Laboratorio di Biologia Molecolare, Scuola Normale Superiore, Via Moruzzi 1, Pisa I-56124, Italy, Departments of Pathology, Genome Sciences, University of Washington, Seattle, Washington 98195-7705, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224, Istituto di Fisiologia Clinica, CNR, Via Moruzzi 1, I-56124 Pisa, Italy
| | - Raymond J. Monnat
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy, Laboratorio di Biologia Molecolare, Scuola Normale Superiore, Via Moruzzi 1, Pisa I-56124, Italy, Departments of Pathology, Genome Sciences, University of Washington, Seattle, Washington 98195-7705, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224, Istituto di Fisiologia Clinica, CNR, Via Moruzzi 1, I-56124 Pisa, Italy
| | - Arturo Falaschi
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy, Laboratorio di Biologia Molecolare, Scuola Normale Superiore, Via Moruzzi 1, Pisa I-56124, Italy, Departments of Pathology, Genome Sciences, University of Washington, Seattle, Washington 98195-7705, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224, Istituto di Fisiologia Clinica, CNR, Via Moruzzi 1, I-56124 Pisa, Italy
| | - Alessandro Vindigni
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy, Laboratorio di Biologia Molecolare, Scuola Normale Superiore, Via Moruzzi 1, Pisa I-56124, Italy, Departments of Pathology, Genome Sciences, University of Washington, Seattle, Washington 98195-7705, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, Baltimore, Maryland 21224, Istituto di Fisiologia Clinica, CNR, Via Moruzzi 1, I-56124 Pisa, Italy
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31
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Rossi ML, Ghosh AK, Bohr VA. Roles of Werner syndrome protein in protection of genome integrity. DNA Repair (Amst) 2010; 9:331-44. [PMID: 20075015 DOI: 10.1016/j.dnarep.2009.12.011] [Citation(s) in RCA: 146] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Werner syndrome protein (WRN) is one of a family of five human RecQ helicases implicated in the maintenance of genome stability. The conserved RecQ family also includes RecQ1, Bloom syndrome protein (BLM), RecQ4, and RecQ5 in humans, as well as Sgs1 in Saccharomyces cerevisiae, Rqh1 in Schizosaccharomyces pombe, and homologs in Caenorhabditis elegans, Xenopus laevis, and Drosophila melanogaster. Defects in three of the RecQ helicases, RecQ4, BLM, and WRN, cause human pathologies linked with cancer predisposition and premature aging. Mutations in the WRN gene are the causative factor of Werner syndrome (WS). WRN is one of the best characterized of the RecQ helicases and is known to have roles in DNA replication and repair, transcription, and telomere maintenance. Studies both in vitro and in vivo indicate that the roles of WRN in a variety of DNA processes are mediated by post-translational modifications, as well as several important protein-protein interactions. In this work, we will summarize some of the early studies on the cellular roles of WRN and highlight the recent findings that shed some light on the link between the protein with its cellular functions and the disease pathology.
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Affiliation(s)
- Marie L Rossi
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD 21224, USA
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32
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Shah SN, Opresko PL, Meng X, Lee MYWT, Eckert KA. DNA structure and the Werner protein modulate human DNA polymerase delta-dependent replication dynamics within the common fragile site FRA16D. Nucleic Acids Res 2009; 38:1149-62. [PMID: 19969545 PMCID: PMC2831333 DOI: 10.1093/nar/gkp1131] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Common fragile sites (CFS) are chromosomal regions that exhibit instability during DNA replication stress. Although the mechanism of CFS expression has not been fully elucidated, one known feature is a severely delayed S-phase. We used an in vitro primer extension assay to examine the progression of DNA synthesis through various sequences within FRA16D by the replicative human DNA polymerases δ and α, and with human cell-free extracts. We found that specific cis-acting sequence elements perturb DNA elongation, causing inconsistent DNA synthesis rates between regions on the same strand and complementary strands. Pol δ was significantly inhibited in regions containing hairpins and microsatellites, [AT/TA]24 and [A/T]19–28, compared with a control region with minimal secondary structure. Pol δ processivity was enhanced by full length Werner Syndrome protein (WRN) and by WRN fragments containing either the helicase domain or DNA-binding C-terminal domain. In cell-free extracts, stalling was eliminated at smaller hairpins, but persisted in larger hairpins and microsatellites. Our data support a model whereby CFS expression during cellular stress is due to a combination of factors—density of specific DNA secondary-structures within a genomic region and asymmetric rates of strand synthesis.
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Affiliation(s)
- Sandeep N Shah
- Department of Pathology, Gittlen Cancer Research Foundation and the Intercollege Graduate Degree Program in Genetics, College of Medicine, The Pennsylvania State University, Hershey, PA 17033, USA
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33
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Divergent cellular phenotypes of human and mouse cells lacking the Werner syndrome RecQ helicase. DNA Repair (Amst) 2009; 9:11-22. [PMID: 19896421 DOI: 10.1016/j.dnarep.2009.09.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 09/13/2009] [Accepted: 09/25/2009] [Indexed: 01/06/2023]
Abstract
Werner syndrome (WS) is a human autosomal recessive genetic instability and cancer predisposition syndrome with features of premature aging. Several genetically determined mouse models of WS have been generated, however, none develops features of premature aging or an elevated risk of neoplasia unless additional genetic perturbations are introduced. In order to determine whether differences in cellular phenotype could explain the discrepant phenotypes of Wrn-/- mice and WRN-deficient humans, we compared the cellular phenotype of newly derived Wrn-/- mouse primary fibroblasts with previous analyses of primary and transformed fibroblasts from WS patients and with newly derived, WRN-depleted human primary fibroblasts. These analyses confirmed previously reported cellular phenotypes of WRN-mutant and WRN-deficient human fibroblasts, and demonstrated that the human WRN-deficient cellular phenotype can be detected in cells grown in 5% or in 20% oxygen. In contrast, we did not identify prominent cellular phenotypes present in WRN-deficient human cells in Wrn-/- mouse fibroblasts. Our results indicate that human and mouse fibroblasts have different functional requirements for WRN protein, and that the absence of a strong cellular phenotype may in part explain the failure of Wrn-/- mice to develop an organismal phenotype resembling Werner syndrome.
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34
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Sowd G, Wang H, Pretto D, Chazin WJ, Opresko PL. Replication protein A stimulates the Werner syndrome protein branch migration activity. J Biol Chem 2009; 284:34682-91. [PMID: 19812417 DOI: 10.1074/jbc.m109.049031] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Loss of the RecQ DNA helicase WRN protein causes Werner syndrome, in which patients exhibit features of premature aging and increased cancer. WRN deficiency induces cellular defects in DNA replication, mitotic homologous recombination (HR), and telomere stability. In addition to DNA unwinding activity, WRN also possesses exonuclease, strand annealing, and branch migration activities. The single strand binding proteins replication protein A (RPA) and telomere-specific POT1 specifically stimulate WRN DNA unwinding activity. To determine whether RPA and POT1 also modulate WRN branch migration activity, we examined biologically relevant mobile D-loops that mimic structures in HR strand invasion and at telomere ends. Both RPA and POT1 block WRN exonuclease digestion of the invading strand by loading on the strand. However, only RPA robustly stimulates WRN branch migration activity and increases the percentage of D-loops that are disrupted. Our results are consistent with cellular data that support RPA enhancement of branch migration during HR repair and, conversely, POT1 limitation of inappropriate recombination and branch migration at telomeric ends. This is, to our knowledge, the first evidence that RPA can stimulate branch migration activity.
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Affiliation(s)
- Gregory Sowd
- Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania 15219, USA
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35
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Zecevic A, Menard H, Gurel V, Hagan E, DeCaro R, Zhitkovich A. WRN helicase promotes repair of DNA double-strand breaks caused by aberrant mismatch repair of chromium-DNA adducts. Cell Cycle 2009; 8:2769-78. [PMID: 19652551 DOI: 10.4161/cc.8.17.9410] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Recent studies in yeast have found that processing of DNA double-strand breaks (DSB) for recombination repair involves Sgs1 helicase. Human cells have five Sgs1 homologues with unknown selectivity and significance for repair of different DSB types. Here we examined the importance of WRN helicase in repair of G(2)-specific DSB caused by abnormal mismatch repair (MMR) of ternary Cr-DNA adducts. We found that Cr(VI) induced a rapid dispersal of WRN from the nucleolus resulting in its prolonged retention in the nucleoplasm. The loss of MSH2 or MLH1 MMR proteins abolished the long-term but not the initial WRN relocalization. WRN-deficient fibroblasts were hypersensitive to Cr(VI)-induced clonogenic death and contained high levels of persistent DSB detected by gamma-H2AX/53BP1 foci and pulsed-field gel electrophoresis. WRN was involved in recombination repair of Cr-induced DNA damage, as evidenced by WRN-RAD51 colocalization and defective formation of RAD51 foci in the absence of WRN. The accumulation of unrepaired DSB in WRN-depleted cells was rescued by the inactivation of MMR, indicating that MMR-generated DSB were a key substrate for WRN action in Cr(VI)-treated cells. Competition for the limited amounts of WRN in primary cells between G(2) processes of telomere rebuilding and recombinational repair is expected to increase persistence of Cr-induced DSB and may cause telomeric abnormalities in tissues of chronically chromate-exposed workers. Our work provides the first demonstration of the major importance of WRN in repair of a specific class of DSB in human cells.
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Affiliation(s)
- Alma Zecevic
- Brown University, Department of Pathology and Laboratory Medicine, Providence, RI 02912, USA
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36
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Robinson K, Asawachaicharn N, Galloway DA, Grandori C. c-Myc accelerates S-phase and requires WRN to avoid replication stress. PLoS One 2009; 4:e5951. [PMID: 19554081 PMCID: PMC2694031 DOI: 10.1371/journal.pone.0005951] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Accepted: 05/05/2009] [Indexed: 12/31/2022] Open
Abstract
c-Myc interacts with components of the pre-replication complex and directly regulates DNA replication [1]. However the consequences of this novel c-Myc function on cell cycle dynamics and replication-associated damage are unknown. Here, we show that c-Myc overexpression in primary human fibroblasts markedly accelerates S-phase while c-Myc deficient fibroblasts exhibit a prolonged S-phase. We also show that the Werner DNA helicase protein (WRN) plays a critical role in supporting c-Myc-driven S-phase, as depletion of WRN in c-Myc overexpressing cells increases DNA damage specifically at sites of DNA synthesis. This excess DNA damage activates a “replication stress” pathway involving ATR, CHK1, CHK2, and p53, leading to rapid senescence of WRN deficient c-Myc overexpressing cells. Indeed, depletion of p53 rescues this senescence response. We propose that WRN functions to repair abnormal replication structures caused by the acceleration of DNA replication by c-Myc. This work provides an additional mechanistic explanation for c-Myc-induced DNA damage and senescence, and reveals a vulnerability of c-Myc overexpressing cells that could potentially be exploited in cancer therapy.
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Affiliation(s)
- Kristin Robinson
- Program in Cancer Biology and Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Nichaya Asawachaicharn
- Program in Cancer Biology and Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Denise A. Galloway
- Program in Cancer Biology and Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Carla Grandori
- Program in Cancer Biology and Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- * E-mail:
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37
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Liu FJ, Barchowsky A, Opresko PL. The Werner syndrome protein functions in repair of Cr(VI)-induced replication-associated DNA damage. Toxicol Sci 2009; 110:307-18. [PMID: 19487340 DOI: 10.1093/toxsci/kfp104] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Werner syndrome is a premature aging disorder characterized by cancer predisposition that is caused by loss of the Werner syndrome protein (WRN) helicase/exonuclease DNA repair protein. Hexavalent chromium is an environmental carcinogen and genotoxicant that is associated with respiratory cancers and induces several forms of DNA damage, including lesions that interfere with DNA replication. Based on the evidence that WRN protein facilitates repair of stalled and collapsed replication forks, we hypothesized that WRN functions in the cellular response to and recovery from Cr(VI)-induced genotoxicity and genomic instability. Here we report that human cells deficient in WRN protein are hypersensitive to Cr(VI) toxicity, and exhibit a delayed reduction in DNA breaks and stalled replication forks, indicated by gammaH2AX foci, during recovery from Cr(VI) exposure. Cr(VI)-induced WRN protein translocation from the nucleoli into nucleoplasmic foci in S-phase cells, and these foci colocalized with gammaH2AX foci indicating WRN responds to replication-associated DNA damage. As further evidence that Cr(VI) triggers stalled DNA replication, we observed Cr(VI) treatment induced an accumulation of cells in S-phase that exhibited high levels of gammaH2AX foci. Therefore, these data demonstrate a novel role for WRN protein in cellular protection against the environmental genotoxicant Cr(VI) and further provide evidence that Cr(VI) induces DNA replicative stress which has implications for aging and cancer.
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Affiliation(s)
- Fu-Jun Liu
- Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania 15219, USA
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38
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Opresko PL, Sowd G, Wang H. The Werner syndrome helicase/exonuclease processes mobile D-loops through branch migration and degradation. PLoS One 2009; 4:e4825. [PMID: 19283071 PMCID: PMC2653227 DOI: 10.1371/journal.pone.0004825] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Accepted: 01/16/2009] [Indexed: 11/18/2022] Open
Abstract
RecQ DNA helicases are critical for preserving genome integrity. Of the five RecQ family members identified in humans, only the Werner syndrome protein (WRN) possesses exonuclease activity. Loss of WRN causes the progeroid disorder Werner syndrome which is marked by cancer predisposition. Cellular evidence indicates that WRN disrupts potentially deleterious intermediates in homologous recombination (HR) that arise in genomic and telomeric regions during DNA replication and repair. Precisely how the WRN biochemical activities process these structures is unknown, especially since the DNA unwinding activity is poorly processive. We generated biologically relevant mobile D-loops which mimic the initial DNA strand invasion step in HR to investigate whether WRN biochemical activities can disrupt this joint molecule. We show that WRN helicase alone can promote branch migration through an 84 base pair duplex region to completely displace the invading strand from the D-loop. However, substrate processing is altered in the presence of the WRN exonuclease activity which degrades the invading strand both prior to and after release from the D-loop. Furthermore, telomeric D-loops are more refractory to disruption by WRN, which has implications for tighter regulation of D-loop processing at telomeres. Finally, we show that WRN can recognize and initiate branch migration from both the 5′ and 3′ ends of the invading strand in the D-loops. These findings led us to propose a novel model for WRN D-loop disruption. Our biochemical results offer an explanation for the cellular studies that indicate both WRN activities function in processing HR intermediates.
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Affiliation(s)
- Patricia L Opresko
- Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania, United States of America.
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39
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Boubriak I, Mason PA, Clancy DJ, Dockray J, Saunders RDC, Cox LS. DmWRNexo is a 3'-5' exonuclease: phenotypic and biochemical characterization of mutants of the Drosophila orthologue of human WRN exonuclease. Biogerontology 2008; 10:267-77. [PMID: 18956248 DOI: 10.1007/s10522-008-9181-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Accepted: 09/25/2008] [Indexed: 12/21/2022]
Abstract
The premature human ageing Werner's syndrome is caused by loss or mutation of the WRN helicase/exonuclease. We have recently identified the orthologue of the WRN exonuclease in flies, DmWRNexo, encoded by the CG7670 locus, and showed very high levels of mitotic recombination in a hypomorphic PiggyBac insertional mutant. Here, we report a novel allele of CG7670, with a point mutation resulting in the change of the conserved aspartate (229) to valine. Flies bearing this mutation show levels of mitotic recombination 20-fold higher than wild type. Molecular modelling suggests that D229 lies towards the outside of the molecule distant from the nuclease active site. We have produced recombinant protein of the D229V mutant, assayed its nuclease activity in vitro, and compared activity with that of wild type DmWRNexo and a D162A E164A double active site mutant we have created. We show for the first time that DmWRNexo has 3'-5' exonuclease activity and that mutation within the presumptive active site disrupts exonuclease activity. Furthermore, we show that the D229V mutant has very limited exonuclease activity in vitro. Using Drosophila, we can therefore analyse WRN exonuclease from enzyme activity in vitro through to fly phenotype, and show that loss of exonuclease activity contributes to genome instability.
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Affiliation(s)
- Ivan Boubriak
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK
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40
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Sidorova JM. Roles of the Werner syndrome RecQ helicase in DNA replication. DNA Repair (Amst) 2008; 7:1776-86. [PMID: 18722555 DOI: 10.1016/j.dnarep.2008.07.017] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Accepted: 07/23/2008] [Indexed: 01/20/2023]
Abstract
Congenital deficiency in the WRN protein, a member of the human RecQ helicase family, gives rise to Werner syndrome, a genetic instability and cancer predisposition disorder with features of premature aging. Cellular roles of WRN are not fully elucidated. WRN has been implicated in telomere maintenance, homologous recombination, DNA repair, and other processes. Here I review the available data that directly address the role of WRN in preserving DNA integrity during replication and propose that WRN can function in coordinating replication fork progression with replication stress-induced fork remodeling. I further discuss this role of WRN within the contexts of damage tolerance group of regulatory pathways, and redundancy and cooperation with other RecQ helicases.
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Affiliation(s)
- Julia M Sidorova
- Department of Pathology, University of Washington, Seattle, WA 98195-7705, USA.
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41
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Gupta R, Brosh RM. Helicases as prospective targets for anti-cancer therapy. Anticancer Agents Med Chem 2008; 8:390-401. [PMID: 18473724 DOI: 10.2174/187152008784220339] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
It has been proposed that selective inactivation of a DNA repair pathway may enhance anti-cancer therapies that eliminate cancerous cells through the cytotoxic effects of DNA damaging agents or radiation. Given the unique and critically important roles of DNA helicases in the DNA damage response, DNA repair, and maintenance of genomic stability, a number of strategies currently being explored or in use to combat cancer may be either mediated or enhanced through the modulation of helicase function. The focus of this review will be to examine the roles of helicases in DNA repair that might be suitably targeted by cancer therapeutic approaches. Treatment of cancers with anti-cancer drugs such as small molecule compounds that modulate helicase expression or function is a viable approach to selectively kill cancer cells through the inactivation of helicase-dependent DNA repair pathways, particularly those associated with DNA recombination, replication restart, and cell cycle checkpoint.
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Affiliation(s)
- Rigu Gupta
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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42
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Saunders RDC, Boubriak I, Clancy DJ, Cox LS. Identification and characterization of a Drosophila ortholog of WRN exonuclease that is required to maintain genome integrity. Aging Cell 2008; 7:418-25. [PMID: 18346216 PMCID: PMC2408639 DOI: 10.1111/j.1474-9726.2008.00388.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/07/2008] [Indexed: 01/08/2023] Open
Abstract
The premature human aging Werner syndrome (WS) is caused by mutation of the RecQ-family WRN helicase, which is unique in possessing also 3'-5' exonuclease activity. WS patients show significant genomic instability with elevated cancer incidence. WRN is implicated in restraining illegitimate recombination, especially during DNA replication. Here we identify a Drosophila ortholog of the WRN exonuclease encoded by the CG7670 locus. The predicted DmWRNexo protein shows conservation of structural motifs and key catalytic residues with human WRN exonuclease, but entirely lacks a helicase domain. Insertion of a piggyBac element into the 5' UTR of CG7670 severely reduces gene expression. DmWRNexo mutant flies homozygous for this insertional allele of CG7670 are thus severely hypomorphic; although adults show no gross morphological abnormalities, females are sterile. Like human WS cells, we show that the DmWRNexo mutant flies are hypersensitive to the topoisomerase I inhibitor camptothecin. Furthermore, these mutant flies show highly elevated rates of mitotic DNA recombination resulting from excessive reciprocal exchange. This study identifies a novel WRN ortholog in flies and demonstrates an important role for WRN exonuclease in maintaining genome stability.
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Affiliation(s)
- Robert D C Saunders
- Department of Biological Sciences, The Open University, Milton Keynes MK7 6AA, UK.
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43
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Sensitivity of RECQL4-deficient fibroblasts from Rothmund-Thomson syndrome patients to genotoxic agents. Hum Genet 2008; 123:643-53. [PMID: 18504617 DOI: 10.1007/s00439-008-0518-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Accepted: 05/19/2008] [Indexed: 01/12/2023]
Abstract
RECQ helicase protein-like 4 (RECQL4) is a member of the human RECQ family of DNA helicases. Two-thirds of patients with Rothmund-Thomson syndrome (RTS) carry biallelic inactivating mutations in the RECQL4 gene. RTS is an autosomal recessive disorder characterized by poikiloderma, sparse hair, small stature, skeletal abnormalities, cataracts, and an increased risk of cancer. Mutations in two other RECQ helicases, BLM and WRN, are responsible for the cancer predisposition conditions Bloom and Werner syndromes, respectively. Previous studies have shown that BLM and WRN-deficient cells demonstrate increased sensitivity to hydroxyurea (HU), camptothecin (CPT), and 4-nitroquinoline 1-oxide (4NQO). Little is known about the sensitivity of RECQL4-deficient cells to these and other genotoxic agents. The purpose of this study was to determine if RTS cells display any distinct cellular phenotypes in response to DNA damaging agents or replication blocks that could provide insight into the molecular function of the RECQL4 protein. Our results show that primary fibroblasts from RTS patients carrying two deleterious RECQL4 mutations, compared to wild type (WT) fibroblasts, have increased sensitivity to HU, CPT, and doxorubicin (DOX), modest sensitivity to other DNA damaging agents including ultraviolet (UV) irradiation, ionizing radiation (IR), and cisplatin (CDDP), and relative resistance to 4NQO. The RECQ family of DNA helicases has been implicated in the regulation of DNA replication, recombination, and repair. Because HU, CPT, and DOX exert their effects primarily during S phase, these results support a greater role for the RECQL4 protein in DNA replication as opposed to repair of exogenous damage.
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44
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Abstract
Disruption of the Rb (retinoblastoma protein)/E2F cell-cycle pathway and Ras activation are two of the most frequent events in cancer, and both of these mutations place oncogenic stress on cells to increase DNA replication. In the present study, we demonstrate that these mutations have an additive effect on induction of members of the RecQ DNA helicase family. RecQ activity is important for genomic stability, initiation of DNA replication and telomere maintenance, and mutation of the BLM (Bloom's syndrome gene), WRN (Werner's syndrome gene) or RECQL4 (Rothmund–Thomson syndrome gene) family members leads to premature aging syndromes characterized by genetic instability and telomere loss. RecQ family members are frequently overexpressed in cancers, and overexpression of BLM has been shown to cause telomere elongation. Concomitant with induction of RecQ genes in response to Rb family mutation and Ras activation, we show an increase in the number of telomeric repeats. We suggest that this induction of RecQ genes in response to common oncogenic mutations may explain the up-regulation of the genes seen in cancers, and it may provide a means for transformed cells to respond to an increased demand for DNA replication.
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45
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Wiktor-Brown DM, Olipitz W, Hendricks CA, Rugo RE, Engelward BP. Tissue-specific differences in the accumulation of sequence rearrangements with age. DNA Repair (Amst) 2008; 7:694-703. [PMID: 18358792 DOI: 10.1016/j.dnarep.2008.01.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2007] [Revised: 12/12/2007] [Accepted: 01/15/2008] [Indexed: 01/31/2023]
Abstract
Mitotic homologous recombination (HR) is a critical pathway for the accurate repair of DNA double strand breaks (DSBs) and broken replication forks. While generally error-free, HR can occur between misaligned sequences, resulting in deleterious sequence rearrangements that can contribute to cancer and aging. To learn more about the extent to which HR occurs in different tissues during the aging process, we used Fluorescent Yellow Direct Repeat (FYDR) mice in which an HR event in a transgene yields a fluorescent phenotype. Here, we show tissue-specific differences in the accumulation of recombinant cells with age. Unlike pancreas, which shows a dramatic 23-fold increase in recombinant cell frequency with age, skin shows no increase in vivo. In vitro studies indicate that juvenile and aged primary fibroblasts are similarly able to undergo HR in response to endogenous and exogenous DNA damage. Therefore, the lack of recombinant cell accumulation in the skin is most likely not due to an inability to undergo de novo HR events. We propose that tissue-specific differences in the accumulation of recombinant cells with age result from differences in the ability of recombinant cells to persist and clonally expand within tissues.
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Affiliation(s)
- Dominika M Wiktor-Brown
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
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46
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Hjm/Hel308A DNA helicase from Sulfolobus tokodaii promotes replication fork regression and interacts with Hjc endonuclease in vitro. J Bacteriol 2008; 190:3006-17. [PMID: 18296528 DOI: 10.1128/jb.01662-07] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Hjm and Hel308a are novel, RecQ-like DNA helicases recently identified in the euryarchaeotes Pyrococcus furiosus and Methanothermobacter thermautotrophicus, respectively. In this study, an Hjm/Hel308 homologue (designated StoHjm) from Sulfolobus tokodaii, a hyperthermophilic archaeon belonging to the Crenarchaeota subdomain of archaea, was cloned, purified, and characterized. Unlike Hjm and Hel308a, which unwind DNA in a 3'-to-5' direction, StoHjm unwound DNA in both 3'-to-5' and 5'-to-3' directions. Remarkably, StoHjm exhibited structure-specific single-stranded-DNA-annealing and fork regression activities in vitro. In addition, gel filtration, affinity pulldown, and yeast two-hybrid analyses revealed that StoHjm physically interacted with StoHjc, the Holliday junction-specific endonuclease from S. tokodaii. This interaction may have functional significance, because the unwinding activity of StoHjm was inhibited by StoHjc in vitro. These results may suggest that the Hjm/Hel308 family helicases, in association with Hjc endonucleases, are involved in processing of stalled replication forks.
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Sharma S, Brosh RM. Unique and important consequences of RECQ1 deficiency in mammalian cells. Cell Cycle 2008; 7:989-1000. [PMID: 18414032 DOI: 10.4161/cc.7.8.5707] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Five members of the RecQ subfamily of DEx-H-containing DNA helicases have been identified in both human and mouse, and mutations in BLM, WRN, and RECQ4 are associated with human diseases of premature aging, cancer, and chromosomal instability. Although a genetic disease has not been linked to RECQ1 mutations, RECQ1 helicase is the most highly expressed of the human RecQ helicases, suggesting an important role in cellular DNA metabolism. Recent advances have elucidated a unique role of RECQ1 to suppress genomic instability. Embryonic fibroblasts from RECQ1-deficient mice displayed aneuploidy, chromosomal instability, and increased load of DNA damage.(1) Acute depletion of human RECQ1 renders cells sensitive to DNA damage and results in spontaneous gamma-H2AX foci and elevated sister chromatid exchanges, indicating aberrant repair of DNA breaks.(2) Consistent with a role in DNA repair, RECQ1 relocalizes to irradiation-induced nuclear foci and associates with chromatin.(2) RECQ1 catalytic activities(3) and interactions with DNA repair proteins(2,4,5) are likely to be important for its molecular functions in genome homeostasis. Collectively, these studies provide the first evidence for an important role of RECQ1 to confer chromosomal stability that is unique from that of other RecQ helicases and suggest its potential involvement in tumorigenesis.
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Affiliation(s)
- Sudha Sharma
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland, USA
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Sidorova JM, Li N, Folch A, Monnat RJ. The RecQ helicase WRN is required for normal replication fork progression after DNA damage or replication fork arrest. Cell Cycle 2008; 7:796-807. [PMID: 18250621 DOI: 10.4161/cc.7.6.5566] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Werner syndrome is an autosomal recessive genetic instability and cancer predisposition syndrome with features of premature aging. Several lines of evidence have suggested that the Werner syndrome protein WRN plays a role in DNA replication and S-phase progression. In order to define the exact role of WRN in genomic replication we examined cell cycle kinetics during normal cell division and after methyl-methane-sulfonate (MMS) DNA damage or hydroxyurea (HU)-mediated replication arrest following acute depletion of WRN from human fibroblasts. Loss of WRN markedly extended the time cells needed to complete the cell cycle after either of these genotoxic treatments. Moreover, replication track analysis of individual, stretched DNA fibers showed that WRN depletion significantly reduced the speed at which replication forks elongated in vivo after MMS or HU treatment. These results establish the importance of WRN during genomic replication and indicate that WRN acts to facilitate fork progression after DNA damage or replication arrest. The data provide a mechanistic basis for a better understanding of WRN-mediated maintenance of genomic stability and for predicting the outcomes of DNA-targeting chemotherapy in several adult cancers that silence WRN expression.
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Affiliation(s)
- Julia M Sidorova
- Department of Pathology, University of Washington, Seattle, Washington 98195-7705, USA.
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Sedelnikova OA, Horikawa I, Redon C, Nakamura A, Zimonjic DB, Popescu NC, Bonner WM. Delayed kinetics of DNA double-strand break processing in normal and pathological aging. Aging Cell 2008; 7:89-100. [PMID: 18005250 DOI: 10.1111/j.1474-9726.2007.00354.x] [Citation(s) in RCA: 168] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Accumulation of DNA damage may play an essential role in both cellular senescence and organismal aging. The ability of cells to sense and repair DNA damage declines with age. However, the underlying molecular mechanism for this age-dependent decline is still elusive. To understand quantitative and qualitative changes in the DNA damage response during human aging, DNA damage-induced foci of phosphorylated histone H2AX (gamma-H2AX), which occurs specifically at sites of DNA double-strand breaks (DSBs) and eroded telomeres, were examined in human young and senescing fibroblasts, and in lymphocytes of peripheral blood. Here, we show that the incidence of endogenous gamma-H2AX foci increases with age. Fibroblasts taken from patients with Werner syndrome, a disorder associated with premature aging, genomic instability and increased incidence of cancer, exhibited considerably higher incidence of gamma-H2AX foci than those taken from normal donors of comparable age. Further increases in gamma-H2AX focal incidence occurred in culture as both normal and Werner syndrome fibroblasts progressed toward senescence. The rates of recruitment of DSB repair proteins to gamma-H2AX foci correlated inversely with age for both normal and Werner syndrome donors, perhaps due in part to the slower growth of gamma-H2AX foci in older donors. Because genomic stability may depend on the efficient processing of DSBs, and hence the rapid formation of gamma-H2AX foci and the rapid accumulation of DSB repair proteins on these foci at sites of nascent DSBs, our findings suggest that decreasing efficiency in these processes may contribute to genome instability associated with normal and pathological aging.
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Affiliation(s)
- Olga A Sedelnikova
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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Grillari J, Katinger H, Voglauer R. Contributions of DNA interstrand cross-links to aging of cells and organisms. Nucleic Acids Res 2007; 35:7566-76. [PMID: 18083760 PMCID: PMC2190700 DOI: 10.1093/nar/gkm1065] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 11/11/2007] [Accepted: 11/11/2007] [Indexed: 01/05/2023] Open
Abstract
Impaired DNA damage repair, especially deficient transcription-coupled nucleotide excision repair, leads to segmental progeroid syndromes in human patients as well as in rodent models. Furthermore, DNA double-strand break signalling has been pinpointed as a key inducer of cellular senescence. Several recent findings suggest that another DNA repair pathway, interstrand cross-link (ICL) repair, might also contribute to cell and organism aging. Therefore, we summarize and discuss here that (i) systemic administration of anti-cancer chemotherapeutics, in many cases DNA cross-linking drugs, induces premature progeroid frailty in long-term survivors; (ii) that ICL-inducing 8-methoxy-psoralen/UVA phototherapy leads to signs of premature skin aging as prominent long-term side effect and (iii) that mutated factors involved in ICL repair like ERCC1/XPF, the Fanconi anaemia proteins, WRN and SNEV lead to reduced replicative life span in vitro and segmental progeroid syndromes in vivo. However, since ICL-inducing drugs cause damage different from ICL and since all currently known ICL repair factors work in more than one pathway, further work will be needed to dissect the actual contribution of ICL damage to aging.
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Affiliation(s)
- Johannes Grillari
- Institute of Applied Microbiology, Department of Biotechnology, BOKU - University of Natural Resources and Applied Life Sciences, Vienna, Muthgasse 18 1190 Vienna, Austria.
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