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Sato K, Knipscheer P. G-quadruplex resolution: From molecular mechanisms to physiological relevance. DNA Repair (Amst) 2023; 130:103552. [PMID: 37572578 DOI: 10.1016/j.dnarep.2023.103552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 07/29/2023] [Accepted: 08/01/2023] [Indexed: 08/14/2023]
Abstract
Guanine-rich DNA sequences can fold into stable four-stranded structures called G-quadruplexes or G4s. Research in the past decade demonstrated that G4 structures are widespread in the genome and prevalent in regulatory regions of actively transcribed genes. The formation of G4s has been tightly linked to important biological processes including regulation of gene expression and genome maintenance. However, they can also pose a serious threat to genome integrity especially by impeding DNA replication, and G4-associated somatic mutations have been found accumulated in the cancer genomes. Specialised DNA helicases and single stranded DNA binding proteins that can resolve G4 structures play a crucial role in preventing genome instability. The large variety of G4 unfolding proteins suggest the presence of multiple G4 resolution mechanisms in cells. Recently, there has been considerable progress in our detailed understanding of how G4s are resolved, especially during DNA replication. In this review, we first discuss the current knowledge of the genomic G4 landscapes and the impact of G4 structures on DNA replication and genome integrity. We then describe the recent progress on the mechanisms that resolve G4 structures and their physiological relevance. Finally, we discuss therapeutic opportunities to target G4 structures.
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Affiliation(s)
- Koichi Sato
- Oncode Institute, Hubrecht Institute-KNAW & University Medical Center Utrecht, Utrecht, the Netherlands.
| | - Puck Knipscheer
- Oncode Institute, Hubrecht Institute-KNAW & University Medical Center Utrecht, Utrecht, the Netherlands; Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands.
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2
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Abu-Libdeh B, Jhujh SS, Dhar S, Sommers JA, Datta A, Longo GM, Grange LJ, Reynolds JJ, Cooke SL, McNee GS, Hollingworth R, Woodward BL, Ganesh AN, Smerdon SJ, Nicolae CM, Durlacher-Betzer K, Molho-Pessach V, Abu-Libdeh A, Meiner V, Moldovan GL, Roukos V, Harel T, Brosh RM, Stewart GS. RECON syndrome is a genome instability disorder caused by mutations in the DNA helicase RECQL1. J Clin Invest 2022; 132:147301. [PMID: 35025765 PMCID: PMC8884905 DOI: 10.1172/jci147301] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 01/11/2022] [Indexed: 11/17/2022] Open
Abstract
Despite being the first homolog of the bacterial RecQ helicase to be identified in humans, the function of RECQL1 remains poorly characterized. Furthermore, unlike other members of the human RECQ family of helicases, mutations in RECQL1 have not been associated with a genetic disease. Here, we identify 2 families with a genome instability disorder that we have named RECON (RECql ONe) syndrome, caused by biallelic mutations in the RECQL gene. The affected individuals had short stature, progeroid facial features, a hypoplastic nose, xeroderma, and skin photosensitivity and were homozygous for the same missense mutation in RECQL1 (p.Ala459Ser), located within its zinc binding domain. Biochemical analysis of the mutant RECQL1 protein revealed that the p.A459S missense mutation compromised its ATPase, helicase, and fork restoration activity, while its capacity to promote single-strand DNA annealing was largely unaffected. At the cellular level, this mutation in RECQL1 gave rise to a defect in the ability to repair DNA damage induced by exposure to topoisomerase poisons and a failure of DNA replication to progress efficiently in the presence of abortive topoisomerase lesions. Taken together, RECQL1 is the fourth member of the RecQ family of helicases to be associated with a human genome instability disorder.
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Affiliation(s)
- Bassam Abu-Libdeh
- Department of Pediatrics & Genetics, Makassed Hospital & Al-Quds Medical School, Jerusalem, Israel
| | - Satpal S Jhujh
- Institute for Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Srijita Dhar
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Canada
| | - Joshua A Sommers
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Canada
| | - Arindam Datta
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Canada
| | - Gabriel Mc Longo
- Institute of Molecular Biology, Institute of Molecular Biology, Mainz, Germany
| | - Laura J Grange
- Institute for Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom
| | - John J Reynolds
- Institute for Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Sophie L Cooke
- Institute for Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Gavin S McNee
- Institute for Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Robert Hollingworth
- Institute for Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Beth L Woodward
- Institute for Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Anil N Ganesh
- Institute for Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Stephen J Smerdon
- Institute for Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Claudia M Nicolae
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, United States of America
| | | | - Vered Molho-Pessach
- Department of Dermatology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Abdulsalam Abu-Libdeh
- Department of Pediatrics & Genetics, Makassed Hospital & Al-Quds Medical School, Jerusalem, Israel
| | - Vardiella Meiner
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - George-Lucian Moldovan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, United States of America
| | - Vassilis Roukos
- Institute of Molecular Biology, Institute of Molecular Biology, Mainz, Germany
| | - Tamar Harel
- Faculty of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Robert M Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Canada
| | - Grant S Stewart
- Institute for Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom
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3
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Gönenc II, Wolff A, Schmidt J, Zibat A, Müller C, Cyganek L, Argyriou L, Räschle M, Yigit G, Wollnik B. OUP accepted manuscript. Hum Mol Genet 2022; 31:2185-2193. [PMID: 35099000 PMCID: PMC9262399 DOI: 10.1093/hmg/ddab373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 12/02/2021] [Accepted: 12/27/2021] [Indexed: 11/12/2022] Open
Abstract
Bloom syndrome (BS) is an autosomal recessive disease clinically characterized by primary microcephaly, growth deficiency, immunodeficiency and predisposition to cancer. It is mainly caused by biallelic loss-of-function mutations in the BLM gene, which encodes the BLM helicase, acting in DNA replication and repair processes. Here, we describe the gene expression profiles of three BS fibroblast cell lines harboring causative, biallelic truncating mutations obtained by single-cell (sc) transcriptome analysis. We compared the scRNA transcription profiles from three BS patient cell lines to two age-matched wild-type controls and observed specific deregulation of gene sets related to the molecular processes characteristically affected in BS, such as mitosis, chromosome segregation, cell cycle regulation and genomic instability. We also found specific upregulation of genes of the Fanconi anemia pathway, in particular FANCM, FANCD2 and FANCI, which encode known interaction partners of BLM. The significant deregulation of genes associated with inherited forms of primary microcephaly observed in our study might explain in part the molecular pathogenesis of microcephaly in BS, one of the main clinical characteristics in patients. Finally, our data provide first evidence of a novel link between BLM dysfunction and transcriptional changes in condensin complex I and II genes. Overall, our study provides novel insights into gene expression profiles in BS on an sc level, linking specific genes and pathways to BLM dysfunction.
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Affiliation(s)
| | | | - Julia Schmidt
- Institute of Human Genetics, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Arne Zibat
- Institute of Human Genetics, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Christian Müller
- Institute of Human Genetics, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Lukas Cyganek
- Stem Cell Unit, Clinic for Cardiology and Pneumology, University Medical Center Göttingen, 37075 Göttingen, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Göttingen, 37075 Göttingen, Germany
| | - Loukas Argyriou
- Institute of Human Genetics, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Markus Räschle
- Department of Molecular Genetics, Technical University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Gökhan Yigit
- Institute of Human Genetics, University Medical Center Göttingen, 37073 Göttingen, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Göttingen, 37075 Göttingen, Germany
| | - Bernd Wollnik
- To whom correspondence should be addressed at: Institute of Human Genetics, University Medical Center Göttingen, Heinrich-Düker-Weg 12, 37073 Göttingen, Germany. Tel: +49 5513960606; Fax: +49 5513969303;
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4
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Rieckher M, Garinis GA, Schumacher B. Molecular pathology of rare progeroid diseases. Trends Mol Med 2021; 27:907-922. [PMID: 34272172 DOI: 10.1016/j.molmed.2021.06.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 06/18/2021] [Accepted: 06/22/2021] [Indexed: 12/21/2022]
Abstract
Progeroid syndromes (PSs) are characterized by the premature onset of age-related pathologies. The genetic mutations underlying PSs are functionally linked to genome maintenance and repair, supporting the causative role of DNA damage accumulation in aging. Recent advances from studies in animal models of PSs have provided new insight into the role of DNA repair mechanisms in human disease and the physiological adaptations to accumulating DNA damage during aging. The molecular pathology of PSs is reminiscent of the natural aging process, highlighting the relevance for a wide range of age-related diseases. Recent progress has led to the development of novel therapeutic strategies against age-related diseases that are relevant to rare diseases as well as the general aging population.
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Affiliation(s)
- Matthias Rieckher
- Institute for Genome Stability in Aging and Disease, Medical Faculty, University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany; Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Center for Molecular Medicine (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - George A Garinis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, GR70013, Heraklion, Crete, Greece; Department of Biology, University of Crete, Heraklion, Crete, Greece
| | - Björn Schumacher
- Institute for Genome Stability in Aging and Disease, Medical Faculty, University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany; Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Center for Molecular Medicine (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany.
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5
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Checkpoint functions of RecQ helicases at perturbed DNA replication fork. Curr Genet 2021; 67:369-382. [PMID: 33427950 DOI: 10.1007/s00294-020-01147-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 12/07/2020] [Accepted: 12/12/2020] [Indexed: 01/17/2023]
Abstract
DNA replication checkpoint is a cell signaling pathway that is activated in response to perturbed replication. Although it is crucial for maintaining genomic integrity and cell survival, the exact mechanism of the checkpoint signaling remains to be understood. Emerging evidence has shown that RecQ helicases, a large family of helicases that are conserved from bacteria to yeasts and humans, contribute to the replication checkpoint as sensors, adaptors, or regulation targets. Here, we highlight the multiple functions of RecQ helicases in the replication checkpoint in four model organisms and present additional evidence that fission yeast RecQ helicase Rqh1 may participate in the replication checkpoint as a sensor.
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6
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Bythell-Douglas R, Deans AJ. A Structural Guide to the Bloom Syndrome Complex. Structure 2020; 29:99-113. [PMID: 33357470 DOI: 10.1016/j.str.2020.11.020] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 09/03/2020] [Accepted: 11/25/2020] [Indexed: 01/19/2023]
Abstract
The Bloom syndrome complex is a DNA damage repair machine. It consists of several protein components which are functional in isolation, but interdependent in cells for the maintenance of accurate homologous recombination. Mutations to any of the genes encoding these proteins cause numerous physical and developmental markers as well as phenotypes of genome instability, infertility, and cancer predisposition. Here we review the published structural and biochemical data on each of the components of the complex: the helicase BLM, the type IA topoisomerase TOP3A, and the OB-fold-containing RMI and RPA subunits. We describe how each component contributes to function, interacts with each other, and the DNA that it manipulates/repairs.
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Affiliation(s)
- Rohan Bythell-Douglas
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC, 3056, Australia.
| | - Andrew J Deans
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC, 3056, Australia; Department of Medicine (St Vincent's), University of Melbourne, Fitzroy, VIC, 3056, Australia.
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7
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Domingues-Silva B, Silva B, Azzalin CM. ALTernative Functions for Human FANCM at Telomeres. Front Mol Biosci 2019; 6:84. [PMID: 31552268 PMCID: PMC6743340 DOI: 10.3389/fmolb.2019.00084] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 08/26/2019] [Indexed: 01/13/2023] Open
Abstract
The human FANCM ATPase/translocase is involved in various cellular pathways including DNA damage repair, replication fork remodeling and R-loop resolution. Recently, reports from three independent laboratories have disclosed a previously unappreciated role for FANCM in telomerase-negative human cancer cells that maintain their telomeres through the Alternative Lengthening of Telomeres (ALT) pathway. In ALT cells, FANCM limits telomeric replication stress and damage, and, in turn, ALT activity by suppressing accumulation of telomeric R-loops and by regulating the action of the BLM helicase. As a consequence, FANCM inactivation leads to exaggerated ALT activity and ultimately cell death. The studies reviewed here not only unveil a novel function for human FANCM, but also point to this enzyme as a promising target for anti-ALT cancer therapy.
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Affiliation(s)
- Beatriz Domingues-Silva
- Instituto de Medicina Molecular João Lobo Antunes (iMM), Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal
| | - Bruno Silva
- Instituto de Medicina Molecular João Lobo Antunes (iMM), Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal
| | - Claus M Azzalin
- Instituto de Medicina Molecular João Lobo Antunes (iMM), Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal
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8
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Turner KJ, Vasu V, Griffin DK. Telomere Biology and Human Phenotype. Cells 2019; 8:cells8010073. [PMID: 30669451 PMCID: PMC6356320 DOI: 10.3390/cells8010073] [Citation(s) in RCA: 195] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Revised: 01/14/2019] [Accepted: 01/16/2019] [Indexed: 12/15/2022] Open
Abstract
Telomeres are nucleoprotein structures that cap the end of each chromosome arm and function to maintain genome stability. The length of telomeres is known to shorten with each cell division and it is well-established that telomere attrition is related to replicative capacity in vitro. Moreover, telomere loss is also correlated with the process of aging in vivo. In this review, we discuss the mechanisms that lead to telomere shortening and summarise telomere homeostasis in humans throughout a lifetime. In addition, we discuss the available evidence that shows that telomere shortening is related to human aging and the onset of age-related disease.
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Affiliation(s)
- Kara J Turner
- University of Kent, School of Biosciences, Giles Lane, Canterbury, Kent, CT2-7NJ, UK.
| | - Vimal Vasu
- University of Kent, School of Biosciences, Giles Lane, Canterbury, Kent, CT2-7NJ, UK.
- Department of Child Health, East Kent Hospitals University Foundation NHS Trust, William Harvey Hospital, Ashford, Kent, TN24-0LZ, UK.
| | - Darren K Griffin
- University of Kent, School of Biosciences, Giles Lane, Canterbury, Kent, CT2-7NJ, UK.
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9
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Wang H, Li S, Zhang H, Wang Y, Hao S, Wu X. BLM prevents instability of structure-forming DNA sequences at common fragile sites. PLoS Genet 2018; 14:e1007816. [PMID: 30496191 PMCID: PMC6289451 DOI: 10.1371/journal.pgen.1007816] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 12/11/2018] [Accepted: 11/07/2018] [Indexed: 01/04/2023] Open
Abstract
Genome instability often arises at common fragile sites (CFSs) leading to cancer-associated chromosomal rearrangements. However, the underlying mechanisms of how CFS protection is achieved is not well understood. We demonstrate that BLM plays an important role in the maintenance of genome stability of structure-forming AT-rich sequences derived from CFSs (CFS-AT). BLM deficiency leads to increased DSB formation and hyper mitotic recombination at CFS-AT and induces instability of the plasmids containing CFS-AT. We further showed that BLM is required for suppression of CFS breakage upon oncogene expression. Both helicase activity and ATR-mediated phosphorylation of BLM are important for preventing genetic instability at CFS-AT sequences. Furthermore, the role of BLM in protecting CFS-AT is not epistatic to that of FANCM, a translocase that is involved in preserving CFS stability. Loss of BLM helicase activity leads to drastic decrease of cell viability in FANCM deficient cells. We propose that BLM and FANCM utilize different mechanisms to remove DNA secondary structures forming at CFS-AT on replication forks, thereby preventing DSB formation and maintaining CFS stability. Common fragile sites (CFSs) are large chromosomal regions which are more prone to breakage than other places in the genome. They are a part of normal chromosome structure and are present in all human beings, but are also hotspots for chromosomal rearrangement during oncogenesis. Understanding how CFSs are protected to prevent genome instability is thus extremely important for revealing the mechanism underlying cancer development. We found that Bloom syndrome protein BLM is involved in resolving DNA secondary structures that arise at AT-rich sequences in CFSs, suggesting a critical function of BLM in protecting CFSs. We also found that this BLM function is distinct from the role of Fanconi anemia protein FANCM in protecting CFSs, and loss of both BLM and FANCM activities leads to cell death. These studies reveal important mechanisms of the maintenance of CFS stability in mammalian cells.
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Affiliation(s)
- Hailong Wang
- Beijing Key Laboratory of DNA Damage Response and College of Life Science, Capital Normal University, Beijing, China
| | - Shibo Li
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, United States of America
| | - Huimin Zhang
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, United States of America
| | - Ya Wang
- Beijing Key Laboratory of DNA Damage Response and College of Life Science, Capital Normal University, Beijing, China
| | - Shuailin Hao
- Beijing Key Laboratory of DNA Damage Response and College of Life Science, Capital Normal University, Beijing, China
| | - Xiaohua Wu
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, United States of America
- * E-mail:
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10
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Chang EYC, Novoa CA, Aristizabal MJ, Coulombe Y, Segovia R, Chaturvedi R, Shen Y, Keong C, Tam AS, Jones SJM, Masson JY, Kobor MS, Stirling PC. RECQ-like helicases Sgs1 and BLM regulate R-loop-associated genome instability. J Cell Biol 2017; 216:3991-4005. [PMID: 29042409 PMCID: PMC5716281 DOI: 10.1083/jcb.201703168] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 08/16/2017] [Accepted: 09/18/2017] [Indexed: 01/01/2023] Open
Abstract
Sgs1, the orthologue of human Bloom's syndrome helicase BLM, is a yeast DNA helicase functioning in DNA replication and repair. We show that SGS1 loss increases R-loop accumulation and sensitizes cells to transcription-replication collisions. Yeast lacking SGS1 accumulate R-loops and γ-H2A at sites of Sgs1 binding, replication pausing regions, and long genes. The mutation signature of sgs1Δ reveals copy number changes flanked by repetitive regions with high R-loop-forming potential. Analysis of BLM in Bloom's syndrome fibroblasts or by depletion of BLM from human cancer cells confirms a role for Sgs1/BLM in suppressing R-loop-associated genome instability across species. In support of a potential direct effect, BLM is found physically proximal to DNA:RNA hybrids in human cells, and can efficiently unwind R-loops in vitro. Together, our data describe a conserved role for Sgs1/BLM in R-loop suppression and support an increasingly broad view of DNA repair and replication fork stabilizing proteins as modulators of R-loop-mediated genome instability.
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Affiliation(s)
| | - Carolina A Novoa
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, Canada
| | | | - Yan Coulombe
- Genome Stability Laboratory, Centre Hospitalier Universitaire de Québec Research Center, Québec City, Canada.,Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, Québec City, Canada
| | - Romulo Segovia
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, Canada
| | - Richa Chaturvedi
- Genome Stability Laboratory, Centre Hospitalier Universitaire de Québec Research Center, Québec City, Canada.,Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, Québec City, Canada
| | - Yaoqing Shen
- Michael Smith Genome Sciences Centre, Vancouver, Canada
| | - Christelle Keong
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, Canada
| | - Annie S Tam
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, Canada.,Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Steven J M Jones
- Michael Smith Genome Sciences Centre, Vancouver, Canada.,Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Jean-Yves Masson
- Genome Stability Laboratory, Centre Hospitalier Universitaire de Québec Research Center, Québec City, Canada.,Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, Québec City, Canada
| | - Michael S Kobor
- Centre for Molecular Medicine and Therapeutics, Vancouver, Canada.,Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Peter C Stirling
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, Canada .,Department of Medical Genetics, University of British Columbia, Vancouver, Canada
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11
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Sobinoff AP, Allen JA, Neumann AA, Yang SF, Walsh ME, Henson JD, Reddel RR, Pickett HA. BLM and SLX4 play opposing roles in recombination-dependent replication at human telomeres. EMBO J 2017; 36:2907-2919. [PMID: 28877996 DOI: 10.15252/embj.201796889] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 08/03/2017] [Accepted: 08/09/2017] [Indexed: 11/09/2022] Open
Abstract
Alternative lengthening of telomeres (ALT) is a telomere lengthening pathway that predominates in aggressive tumors of mesenchymal origin; however, the underlying mechanism of telomere synthesis is not fully understood. Here, we show that the BLM-TOP3A-RMI (BTR) dissolvase complex is required for ALT-mediated telomere synthesis. We propose that recombination intermediates formed during strand invasion are processed by the BTR complex, initiating rapid and extensive POLD3-dependent telomere synthesis followed by dissolution, with no overall exchange of telomeric DNA. This process is counteracted by the SLX4-SLX1-ERCC4 complex, which promotes resolution of the recombination intermediate, resulting in telomere exchange in the absence of telomere extension. Our data are consistent with ALT being a conservative DNA replication process, analogous to break-induced replication, which is dependent on BTR and counteracted by SLX4 complex-mediated resolution events.
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Affiliation(s)
- Alexander P Sobinoff
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Joshua Am Allen
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Axel A Neumann
- Cancer Research Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Sile F Yang
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Monica E Walsh
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Jeremy D Henson
- Cancer Cell Immortality Group, Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - Roger R Reddel
- Cancer Research Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
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12
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Cunniff C, Bassetti JA, Ellis NA. Bloom's Syndrome: Clinical Spectrum, Molecular Pathogenesis, and Cancer Predisposition. Mol Syndromol 2017; 8:4-23. [PMID: 28232778 PMCID: PMC5260600 DOI: 10.1159/000452082] [Citation(s) in RCA: 160] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/22/2016] [Indexed: 01/07/2023] Open
Abstract
Bloom's syndrome is an autosomal recessive disorder characterized by prenatal and postnatal growth deficiency, photosensitive skin changes, immune deficiency, insulin resistance, and a greatly increased risk of early onset of cancer and for the development of multiple cancers. Loss-of-function mutations of BLM, which codes for a RecQ helicase, cause Bloom's syndrome. The absence of a functional BLM protein causes chromosome instability, excessive homologous recombination, and a greatly increased number of sister chromatid exchanges that are pathognomonic of the syndrome. A common founder mutation designated blmAsh is present in about 1 in 100 persons of Eastern European Jewish ancestry, and there are additional recurrent founder mutations among other populations. Missense, nonsense, and frameshift mutations as well as multiexonic deletions have all been observed. Bloom's syndrome is a prototypical chromosomal instability syndrome, and the somatic mutations that occur as a result of that instability are responsible for the increased cancer risk. Although there is currently no treatment aimed at the underlying genetic abnormality, persons with Bloom's syndrome benefit from sun protection, aggressive treatment of infections, surveillance for insulin resistance, and early identification of cancer.
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Affiliation(s)
- Christopher Cunniff
- Division of Medical Genetics, Department of Pediatrics, Weill Cornell Medical College, New York, N.Y, USA
| | - Jennifer A. Bassetti
- Division of Medical Genetics, Department of Pediatrics, Weill Cornell Medical College, New York, N.Y, USA
| | - Nathan A. Ellis
- Department of Cellular and Molecular Medicine, University of Arizona Cancer Center, Tucson, Ariz., USA
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13
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Rahman F, Tarique M, Tuteja R. Plasmodium falciparum Bloom homologue, a nucleocytoplasmic protein, translocates in 3' to 5' direction and is essential for parasite growth. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:594-608. [PMID: 26917473 DOI: 10.1016/j.bbapap.2016.02.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 02/16/2016] [Accepted: 02/18/2016] [Indexed: 12/25/2022]
Abstract
Malaria caused by Plasmodium, particularly Plasmodium falciparum, is the most serious and widespread parasitic disease of humans. RecQ helicase family members are essential in homologous recombination-based error-free DNA repair processes in all domains of life. RecQ helicases present in each organism differ and several homologues have been identified in various multicellular organisms. These proteins are involved in various pathways of DNA metabolism by providing duplex unwinding function. Five members of RecQ family are present in Homo sapiens but P. falciparum contains only two members of this family. Here we report the detailed biochemical and functional characterization of the Bloom (Blm) homologue (PfBlm) from P. falciparum 3D7 strain. Purified PfBlm exhibits ATPase and 3' to 5' direction specific DNA helicase activity. The calculated average reaction rate of ATPase was ~13 pmol of ATP hydrolyzed/min/pmol of enzyme. The immunofluorescence assay results show that PfBlm is expressed in all the stages of intraerythrocytic development of the P. falciparum 3D7 strain. In some stages of development in addition to nucleus PfBlm also localizes in the cytoplasm. The gene disruption studies of PfBlm by dsRNA showed that it is required for the ex-vivo intraerythrocytic development of the parasite P. falciparum 3D7 strain. The dsRNA mediated inhibition of parasite growth suggests that a variety of pathways are affected resulting in curtailing of the parasite growth. This study will be helpful in unravelling the basic mechanism of DNA transaction in the malaria parasite and additionally it may provide leads to understand the parasite specific characteristics of this protein.
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Affiliation(s)
- Farhana Rahman
- Malaria Group, International Centre for Genetic Engineering and Biotechnology, P. O. Box 10504, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Mohammed Tarique
- Malaria Group, International Centre for Genetic Engineering and Biotechnology, P. O. Box 10504, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Renu Tuteja
- Malaria Group, International Centre for Genetic Engineering and Biotechnology, P. O. Box 10504, Aruna Asaf Ali Marg, New Delhi 110067, India.
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14
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Perreault-Micale C, Davie J, Breton B, Hallam S, Greger V. A rigorous approach for selection of optimal variant sets for carrier screening with demonstration of clinical utility. Mol Genet Genomic Med 2015; 3:363-73. [PMID: 26247052 PMCID: PMC4521971 DOI: 10.1002/mgg3.148] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 03/24/2015] [Accepted: 03/24/2015] [Indexed: 11/29/2022] Open
Abstract
Carrier screening for certain diseases is recommended by major medical and Ashkenazi Jewish (AJ) societies. Most carrier screening panels test only for common, ethnic-specific variants. However, with formerly isolated ethnic groups becoming increasingly intermixed, this approach is becoming inadequate. Our objective was to develop a rigorous process to curate all variants, for relevant genes, into a database and then apply stringent clinical validity classification criteria to each in order to retain only those with clear evidence for pathogenicity. The resulting variant set, in conjunction with next-generation DNA sequencing (NGS), then affords the capability for an ethnically diverse, comprehensive, highly specific carrier-screening assay. The clinical utility of our approach was demonstrated by screening a pan-ethnic population of 22,864 individuals for Bloom syndrome carrier status using a BLM variant panel comprised of 50 pathogenic variants. In addition to carriers of the common AJ founder variant, we identified 57 carriers of other pathogenic BLM variants. All variants reported had previously been curated and their clinical validity documented, or were of a type that met our stringent, preassigned validity criteria. Thus, it was possible to confidently report an increased number of Bloom’s syndrome carriers compared to traditional, ethnicity-based screening, while not reducing the specificity of the screening due to reporting variants of unknown clinical significance.
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Affiliation(s)
| | - Jocelyn Davie
- Good Start Genetics, Inc. 237 Putnam Avenue, Cambridge, Massachusetts, 02139
| | - Benjamin Breton
- Good Start Genetics, Inc. 237 Putnam Avenue, Cambridge, Massachusetts, 02139
| | - Stephanie Hallam
- Good Start Genetics, Inc. 237 Putnam Avenue, Cambridge, Massachusetts, 02139
| | - Valerie Greger
- Good Start Genetics, Inc. 237 Putnam Avenue, Cambridge, Massachusetts, 02139
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15
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Budhathoki JB, Ray S, Urban V, Janscak P, Yodh JG, Balci H. RecQ-core of BLM unfolds telomeric G-quadruplex in the absence of ATP. Nucleic Acids Res 2014; 42:11528-45. [PMID: 25245947 PMCID: PMC4191421 DOI: 10.1093/nar/gku856] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Various helicases and single-stranded DNA (ssDNA) binding proteins are known to destabilize G-quadruplex (GQ) structures, which otherwise result in genomic instability. Bulk biochemical studies have shown that Bloom helicase (BLM) unfolds both intermolecular and intramolecular GQ in the presence of ATP. Using single molecule FRET, we show that binding of RecQ-core of BLM (will be referred to as BLM) to ssDNA in the vicinity of an intramolecular GQ leads to destabilization and unfolding of the GQ in the absence of ATP. We show that the efficiency of BLM-mediated GQ unfolding correlates with the binding stability of BLM to ssDNA overhang, as modulated by the nucleotide state, ionic conditions, overhang length and overhang directionality. In particular, we observed enhanced GQ unfolding by BLM in the presence of non-hydrolysable ATP analogs, which has implications for the underlying mechanism. We also show that increasing GQ stability, via shorter loops or higher ionic strength, reduces BLM-mediated GQ unfolding. Finally, we show that while WRN has similar activity as BLM, RecQ and RECQ5 helicases do not unfold GQ in the absence of ATP at physiological ionic strength. In summary, our study points to a novel and potentially very common mechanism of GQ destabilization mediated by proteins binding to the vicinity of these structures.
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Affiliation(s)
| | - Sujay Ray
- Department of Physics, Kent State University, Kent, OH 44242, USA
| | - Vaclav Urban
- Institute of Molecular Genetics AS CR, Prague, Czech Republic
| | - Pavel Janscak
- Institute of Molecular Genetics AS CR, Prague, Czech Republic Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Jaya G Yodh
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Hamza Balci
- Department of Physics, Kent State University, Kent, OH 44242, USA
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16
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Ben Salah G, Hadj Salem I, Masmoudi A, Kallabi F, Turki H, Fakhfakh F, Ayadi H, Kamoun H. A novel frameshift mutation in BLM gene associated with high sister chromatid exchanges (SCE) in heterozygous family members. Mol Biol Rep 2014; 41:7373-80. [PMID: 25129257 DOI: 10.1007/s11033-014-3624-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 07/19/2014] [Indexed: 12/01/2022]
Abstract
The Bloom syndrome (BS) is an autosomic recessive disorder comprising a wide range of abnormalities, including stunted growth, immunodeficiency, sun sensitivity and increased frequency of various types of cancer. Bloom syndrome cells display a high level of genetic instability, including a 10-fold increase in the sister chromatid exchanges (SCE) level. Bloom syndrome arises through mutations in both alleles of the BLM gene, which was identified as a member of the RecQ helicase family. In this study, we screened a Tunisian family with three BS patients. Cytogenetic analysis showed several chromosomal aberrations, and an approximately 14-fold elevated SCE frequency in BS cells. A significant increase in SCE frequency was observed in some family members but not reaching the BS patients values, leading to suggest that this could be due to the heterozygous profile. Microsatellite genotyping using four fluorescent dye-labeled microsatellite markers revealed evidence of linkage to BLM locus and the healthy members, sharing higher SCE frequency, showed heterozygous haplotypes as expected. Additionally, the direct BLM gene sequencing identified a novel homozygous frameshift mutation c.3617-3619delAA (p.K1207fsX9) in BS patients and a heterozygous BLM mutation in the family members with higher SCE frequency. Our findings suggest that this latter mutation likely leads to a reduced BLM activity explaining the homologous recombination repair defect and, therefore, the increase in SCE. Based on the present data, the screening of this mutation could contribute to the rapid diagnosis of BS. The genetic confirmation of the mutation in BLM gene provides crucial information for genetic counseling and prenatal diagnosis.
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Affiliation(s)
- Ghada Ben Salah
- Laboratory of Human Molecular Genetics, Faculty of Medicine, University of Sfax, Av. Majida Boulila, 3029, Sfax, Tunisia,
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17
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Swan MK, Legris V, Tanner A, Reaper PM, Vial S, Bordas R, Pollard JR, Charlton PA, Golec JMC, Bertrand JA. Structure of human Bloom's syndrome helicase in complex with ADP and duplex DNA. ACTA ACUST UNITED AC 2014; 70:1465-75. [PMID: 24816114 DOI: 10.1107/s139900471400501x] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 03/05/2014] [Indexed: 01/18/2023]
Abstract
Bloom's syndrome is an autosomal recessive genome-instability disorder associated with a predisposition to cancer, premature aging and developmental abnormalities. It is caused by mutations that inactivate the DNA helicase activity of the BLM protein or nullify protein expression. The BLM helicase has been implicated in the alternative lengthening of telomeres (ALT) pathway, which is essential for the limitless replication of some cancer cells. This pathway is used by 10-15% of cancers, where inhibitors of BLM are expected to facilitate telomere shortening, leading to apoptosis or senescence. Here, the crystal structure of the human BLM helicase in complex with ADP and a 3'-overhang DNA duplex is reported. In addition to the helicase core, the BLM construct used for crystallization (residues 640-1298) includes the RecQ C-terminal (RQC) and the helicase and ribonuclease D C-terminal (HRDC) domains. Analysis of the structure provides detailed information on the interactions of the protein with DNA and helps to explain the mechanism coupling ATP hydrolysis and DNA unwinding. In addition, mapping of the missense mutations onto the structure provides insights into the molecular basis of Bloom's syndrome.
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Affiliation(s)
- Michael K Swan
- Vertex Pharmaceuticals (Europe), Abingdon, Oxfordshire, England
| | - Valerie Legris
- Vertex Pharmaceuticals (Europe), Abingdon, Oxfordshire, England
| | - Adam Tanner
- Vertex Pharmaceuticals (Europe), Abingdon, Oxfordshire, England
| | - Philip M Reaper
- Vertex Pharmaceuticals (Europe), Abingdon, Oxfordshire, England
| | - Sarah Vial
- Vertex Pharmaceuticals (Europe), Abingdon, Oxfordshire, England
| | - Rebecca Bordas
- Vertex Pharmaceuticals (Europe), Abingdon, Oxfordshire, England
| | - John R Pollard
- Vertex Pharmaceuticals (Europe), Abingdon, Oxfordshire, England
| | | | | | - Jay A Bertrand
- Vertex Pharmaceuticals (Europe), Abingdon, Oxfordshire, England
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18
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The tumor suppressor PML specifically accumulates at RPA/Rad51-containing DNA damage repair foci but is nonessential for DNA damage-induced fibroblast senescence. Mol Cell Biol 2014; 34:1733-46. [PMID: 24615016 DOI: 10.1128/mcb.01345-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The PML tumor suppressor has been functionally implicated in DNA damage response and cellular senescence. Direct evidence for such a role based on PML knockdown or knockout approaches is still lacking. We have therefore analyzed the irradiation-induced DNA damage response and cellular senescence in human and mouse fibroblasts lacking PML. Our data show that PML nuclear bodies (NBs) nonrandomly associate with persistent DNA damage foci in unperturbed human skin and in high-dose-irradiated cell culture systems. PML bodies do not associate with transient γH2AX foci after low-dose gamma irradiation. Superresolution microscopy reveals that all PML bodies within a nucleus are engaged at Rad51- and RPA-containing repair foci during ongoing DNA repair. The lack of PML (i) does not majorly affect the DNA damage response, (ii) does not alter the efficiency of senescence induction after DNA damage, and (iii) does not affect the proliferative potential of primary mouse embryonic fibroblasts during serial passaging. Thus, while PML NBs specifically accumulate at Rad51/RPA-containing lesions and senescence-derived persistent DNA damage foci, they are not essential for DNA damage-induced and replicative senescence of human and murine fibroblasts.
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19
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Schröpfer S, Kobbe D, Hartung F, Knoll A, Puchta H. Defining the roles of the N-terminal region and the helicase activity of RECQ4A in DNA repair and homologous recombination in Arabidopsis. Nucleic Acids Res 2013; 42:1684-97. [PMID: 24174542 PMCID: PMC3919593 DOI: 10.1093/nar/gkt1004] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
RecQ helicases are critical for the maintenance of genomic stability. The Arabidopsis RecQ helicase RECQ4A is the functional counterpart of human BLM, which is mutated in the genetic disorder Bloom’s syndrome. RECQ4A performs critical roles in regulation of homologous recombination (HR) and DNA repair. Loss of RECQ4A leads to elevated HR frequencies and hypersensitivity to genotoxic agents. Through complementation studies, we were now able to demonstrate that the N-terminal region and the helicase activity of RECQ4A are both essential for the cellular response to replicative stress induced by methyl methanesulfonate and cisplatin. In contrast, loss of helicase activity or deletion of the N-terminus only partially complemented the mutant hyper-recombination phenotype. Furthermore, the helicase-deficient protein lacking its N-terminus did not complement the hyper-recombination phenotype at all. Therefore, RECQ4A seems to possess at least two different and independent sub-functions involved in the suppression of HR. By in vitro analysis, we showed that the helicase core was able to regress an artificial replication fork. Swapping of the terminal regions of RECQ4A with the closely related but functionally distinct helicase RECQ4B indicated that in contrast to the C-terminus, the N-terminus of RECQ4A was required for its specific functions in DNA repair and recombination.
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Affiliation(s)
- Susan Schröpfer
- Botanical Institute II, Karlsruhe Institute of Technology, Hertzstrasse 16, Karlsruhe 76187, Germany and Institute for Biosafety in Plant Biotechnology, Julius Kühn Institute (JKI), Erwin-Baur-Strasse 27, Quedlinburg 06484, Germany
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20
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Rosenthal AS, Dexheimer TS, Gileadi O, Nguyen GH, Chu WK, Hickson ID, Jadhav A, Simeonov A, Maloney DJ. Synthesis and SAR studies of 5-(pyridin-4-yl)-1,3,4-thiadiazol-2-amine derivatives as potent inhibitors of Bloom helicase. Bioorg Med Chem Lett 2013; 23:5660-6. [PMID: 24012121 DOI: 10.1016/j.bmcl.2013.08.025] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 07/26/2013] [Accepted: 08/05/2013] [Indexed: 11/15/2022]
Abstract
Human cells utilize a variety of complex DNA repair mechanisms in order to combat constant mutagenic and cytotoxic threats from both exogenous and endogenous sources. The RecQ family of DNA helicases, which includes Bloom helicase (BLM), plays an important function in DNA repair by unwinding complementary strands of duplex DNA as well as atypical DNA structures such as Holliday junctions. Mutations of the BLM gene can result in Bloom syndrome, an autosomal recessive disorder associated with cancer predisposition. BLM-deficient cells exhibit increased sensitivity to DNA damaging agents indicating that a selective BLM inhibitor could be useful in potentiating the anticancer activity of these agents. In this work, we describe the medicinal chemistry optimization of the hit molecule following a quantitative high-throughput screen of >355,000 compounds. These efforts lead to the identification of ML216 and related analogs, which possess potent BLM inhibition and exhibit selectivity over related helicases. Moreover, these compounds demonstrated cellular activity by inducing sister chromatid exchanges, a hallmark of Bloom syndrome.
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Affiliation(s)
- Andrew S Rosenthal
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, MD, 20892
| | - Thomas S Dexheimer
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, MD, 20892
| | - Opher Gileadi
- The Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK
| | - Giang H Nguyen
- Department of Medical Oncology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK.,Laboratory of Human Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD
| | - Wai Kit Chu
- Department of Cellular and Molecular Medicine, Nordea Center for Healthy Aging, University of Copenhagen, '2200 Copenhagen N, Denmark
| | - Ian D Hickson
- Department of Medical Oncology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK.,Department of Cellular and Molecular Medicine, Nordea Center for Healthy Aging, University of Copenhagen, '2200 Copenhagen N, Denmark
| | - Ajit Jadhav
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, MD, 20892
| | - Anton Simeonov
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, MD, 20892
| | - David J Maloney
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, MD, 20892
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21
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Jensen MB, Dunn CA, Keijzers G, Kulikowicz T, Rasmussen LJ, Croteau DL, Bohr VA. The helicase and ATPase activities of RECQL4 are compromised by mutations reported in three human patients. Aging (Albany NY) 2013; 4:790-802. [PMID: 23238538 PMCID: PMC3560432 DOI: 10.18632/aging.100506] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
RECQL4 is one of five members of the human RecQ helicase family, and is implicated in three syndromes displaying accelerating aging, developmental abnormalities and a predisposition to cancer. In this study, we purified three variants of RECQL4 carrying previously reported patient mutations. These three mutant proteins were analyzed for the known biochemical activities of RECQL4: DNA binding, unwinding of duplex DNA, ATP hydrolysis and annealing of simplex DNA. Further, the mutant proteins were evaluated for stability and recruitment to sites of laser-induced DNA damage. One mutant was helicase-dead, had marginal ATPase activity and may be structurally compromised, while the other two showed greatly reduced helicase and ATPase activities. The remaining biochemical activities and ability to recruit to damage sites were not significantly impaired for any of the mutants. Our findings demonstrate a consistent pattern of functional deficiency and provide further support for a helicase-dependent cellular function of RECQL4 in addition to its Nterminus-dependent role in initiation of replication, a function that may underlie the phenotype of RECQL4-linked disease.
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Affiliation(s)
- Martin Borch Jensen
- Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
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22
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Manthei KA, Keck JL. The BLM dissolvasome in DNA replication and repair. Cell Mol Life Sci 2013; 70:4067-84. [PMID: 23543275 DOI: 10.1007/s00018-013-1325-1] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Revised: 02/21/2013] [Accepted: 03/14/2013] [Indexed: 02/07/2023]
Abstract
RecQ DNA helicases are critical for proper maintenance of genomic stability, and mutations in multiple human RecQ genes are linked with genetic disorders characterized by a predisposition to cancer. RecQ proteins are conserved from prokaryotes to humans and in all cases form higher-order complexes with other proteins to efficiently execute their cellular functions. The focus of this review is a conserved complex that is formed between RecQ helicases and type-I topoisomerases. In humans, this complex is referred to as the BLM dissolvasome or BTR complex, and is comprised of the RecQ helicase BLM, topoisomerase IIIα, and the RMI proteins. The BLM dissolvasome functions to resolve linked DNA intermediates without exchange of genetic material, which is critical in somatic cells. We will review the history of this complex and highlight its roles in DNA replication, recombination, and repair. Additionally, we will review recently established interactions between BLM dissolvasome and a second set of genome maintenance factors (the Fanconi anemia proteins) that appear to allow coordinated genome maintenance efforts between the two systems.
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Affiliation(s)
- Kelly A Manthei
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI, 53706, USA
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23
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DNA helicases associated with genetic instability, cancer, and aging. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 767:123-44. [PMID: 23161009 DOI: 10.1007/978-1-4614-5037-5_6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
DNA helicases have essential roles in the maintenance of genomic -stability. They have achieved even greater prominence with the discovery that mutations in human helicase genes are responsible for a variety of genetic disorders and are associated with tumorigenesis. A number of missense mutations in human helicase genes are linked to chromosomal instability diseases characterized by age-related disease or associated with cancer, providing incentive for the characterization of molecular defects underlying aberrant cellular phenotypes. In this chapter, we discuss some examples of clinically relevant missense mutations in various human DNA helicases, particularly those of the Iron-Sulfur cluster and RecQ families. Clinically relevant mutations in the XPD helicase can lead to Xeroderma pigmentosum, Cockayne's syndrome, Trichothiodystrophy, or COFS syndrome. FANCJ mutations are associated with Fanconi anemia or breast cancer. Mutations of the Fe-S helicase ChlR1 (DDX11) are linked to Warsaw Breakage syndrome. Mutations in the RecQ helicases BLM and WRN are linked to the cancer-prone disorder Bloom's syndrome and premature aging condition Werner syndrome, respectively. RECQL4 mutations can lead to Rothmund-Thomson syndrome, Baller-Gerold syndrome, or RAPADILINO. Mutations in the Twinkle mitochondrial helicase are responsible for several neuromuscular degenerative disorders. We will discuss some insights gained from biochemical and genetic studies of helicase variants, and highlight some hot areas of helicase research based on recent developments.
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24
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Suhasini AN, Brosh RM. Disease-causing missense mutations in human DNA helicase disorders. Mutat Res 2012; 752:138-152. [PMID: 23276657 DOI: 10.1016/j.mrrev.2012.12.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 12/18/2012] [Accepted: 12/19/2012] [Indexed: 01/22/2023]
Abstract
Helicases have important roles in nucleic acid metabolism, and their prominence is marked by the discovery of genetic disorders arising from disease-causing mutations. Missense mutations can yield unique insight to molecular functions and basis for disease pathology. XPB or XPD missense mutations lead to Xeroderma pigmentosum, Cockayne's syndrome, Trichothiodystrophy, or COFS syndrome, suggesting that DNA repair and transcription defects are responsible for clinical heterogeneity. Complex phenotypes are also observed for RECQL4 helicase mutations responsible for Rothmund-Thomson syndrome, Baller-Gerold syndrome, or RAPADILINO. Bloom's syndrome causing missense mutations are found in the conserved helicase and RecQ C-terminal domain of BLM that interfere with helicase function. Although rare, patient-derived missense mutations in the exonuclease or helicase domain of Werner syndrome protein exist. Characterization of WRN separation-of-function mutants may provide insight to catalytic requirements for suppression of phenotypes associated with the premature aging disorder. Characterized FANCJ missense mutations associated with breast cancer or Fanconi anemia interfere with FANCJ helicase activity required for DNA repair and the replication stress response. For example, a FA patient-derived mutation in the FANCJ Iron-Sulfur domain was shown to uncouple its ATPase and translocase activity from DNA unwinding. Mutations in DDX11 (ChlR1) are responsible for Warsaw Breakage syndrome, a recently discovered autosomal recessive cohesinopathy. Ongoing and future studies will address clinically relevant helicase mutations and polymorphisms, including those that interfere with key protein interactions or exert dominant negative phenotypes (e.g., certain mutant alleles of Twinkle mitochondrial DNA helicase). Chemical rescue may be an approach to restore helicase activity in loss-of-function helicase disorders. Genetic and biochemical analyses of disease-causing missense mutations in human helicase disorders have led to new insights to the molecular defects underlying aberrant cellular and clinical phenotypes.
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Affiliation(s)
- Avvaru N Suhasini
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, 251 Bayview Drive, Baltimore, MD 21224, USA
| | - Robert M Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, 251 Bayview Drive, Baltimore, MD 21224, USA.
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25
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Xu YN, Bazeille N, Ding XY, Lu XM, Wang PY, Bugnard E, Grondin V, Dou SX, Xi XG. Multimeric BLM is dissociated upon ATP hydrolysis and functions as monomers in resolving DNA structures. Nucleic Acids Res 2012; 40:9802-14. [PMID: 22885301 PMCID: PMC3479192 DOI: 10.1093/nar/gks728] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Bloom (BLM) syndrome is an autosomal recessive disorder characterized by an increased risk for many types of cancers. Previous studies have shown that BLM protein forms a hexameric ring structure, but its oligomeric form in DNA unwinding is still not well clarified. In this work, we have used dynamic light scattering and various stopped-flow assays to study the active form and kinetic mechanism of BLM in DNA unwinding. It was found that BLM multimers were dissociated upon ATP hydrolysis. Steady-state and single-turnover kinetic studies revealed that BLM helicase always unwound duplex DNA in the monomeric form under conditions of varying enzyme and ATP concentrations as well as 3'-ssDNA tail lengths, with no sign of oligomerization being discerned. Measurements of ATPase activity further indicated that BLM helicase might still function as monomers in resolving highly structured DNAs such as Holliday junctions and D-loops. These results shed new light on the underlying mechanism of BLM-mediated DNA unwinding and on the molecular and functional basis for the phenotype of heterozygous carriers of BLM syndrome.
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Affiliation(s)
- Ya-Nan Xu
- Beijing National Laboratory for Condensed Matter Physics and CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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26
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Schreiner S, Wimmer P, Dobner T. Adenovirus degradation of cellular proteins. Future Microbiol 2012; 7:211-25. [PMID: 22324991 DOI: 10.2217/fmb.11.153] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Eukaryotic cells orchestrate constant synthesis and degradation of intracellular components, including soluble proteins and organelles. The two major intracellular degradation pathways are the ubiquitin/proteasome system and autophagy. Whereas ubiquitin/proteasome system is involved in rapid degradation of proteins, autophagy selectively removes protein aggregates and damaged organelles. Failure of these highly adjusted proteolytic systems to maintain basal turnover leads to altered cellular homeostasis. During evolution, certain viruses have developed mechanisms to exploit their functions to facilitate their own replication, prevent viral clearance and promote the outcome of infection. In this article, we summarize the current opinion on adenoviruses (Ad) and molecular host cell targets, extending on recent evidences for protein degradation pathways in infected cells. We describe recently identified connections between Ad-mediated proteolysis and viral replication with main emphasis on the function of certain Ad proteins.
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Affiliation(s)
- Sabrina Schreiner
- Heinrich-Pette-Institute, Leibniz-Institute for Experimental Virology, Martinistrasse 52, 20251 Hamburg, Germany. sabrina.schreiner@hpi. uni-hamburg.de
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27
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Wu Y, Sommers JA, Loiland JA, Kitao H, Kuper J, Kisker C, Brosh RM. The Q motif of Fanconi anemia group J protein (FANCJ) DNA helicase regulates its dimerization, DNA binding, and DNA repair function. J Biol Chem 2012; 287:21699-716. [PMID: 22582397 DOI: 10.1074/jbc.m112.351338] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The Q motif, conserved in a number of RNA and DNA helicases, is proposed to be important for ATP binding based on structural data, but its precise biochemical functions are less certain. FANCJ encodes a Q motif DEAH box DNA helicase implicated in Fanconi anemia and breast cancer. A Q25A mutation of the invariant glutamine in the Q motif abolished its ability to complement cisplatin or telomestatin sensitivity of a fancj null cell line and exerted a dominant negative effect. Biochemical characterization of the purified recombinant FANCJ-Q25A protein showed that the mutation disabled FANCJ helicase activity and the ability to disrupt protein-DNA interactions. FANCJ-Q25A showed impaired DNA binding and ATPase activity but displayed ATP binding and temperature-induced unfolding transition similar to FANCJ-WT. Size exclusion chromatography and sedimentation velocity analyses revealed that FANCJ-WT existed as molecular weight species corresponding to a monomer and a dimer, and the dimeric form displayed a higher specific activity for ATPase and helicase, as well as greater DNA binding. In contrast, FANCJ-Q25A existed only as a monomer, devoid of helicase activity. Thus, the Q motif is essential for FANCJ enzymatic activity in vitro and DNA repair function in vivo.
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Affiliation(s)
- Yuliang Wu
- Laboratory of Molecular Gerontology, National Institutes of Health Biomedical Research Center, NIA, Baltimore, Maryland 21224, USA
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Gyimesi M, Harami GM, Sarlós K, Hazai E, Bikádi Z, Kovács M. Complex activities of the human Bloom's syndrome helicase are encoded in a core region comprising the RecA and Zn-binding domains. Nucleic Acids Res 2012; 40:3952-63. [PMID: 22253018 PMCID: PMC3351180 DOI: 10.1093/nar/gks008] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Bloom's syndrome DNA helicase (BLM), a member of the RecQ family, is a key player in homologous recombination (HR)-based error-free DNA repair processes. During HR, BLM exerts various biochemical activities including single-stranded (ss) DNA translocation, separation and annealing of complementary DNA strands, disruption of complex DNA structures (e.g. displacement loops) and contributes to quality control of HR via clearance of Rad51 nucleoprotein filaments. We performed a quantitative mechanistic analysis of truncated BLM constructs that are shorter than the previously identified minimal functional module. Surprisingly, we found that a BLM construct comprising only the two conserved RecA domains and the Zn2+-binding domain (residues 642–1077) can efficiently perform all mentioned HR-related activities. The results demonstrate that the Zn2+-binding domain is necessary for functional interaction with DNA. We show that the extensions of this core, including the winged-helix domain and the strand separation hairpin identified therein in other RecQ-family helicases, are not required for mechanochemical activity per se and may instead play modulatory roles and mediate protein–protein interactions.
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Affiliation(s)
- Máté Gyimesi
- Department of Biochemistry, ELTE-MTA Momentum Motor Enzymology Research Group, Eötvös University, Pázmány P. s. 1/c, H-1117 Budapest, Hungary
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Identification of Trypanosoma brucei RMI1/BLAP75 homologue and its roles in antigenic variation. PLoS One 2011; 6:e25313. [PMID: 21980422 PMCID: PMC3182221 DOI: 10.1371/journal.pone.0025313] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 08/31/2011] [Indexed: 11/30/2022] Open
Abstract
At any time, each cell of the protozoan parasite Trypanosoma brucei expresses a single species of its major antigenic protein, the variant surface glycoprotein (VSG), from a repertoire of >2,000 VSG genes and pseudogenes. The potential to express different VSGs by transcription and recombination allows the parasite to escape the antibody-mediated host immune response, a mechanism known as antigenic variation. The active VSG is transcribed from a sub-telomeric polycistronic unit called the expression site (ES), whose promoter is 40–60 kb upstream of the VSG. While the mechanisms that initiate recombination remain unclear, the resolution phase of these reactions results in the recombinational replacement of the expressed VSG with a donor from one of three distinct chromosomal locations; sub-telomeric loci on the 11 essential chromosomes, on minichromosomes, or at telomere-distal loci. Depending on the type of recombinational replacement (single or double crossover, duplicative gene conversion, etc), several DNA-repair pathways have been thought to play a role. Here we show that VSG recombination relies on at least two distinct DNA-repair pathways, one of which requires RMI1-TOPO3α to suppress recombination and one that is dependent on RAD51 and RMI1. These genetic interactions suggest that both RAD51-dependent and RAD51-independent recombination pathways operate in antigenic switching and that trypanosomes differentially utilize recombination factors for VSG switching, depending on currently unknown parameters within the ES.
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RecQ helicases; at the crossroad of genome replication, repair, and recombination. Mol Biol Rep 2011; 39:4527-43. [PMID: 21947842 DOI: 10.1007/s11033-011-1243-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 09/14/2011] [Indexed: 01/07/2023]
Abstract
DNA helicases are ubiquitous enzymes that unwind double-stranded DNA in an ATP-dependent and directionally specific manner. Such an action is essential for the processes of DNA repair, recombination, transcription, and DNA replication. Here, I focus on a subgroup of DNA helicases, the RecQ family, which is highly conserved in evolution. Members of this conserved family of proteins have a key role in protecting and stabilizing the genome against deleterious changes. Deficiencies in RecQ helicases can lead to high levels of genomic instability and, in humans, to premature aging and increased susceptibility to cancer. Their diverse roles in DNA metabolism, which include a role in telomere maintenance, reflect interactions with multiple cellular proteins, some of which are multifunctional and also have very diverse functions. In this review, protein structural motifs and the roles of different domains will be discussed first. The Review moves on to speculate about the different models to explain why RecQ helicases are required to protect against genome instability.
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Wu Y, Brosh RM. Helicase-inactivating mutations as a basis for dominant negative phenotypes. Cell Cycle 2011; 9:4080-90. [PMID: 20980836 DOI: 10.4161/cc.9.20.13667] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
There is ample evidence from studies of both unicellular and multicellular organisms that helicase-inactivating mutations lead to cellular dysfunction and disease phenotypes. In this review, we will discuss the mechanisms underlying the basis for abnormal phenotypes linked to mutations in genes encoding DNA helicases. Recent evidence demonstrates that a clinically relevant patient missense mutation in Fanconi Anemia Complementation Group J exerts detrimental effects on the biochemical activities of the FANCJ helicase, and these molecular defects are responsible for aberrant genomic stability and a poor DNA damage response. The ability of FANCJ to use the energy from ATP hydrolysis to produce the force required to unwind duplex or G-quadruplex DNA structures or destabilize protein bound to DNA is required for its DNA repair functions in vivo. Strikingly, helicase-inactivating mutations can exert a spectrum of dominant negative phenotypes, indicating that expression of the mutant helicase protein potentially interferes with normal DNA metabolism and has an effect on basic cellular processes such as DNA replication, the DNA damage response and protein trafficking. This review emphasizes that future studies of clinically relevant mutations in helicase genes will be important to understand the molecular pathologies of the associated diseases and their impact on heterozygote carriers.
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Affiliation(s)
- Yuliang Wu
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, Baltimore, MD, USA
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The adenovirus E1b55K/E4orf6 complex induces degradation of the Bloom helicase during infection. J Virol 2010; 85:1887-92. [PMID: 21123383 DOI: 10.1128/jvi.02134-10] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The adenovirus (Ad) E1b55K and E4orf6 gene products assemble an E3 ubiquitin ligase complex that promotes degradation of cellular proteins. Among the known substrates are p53 and the Mre11-Rad50-Nbs1 (MRN) complex. Since members of the RecQ helicase family function together with MRN in genome maintenance, we investigated whether adenovirus affects RecQ proteins. We show that Bloom helicase (BLM) is degraded during adenovirus type 5 (Ad5) infection. BLM degradation is mediated by E1b55K/E4orf6 but is independent of MRN. We detected BLM localized at discrete foci around viral replication centers. These studies identify BLM as a new substrate for degradation by the adenovirus E1b55K/E4orf6 complex.
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TOPO3alpha influences antigenic variation by monitoring expression-site-associated VSG switching in Trypanosoma brucei. PLoS Pathog 2010; 6:e1000992. [PMID: 20628569 PMCID: PMC2900300 DOI: 10.1371/journal.ppat.1000992] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Accepted: 06/08/2010] [Indexed: 12/24/2022] Open
Abstract
Homologous recombination (HR) mediates one of the major mechanisms of trypanosome antigenic variation by placing a different variant surface glycoprotein (VSG) gene under the control of the active expression site (ES). It is believed that the majority of VSG switching events occur by duplicative gene conversion, but only a few DNA repair genes that are central to HR have been assigned a role in this process. Gene conversion events that are associated with crossover are rarely seen in VSG switching, similar to mitotic HR. In other organisms, TOPO3alpha (Top3 in yeasts), a type IA topoisomerase, is part of a complex that is involved in the suppression of crossovers. We therefore asked whether a related mechanism might suppress VSG recombination. Using a set of reliable recombination and switching assays that could score individual switching mechanisms, we discovered that TOPO3alpha function is conserved in Trypanosoma brucei and that TOPO3alpha plays a critical role in antigenic switching. Switching frequency increased 10-40-fold in the absence of TOPO3alpha and this hyper-switching phenotype required RAD51. Moreover, the preference of 70-bp repeats for VSG recombination was mitigated, while homology regions elsewhere in ES were highly favored, in the absence of TOPO3alpha. Our data suggest that TOPO3alpha may remove undesirable recombination intermediates constantly arising between active and silent ESs, thereby balancing ES integrity against VSG recombination.
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Rossi ML, Ghosh AK, Kulikowicz T, Croteau DL, Bohr VA. Conserved helicase domain of human RecQ4 is required for strand annealing-independent DNA unwinding. DNA Repair (Amst) 2010; 9:796-804. [PMID: 20451470 DOI: 10.1016/j.dnarep.2010.04.003] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2010] [Revised: 04/01/2010] [Accepted: 04/01/2010] [Indexed: 12/16/2022]
Abstract
Humans have five members of the well conserved RecQ helicase family: RecQ1, Bloom syndrome protein (BLM), Werner syndrome protein (WRN), RecQ4, and RecQ5, which are all known for their roles in maintaining genome stability. BLM, WRN, and RecQ4 are associated with premature aging and cancer predisposition. Of the three, RecQ4's biological and cellular roles have been least thoroughly characterized. Here we tested the helicase activity of purified human RecQ4 on various substrates. Consistent with recent results, we detected ATP-dependent RecQ4 unwinding of forked duplexes. However, our results provide the first evidence that human RecQ4's unwinding is independent of strand annealing, and that it does not require the presence of excess ssDNA. Moreover, we demonstrate that a point mutation of the conserved lysine in the Walker A motif abolished helicase activity, implying that not the N-terminal portion, but the helicase domain is solely responsible for the enzyme's unwinding activity. In addition, we demonstrate a novel stimulation of RecQ4's helicase activity by replication protein A, similar to that of RecQ1, BLM, WRN, and RecQ5. Together, these data indicate that specific biochemical activities and protein partners of RecQ4 are conserved with those of the other RecQ helicases.
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Affiliation(s)
- Marie L Rossi
- National Institute on Aging, Baltimore, MD 21224, United States
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Homologous recombination and maintenance of genome integrity: Cancer and aging through the prism of human RecQ helicases. Mech Ageing Dev 2008; 129:425-40. [DOI: 10.1016/j.mad.2008.03.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Revised: 03/07/2008] [Accepted: 03/07/2008] [Indexed: 01/05/2023]
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Gupta R, Brosh RM. Helicases as prospective targets for anti-cancer therapy. Anticancer Agents Med Chem 2008; 8:390-401. [PMID: 18473724 DOI: 10.2174/187152008784220339] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
It has been proposed that selective inactivation of a DNA repair pathway may enhance anti-cancer therapies that eliminate cancerous cells through the cytotoxic effects of DNA damaging agents or radiation. Given the unique and critically important roles of DNA helicases in the DNA damage response, DNA repair, and maintenance of genomic stability, a number of strategies currently being explored or in use to combat cancer may be either mediated or enhanced through the modulation of helicase function. The focus of this review will be to examine the roles of helicases in DNA repair that might be suitably targeted by cancer therapeutic approaches. Treatment of cancers with anti-cancer drugs such as small molecule compounds that modulate helicase expression or function is a viable approach to selectively kill cancer cells through the inactivation of helicase-dependent DNA repair pathways, particularly those associated with DNA recombination, replication restart, and cell cycle checkpoint.
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Affiliation(s)
- Rigu Gupta
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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Guo RB, Rigolet P, Ren H, Zhang B, Zhang XD, Dou SX, Wang PY, Amor-Gueret M, Xi XG. Structural and functional analyses of disease-causing missense mutations in Bloom syndrome protein. Nucleic Acids Res 2007; 35:6297-310. [PMID: 17878217 PMCID: PMC2094094 DOI: 10.1093/nar/gkm536] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Bloom syndrome (BS) is an autosomal recessive disorder characterized by genomic instability and the early development of many types of cancer. Missense mutations have been identified in the BLM gene (encoding a RecQ helicase) in affected individuals, but the molecular mechanism and the structural basis of the effects of these mutations remain to be elucidated. We analysed five disease-causing missense mutations that are localized in the BLM helicase core region: Q672R, I841T, C878R, G891E and C901Y. The disease-causing mutants had low ATPase and helicase activities but their ATP binding abilities were normal, except for Q672, whose ATP binding activity was lower than that of the intact BLM helicase. Mutants C878R, mapping near motif IV, and G891E and C901Y, mapping in motif IV, displayed severe DNA-binding defects. We used molecular modelling to analyse these mutations. Our work provides insights into the molecular basis of BLM pathology, and reveals structural elements implicated in coupling DNA binding to ATP hydrolysis and DNA unwinding. Our findings will help to explain the mechanism underlying BLM catalysis and interpreting new BLM causing mutations identified in the future.
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Affiliation(s)
- Rong-Bing Guo
- CNRS, UMR 2027, Institut Curie – Section de Recherche, Centre Universitaire, Bâtiment 110, F-91405 Orsay, CNRS UMR 8113, Ecole Normale Supérieure (ENS) Cachan, 61 avenue du Président Wilson, 94235 Cachan cedex, France, School of Life Science, East China Normal University, Science Building, 3663 North Zhongshan Road, Shanghai 200062 and Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
| | - Pascal Rigolet
- CNRS, UMR 2027, Institut Curie – Section de Recherche, Centre Universitaire, Bâtiment 110, F-91405 Orsay, CNRS UMR 8113, Ecole Normale Supérieure (ENS) Cachan, 61 avenue du Président Wilson, 94235 Cachan cedex, France, School of Life Science, East China Normal University, Science Building, 3663 North Zhongshan Road, Shanghai 200062 and Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
| | - Hua Ren
- CNRS, UMR 2027, Institut Curie – Section de Recherche, Centre Universitaire, Bâtiment 110, F-91405 Orsay, CNRS UMR 8113, Ecole Normale Supérieure (ENS) Cachan, 61 avenue du Président Wilson, 94235 Cachan cedex, France, School of Life Science, East China Normal University, Science Building, 3663 North Zhongshan Road, Shanghai 200062 and Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
| | - Bo Zhang
- CNRS, UMR 2027, Institut Curie – Section de Recherche, Centre Universitaire, Bâtiment 110, F-91405 Orsay, CNRS UMR 8113, Ecole Normale Supérieure (ENS) Cachan, 61 avenue du Président Wilson, 94235 Cachan cedex, France, School of Life Science, East China Normal University, Science Building, 3663 North Zhongshan Road, Shanghai 200062 and Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
| | - Xing-Dong Zhang
- CNRS, UMR 2027, Institut Curie – Section de Recherche, Centre Universitaire, Bâtiment 110, F-91405 Orsay, CNRS UMR 8113, Ecole Normale Supérieure (ENS) Cachan, 61 avenue du Président Wilson, 94235 Cachan cedex, France, School of Life Science, East China Normal University, Science Building, 3663 North Zhongshan Road, Shanghai 200062 and Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
| | - Shuo-Xing Dou
- CNRS, UMR 2027, Institut Curie – Section de Recherche, Centre Universitaire, Bâtiment 110, F-91405 Orsay, CNRS UMR 8113, Ecole Normale Supérieure (ENS) Cachan, 61 avenue du Président Wilson, 94235 Cachan cedex, France, School of Life Science, East China Normal University, Science Building, 3663 North Zhongshan Road, Shanghai 200062 and Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
| | - Peng-Ye Wang
- CNRS, UMR 2027, Institut Curie – Section de Recherche, Centre Universitaire, Bâtiment 110, F-91405 Orsay, CNRS UMR 8113, Ecole Normale Supérieure (ENS) Cachan, 61 avenue du Président Wilson, 94235 Cachan cedex, France, School of Life Science, East China Normal University, Science Building, 3663 North Zhongshan Road, Shanghai 200062 and Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
| | - Mounira Amor-Gueret
- CNRS, UMR 2027, Institut Curie – Section de Recherche, Centre Universitaire, Bâtiment 110, F-91405 Orsay, CNRS UMR 8113, Ecole Normale Supérieure (ENS) Cachan, 61 avenue du Président Wilson, 94235 Cachan cedex, France, School of Life Science, East China Normal University, Science Building, 3663 North Zhongshan Road, Shanghai 200062 and Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
| | - Xu Guang Xi
- CNRS, UMR 2027, Institut Curie – Section de Recherche, Centre Universitaire, Bâtiment 110, F-91405 Orsay, CNRS UMR 8113, Ecole Normale Supérieure (ENS) Cachan, 61 avenue du Président Wilson, 94235 Cachan cedex, France, School of Life Science, East China Normal University, Science Building, 3663 North Zhongshan Road, Shanghai 200062 and Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
- *To whom correspondence should be addressed. +33 1 69 86 31 81+33 1 69 86 94 29
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German J, Sanz MM, Ciocci S, Ye TZ, Ellis NA. Syndrome-causing mutations of the BLM gene in persons in the Bloom's Syndrome Registry. Hum Mutat 2007; 28:743-53. [PMID: 17407155 DOI: 10.1002/humu.20501] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Bloom syndrome (BS) is caused by homozygous or compound heterozygous mutations in the RecQ DNA helicase gene BLM. Since the molecular isolation of BLM, characterization of BS-causing mutations has been carried out systematically using samples stored in the Bloom's Syndrome Registry. In a survey of 134 persons with BS from the Registry, 64 different mutations were identified in 125 of them, 54 that cause premature protein-translation termination and 10 missense mutations. In 102 of the 125 persons in whom at least one BLM mutation was identified, the mutation was recurrent, that is, it was shared by two or more persons with BS; 19 of the 64 different mutations were recurrent. Ethnic affiliations of the persons who carry recurrent mutations indicate that the majority of such persons inherit their BLM mutation identical-by-descent from a recent common ancestor, a founder. The presence of widespread founder mutations in persons with BS points to population genetic processes that repeatedly and pervasively generate mutations that recur in unrelated persons.
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Affiliation(s)
- James German
- Weill Medical College of Cornell University, New York, New York, USA
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Heinicke S, Livstone MS, Lu C, Oughtred R, Kang F, Angiuoli SV, White O, Botstein D, Dolinski K. The Princeton Protein Orthology Database (P-POD): a comparative genomics analysis tool for biologists. PLoS One 2007; 2:e766. [PMID: 17712414 PMCID: PMC1942082 DOI: 10.1371/journal.pone.0000766] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2007] [Accepted: 07/18/2007] [Indexed: 02/07/2023] Open
Abstract
Many biological databases that provide comparative genomics information and tools are now available on the internet. While certainly quite useful, to our knowledge none of the existing databases combine results from multiple comparative genomics methods with manually curated information from the literature. Here we describe the Princeton Protein Orthology Database (P-POD, http://ortholog.princeton.edu), a user-friendly database system that allows users to find and visualize the phylogenetic relationships among predicted orthologs (based on the OrthoMCL method) to a query gene from any of eight eukaryotic organisms, and to see the orthologs in a wider evolutionary context (based on the Jaccard clustering method). In addition to the phylogenetic information, the database contains experimental results manually collected from the literature that can be compared to the computational analyses, as well as links to relevant human disease and gene information via the OMIM, model organism, and sequence databases. Our aim is for the P-POD resource to be extremely useful to typical experimental biologists wanting to learn more about the evolutionary context of their favorite genes. P-POD is based on the commonly used Generic Model Organism Database (GMOD) schema and can be downloaded in its entirety for installation on one's own system. Thus, bioinformaticians and software developers may also find P-POD useful because they can use the P-POD database infrastructure when developing their own comparative genomics resources and database tools.
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Affiliation(s)
- Sven Heinicke
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Michael S. Livstone
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Charles Lu
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Rose Oughtred
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Fan Kang
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Samuel V. Angiuoli
- The Institute for Genomic Research, Rockville, Maryland, United States of America
- Center for Bioinformatics and Computational Biology, University of Maryland, College Park, Maryland, United States of America
| | - Owen White
- The Institute for Genomic Research, Rockville, Maryland, United States of America
| | - David Botstein
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Kara Dolinski
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
- * To whom correspondence should be addressed. E-mail:
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40
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Davies SL, North PS, Hickson ID. Role for BLM in replication-fork restart and suppression of origin firing after replicative stress. Nat Struct Mol Biol 2007; 14:677-9. [PMID: 17603497 DOI: 10.1038/nsmb1267] [Citation(s) in RCA: 182] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Accepted: 06/06/2007] [Indexed: 11/09/2022]
Abstract
Mutations in BLM give rise to Bloom's syndrome, a genetic disorder associated with cancer predisposition and chromosomal instability. Using a dual-labeling system in isolated chromosome fibers, we show that the BLM protein is required for two aspects of the cellular response to replicative stress: efficient replication-fork restart and suppression of new origin firing. These functions require the helicase activity of BLM and the Thr99 residue targeted by stress-activated kinases.
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Affiliation(s)
- Sally L Davies
- Cancer Research UK Laboratories, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
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Xie J, Bessling SL, Cooper TK, Dietz HC, McCallion AS, Fisher S. Manipulating mitotic recombination in the zebrafish embryo through RecQ helicases. Genetics 2007; 176:1339-42. [PMID: 17483412 PMCID: PMC1894594 DOI: 10.1534/genetics.107.072983] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
RecQ DNA helicases resolve Rad-51-mediated recombination and suppress aberrant homologous recombination. RecQ gene loss is associated with cancer susceptibility and increased mitotic recombination. We have developed an in vivo assay based on a zebrafish pigment mutant for suppression of RecQ activity, and demonstrate that zebrafish RecQ genes have conserved function in suppressing mitotic recombination.
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Affiliation(s)
- Jing Xie
- McKusick–Nathans Institute of Genetic Medicine, Department of Molecular and Comparative Pathobiology and Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Seneca L. Bessling
- McKusick–Nathans Institute of Genetic Medicine, Department of Molecular and Comparative Pathobiology and Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Timothy K. Cooper
- McKusick–Nathans Institute of Genetic Medicine, Department of Molecular and Comparative Pathobiology and Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Harry C. Dietz
- McKusick–Nathans Institute of Genetic Medicine, Department of Molecular and Comparative Pathobiology and Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Andrew S. McCallion
- McKusick–Nathans Institute of Genetic Medicine, Department of Molecular and Comparative Pathobiology and Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Shannon Fisher
- McKusick–Nathans Institute of Genetic Medicine, Department of Molecular and Comparative Pathobiology and Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Corresponding author: The McKusick–Nathans Institute of Genetic Medicine, The Johns Hopkins University School of Medicine, 733 N. Broadway, BRB 455, Baltimore, MD 21205. E-mail:
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Abstract
The RecQ family of DNA helicases consists of specialized DNA unwinding enzymes that promote genomic stability through their participation in a number of cellular processes, including DNA replication, recombination, DNA damage signaling, and DNA repair pathways. Mutations resulting in the inactivation of some but not all members of the RecQ helicase family can lead to human syndromes which are characterized by marked chromosomal instability and an increased predisposition to cancer. An evolutionarily conserved interaction between RecQ helicases and topoisomerase 3s has been established, and this interaction is important in the regulation of recombination and genomic stability. Topoisomerases are critical in the cell because they relieve helical stress that arises when DNA is unwound. Topoisomerases function by breaking and rejoining DNA. By inhibition of the rejoining function, topoisomerase inhibitors are potent chemotherapeutic agents that have been used successfully in the treatment of hematologic malignancies and other cancers. This review discusses the roles of RecQ helicases in genomic stability, the interplay between RecQ helicases and topoisomerase 3s, and current and future prospects for targeting these interactions to develop novel anticancer therapies.
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Affiliation(s)
- Leslie L Woo
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
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43
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Sharma S, Doherty K, Brosh R. Mechanisms of RecQ helicases in pathways of DNA metabolism and maintenance of genomic stability. Biochem J 2006; 398:319-37. [PMID: 16925525 PMCID: PMC1559444 DOI: 10.1042/bj20060450] [Citation(s) in RCA: 193] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Helicases are molecular motor proteins that couple the hydrolysis of NTP to nucleic acid unwinding. The growing number of DNA helicases implicated in human disease suggests that their vital specialized roles in cellular pathways are important for the maintenance of genome stability. In particular, mutations in genes of the RecQ family of DNA helicases result in chromosomal instability diseases of premature aging and/or cancer predisposition. We will discuss the mechanisms of RecQ helicases in pathways of DNA metabolism. A review of RecQ helicases from bacteria to human reveals their importance in genomic stability by their participation with other proteins to resolve DNA replication and recombination intermediates. In the light of their known catalytic activities and protein interactions, proposed models for RecQ function will be summarized with an emphasis on how this distinct class of enzymes functions in chromosomal stability maintenance and prevention of human disease and cancer.
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Affiliation(s)
- Sudha Sharma
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, U.S.A
| | - Kevin M. Doherty
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, U.S.A
| | - Robert M. Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, U.S.A
- To whom correspondence should be addressed (email )
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Leng M, Chan DW, Luo H, Zhu C, Qin J, Wang Y. MPS1-dependent mitotic BLM phosphorylation is important for chromosome stability. Proc Natl Acad Sci U S A 2006; 103:11485-90. [PMID: 16864798 PMCID: PMC1518802 DOI: 10.1073/pnas.0601828103] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2006] [Indexed: 01/08/2023] Open
Abstract
Spindle assembly checkpoint (SAC) ensures bipolar attachment of chromosomes to the mitotic spindle and is essential for faithful chromosome segregation, thereby preventing chromosome instability (CIN). Genetic evidence suggests a causal link between compromised SAC, CIN, and cancer. Bloom syndrome (BS) is a genetic disorder that predisposes affected individuals to cancer. BS cells exhibit elevated rates of sister chromatid exchange, chromosome breaks, and CIN. The BS gene product, BLM, is a member of the RecQ helicases that are required for maintenance of genome stability. The BLM helicase interacts with proteins involved in DNA replication, recombination, and repair and is required for the repair of stalled-replication forks and in the DNA damage response. Here we present biochemical evidence to suggest a role of BLM phosphorylation during mitosis in maintaining chromosome stability. BLM is associated with the SAC kinase MPS1 and is phosphorylated at S144 in a MPS1-dependent manner. Phosphorylated BLM interacts with polo-like kinase 1, a mitotic kinase that binds to phosphoserine/threonine through its polo-box domain (PBD). Furthermore, BS cells expressing BLM-S144A show normal levels of sister chromatid exchange but fail to maintain the mitotic arrest when SAC is activated and exhibit a broad distribution of chromosome numbers. We propose that MPS1-dependent BLM phosphorylation is important for ensuring accurate chromosome segregation, and its deregulation may contribute to cancer.
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Affiliation(s)
- Mei Leng
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology and Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030
| | - Doug W. Chan
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology and Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030
| | - Hao Luo
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology and Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030
| | - Cihui Zhu
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology and Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030
| | - Jun Qin
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology and Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030
| | - Yi Wang
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology and Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030
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Spillare EA, Wang XW, von Kobbe C, Bohr VA, Hickson ID, Harris CC. Redundancy of DNA helicases in p53-mediated apoptosis. Oncogene 2006; 25:2119-23. [PMID: 16288211 PMCID: PMC1420682 DOI: 10.1038/sj.onc.1209242] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A subset of DNA helicases, the RecQ family, has been found to be associated with the p53-mediated apoptotic pathway and is involved in maintaining genomic integrity. This family contains the BLM and WRN helicases, in which germline mutations are responsible for Bloom and Werner syndromes, respectively. TFIIH DNA helicases, XPB and XPD, are also components in this apoptotic pathway. We hypothesized that there may be some redundancy between helicases in their ability to complement the attenuated p53-mediated apoptotic levels seen in cells from individuals with diseases associated with these defective helicase genes. The attenuated apoptotic phenotype in Bloom syndrome cells was rescued not only by ectopic expression of BLM, but also by WRN or XPB, both 3' --> 5' helicases, but not expression of the 5' --> 3' helicase XPD. Overexpression of Sgs1, a WRN/BLM yeast homolog, corrected the reduction in BS cells only, which is consistent with Sgs1 being evolutionarily most homologous to BLM. A restoration of apoptotic levels in cells from WS, XPB or XPD patients was attained only by overexpression of the specific helicase. Our data suggest a limited redundancy in the pathways of these RecQ helicases in p53-induced apoptosis.
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Affiliation(s)
- E A Spillare
- Laboratory of Human Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA
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Cohen PE, Pollack SE, Pollard JW. Genetic analysis of chromosome pairing, recombination, and cell cycle control during first meiotic prophase in mammals. Endocr Rev 2006; 27:398-426. [PMID: 16543383 DOI: 10.1210/er.2005-0017] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Meiosis is a double-division process that is preceded by only one DNA replication event to produce haploid gametes. The defining event in meiosis is prophase I, during which chromosome pairs locate each other, become physically connected, and exchange genetic information. Although many aspects of this process have been elucidated in lower organisms, there has been scant information available until now about the process in mammals. Recent advances in genetic analysis, especially in mice and humans, have revealed many genes that play essential roles in meiosis in mammals. These include cell cycle-regulatory proteins that couple the exit from the premeiotic DNA synthesis to the progression through prophase I, the chromosome structural proteins involved in synapsis, and the repair and recombination proteins that process the recombination events. Failure to adequately repair the DNA damage caused by recombination triggers meiotic checkpoints that result in ablation of the germ cells by apoptosis. These analyses have revealed surprising sexual dimorphism in the requirements of different gene products and a much less stringent checkpoint regulation in females. This may provide an explanation for the 10-fold increase in meiotic errors in females compared with males. This review provides a comprehensive analysis of the use of genetic manipulation, particularly in mice, but also of the analysis of mutations in humans, to elucidate the mechanisms that are required for traverse through prophase I.
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Affiliation(s)
- P E Cohen
- Department of Molecular Genetics, Center for the Study of Reproduction and Women's Health, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
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Huber MD, Duquette ML, Shiels JC, Maizels N. A Conserved G4 DNA Binding Domain in RecQ Family Helicases. J Mol Biol 2006; 358:1071-80. [PMID: 16530788 DOI: 10.1016/j.jmb.2006.01.077] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Revised: 01/17/2006] [Accepted: 01/20/2006] [Indexed: 11/18/2022]
Abstract
RecQ family helicases play important roles at G-rich domains of the genome, including the telomeres, rDNA, and immunoglobulin switch regions. This appears to reflect the unusual ability of enzymes in this family to unwind G4 DNA. How RecQ family helicases recognize this substrate has not been established. Here, we show that G4 DNA is a preferred target for BLM helicase within the context of long DNA molecules. We identify the RQC domain, found only in RecQ family enzymes, as an independent, high affinity and conserved G4 DNA binding domain; and show that binding to Holliday junctions involves both the RQC and the HRDC domains. These results provide mechanistic understanding of differences and redundancies of function and activities among RecQ family helicases, and of how deficiencies in human members of this family may contribute to genomic instability and disease.
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Affiliation(s)
- Michael D Huber
- Department of Biochemistry, University of Washington Medical School, Seattle, WA 98195, USA
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Hartung F, Puchta H. The RecQ gene family in plants. JOURNAL OF PLANT PHYSIOLOGY 2006; 163:287-96. [PMID: 16371241 DOI: 10.1016/j.jplph.2005.10.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Accepted: 10/15/2005] [Indexed: 05/05/2023]
Abstract
RecQ helicases are conserved throughout all kingdoms of life regarding their overall structure and function. They are 3'-5' DNA helicases resolving different recombinogenic DNA structures. The RecQ helicases are key factors in a number of DNA repair and recombination pathways involved in the maintenance of genome integrity. In eukaryotes the number of RecQ genes and the structure of RecQ proteins vary strongly between organisms. Therefore, they have been named RecQ-like genes. Knockouts of several RecQ-like genes cause severe diseases in animals or harmful cellular phenotypes in yeast. Until now the largest number of RecQ-like genes per organism has been found in plants. Arabidopsis and rice possess seven different RecQ-like genes each. In the almost completely sequenced genome of the moss Physcomitrella patens at least five RecQ-like genes are present. One of the major present and future research aims is to define putative plant-specific functions and to assign their roles in DNA repair and recombination pathways in relation to RecQ genes from other eukaryotes. Regarding their intron positions, the structures of six RecQ-like genes of dicots and monocots are virtually identical indicating a conservation over a time scale of 150 million years. In contrast to other eukaryotes one gene (RecQsim) exists exclusively in plants. It possesses an interrupted helicase domain but nevertheless seems to have maintained the RecQ function. Owing to a recent gene duplication besides the AtRecQl4A gene an additional RecQ-like gene (AtRecQl4B) exists in the Brassicaceae only. Genetic studies indicate that a AtRecQl4A knockout results in sensitivity to mutagens as well as an hyper-recombination phenotype. Since AtRecQl4B was still present, both genes must have non-redundant roles. Analysis of plant RecQ-like genes will not only increase the knowledge on DNA repair and recombination, but also on the evolution and radiation of protein families.
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Affiliation(s)
- Frank Hartung
- Botanisches Institut II, Universität Karlsruhe (TH), Kaiserstr. 12, 76128 Karlsruhe, Germany.
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Szekely AM, Bleichert F, Nümann A, Van Komen S, Manasanch E, Ben Nasr A, Canaan A, Weissman SM. Werner protein protects nonproliferating cells from oxidative DNA damage. Mol Cell Biol 2005; 25:10492-506. [PMID: 16287861 PMCID: PMC1291253 DOI: 10.1128/mcb.25.23.10492-10506.2005] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2004] [Revised: 01/10/2005] [Accepted: 08/31/2005] [Indexed: 02/06/2023] Open
Abstract
Werner syndrome, caused by mutations of the WRN gene, mimics many changes of normal aging. Although roles for WRN protein in DNA replication, recombination, and telomere maintenance have been suggested, the pathology of rapidly dividing cells is not a feature of Werner syndrome. To identify cellular events that are specifically vulnerable to WRN deficiency, we used RNA interference (RNAi) to knockdown WRN or BLM (the RecQ helicase mutated in Bloom syndrome) expression in primary human fibroblasts. Withdrawal of WRN or BLM produced accelerated cellular senescence phenotype and DNA damage response in normal fibroblasts, as evidenced by induction of gammaH2AX and 53BP1 nuclear foci. After WRN depletion, the induction of these foci was seen most prominently in nondividing cells. Growth in physiological (3%) oxygen or in the presence of an antioxidant prevented the development of the DNA damage foci in WRN-depleted cells, whereas acute oxidative stress led to inefficient repair of the lesions. Furthermore, WRN RNAi-induced DNA damage was suppressed by overexpression of the telomere-binding protein TRF2. These conditions, however, did not prevent the DNA damage response in BLM-ablated cells, suggesting a distinct role for WRN in DNA homeostasis in vivo. Thus, manifestations of Werner syndrome may reflect an impaired ability of slowly dividing cells to limit oxidative DNA damage.
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Affiliation(s)
- Anna M Szekely
- Department of Genetics, Yale University School of Medicine, TAC Bldg., Rm. S319, 300 Cedar St., New Haven, CT 06510, USA
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Paz-Elizur T, Brenner DE, Livneh Z. Interrogating DNA repair in cancer risk assessment. Cancer Epidemiol Biomarkers Prev 2005; 14:1585-7. [PMID: 16030087 DOI: 10.1158/1055-9965.epi-14-7-ed] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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