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Sember E, Chennakesavula R, Beard B, Opoola M, Hwangbo DS. Dietary restriction fails to extend lifespan of Drosophila model of Werner syndrome. G3 (BETHESDA, MD.) 2024; 14:jkae056. [PMID: 38491858 PMCID: PMC11075538 DOI: 10.1093/g3journal/jkae056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 02/28/2024] [Accepted: 03/04/2024] [Indexed: 03/18/2024]
Abstract
Werner syndrome (WS) is a rare genetic disease in humans, caused by mutations in the WRN gene that encodes a protein containing helicase and exonuclease domains. WS is characterized by symptoms of accelerated aging in multiple tissues and organs, involving increased risk of cancer, heart failure, and metabolic dysfunction. These conditions ultimately lead to the premature mortality of patients with WS. In this study, using the null mutant flies (WRNexoΔ) for the gene WRNexo (CG7670), homologous to the exonuclease domain of WRN in humans, we examined how diets affect the lifespan, stress resistance, and sleep/wake patterns of a Drosophila model of WS. We observed that dietary restriction (DR), one of the most robust nongenetic interventions to extend lifespan in animal models, failed to extend the lifespan of WRNexoΔ mutant flies and even had a detrimental effect in females. Interestingly, the mean lifespan of WRNexoΔ mutant flies was not reduced on a protein-rich diet compared to that of wild-type (WT) flies. Compared to WT control flies, the mutant flies also exhibited altered responses to DR in their resistance to starvation and oxidative stress, as well as changes in sleep/wake patterns. These findings show that the WRN protein is necessary for mediating the effects of DR and suggest that the exonuclease domain of WRN plays an important role in metabolism in addition to its primary role in DNA-repair and genome stability.
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Affiliation(s)
- Eileen Sember
- Department of Biology, University of Louisville, Louisville, KY 40292, USA
| | | | - Breanna Beard
- Department of Biology, University of Louisville, Louisville, KY 40292, USA
| | - Mubaraq Opoola
- Department of Biology, University of Louisville, Louisville, KY 40292, USA
| | - Dae-Sung Hwangbo
- Department of Biology, University of Louisville, Louisville, KY 40292, USA
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2
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Mackay HL, Stone HR, Ellis K, Ronson GE, Walker AK, Starowicz K, Garvin AJ, van Eijk P, Vaitsiankova A, Vijayendran S, Beesley JF, Petermann E, Brown EJ, Densham RM, Reed SH, Dobbs F, Saponaro M, Morris JR. USP50 suppresses alternative RecQ helicase use and deleterious DNA2 activity during replication. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.10.574674. [PMID: 38260523 PMCID: PMC10802463 DOI: 10.1101/2024.01.10.574674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Mammalian DNA replication employs several RecQ DNA helicases to orchestrate the faithful duplication of genetic information. Helicase function is often coupled to the activity of specific nucleases, but how helicase and nuclease activities are co-directed is unclear. Here we identify the inactive ubiquitin-specific protease, USP50, as a ubiquitin-binding and chromatin-associated protein required for ongoing replication, fork restart, telomere maintenance and cellular survival during replicative stress. USP50 supports WRN:FEN1 at stalled replication forks, suppresses MUS81-dependent fork collapse and restricts double-strand DNA breaks at GC-rich sequences. Surprisingly we find that cells depleted for USP50 and recovering from a replication block exhibit increased DNA2 and RECQL4 foci and that the defects in ongoing replication, poor fork restart and increased fork collapse seen in these cells are mediated by DNA2, RECQL4 and RECQL5. These data define a novel ubiquitin-dependent pathway that promotes the balance of helicase: nuclease use at ongoing and stalled replication forks.
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3
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Datta A, Brosh RM. WRN rescues replication forks compromised by a BRCA2 deficiency: Predictions for how inhibition of a helicase that suppresses premature aging tilts the balance to fork demise and chromosomal instability in cancer. Bioessays 2022; 44:e2200057. [PMID: 35751457 PMCID: PMC9527950 DOI: 10.1002/bies.202200057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 06/03/2022] [Accepted: 06/08/2022] [Indexed: 11/08/2022]
Abstract
Hereditary breast and ovarian cancers are frequently attributed to germline mutations in the tumor suppressor genes BRCA1 and BRCA2. BRCA1/2 act to repair double-strand breaks (DSBs) and suppress the demise of unstable replication forks. Our work elucidated a dynamic interplay between BRCA2 and the WRN DNA helicase/exonuclease defective in the premature aging disorder Werner syndrome. WRN and BRCA2 participate in complementary pathways to stabilize replication forks in cancer cells, allowing them to proliferate. Whether the functional overlap of WRN and BRCA2 is relevant to replication at gaps between newly synthesized DNA fragments, protection of telomeres, and/or metabolism of secondary DNA structures remain to be determined. Advances in understanding the mechanisms elicited during replication stress have prompted the community to reconsider avenues for cancer therapy. Insights from studies of PARP or topoisomerase inhibitors provide working models for the investigation of WRN's mechanism of action. We discuss these topics, focusing on the implications of the WRN-BRCA2 genetic interaction under conditions of replication stress.
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Affiliation(s)
- Arindam Datta
- Helicases and Genomic Integrity Section, Translational Gerontology Branch, National Institute on Aging, NIH, Baltimore, Maryland, USA
| | - Robert M Brosh
- Helicases and Genomic Integrity Section, Translational Gerontology Branch, National Institute on Aging, NIH, Baltimore, Maryland, USA
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Thakkar MK, Lee J, Meyer S, Chang VY. RecQ Helicase Somatic Alterations in Cancer. Front Mol Biosci 2022; 9:887758. [PMID: 35782872 PMCID: PMC9240438 DOI: 10.3389/fmolb.2022.887758] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 05/23/2022] [Indexed: 11/13/2022] Open
Abstract
Named the “caretakers” of the genome, RecQ helicases function in several pathways to maintain genomic stability and repair DNA. This highly conserved family of enzymes consist of five different proteins in humans: RECQL1, BLM, WRN, RECQL4, and RECQL5. Biallelic germline mutations in BLM, WRN, and RECQL4 have been linked to rare cancer-predisposing syndromes. Emerging research has also implicated somatic alterations in RecQ helicases in a variety of cancers, including hematological malignancies, breast cancer, osteosarcoma, amongst others. These alterations in RecQ helicases, particularly overexpression, may lead to increased resistance of cancer cells to conventional chemotherapy. Downregulation of these proteins may allow for increased sensitivity to chemotherapy, and, therefore, may be important therapeutic targets. Here we provide a comprehensive review of our current understanding of the role of RecQ DNA helicases in cancer and discuss the potential therapeutic opportunities in targeting these helicases.
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Affiliation(s)
- Megha K. Thakkar
- Department of Pediatrics, Division of Pediatric Hematology-Oncology, University of California, Los Angeles, Los Angeles, CA, United States
| | - Jamie Lee
- Department of Pediatrics, Division of Pediatric Hematology-Oncology, University of California, Los Angeles, Los Angeles, CA, United States
| | - Stefan Meyer
- Division of Cancer Studies, University of Manchester, Manchester, United Kingdom
- Department of Pediatric Hematology Oncology, Royal Manchester Children’s Hospital and Christie NHS Foundation Trust, Manchester, United Kingdom
| | - Vivian Y. Chang
- Department of Pediatrics, Division of Pediatric Hematology-Oncology, University of California, Los Angeles, Los Angeles, CA, United States
- Childrens Discovery and Innovation Institute, UCLA, Los Angeles, CA, United States
- Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, CA, United States
- *Correspondence: Vivian Y. Chang,
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5
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Epiney DG, Salameh C, Cassidy D, Zhou LT, Kruithof J, Milutinović R, Andreani TS, Schirmer AE, Bolterstein E. Characterization of Stress Responses in a Drosophila Model of Werner Syndrome. Biomolecules 2021; 11:1868. [PMID: 34944512 PMCID: PMC8699552 DOI: 10.3390/biom11121868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/04/2021] [Accepted: 12/07/2021] [Indexed: 11/16/2022] Open
Abstract
As organisms age, their resistance to stress decreases while their risk of disease increases. This can be shown in patients with Werner syndrome (WS), which is a genetic disease characterized by accelerated aging along with increased risk of cancer and metabolic disease. WS is caused by mutations in WRN, a gene involved in DNA replication and repair. Recent research has shown that WRN mutations contribute to multiple hallmarks of aging including genomic instability, telomere attrition, and mitochondrial dysfunction. However, questions remain regarding the onset and effect of stress on early aging. We used a fly model of WS (WRNexoΔ) to investigate stress response during different life stages and found that stress sensitivity varies according to age and stressor. While larvae and young WRNexoΔ adults are not sensitive to exogenous oxidative stress, high antioxidant activity suggests high levels of endogenous oxidative stress. WRNexoΔ adults are sensitive to stress caused by elevated temperature and starvation suggesting abnormalities in energy storage and a possible link to metabolic dysfunction in WS patients. We also observed higher levels of sleep in aged WRNexoΔ adults suggesting an additional adaptive mechanism to protect against age-related stress. We suggest that stress response in WRNexoΔ is multifaceted and evokes a systemic physiological response to protect against cellular damage. These data further validate WRNexoΔ flies as a WS model with which to study mechanisms of early aging and provide a foundation for development of treatments for WS and similar diseases.
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Affiliation(s)
- Derek G. Epiney
- Department of Biology, Northeastern Illinois University, Chicago, IL 60625, USA; (D.G.E.); (C.S.); (D.C.); (L.T.Z.); (J.K.); (R.M.); (A.E.S.)
| | - Charlotte Salameh
- Department of Biology, Northeastern Illinois University, Chicago, IL 60625, USA; (D.G.E.); (C.S.); (D.C.); (L.T.Z.); (J.K.); (R.M.); (A.E.S.)
| | - Deirdre Cassidy
- Department of Biology, Northeastern Illinois University, Chicago, IL 60625, USA; (D.G.E.); (C.S.); (D.C.); (L.T.Z.); (J.K.); (R.M.); (A.E.S.)
| | - Luhan T. Zhou
- Department of Biology, Northeastern Illinois University, Chicago, IL 60625, USA; (D.G.E.); (C.S.); (D.C.); (L.T.Z.); (J.K.); (R.M.); (A.E.S.)
| | - Joshua Kruithof
- Department of Biology, Northeastern Illinois University, Chicago, IL 60625, USA; (D.G.E.); (C.S.); (D.C.); (L.T.Z.); (J.K.); (R.M.); (A.E.S.)
| | - Rolan Milutinović
- Department of Biology, Northeastern Illinois University, Chicago, IL 60625, USA; (D.G.E.); (C.S.); (D.C.); (L.T.Z.); (J.K.); (R.M.); (A.E.S.)
| | - Tomas S. Andreani
- Department of Neurobiology, Northwestern University, Evanston, IL 60208, USA;
| | - Aaron E. Schirmer
- Department of Biology, Northeastern Illinois University, Chicago, IL 60625, USA; (D.G.E.); (C.S.); (D.C.); (L.T.Z.); (J.K.); (R.M.); (A.E.S.)
| | - Elyse Bolterstein
- Department of Biology, Northeastern Illinois University, Chicago, IL 60625, USA; (D.G.E.); (C.S.); (D.C.); (L.T.Z.); (J.K.); (R.M.); (A.E.S.)
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6
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Suzuki T, Masuda H, Mori M, Ito R, Kamiya H. Action-at-a-distance mutations at 5'-GpA-3' sites induced by oxidized guanine in WRN-knockdown cells. Mutagenesis 2021; 36:349-357. [PMID: 34272950 DOI: 10.1093/mutage/geab027] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 07/16/2021] [Indexed: 12/14/2022] Open
Abstract
G:C sites distant from 8-oxo-7,8-dihydroguanine (G O, 8-hydroxyguanine) are frequently mutated when the lesion-bearing plasmid DNA is replicated in human cells with reduced Werner syndrome (WRN) protein. To detect the untargeted mutations preferentially, the oxidized guanine base was placed downstream of the reporter supF gene and the plasmid DNA was introduced into WRN-knockdown cells. The total mutant frequency seemed higher in the WRN-knockdown cells as compared to the control cells. Mutation analyses revealed that substitution mutations occurred at the G:C pairs of 5'-GpA-3'/5'-TpC-3' sites, the preferred sequence for the apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3 (APOBEC3)-family cytosine deaminases, in the supF gene in both control and knockdown cells. These mutations were observed more frequently at G sites than C sites on the DNA strand where the G O base was originally located. This tendency was promoted by the knockdown of the WRN protein. The present results imply the possible involvement of APOBEC3-family cytosine deaminases in the action-at-a-distance (untargeted) mutations at G:C (or G) sites induced by G O and in cancer initiation by oxidative stress.
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Affiliation(s)
- Tetsuya Suzuki
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
| | - Hiroshi Masuda
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
| | - Madoka Mori
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
| | - Rikako Ito
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
| | - Hiroyuki Kamiya
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Kasumi, Minami-ku, Hiroshima, Japan
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Das T, Pal S, Ganguly A. Human RecQ helicases in transcription-associated stress management: bridging the gap between DNA and RNA metabolism. Biol Chem 2021; 402:617-636. [PMID: 33567180 DOI: 10.1515/hsz-2020-0324] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 01/24/2021] [Indexed: 12/13/2022]
Abstract
RecQ helicases are a highly conserved class of DNA helicases that play crucial role in almost all DNA metabolic processes including replication, repair and recombination. They are able to unwind a wide variety of complex intermediate DNA structures that may result from cellular DNA transactions and hence assist in maintaining genome integrity. Interestingly, a huge number of recent reports suggest that many of the RecQ family helicases are directly or indirectly involved in regulating transcription and gene expression. On one hand, they can remove complex structures like R-loops, G-quadruplexes or RNA:DNA hybrids formed at the intersection of transcription and replication. On the other hand, emerging evidence suggests that they can also regulate transcription by directly interacting with RNA polymerase or recruiting other protein factors that may regulate transcription. This review summarizes the up to date knowledge on the involvement of three human RecQ family proteins BLM, WRN and RECQL5 in transcription regulation and management of transcription associated stress.
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Affiliation(s)
- Tulika Das
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur721302, India
| | - Surasree Pal
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur721302, India
| | - Agneyo Ganguly
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur721302, India
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8
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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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9
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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: 43] [Impact Index Per Article: 10.8] [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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10
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Gupta SV, Schmidt KH. Maintenance of Yeast Genome Integrity by RecQ Family DNA Helicases. Genes (Basel) 2020; 11:E205. [PMID: 32085395 PMCID: PMC7074392 DOI: 10.3390/genes11020205] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 02/11/2020] [Accepted: 02/14/2020] [Indexed: 12/28/2022] Open
Abstract
With roles in DNA repair, recombination, replication and transcription, members of the RecQ DNA helicase family maintain genome integrity from bacteria to mammals. Mutations in human RecQ helicases BLM, WRN and RecQL4 cause incurable disorders characterized by genome instability, increased cancer predisposition and premature adult-onset aging. Yeast cells lacking the RecQ helicase Sgs1 share many of the cellular defects of human cells lacking BLM, including hypersensitivity to DNA damaging agents and replication stress, shortened lifespan, genome instability and mitotic hyper-recombination, making them invaluable model systems for elucidating eukaryotic RecQ helicase function. Yeast and human RecQ helicases have common DNA substrates and domain structures and share similar physical interaction partners. Here, we review the major cellular functions of the yeast RecQ helicases Sgs1 of Saccharomyces cerevisiae and Rqh1 of Schizosaccharomyces pombe and provide an outlook on some of the outstanding questions in the field.
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Affiliation(s)
- Sonia Vidushi Gupta
- Department of Cell Biology, Microbiology and Molecular Biology, University of South, Florida, Tampa, FL 33620, USA;
| | - Kristina Hildegard Schmidt
- Department of Cell Biology, Microbiology and Molecular Biology, University of South, Florida, Tampa, FL 33620, USA;
- Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research, Institute, Tampa, FL 33612, USA
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11
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Xu H, Shi R, Han W, Cheng J, Xu X, Cheng K, Wang L, Tian B, Zheng L, Shen B, Hua Y, Zhao Y. Structural basis of 5' flap recognition and protein-protein interactions of human flap endonuclease 1. Nucleic Acids Res 2019; 46:11315-11325. [PMID: 30295841 PMCID: PMC6265464 DOI: 10.1093/nar/gky911] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 10/06/2018] [Indexed: 01/30/2023] Open
Abstract
Human flap endonuclease 1 (hFEN1) is a structure-specific nuclease essential for DNA replication and repair processes. hFEN1 has 5′ flap removal activity, as well as gap endonuclease activity that is critical for restarting stalled replication forks. Here, we report the crystal structures of wild-type and mutant hFEN1 proteins in complex with DNA substrates, followed by mutagenesis studies that provide mechanistic insight into the protein–protein interactions of hFEN1. We found that in an α-helix forming the helical gateway of hFEN1 recognizes the 5′ flap prior to its threading into the active site for cleavage. We also found that the β-pin region is rigidified into a short helix in R192F hFEN1–DNA structures, suppressing its gap endonuclease activity and cycle-dependent kinase interactions. Our findings suggest that a single mutation at the primary methylation site can alter the function of hFEN1 and provide insight into the role of the β-pin region in hFEN1 protein interactions that are essential for DNA replication and repair.
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Affiliation(s)
- Hong Xu
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, China
| | - Rongyi Shi
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, China
| | - Wanchun Han
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, China
| | - Jiahui Cheng
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, China
| | - Xiaoli Xu
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, China
| | - Kaiying Cheng
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, China
| | - Liangyan Wang
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, China
| | - Bing Tian
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, China
| | - Li Zheng
- Department of Cancer Genetics and Epigenetics, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA 91010, USA
| | - Binghui Shen
- Department of Cancer Genetics and Epigenetics, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA 91010, USA
| | - Yuejin Hua
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, China
| | - Ye Zhao
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, China
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12
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Acetylation of Werner protein at K1127 and K1117 is important for nuclear trafficking and DNA repair. DNA Repair (Amst) 2019; 79:22-31. [PMID: 31085421 DOI: 10.1016/j.dnarep.2019.04.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Revised: 03/28/2019] [Accepted: 04/24/2019] [Indexed: 11/20/2022]
Abstract
Werner syndrome is a rare autosomal recessive disorder where Werner (WRN) gene is mutated. Being a nucleolar protein, during DNA damage, WRN translocates at the damage site where its catalytic function is required in DNA repair. Several studies have indicated that WRN acetylation may modulate WRN trafficking and catalytic function (Blander et al., 2002; Lozada et al., 2014). Among the six acetylation sites in WRN protein identified by mass-spectrometry analysis (Li et al., 2010) we here explore the role of acetylation sites in C-terminal of WRN (K1127, K1117, K1389, K1413) because the C- terminal domain is the hub for protein- protein interaction and DNA binding activity (Brosh et al. [4]; Muftuoglu et al., 2008; Huang et al., 2006). To explore their functional activity, we created mutations in these sites by changing the acetylation residue lysine (K) to a non-acetylation residue arginine (R) and expressed them in WRN mutant cell lines. We observed that K1127R and K1117R mutants are sensitive to the DNA damaging agents etoposide and mitomycin C and display deficient DNA repair. Importantly, deacetylation of WRN by SIRT1 (Mammalian Sir2) is necessary for restoration of WRN localization at nucleoli after completion of DNA repair. Among all putative acetylation sites, K1127R, K1117R and the double mutant K1127R/K1117R showed significantly delayed re-entry to the nucleolus after damage recovery, even when SIRT1 is overexpressed. These mutants showed partial interaction with SIRT1 compared to WT WRN. Thus, our results suggest that K1127 and K1117 are the major sites of acetylation, necessary for DNA repair. These results elucidate the mechanism by which SIRT1 regulates WRN trafficking via these acetylation sites during DNA damage.
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13
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Sommers JA, Kulikowicz T, Croteau DL, Dexheimer T, Dorjsuren D, Jadhav A, Maloney DJ, Simeonov A, Bohr VA, Brosh RM. A high-throughput screen to identify novel small molecule inhibitors of the Werner Syndrome Helicase-Nuclease (WRN). PLoS One 2019; 14:e0210525. [PMID: 30625228 PMCID: PMC6326523 DOI: 10.1371/journal.pone.0210525] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 12/26/2018] [Indexed: 01/26/2023] Open
Abstract
Werner syndrome (WS), an autosomal recessive genetic disorder, displays accelerated clinical symptoms of aging leading to a mean lifespan less than 50 years. The WS helicase-nuclease (WRN) is involved in many important pathways including DNA replication, recombination and repair. Replicating cells are dependent on helicase activity, leading to the pursuit of human helicases as potential therapeutic targets for cancer treatment. Small molecule inhibitors of DNA helicases can be used to induce synthetic lethality, which attempts to target helicase-dependent compensatory DNA repair pathways in tumor cells that are already genetically deficient in a specific pathway of DNA repair. Alternatively, helicase inhibitors may be useful as tools to study the specialized roles of helicases in replication and DNA repair. In this study, approximately 350,000 small molecules were screened based on their ability to inhibit duplex DNA unwinding by a catalytically active WRN helicase domain fragment in a high-throughput fluorometric assay to discover new non-covalent small molecule inhibitors of the WRN helicase. Select compounds were screened to exclude ones that inhibited DNA unwinding by other helicases in the screen, bound non-specifically to DNA, acted as irreversible inhibitors, or possessed unfavorable chemical properties. Several compounds were tested for their ability to impair proliferation of cultured tumor cells. We observed that two of the newly identified WRN helicase inhibitors inhibited proliferation of cancer cells in a lineage-dependent manner. These studies represent the first high-throughput screen for WRN helicase inhibitors and the results have implications for anti-cancer strategies targeting WRN in different cancer cells and genetic backgrounds.
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Affiliation(s)
- Joshua A. Sommers
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Tomasz Kulikowicz
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Deborah L. Croteau
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Thomas Dexheimer
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, United States of America
| | - Dorjbal Dorjsuren
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, United States of America
| | - Ajit Jadhav
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, United States of America
| | - David J. Maloney
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, United States of America
| | - Anton Simeonov
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, United States of America
| | - Vilhelm A. Bohr
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Robert M. Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
- * E-mail:
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14
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Kim SM, Forsburg SL. Regulation of Structure-Specific Endonucleases in Replication Stress. Genes (Basel) 2018; 9:genes9120634. [PMID: 30558228 PMCID: PMC6316474 DOI: 10.3390/genes9120634] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 12/11/2018] [Accepted: 12/12/2018] [Indexed: 12/16/2022] Open
Abstract
Replication stress results in various forms of aberrant replication intermediates that need to be resolved for faithful chromosome segregation. Structure-specific endonucleases (SSEs) recognize DNA secondary structures rather than primary sequences and play key roles during DNA repair and replication stress. Holliday junction resolvase MUS81 (methyl methane sulfonate (MMS), and UV-sensitive protein 81) and XPF (xeroderma pigmentosum group F-complementing protein) are a subset of SSEs that resolve aberrant replication structures. To ensure genome stability and prevent unnecessary DNA breakage, these SSEs are tightly regulated by the cell cycle and replication checkpoints. We discuss the regulatory network that control activities of MUS81 and XPF and briefly mention other SSEs involved in the resolution of replication intermediates.
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Affiliation(s)
- Seong Min Kim
- Program in Molecular & Computational Biology, University of Southern California, Los Angeles, CA 90089, USA.
| | - Susan L Forsburg
- Program in Molecular & Computational Biology, University of Southern California, Los Angeles, CA 90089, USA.
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15
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Kamiya H, Makino T, Suzuki T, Kobayashi M, Matsuoka I. Mutations induced by 8-oxo-7,8-dihydroguanine in WRN- and DNA polymerase λ-double knockdown cells. Mutagenesis 2018; 33:301-310. [DOI: 10.1093/mutage/gey024] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Accepted: 08/07/2018] [Indexed: 11/14/2022] Open
Affiliation(s)
- Hiroyuki Kamiya
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Minami-ku, Hiroshima, Japan
- Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan
- College of Pharmaceutical Sciences, Matsuyama University, Matsuyama, Japan
| | - Tetsuaki Makino
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Minami-ku, Hiroshima, Japan
- Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan
| | - Tetsuya Suzuki
- Graduate School of Biomedical and Health Sciences, Hiroshima University, Minami-ku, Hiroshima, Japan
| | - Miwako Kobayashi
- College of Pharmaceutical Sciences, Matsuyama University, Matsuyama, Japan
| | - Ichiro Matsuoka
- College of Pharmaceutical Sciences, Matsuyama University, Matsuyama, Japan
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16
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Suzuki T, Kuramoto Y, Kamiya H. Reduction of Werner Syndrome Protein Enhances G:C → A:T Transition byO6-Methylguanine in Human Cells. Chem Res Toxicol 2018; 31:319-324. [DOI: 10.1021/acs.chemrestox.8b00009] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tetsuya Suzuki
- Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan
| | - Yoshie Kuramoto
- Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan
| | - Hiroyuki Kamiya
- Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan
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17
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Abstract
Accurate repair of DNA double-strand breaks (DSBs) is carried out by homologous recombination. In order to repair DNA breaks by the recombination pathway, the 5'-terminated DNA strand at DSB sites must be first nucleolytically processed to produce 3'-overhang. The process is termed DNA end resection and involves the interplay of several nuclease complexes. DNA end resection commits DSB repair to the recombination pathway including a process termed single-strand annealing, as resected DNA ends are generally nonligatable by the competing nonhomologous end-joining machinery. Biochemical reconstitution experiments provided invaluable mechanistic insights into the DNA end resection pathways. In this chapter, we describe preparation procedures of key proteins involved in DNA end resection in human cells, including the MRE11-RAD50-NBS1 complex, phosphorylated variant of CtIP, the DNA2 nuclease-helicase with its helicase partners Bloom (BLM) or Werner (WRN), as well as the single-stranded DNA-binding protein replication protein A. The availability of recombinant DNA end resection factors will help to further elucidate resection mechanisms and regulatory processes that may involve novel protein partners and posttranslational modifications.
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Affiliation(s)
- Roopesh Anand
- Institute for Research in Biomedicine, Università della Svizzera italiana, Bellinzona, Switzerland
| | - Cosimo Pinto
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Petr Cejka
- Institute for Research in Biomedicine, Università della Svizzera italiana, Bellinzona, Switzerland; Institute of Biochemistry, Swiss Federal Institute of Technology, Zurich, Switzerland.
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18
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RecQ and Fe-S helicases have unique roles in DNA metabolism dictated by their unwinding directionality, substrate specificity, and protein interactions. Biochem Soc Trans 2017; 46:77-95. [PMID: 29273621 DOI: 10.1042/bst20170044] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 11/15/2017] [Accepted: 11/17/2017] [Indexed: 12/11/2022]
Abstract
Helicases are molecular motors that play central roles in nucleic acid metabolism. Mutations in genes encoding DNA helicases of the RecQ and iron-sulfur (Fe-S) helicase families are linked to hereditary disorders characterized by chromosomal instabilities, highlighting the importance of these enzymes. Moreover, mono-allelic RecQ and Fe-S helicase mutations are associated with a broad spectrum of cancers. This review will discuss and contrast the specialized molecular functions and biological roles of RecQ and Fe-S helicases in DNA repair, the replication stress response, and the regulation of gene expression, laying a foundation for continued research in these important areas of study.
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19
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Telomeres, Aging and Exercise: Guilty by Association? Int J Mol Sci 2017; 18:ijms18122573. [PMID: 29186077 PMCID: PMC5751176 DOI: 10.3390/ijms18122573] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 11/24/2017] [Accepted: 11/25/2017] [Indexed: 02/07/2023] Open
Abstract
Telomeres are repetitive tandem DNA sequences that cap chromosomal ends protecting genomic DNA from enzymatic degradation. Telomeres progressively shorten with cellular replication and are therefore assumed to correlate with biological and chronological age. An expanding body of evidence suggests (i) a predictable inverse association between telomere length, aging and age-related diseases and (ii) a positive association between physical activity and telomere length. Both hypotheses have garnered tremendous research attention and broad consensus; however, the evidence for each proposition is inconsistent and equivocal at best. Telomere length does not meet the basic criteria for an aging biomarker and at least 50% of key studies fail to find associations with physical activity. In this review, we address the evidence in support and refutation of the putative associations between telomere length, aging and physical activity. We finish with a brief review of plausible mechanisms and potential future research directions.
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20
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Sun L, Nakajima S, Teng Y, Chen H, Yang L, Chen X, Gao B, Levine AS, Lan L. WRN is recruited to damaged telomeres via its RQC domain and tankyrase1-mediated poly-ADP-ribosylation of TRF1. Nucleic Acids Res 2017; 45:3844-3859. [PMID: 28158503 PMCID: PMC5397154 DOI: 10.1093/nar/gkx065] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 01/24/2017] [Indexed: 01/15/2023] Open
Abstract
Werner syndrome (WS) is a progeroid-like syndrome caused by WRN gene mutations. WS cells exhibit shorter telomere length compared to normal cells, but it is not fully understood how WRN deficiency leads directly to telomere dysfunction. By generating localized telomere-specific DNA damage in a real-time fashion and a dose-dependent manner, we found that the damage response of WRN at telomeres relies on its RQC domain, which is different from the canonical damage response at genomic sites via its HRDC domain. We showed that in addition to steady state telomere erosion, WRN depleted cells are also sensitive to telomeric damage. WRN responds to site-specific telomeric damage via its RQC domain, interacting at Lysine 1016 and Phenylalanine1037 with the N-terminal acidic domain of the telomere shelterin protein TRF1 and demonstrating a novel mechanism for WRN's role in telomere protection. We also found that tankyrase1-mediated poly-ADP-ribosylation of TRF1 is important for both the interaction between WRN and TRF1 and the damage recruitment of WRN to telomeres. Mutations of potential tankyrase1 ADP-ribosylation sites within the RGCADG motif of TRF1 strongly diminish the interaction with WRN and the damage response of WRN only at telomeres. Taken together, our results reveal a novel mechanism as to how WRN protects telomere integrity from damage and telomere erosion.
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Affiliation(s)
- Luxi Sun
- School of Medicine, Tsinghua University, No.1 Tsinghua Yuan, Haidian District, Beijing 100084, China.,University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 5117 Centre Avenue, Pittsburgh, PA 15213, USA.,Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 450 Technology Drive, 523 Bridgeside Point II, Pittsburgh, PA 15219, USA
| | - Satoshi Nakajima
- University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 5117 Centre Avenue, Pittsburgh, PA 15213, USA.,Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 450 Technology Drive, 523 Bridgeside Point II, Pittsburgh, PA 15219, USA
| | - Yaqun Teng
- School of Medicine, Tsinghua University, No.1 Tsinghua Yuan, Haidian District, Beijing 100084, China.,University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 5117 Centre Avenue, Pittsburgh, PA 15213, USA.,Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 450 Technology Drive, 523 Bridgeside Point II, Pittsburgh, PA 15219, USA
| | - Hao Chen
- School of Medicine, Tsinghua University, No.1 Tsinghua Yuan, Haidian District, Beijing 100084, China.,University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 5117 Centre Avenue, Pittsburgh, PA 15213, USA.,Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 450 Technology Drive, 523 Bridgeside Point II, Pittsburgh, PA 15219, USA
| | - Lu Yang
- School of Medicine, Tsinghua University, No.1 Tsinghua Yuan, Haidian District, Beijing 100084, China.,University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 5117 Centre Avenue, Pittsburgh, PA 15213, USA.,Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 450 Technology Drive, 523 Bridgeside Point II, Pittsburgh, PA 15219, USA
| | - Xiukai Chen
- University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 5117 Centre Avenue, Pittsburgh, PA 15213, USA.,Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 450 Technology Drive, 523 Bridgeside Point II, Pittsburgh, PA 15219, USA
| | - Boya Gao
- University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 5117 Centre Avenue, Pittsburgh, PA 15213, USA
| | - Arthur S Levine
- University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 5117 Centre Avenue, Pittsburgh, PA 15213, USA.,Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 450 Technology Drive, 523 Bridgeside Point II, Pittsburgh, PA 15219, USA
| | - Li Lan
- University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 5117 Centre Avenue, Pittsburgh, PA 15213, USA.,Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 450 Technology Drive, 523 Bridgeside Point II, Pittsburgh, PA 15219, USA
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21
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Crouch JD, Brosh RM. Mechanistic and biological considerations of oxidatively damaged DNA for helicase-dependent pathways of nucleic acid metabolism. Free Radic Biol Med 2017; 107:245-257. [PMID: 27884703 PMCID: PMC5440220 DOI: 10.1016/j.freeradbiomed.2016.11.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 11/11/2016] [Accepted: 11/13/2016] [Indexed: 12/21/2022]
Abstract
Cells are under constant assault from reactive oxygen species that occur endogenously or arise from environmental agents. An important consequence of such stress is the generation of oxidatively damaged DNA, which is represented by a wide range of non-helix distorting and helix-distorting bulkier lesions that potentially affect a number of pathways including replication and transcription; consequently DNA damage tolerance and repair pathways are elicited to help cells cope with the lesions. The cellular consequences and metabolism of oxidatively damaged DNA can be quite complex with a number of DNA metabolic proteins and pathways involved. Many of the responses to oxidative stress involve a specialized class of enzymes known as helicases, the topic of this review. Helicases are molecular motors that convert the energy of nucleoside triphosphate hydrolysis to unwinding of structured polynucleic acids. Helicases by their very nature play fundamentally important roles in DNA metabolism and are implicated in processes that suppress chromosomal instability, genetic disease, cancer, and aging. We will discuss the roles of helicases in response to nuclear and mitochondrial oxidative stress and how this important class of enzymes help cells cope with oxidatively generated DNA damage through their functions in the replication stress response, DNA repair, and transcriptional regulation.
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Affiliation(s)
- Jack D Crouch
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, 251 Bayview Blvd, Baltimore, MD 21224, USA
| | - Robert M Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, 251 Bayview Blvd, Baltimore, MD 21224, USA.
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22
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Dehé PM, Gaillard PHL. Control of structure-specific endonucleases to maintain genome stability. Nat Rev Mol Cell Biol 2017; 18:315-330. [PMID: 28327556 DOI: 10.1038/nrm.2016.177] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Structure-specific endonucleases (SSEs) have key roles in DNA replication, recombination and repair, and emerging roles in transcription. These enzymes have specificity for DNA secondary structure rather than for sequence, and therefore their activity must be precisely controlled to ensure genome stability. In this Review, we discuss how SSEs are controlled as part of genome maintenance pathways in eukaryotes, with an emphasis on the elaborate mechanisms that regulate the members of the major SSE families - including the xeroderma pigmentosum group F-complementing protein (XPF) and MMS and UV-sensitive protein 81 (MUS81)-dependent nucleases, and the flap endonuclease 1 (FEN1), XPG and XPG-like endonuclease 1 (GEN1) enzymes - during processes such as DNA adduct repair, Holliday junction processing and replication stress. We also discuss newly characterized connections between SSEs and other classes of DNA-remodelling enzymes and cell cycle control machineries, which reveal the importance of SSE scaffolds such as the synthetic lethal of unknown function 4 (SLX4) tumour suppressor for the maintenance of genome stability.
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Affiliation(s)
- Pierre-Marie Dehé
- Centre de Recherche en Cancérologie de Marseille, CRCM, CNRS, Aix Marseille Université, INSERM, Institut Paoli-Calmettes, 27 Boulevard Leï Roure, 13009 Marseille, France
| | - Pierre-Henri L Gaillard
- Centre de Recherche en Cancérologie de Marseille, CRCM, CNRS, Aix Marseille Université, INSERM, Institut Paoli-Calmettes, 27 Boulevard Leï Roure, 13009 Marseille, France
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23
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The Werner Syndrome Helicase Coordinates Sequential Strand Displacement and FEN1-Mediated Flap Cleavage during Polymerase δ Elongation. Mol Cell Biol 2017; 37:MCB.00560-16. [PMID: 27849570 DOI: 10.1128/mcb.00560-16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 11/08/2016] [Indexed: 02/01/2023] Open
Abstract
The Werner syndrome protein (WRN) suppresses the loss of telomeres replicated by lagging-strand synthesis by a yet to be defined mechanism. Here, we show that whereas either WRN or the Bloom syndrome helicase (BLM) stimulates DNA polymerase δ progression across telomeric G-rich repeats, only WRN promotes sequential strand displacement synthesis and FEN1 cleavage, a critical step in Okazaki fragment maturation, at these sequences. Helicase activity, as well as the conserved winged-helix (WH) motif and the helicase and RNase D C-terminal (HRDC) domain play important but distinct roles in this process. Remarkably, WRN also influences the formation of FEN1 cleavage products during strand displacement on a nontelomeric substrate, suggesting that WRN recruitment and cooperative interaction with FEN1 during lagging-strand synthesis may serve to regulate sequential strand displacement and flap cleavage at other genomic sites. These findings define a biochemical context for the physiological role of WRN in maintaining genetic stability.
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24
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Bloom's syndrome: Why not premature aging?: A comparison of the BLM and WRN helicases. Ageing Res Rev 2017; 33:36-51. [PMID: 27238185 DOI: 10.1016/j.arr.2016.05.010] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 05/17/2016] [Accepted: 05/19/2016] [Indexed: 01/19/2023]
Abstract
Genomic instability is a hallmark of cancer and aging. Premature aging (progeroid) syndromes are often caused by mutations in genes whose function is to ensure genomic integrity. The RecQ family of DNA helicases is highly conserved and plays crucial roles as genome caretakers. In humans, mutations in three RecQ genes - BLM, WRN, and RECQL4 - give rise to Bloom's syndrome (BS), Werner syndrome (WS), and Rothmund-Thomson syndrome (RTS), respectively. WS is a prototypic premature aging disorder; however, the clinical features present in BS and RTS do not indicate accelerated aging. The BLM helicase has pivotal functions at the crossroads of DNA replication, recombination, and repair. BS cells exhibit a characteristic form of genomic instability that includes excessive homologous recombination. The excessive homologous recombination drives the development in BS of the many types of cancers that affect persons in the normal population. Replication delay and slower cell turnover rates have been proposed to explain many features of BS, such as short stature. More recently, aberrant transcriptional regulation of growth and survival genes has been proposed as a hypothesis to explain features of BS.
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25
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Targeted inhibition of WRN helicase, replication stress and cancer. Biochim Biophys Acta Rev Cancer 2016; 1867:42-48. [PMID: 27902925 DOI: 10.1016/j.bbcan.2016.11.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 11/16/2016] [Accepted: 11/24/2016] [Indexed: 11/21/2022]
Abstract
WRN helicase has several roles in genome maintenance, such as replication, base excision repair, recombination, DNA damage response and transcription. These processes are often found upregulated in human cancers, many of which display increased levels of WRN. Therefore, directed inhibition of this RecQ helicase could be beneficial to selective cancer therapy. Inhibition of WRN is feasible by the use of small-molecule inhibitors or application of RNA interference and EGS/RNase P targeting systems. Remarkably, helicase depletion leads to a severe reduction in cell viability due to mitotic catastrophe, which is triggered by replication stress induced by DNA repair failure and fork progression arrest. Moreover, we present new evidence that WRN depletion results in early changes of RNA polymerase III and RNase P activities, thereby implicating chromatin-associated tRNA enzymes in WRN-related stress response. Combined with the recently discovered roles of RecQ helicases in cancer, current data support the targeting prospect of these genome guardians, as a means of developing clinical phases aimed at diminishing adaptive resistance to present targeted therapies.
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26
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Zhou L, Dai H, Wu J, Zhou M, Yuan H, Du J, Yang L, Wu X, Xu H, Hua Y, Xu J, Zheng L, Shen B. Role of FEN1 S187 phosphorylation in counteracting oxygen-induced stress and regulating postnatal heart development. FASEB J 2016; 31:132-147. [PMID: 27694478 DOI: 10.1096/fj.201600631r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 09/16/2016] [Indexed: 12/22/2022]
Abstract
Flap endonuclease 1 (FEN1) phosphorylation is proposed to regulate the action of FEN1 in DNA repair as well as Okazaki fragment maturation. However, the biologic significance of FEN1 phosphorylation in response to DNA damage remains unknown. Here, we report an in vivo role for FEN1 phosphorylation, using a mouse line carrying S187A FEN1, which abolishes FEN1 phosphorylation. Although S187A mouse embryonic fibroblast cells showed normal proliferation under low oxygen levels (2%), the mutant cells accumulated oxidative DNA damage, activated DNA damage checkpoints, and showed G1-phase arrest at atmospheric oxygen levels (21%). This suggests an essential role for FEN1 phosphorylation in repairing oxygen-induced DNA damage and maintaining proper cell cycle progression. Consistently, the mutant cardiomyocytes showed G1-phase arrest due to activation of the p53-mediated DNA damage response at the neonatal stage, which reduces the proliferation potential of the cardiomyocytes and impairs heart development. Nearly 50% of newborns with the S187A mutant died in the first week due to failure to undergo the peroxisome proliferator-activated receptor signaling-dependent switch from glycolysis to fatty acid oxidation. The adult mutant mice developed dilated hearts and showed significantly shorter life spans. Altogether, our results reveal an important role of FEN1 phosphorylation to counteract oxygen-induced stress in the heart during the fetal-to-neonatal transition.-Zhou, L., Dai, H., Wu, J., Zhou, M., Yuan, H., Du, J., Yang, L., Wu, X., Xu, H., Hua, Y., Xu, J., Zheng, L., Shen, B. Role of FEN1 S187 phosphorylation in counteracting oxygen-induced stress and regulating postnatal heart development.
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Affiliation(s)
- Lina Zhou
- College of Life Sciences and Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China.,Department of Cancer Genetics and Epigenetics and Beckman Research Institute of City of Hope, Duarte, California, USA
| | - Huifang Dai
- Department of Cancer Genetics and Epigenetics and Beckman Research Institute of City of Hope, Duarte, California, USA
| | - Jian Wu
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, USA
| | - Mian Zhou
- Department of Cancer Genetics and Epigenetics and Beckman Research Institute of City of Hope, Duarte, California, USA
| | - Hua Yuan
- Department of Diagnostic Ultrasound, Shaoxing Women and Children's Hospital, Shaoxing, China
| | - Juan Du
- Department of Cancer Genetics and Epigenetics and Beckman Research Institute of City of Hope, Duarte, California, USA
| | - Lu Yang
- Department of Molecular and Cellular Biology, Beckman Research Institute of City of Hope, Duarte, California, USA; and
| | - Xiwei Wu
- Department of Molecular and Cellular Biology, Beckman Research Institute of City of Hope, Duarte, California, USA; and
| | - Hong Xu
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China
| | - Yuejin Hua
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China
| | - Jian Xu
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, USA
| | - Li Zheng
- Department of Cancer Genetics and Epigenetics and Beckman Research Institute of City of Hope, Duarte, California, USA;
| | - Binghui Shen
- Department of Cancer Genetics and Epigenetics and Beckman Research Institute of City of Hope, Duarte, California, USA;
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27
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Cheng IC, Chen BC, Shuai HH, Chien FC, Chen P, Hsieh TS. Wuho Is a New Member in Maintaining Genome Stability through its Interaction with Flap Endonuclease 1. PLoS Biol 2016; 14:e1002349. [PMID: 26751069 PMCID: PMC4709127 DOI: 10.1371/journal.pbio.1002349] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 12/04/2015] [Indexed: 11/18/2022] Open
Abstract
Replication forks are vulnerable to wayward nuclease activities. We report here our discovery of a new member in guarding genome stability at replication forks. We previously isolated a Drosophila mutation, wuho (wh, no progeny), characterized by a severe fertility defect and affecting expression of a protein (WH) in a family of conserved proteins with multiple WD40 repeats. Knockdown of WH by siRNA in Drosophila, mouse, and human cultured cells results in DNA damage with strand breaks and apoptosis through ATM/Chk2/p53 signaling pathway. Mice with mWh knockout are early embryonic lethal and display DNA damage. We identify that the flap endonuclease 1 (FEN1) is one of the interacting proteins. Fluorescence microscopy showed the localization of WH at the site of nascent DNA synthesis along with other replication proteins, including FEN1 and PCNA. We show that WH is able to modulate FEN1's endonucleolytic activities depending on the substrate DNA structure. The stimulatory or inhibitory effects of WH on FEN1's flap versus gap endonuclease activities are consistent with the proposed WH's functions in protecting the integrity of replication fork. These results suggest that wh is a new member of the guardians of genome stability because it regulates FEN1's potential DNA cleavage threat near the site of replication.
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Affiliation(s)
- I-Cheng Cheng
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Betty Chamay Chen
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Hung-Hsun Shuai
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Fan-Ching Chien
- Department of Optics and Photonics, National Central University, Chung-Li, Taiwan
| | - Peilin Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Tao-shih Hsieh
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan.,Department of Biochemistry, Duke University, Durham, North Carolina, United States of America
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RECQL5 has unique strand annealing properties relative to the other human RecQ helicase proteins. DNA Repair (Amst) 2015; 37:53-66. [PMID: 26717024 DOI: 10.1016/j.dnarep.2015.11.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 11/21/2015] [Accepted: 11/24/2015] [Indexed: 11/24/2022]
Abstract
The RecQ helicases play important roles in genome maintenance and DNA metabolism (replication, recombination, repair, and transcription). Five different homologs are present in humans, three of which are implicated in accelerated aging genetic disorders: Rothmund Thomson (RECQL4), Werner (WRN), and Bloom (BLM) syndromes. While the DNA helicase activities of the 5 human RecQ helicases have been extensively characterized, much less is known about their DNA double strand annealing activities. Strand annealing is an important integral enzymatic activity in DNA metabolism, including DNA repair. Here, we have characterized the strand annealing activities of all five human RecQ helicase proteins and compared them. Interestingly, the relative strand annealing activities of the five RecQ proteins are not directly (inversely) related to their helicase activities. RECQL5 possesses relatively strong annealing activity on long or small duplexed substrates compared to the other RecQs. Additionally, the strand annealing activity of RECQL5 is not inhibited by the presence of ATP, unlike the other RecQs. We also show that RECQL5 efficiently catalyzes annealing of RNA to DNA in vitro in the presence or absence of ATP, revealing a possible new function for RECQL5. Additionally, we investigate how different known RecQ interacting proteins, RPA, Ku, FEN1 and RAD51, regulate their strand annealing activity. Collectively, we find that the human RecQ proteins possess differential DNA double strand annealing activities and we speculate on their individual roles in DNA repair. This insight is important in view of the many cellular DNA metabolic actions of the RecQ proteins and elucidates their unique functions in the cell.
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29
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RecQ helicases and PARP1 team up in maintaining genome integrity. Ageing Res Rev 2015; 23:12-28. [PMID: 25555679 DOI: 10.1016/j.arr.2014.12.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Revised: 12/18/2014] [Accepted: 12/22/2014] [Indexed: 01/04/2023]
Abstract
Genome instability represents a primary hallmark of aging and cancer. RecQL helicases (i.e., RECQL1, WRN, BLM, RECQL4, RECQL5) as well as poly(ADP-ribose) polymerases (PARPs, in particular PARP1) represent two central quality control systems to preserve genome integrity in mammalian cells. Consistently, both enzymatic families have been linked to mechanisms of aging and carcinogenesis in mice and humans. This is in accordance with clinical and epidemiological findings demonstrating that defects in three RecQL helicases, i.e., WRN, BLM, RECQL4, are related to human progeroid and cancer predisposition syndromes, i.e., Werner, Bloom, and Rothmund Thomson syndrome, respectively. Moreover, PARP1 hypomorphy is associated with a higher risk for certain types of cancer. On a molecular level, RecQL helicases and PARP1 are involved in the control of DNA repair, telomere maintenance, and replicative stress. Notably, over the last decade, it became apparent that all five RecQL helicases physically or functionally interact with PARP1 and/or its enzymatic product poly(ADP-ribose) (PAR). Furthermore, a profound body of evidence revealed that the cooperative function of RECQLs and PARP1 represents an important factor for maintaining genome integrity. In this review, we summarize the status quo of this molecular cooperation and discuss open questions that provide a basis for future studies to dissect the cooperative functions of RecQL helicases and PARP1 in aging and carcinogenesis.
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30
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Abstract
RecQ helicases are a family of highly conserved proteins that maintain genomic stability through their important roles in replication restart mechanisms. Cellular phenotypes of RECQ1 deficiency are indicative of aberrant repair of stalled replication forks, but the molecular functions of RECQ1, the most abundant of the five known human RecQ homologues, have remained poorly understood. We show that RECQ1 associates with FEN-1 (flap endonuclease-1) in nuclear extracts and exhibits direct protein interaction in vitro. Recombinant RECQ1 significantly stimulated FEN-1 endonucleolytic cleavage of 5'-flap DNA substrates containing non-telomeric or telomeric repeat sequence. RECQ1 and FEN-1 were constitutively present at telomeres and their binding to the telomeric chromatin was enhanced following DNA damage. Telomere residence of FEN-1 was dependent on RECQ1 since depletion of RECQ1 reduced FEN-1 binding to telomeres in unperturbed cycling cells. Our results confirm a conserved collaboration of human RecQ helicases with FEN-1 and suggest both overlapping and specialized roles of RECQ1 in the processing of DNA structure intermediates proposed to arise during replication, repair and recombination.
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31
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Kamiya H, Yamazaki D, Nakamura E, Makino T, Kobayashi M, Matsuoka I, Harashima H. Action-at-a-Distance Mutagenesis Induced by Oxidized Guanine in Werner Syndrome Protein-Reduced Human Cells. Chem Res Toxicol 2015; 28:621-8. [DOI: 10.1021/tx500418m] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Hiroyuki Kamiya
- Faculty
of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan
- Graduate
School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan
- College
of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama 790-8578, Japan
- Graduate
School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan
| | - Daiki Yamazaki
- Faculty
of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan
| | - Eri Nakamura
- Graduate
School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan
| | - Tetsuaki Makino
- Graduate
School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan
- Graduate
School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan
| | - Miwako Kobayashi
- College
of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama 790-8578, Japan
| | - Ichiro Matsuoka
- College
of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama 790-8578, Japan
| | - Hideyoshi Harashima
- Faculty
of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan
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Kusumoto-Matsuo R, Ghosh D, Karmakar P, May A, Ramsden D, Bohr VA. Serines 440 and 467 in the Werner syndrome protein are phosphorylated by DNA-PK and affects its dynamics in response to DNA double strand breaks. Aging (Albany NY) 2014; 6:70-81. [PMID: 24429382 PMCID: PMC3927811 DOI: 10.18632/aging.100629] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
WRN protein, defective in Werner syndrome (WS), a human segmental progeria, is a target of serine/threonine kinases involved in sensing DNA damage. DNA-PK phosphorylates WRN in response to DNA double strand breaks (DSBs). However, the main phosphorylation sites and functional importance of the phosphorylation of WRN has remained unclear. Here, we identify Ser-440 and -467 in WRN as major phosphorylation sites mediated by DNA-PK.In vitro, DNA-PK fails to phosphorylate a GST-WRN fragment with S440A and/or S467A substitution. In addition, full length WRN with the mutation expressed in 293T cells was not phosphorylated in response to DSBs produced by bleomycin. Accumulation of the mutant WRN at the site of laser-induced DSBs occurred with the same kinetics as wild type WRN in live HeLa cells. While the wild type WRN relocalized to the nucleoli after 24 hours recovery from etoposide-induced DSBs, the mutant WRN remained mostly in the nucleoplasm. Consistent with this, WS cells expressing the mutants exhibited less DNA repair efficiency and more sensitivity to etoposide, compared to those expressing wild type. Our findings indicate that phosphorylation of Ser-440 and -467 in WRN are important for relocalization of WRN to nucleoli, and that it is required for efficient DSB repair.
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Affiliation(s)
- Rika Kusumoto-Matsuo
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, Baltimore, MD 21224, USA
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33
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Jung H, Lee JA, Choi S, Lee H, Ahn B. Characterization of the Caenorhabditis elegans HIM-6/BLM helicase: unwinding recombination intermediates. PLoS One 2014; 9:e102402. [PMID: 25036527 PMCID: PMC4103807 DOI: 10.1371/journal.pone.0102402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 06/12/2014] [Indexed: 02/02/2023] Open
Abstract
Mutations in three human RecQ genes are implicated in heritable human syndromes. Mutations in BLM, a RecQ gene, cause Bloom syndrome (BS), which is characterized by short stature, cancer predisposition, and sensitivity to sunlight. BLM is a RecQ DNA helicase that, with interacting proteins, is able to dissolve various DNA structures including double Holliday junctions. A BLM ortholog, him-6, has been identified in Caenorhabditis elegans, but little is known about its enzymatic activities or its in vivo roles. By purifying recombinant HIM-6 and performing biochemical assays, we determined that the HIM-6 has DNA-dependent ATPase activity HIM-6 and helicase activity that proceeds in the 3'-5' direction and needs at least five 3' overhanging nucleotides. HIM-6 is also able to unwind DNA structures including D-loops and Holliday junctions. Worms with him-6 mutations were defective in recovering the cell cycle arrest after HU treatment. These activities strongly support in vivo roles for HIM-6 in processing recombination intermediates.
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Affiliation(s)
- Hana Jung
- Department of Life Sciences, University of Ulsan, Ulsan, Republic of Korea
| | - Jin A Lee
- Department of Life Sciences, University of Ulsan, Ulsan, Republic of Korea
| | - Seoyoon Choi
- Department of Life Sciences, University of Ulsan, Ulsan, Republic of Korea
| | - Hyunwoo Lee
- Department of Life Sciences, University of Ulsan, Ulsan, Republic of Korea
| | - Byungchan Ahn
- Department of Life Sciences, University of Ulsan, Ulsan, Republic of Korea
- * E-mail:
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34
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León-Ortiz AM, Svendsen J, Boulton SJ. Metabolism of DNA secondary structures at the eukaryotic replication fork. DNA Repair (Amst) 2014; 19:152-62. [PMID: 24815912 DOI: 10.1016/j.dnarep.2014.03.016] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
DNA secondary structures are largely advantageous for numerous cellular processes but can pose specific threats to the progression of the replication machinery and therefore genome duplication and cell division. A number of specialized enzymes dismantle these structures to allow replication fork progression to proceed faithfully. In this review, we discuss the in vitro and in vivo data that has lead to the identification of these enzymes in eukaryotes, and the evidence that suggests that they act specifically at replication forks to resolve secondary structures. We focus on the role of helicases, which catalyze the dissociation of nucleotide complexes, and on the role of nucleases, which cleave secondary structures to allow replication fork progression at the expense of local rearrangements. Finally, we discuss outstanding questions in terms of dismantling DNA secondary structures, as well as the interplay between diverse enzymes that act upon specific types of structures.
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Affiliation(s)
- Ana María León-Ortiz
- DNA Damage Response Laboratory, London Research Institute, Cancer Research UK, Clare Hall, South Mimms EN6 3LD, UK
| | - Jennifer Svendsen
- DNA Damage Response Laboratory, London Research Institute, Cancer Research UK, Clare Hall, South Mimms EN6 3LD, UK
| | - Simon J Boulton
- DNA Damage Response Laboratory, London Research Institute, Cancer Research UK, Clare Hall, South Mimms EN6 3LD, UK.
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35
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Acetylation of Werner syndrome protein (WRN): relationships with DNA damage, DNA replication and DNA metabolic activities. Biogerontology 2014; 15:347-66. [PMID: 24965941 DOI: 10.1007/s10522-014-9506-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Accepted: 05/26/2014] [Indexed: 10/25/2022]
Abstract
Loss of Werner syndrome protein function causes Werner syndrome, characterized by increased genomic instability, elevated cancer susceptibility and premature aging. Although WRN is subject to acetylation, phosphorylation and sumoylation, the impact of these modifications on WRN's DNA metabolic function remains unclear. Here, we examined in further depth the relationship between WRN acetylation and its role in DNA metabolism, particularly in response to induced DNA damage. Our results demonstrate that endogenous WRN is acetylated somewhat under unperturbed conditions. However, levels of acetylated WRN significantly increase after treatment with certain DNA damaging agents or the replication inhibitor HU. Use of DNA repair-deficient cells or repair pathway inhibitors further increase levels of acetylated WRN, indicating that induced DNA lesions and their persistence are at least partly responsible for increased acetylation. Notably, acetylation of WRN correlates with inhibition of DNA synthesis, suggesting that replication blockage might underlie this effect. Moreover, WRN acetylation modulates its affinity for and activity on certain DNA structures, in a manner that may enhance its relative specificity for physiological substrates. Our results also show that acetylation and deacetylation of endogenous WRN is a dynamic process, with sirtuins and other histone deacetylases contributing to WRN deacetylation. These findings advance our understanding of the dynamics of WRN acetylation under unperturbed conditions and following DNA damage induction, linking this modification not only to DNA damage persistence but also potentially to replication stalling caused by specific DNA lesions. Our results are consistent with proposed metabolic roles for WRN and genomic instability phenotypes associated with WRN deficiency.
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36
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Cheung HH, Liu X, Canterel-Thouennon L, Li L, Edmonson C, Rennert OM. Telomerase protects werner syndrome lineage-specific stem cells from premature aging. Stem Cell Reports 2014; 2:534-46. [PMID: 24749076 PMCID: PMC3986587 DOI: 10.1016/j.stemcr.2014.02.006] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 02/20/2014] [Accepted: 02/20/2014] [Indexed: 12/12/2022] Open
Abstract
Werner syndrome (WS) patients exhibit premature aging predominantly in mesenchyme-derived tissues, but not in neural lineages, a consequence of telomere dysfunction and accelerated senescence. The cause of this lineage-specific aging remains unknown. Here, we document that reprogramming of WS fibroblasts to pluripotency elongated telomere length and prevented telomere dysfunction. To obtain mechanistic insight into the origin of tissue-specific aging, we differentiated iPSCs to mesenchymal stem cells (MSCs) and neural stem/progenitor cells (NPCs). We observed recurrence of premature senescence associated with accelerated telomere attrition and defective synthesis of the lagging strand telomeres in MSCs, but not in NPCs. We postulate this “aging” discrepancy is regulated by telomerase. Expression of hTERT or p53 knockdown ameliorated the accelerated aging phenotypein MSC, whereas inhibition of telomerase sensitized NPCs to DNA damage. Our findings unveil a role for telomerase in the protection of accelerated aging in a specific lineage of stem cells. Prevention of premature senescence with corrected telomeres in reprogrammed WS iPSCs Recurrence of premature senescence and telomere dysfunction in WS iPSC-derived MSCs Rescue of premature senescence in WS MSCs by hTERT overexpression or p53 depletion Telomerase protects and prevents NPCs from DNA damage
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Affiliation(s)
- Hoi-Hung Cheung
- Laboratory of Clinical and Developmental Genomics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA ; School of Biomedical Sciences, Faculty of Medicine, the Chinese University of Hong Kong, Shatin, N.T., 852 Hong Kong S.A.R
| | - Xiaozhuo Liu
- Laboratory of Clinical and Developmental Genomics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA ; School of Biomedical Sciences, Faculty of Medicine, the Chinese University of Hong Kong, Shatin, N.T., 852 Hong Kong S.A.R
| | - Lucile Canterel-Thouennon
- Laboratory of Clinical and Developmental Genomics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Lu Li
- School of Biomedical Sciences, Faculty of Medicine, the Chinese University of Hong Kong, Shatin, N.T., 852 Hong Kong S.A.R
| | - Catherine Edmonson
- Laboratory of Clinical and Developmental Genomics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Owen M Rennert
- Laboratory of Clinical and Developmental Genomics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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37
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Croteau DL, Popuri V, Opresko PL, Bohr VA. Human RecQ helicases in DNA repair, recombination, and replication. Annu Rev Biochem 2014; 83:519-52. [PMID: 24606147 DOI: 10.1146/annurev-biochem-060713-035428] [Citation(s) in RCA: 398] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
RecQ helicases are an important family of genome surveillance proteins conserved from bacteria to humans. Each of the five human RecQ helicases plays critical roles in genome maintenance and stability, and the RecQ protein family members are often referred to as guardians of the genome. The importance of these proteins in cellular homeostasis is underscored by the fact that defects in BLM, WRN, and RECQL4 are linked to distinct heritable human disease syndromes. Each human RecQ helicase has a unique set of protein-interacting partners, and these interactions dictate its specialized functions in genome maintenance, including DNA repair, recombination, replication, and transcription. Human RecQ helicases also interact with each other, and these interactions have significant impact on enzyme function. Future research goals in this field include a better understanding of the division of labor among the human RecQ helicases and learning how human RecQ helicases collaborate and cooperate to enhance genome stability.
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Affiliation(s)
- Deborah L Croteau
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, Maryland 21224;
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38
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Werner syndrome: association of premature aging and cancer predisposition. Mol Oncol 2013. [DOI: 10.1017/cbo9781139046947.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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39
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Abstract
Helicases have major roles in genome maintenance by unwinding structured nucleic acids. Their prominence is marked by various cancers and genetic disorders that are linked to helicase defects. Although considerable effort has been made to understand the functions of DNA helicases that are important for genomic stability and cellular homeostasis, the complexity of the DNA damage response leaves us with unanswered questions regarding how helicase-dependent DNA repair pathways are regulated and coordinated with cell cycle checkpoints. Further studies may open the door to targeting helicases in order to improve cancer treatments based on DNA-damaging chemotherapy or radiation.
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Affiliation(s)
- Robert M Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, 251 Bayview Boulevard, Baltimore, Maryland 21224, USA.
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40
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Prereplicative repair of oxidized bases in the human genome is mediated by NEIL1 DNA glycosylase together with replication proteins. Proc Natl Acad Sci U S A 2013; 110:E3090-9. [PMID: 23898192 DOI: 10.1073/pnas.1304231110] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Base oxidation by endogenous and environmentally induced reactive oxygen species preferentially occurs in replicating single-stranded templates in mammalian genomes, warranting prereplicative repair of the mutagenic base lesions. It is not clear how such lesions (which, unlike bulky adducts, do not block replication) are recognized for repair. Furthermore, strand breaks caused by base excision from ssDNA by DNA glycosylases, including Nei-like (NEIL) 1, would generate double-strand breaks during replication, which are not experimentally observed. NEIL1, whose deficiency causes a mutator phenotype and is activated during the S phase, is present in the DNA replication complex isolated from human cells, with enhanced association with DNA in S-phase cells and colocalization with replication foci containing DNA replication proteins. Furthermore, NEIL1 binds to 5-hydroxyuracil, the oxidative deamination product of C, in replication protein A-coated ssDNA template and inhibits DNA synthesis by DNA polymerase δ. We postulate that, upon encountering an oxidized base during replication, NEIL1 initiates prereplicative repair by acting as a "cowcatcher" and preventing nascent chain growth. Regression of the stalled replication fork, possibly mediated by annealing helicases, then allows lesion repair in the reannealed duplex. This model is supported by our observations that NEIL1, whose deficiency slows nascent chain growth in oxidatively stressed cells, is stimulated by replication proteins in vitro. Furthermore, deficiency of the closely related NEIL2 alone does not affect chain elongation, but combined NEIL1/2 deficiency further inhibits DNA replication. These results support a mechanism of NEIL1-mediated prereplicative repair of oxidized bases in the replicating strand, with NEIL2 providing a backup function.
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41
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Liu B, Yip RK, Zhou Z. Chromatin remodeling, DNA damage repair and aging. Curr Genomics 2013; 13:533-47. [PMID: 23633913 PMCID: PMC3468886 DOI: 10.2174/138920212803251373] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 06/19/2012] [Accepted: 07/25/2012] [Indexed: 01/26/2023] Open
Abstract
Cells are constantly exposed to a variety of environmental and endogenous conditions causing DNA damage, which is detected and repaired by conserved DNA repair pathways to maintain genomic integrity. Chromatin remodeling is critical in this process, as the organization of eukaryotic DNA into compact chromatin presents a natural barrier to all DNA-related events. Studies on human premature aging syndromes together with normal aging have suggested that accumulated damages might lead to exhaustion of resources that are required for physiological functions and thus accelerate aging. In this manuscript, combining the present understandings and latest findings, we focus mainly on discussing the role of chromatin remodeling in the repair of DNA double-strand breaks (DSBs) and regulation of aging.
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Affiliation(s)
- Baohua Liu
- Shenzhen Institute of Research and Innovation, The University of Hong Kong, Shenzhen, China ; Department of Biochemistry, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong
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42
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Tadokoro T, Rybanska-Spaeder I, Kulikowicz T, Dawut L, Oshima J, Croteau DL, Bohr VA. Functional deficit associated with a missense Werner syndrome mutation. DNA Repair (Amst) 2013; 12:414-21. [PMID: 23583337 DOI: 10.1016/j.dnarep.2013.03.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2013] [Revised: 03/15/2013] [Accepted: 03/19/2013] [Indexed: 12/23/2022]
Abstract
Werner syndrome (WS) is a rare autosomal recessive disorder caused by mutations in the WRN gene. WRN helicase, a member of the RecQ helicase family, is involved in various DNA metabolic pathways including DNA replication, recombination, DNA repair and telomere maintenance. In this study, we have characterized the G574R missense mutation, which was recently identified in a WS patient. Our biochemical experiments with purified mutant recombinant WRN protein showed that the G574R mutation inhibits ATP binding, and thereby leads to significant decrease in helicase activity. Exonuclease activity of the mutant protein was not significantly affected, whereas its single strand DNA annealing activity was higher than that of wild type. Deficiency in the helicase activity of the mutant may cause defects in replication and other DNA metabolic processes, which in turn could be responsible for the Werner syndrome phenotype in the patient. In contrast to the usual appearance of WS, the G574R patient has normal stature. Thus the short stature normally associated with WS may not be due to helicase deficiency.
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Affiliation(s)
- Takashi Tadokoro
- Laboratory of Molecular Gerontology, National Institute on Aging, 251 Bayview Blvd, Suite 100, Baltimore, MD 21224, USA
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Abstract
First discovered as a structure-specific endonuclease that evolved to cut at the base of single-stranded flaps, flap endonuclease (FEN1) is now recognized as a central component of cellular DNA metabolism. Substrate specificity allows FEN1 to process intermediates of Okazaki fragment maturation, long-patch base excision repair, telomere maintenance, and stalled replication fork rescue. For Okazaki fragments, the RNA primer is displaced into a 5' flap and then cleaved off. FEN1 binds to the flap base and then threads the 5' end of the flap through its helical arch and active site to create a configuration for cleavage. The threading requirement prevents this active nuclease from cutting the single-stranded template between Okazaki fragments. FEN1 efficiency and specificity are critical to the maintenance of genome fidelity. Overall, recent advances in our knowledge of FEN1 suggest that it was an ancient protein that has been fine-tuned over eons to coordinate many essential DNA transactions.
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Affiliation(s)
- Lata Balakrishnan
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
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44
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Tadokoro T, Kulikowicz T, Dawut L, Croteau DL, Bohr VA. DNA binding residues in the RQC domain of Werner protein are critical for its catalytic activities. Aging (Albany NY) 2013; 4:417-29. [PMID: 22713343 PMCID: PMC3409678 DOI: 10.18632/aging.100463] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Werner protein (WRN), member of the RecQ helicase family, is a helicase and exonuclease, and participates in multiple DNA metabolic processes including DNA replication, recombination and DNA repair. Mutations in the WRN gene cause Werner syndrome, associated with premature aging, genome instability and cancer predisposition. The RecQ C-terminal (RQC) domain of WRN, containing α2-α3 loop and β-wing motifs, is important for DNA binding and for many protein interactions. To better understand the critical functions of this domain, we generated recombinant WRN proteins (using a novel purification scheme) with mutations in Arg-993 within the α2-α3 loop of the RQC domain and in Phe-1037 of the -wing motif. We then studied the catalytic activities and DNA binding of these mutant proteins as well as some important functional protein interactions. The mutant proteins were defective in DNA binding and helicase activity, and interestingly, they had deficient exonuclease activity and strand annealing function. The RQC domain of WRN has not previously been implicated in exonuclease or annealing activities. The mutant proteins could not stimulate NEIL1 incision activity as did the wild type. Thus, the Arg-993 and Phe-1037 in the RQC domain play essential roles in catalytic activity, and in functional interactions mediated by WRN.
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Affiliation(s)
- Takashi Tadokoro
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD 21224, USA
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Recruitment of HRDC domain of WRN and BLM to the sites of DNA damage induced by mitomycin C and methyl methanesulfonate. Cell Biol Int 2013; 36:873-81. [PMID: 22657828 DOI: 10.1042/cbi20110510] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The HRDC (helicase and RNase D C-terminal) domain at the C-terminal of WRNp (Werner protein) (1150-1229 amino acids) and BLMp (Bloom protein) (1212-1292 amino acids) recognize laser microirradiation-induced DNA dsbs (double-strand breaks). However, their role in the recognition of DNA damage other than dsbs has not been reported. In this work, we show that HRDC domain of both the proteins can be recruited to the DNA damage induced by MMS (methyl methanesulfonate) and MMC (methyl mitomycin C). GFP (green fluorescent protein)-tagged HRDC domain produces distinct foci-like respective wild-types after DNA damage induced by the said agents and co-localize with γ-H2AX. However, in time course experiment, we observed that the foci of HRDC domain exist after 24 h of removal of the damaging agents, while the foci of full-length protein disappear completely. This indicates that the repair events are not completed by the presence of protein corresponding to only the HRDC domain. Consequently, cells overexpressing the HRDC domain fail to survive after DNA damage, as determined by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] assay. Moreover, 24 h after removal of damaging agents, the extent of DNA damage is greater in cells overexpressing HRDC domain compared with corresponding wild-types, as observed by comet assay. Thus, our observations suggest that HRDC domain of both WRN and BLM can also recognize different types of DNA damages, but for the successful repair they fail to respond to subsequent repair events.
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Mason PA, Cox LS. The role of DNA exonucleases in protecting genome stability and their impact on ageing. AGE (DORDRECHT, NETHERLANDS) 2012; 34:1317-1340. [PMID: 21948156 PMCID: PMC3528374 DOI: 10.1007/s11357-011-9306-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 08/19/2011] [Indexed: 05/30/2023]
Abstract
Exonucleases are key enzymes involved in many aspects of cellular metabolism and maintenance and are essential to genome stability, acting to cleave DNA from free ends. Exonucleases can act as proof-readers during DNA polymerisation in DNA replication, to remove unusual DNA structures that arise from problems with DNA replication fork progression, and they can be directly involved in repairing damaged DNA. Several exonucleases have been recently discovered, with potentially critical roles in genome stability and ageing. Here we discuss how both intrinsic and extrinsic exonuclease activities contribute to the fidelity of DNA polymerases in DNA replication. The action of exonucleases in processing DNA intermediates during normal and aberrant DNA replication is then assessed, as is the importance of exonucleases in repair of double-strand breaks and interstrand crosslinks. Finally we examine how exonucleases are involved in maintenance of mitochondrial genome stability. Throughout the review, we assess how nuclease mutation or loss predisposes to a range of clinical diseases and particularly ageing.
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Affiliation(s)
- Penelope A. Mason
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Lynne S. Cox
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
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Tadokoro T, Ramamoorthy M, Popuri V, May A, Tian J, Sykora P, Rybanska I, Wilson DM, Croteau DL, Bohr VA. Human RECQL5 participates in the removal of endogenous DNA damage. Mol Biol Cell 2012; 23:4273-85. [PMID: 22973052 PMCID: PMC3484104 DOI: 10.1091/mbc.e12-02-0110] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Human RECQL5 is a member of the RecQ helicase family, which maintains genome stability via participation in many DNA metabolic processes, including DNA repair. Human cells lacking RECQL5 display chromosomal instability. We find that cells depleted of RECQL5 are sensitive to oxidative stress, accumulate endogenous DNA damage, and increase the cellular poly(ADP-ribosyl)ate response. In contrast to the RECQ helicase family members WRN, BLM, and RECQL4, RECQL5 accumulates at laser-induced single-strand breaks in normal human cells. RECQL5 depletion affects the levels of PARP-1 and XRCC1, and our collective results suggest that RECQL5 modulates and/or directly participates in base excision repair of endogenous DNA damage, thereby promoting chromosome stability in normal human cells.
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Affiliation(s)
- Takashi Tadokoro
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD 21224, USA
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48
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Beneke S. Regulation of chromatin structure by poly(ADP-ribosyl)ation. Front Genet 2012; 3:169. [PMID: 22969794 PMCID: PMC3432497 DOI: 10.3389/fgene.2012.00169] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 08/17/2012] [Indexed: 12/23/2022] Open
Abstract
The interaction of DNA with proteins in the context of chromatin has to be tightly regulated to achieve so different tasks as packaging, transcription, replication and repair. The very rapid and transient post-translational modification of proteins by poly(ADP-ribose) has been shown to take part in all four. Originally identified as immediate cellular answer to a variety of genotoxic stresses, already early data indicated the ability of this highly charged nucleic acid-like polymer to modulate nucleosome structure, the basic unit of chromatin. At the same time the enzyme responsible for synthesizing poly(ADP-ribose), the zinc-finger protein poly(ADP-ribose) polymerase-1 (PARP1), was shown to control transcription initiation as basic factor TFIIC within the RNA-polymerase II machinery. Later research focused more on PARP-mediated regulation of DNA repair and cell death, but in the last few years, transcription as well as chromatin modulation has re-appeared on the scene. This review will discuss the impact of PARP1 on transcription and transcription factors, its implication in chromatin remodeling for DNA repair and probably also replication, and its role in controlling epigenetic events such as DNA methylation and the functionality of the insulator protein CCCTC-binding factor.
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Affiliation(s)
- Sascha Beneke
- Institute of Veterinary Pharmacology and Toxicology, University of Zurich Zurich, Switzerland
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49
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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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Kanagaraj R, Parasuraman P, Mihaljevic B, van Loon B, Burdova K, König C, Furrer A, Bohr VA, Hübscher U, Janscak P. Involvement of Werner syndrome protein in MUTYH-mediated repair of oxidative DNA damage. Nucleic Acids Res 2012; 40:8449-59. [PMID: 22753033 PMCID: PMC3458577 DOI: 10.1093/nar/gks648] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Reactive oxygen species constantly generated as by-products of cellular metabolism readily attack genomic DNA creating mutagenic lesions such as 7,8-dihydro-8-oxo-guanine (8-oxo-G) that promote aging. 8-oxo-G:A mispairs arising during DNA replication are eliminated by base excision repair initiated by the MutY DNA glycosylase homologue (MUTYH). Here, by using formaldehyde crosslinking in mammalian cell extracts, we demonstrate that the WRN helicase/exonuclease defective in the premature aging disorder Werner syndrome (WS) is recruited to DNA duplex containing an 8-oxo-G:A mispair in a manner dependent on DNA polymerase λ (Polλ) that catalyzes accurate DNA synthesis over 8-oxo-G. Similarly, by immunofluorescence, we show that Polλ is required for accumulation of WRN at sites of 8-oxo-G lesions in human cells. Moreover, we show that nuclear focus formation of WRN and Polλ induced by oxidative stress is dependent on ongoing DNA replication and on the presence of MUTYH. Cell viability assays reveal that depletion of MUTYH suppresses the hypersensitivity of cells lacking WRN and/or Polλ to oxidative stress. Biochemical studies demonstrate that WRN binds to the catalytic domain of Polλ and specifically stimulates DNA gap filling by Polλ over 8-oxo-G followed by strand displacement synthesis. Our results suggest that WRN promotes long-patch DNA repair synthesis by Polλ during MUTYH-initiated repair of 8-oxo-G:A mispairs.
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Affiliation(s)
- Radhakrishnan Kanagaraj
- Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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