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Alterations in the p53 isoform ratio govern breast cancer cell fate in response to DNA damage. Cell Death Dis 2022; 13:907. [PMID: 36307393 PMCID: PMC9616954 DOI: 10.1038/s41419-022-05349-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 10/13/2022] [Accepted: 10/14/2022] [Indexed: 11/07/2022]
Abstract
Our previous studies have shown that p53 isoform expression is altered in breast cancer and related to prognosis. In particular, a high ∆40p53:p53α ratio is associated with worse disease-free survival. In this manuscript, the influence of altered Δ40p53 and p53α levels on the response to standard of care DNA-damaging agents used in breast cancer treatment was investigated in vitro. Our results revealed that a high Δ40p53:p53α ratio causes cells to respond differently to doxorubicin and cisplatin treatments. Δ40p53 overexpression significantly impairs the cells' sensitivity to doxorubicin through reducing apoptosis and DNA damage, whereas Δ40p53 knockdown has the opposite effect. Further, a high Δ40p53:p53α ratio inhibited the differential expression of several genes following doxorubicin and promoted DNA repair, impairing the cells' canonical response. Overall, our results suggest that the response of breast cancer cells to standard of care DNA-damaging therapies is dependent on the expression of p53 isoforms, which may contribute to outcomes in breast cancer.
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2
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Ababou M. Bloom syndrome and the underlying causes of genetic instability. Mol Genet Metab 2021; 133:35-48. [PMID: 33736941 DOI: 10.1016/j.ymgme.2021.03.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 02/01/2021] [Accepted: 03/06/2021] [Indexed: 11/27/2022]
Abstract
Autosomal hereditary recessive diseases characterized by genetic instability are often associated with cancer predisposition. Bloom syndrome (BS), a rare genetic disorder, with <300 cases reported worldwide, combines both. Indeed, patients with Bloom's syndrome are 150 to 300 times more likely to develop cancers than normal individuals. The wide spectrum of cancers developed by BS patients suggests that early initial events occur in BS cells which may also be involved in the initiation of carcinogenesis in the general population and these may be common to several cancers. BS is caused by mutations of both copies of the BLM gene, encoding the RecQ BLM helicase. This review discusses the different aspects of BS and the different cellular functions of BLM in genome surveillance and maintenance through its major roles during DNA replication, repair, and transcription. BLM's activities are essential for the stabilization of centromeric, telomeric and ribosomal DNA sequences, and the regulation of innate immunity. One of the key objectives of this work is to establish a link between BLM functions and the main clinical phenotypes observed in BS patients, as well as to shed new light on the correlation between the genetic instability and diseases such as immunodeficiency and cancer. The different potential implications of the BLM helicase in the tumorigenic process and the use of BLM as new potential target in the field of cancer treatment are also debated.
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Affiliation(s)
- Mouna Ababou
- Laboratory of Human Pathologies Biology, Department of Biology, Faculty of Sciences, University Mohammed V, Rabat, Morocco; Genomic Center of Human Pathologies, Faculty of medicine and Pharmacy, University Mohammed V, Rabat, Morocco.
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3
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Marks D, Heinen N, Bachmann L, Meermeyer S, Werner M, Gallego L, Hemmerich P, Bader V, Winklhofer KF, Schröder E, Knauer SK, Müller T. Amyloid precursor protein elevates fusion of promyelocytic leukemia nuclear bodies in human hippocampal areas with high plaque load. Acta Neuropathol Commun 2021; 9:66. [PMID: 33849647 PMCID: PMC8042982 DOI: 10.1186/s40478-021-01174-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 03/29/2021] [Indexed: 11/10/2022] Open
Abstract
The amyloid precursor protein (APP) is a type I transmembrane protein with unknown physiological function but potential impact in neurodegeneration. The current study demonstrates that APP signals to the nucleus causing the generation of aggregates consisting of its adapter protein FE65, the histone acetyltransferase TIP60 and the tumour suppressor proteins p53 and PML. APP C-terminal (APP-CT50) complexes co-localize and co-precipitate with p53 and PML. The PML nuclear body generation is induced and fusion occurs over time depending on APP signalling and STED imaging revealed active gene expression within the complex. We further show that the nuclear aggregates of APP-CT50 fragments together with PML and FE65 are present in the aged human brain but not in cerebral organoids differentiated from iPS cells. Notably, human Alzheimer’s disease brains reveal a highly significant reduction of these nuclear aggregates in areas with high plaque load compared to plaque-free areas of the same individual. Based on these results we conclude that APP-CT50 signalling to the nucleus takes place in the aged human brain and is involved in the pathophysiology of AD.
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4
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Kaur E, Agrawal R, Sengupta S. Functions of BLM Helicase in Cells: Is It Acting Like a Double-Edged Sword? Front Genet 2021; 12:634789. [PMID: 33777104 PMCID: PMC7994599 DOI: 10.3389/fgene.2021.634789] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Accepted: 02/11/2021] [Indexed: 12/14/2022] Open
Abstract
DNA damage repair response is an important biological process involved in maintaining the fidelity of the genome in eukaryotes and prokaryotes. Several proteins that play a key role in this process have been identified. Alterations in these key proteins have been linked to different diseases including cancer. BLM is a 3′−5′ ATP-dependent RecQ DNA helicase that is one of the most essential genome stabilizers involved in the regulation of DNA replication, recombination, and both homologous and non-homologous pathways of double-strand break repair. BLM structure and functions are known to be conserved across many species like yeast, Drosophila, mouse, and human. Genetic mutations in the BLM gene cause a rare, autosomal recessive disorder, Bloom syndrome (BS). BS is a monogenic disease characterized by genomic instability, premature aging, predisposition to cancer, immunodeficiency, and pulmonary diseases. Hence, these characteristics point toward BLM being a tumor suppressor. However, in addition to mutations, BLM gene undergoes various types of alterations including increase in the copy number, transcript, and protein levels in multiple types of cancers. These results, along with the fact that the lack of wild-type BLM in these cancers has been associated with increased sensitivity to chemotherapeutic drugs, indicate that BLM also has a pro-oncogenic function. While a plethora of studies have reported the effect of BLM gene mutations in various model organisms, there is a dearth in the studies undertaken to investigate the effect of its oncogenic alterations. We propose to rationalize and integrate the dual functions of BLM both as a tumor suppressor and maybe as a proto-oncogene, and enlist the plausible mechanisms of its deregulation in cancers.
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Affiliation(s)
- Ekjot Kaur
- Signal Transduction Laboratory-2, National Institute of Immunology, New Delhi, India
| | - Ritu Agrawal
- Signal Transduction Laboratory-2, National Institute of Immunology, New Delhi, India
| | - Sagar Sengupta
- Signal Transduction Laboratory-2, National Institute of Immunology, New Delhi, India
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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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Heterozygous germline BLM mutations increase susceptibility to asbestos and mesothelioma. Proc Natl Acad Sci U S A 2020; 117:33466-33473. [PMID: 33318203 PMCID: PMC7776606 DOI: 10.1073/pnas.2019652117] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Rare biallelic BLM gene mutations cause Bloom syndrome. Whether BLM heterozygous germline mutations (BLM +/-) cause human cancer remains unclear. We sequenced the germline DNA of 155 mesothelioma patients (33 familial and 122 sporadic). We found 2 deleterious germline BLM +/- mutations within 2 of 33 families with multiple cases of mesothelioma, one from Turkey (c.569_570del; p.R191Kfs*4) and one from the United States (c.968A>G; p.K323R). Some of the relatives who inherited these mutations developed mesothelioma, while none with nonmutated BLM were affected. Furthermore, among 122 patients with sporadic mesothelioma treated at the US National Cancer Institute, 5 carried pathogenic germline BLM +/- mutations. Therefore, 7 of 155 apparently unrelated mesothelioma patients carried BLM +/- mutations, significantly higher (P = 6.7E-10) than the expected frequency in a general, unrelated population from the gnomAD database, and 2 of 7 carried the same missense pathogenic mutation c.968A>G (P = 0.0017 given a 0.00039 allele frequency). Experiments in primary mesothelial cells from Blm +/- mice and in primary human mesothelial cells in which we silenced BLM revealed that reduced BLM levels promote genomic instability while protecting from cell death and promoted TNF-α release. Blm +/- mice injected intraperitoneally with asbestos had higher levels of proinflammatory M1 macrophages and of TNF-α, IL-1β, IL-3, IL-10, and IL-12 in the peritoneal lavage, findings linked to asbestos carcinogenesis. Blm +/- mice exposed to asbestos had a significantly shorter survival and higher incidence of mesothelioma compared to controls. We propose that germline BLM +/- mutations increase the susceptibility to asbestos carcinogenesis, enhancing the risk of developing mesothelioma.
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Amparo C, Clark J, Bedell V, Murata-Collins JL, Martella M, Pichiorri F, Warner EF, Abdelhamid MAS, Waller ZAE, Smith SS. Duplex DNA from Sites of Helicase-Polymerase Uncoupling Links Non-B DNA Structure Formation to Replicative Stress. Cancer Genomics Proteomics 2020; 17:101-115. [PMID: 32108033 DOI: 10.21873/cgp.20171] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 01/25/2020] [Accepted: 01/27/2020] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Replication impediments can produce helicase-polymerase uncoupling allowing lagging strand synthesis to continue for as much as 6 kb from the site of the impediment. MATERIALS AND METHODS We developed a cloning procedure designed to recover fragments from lagging strand near the helicase halt site. RESULTS A total of 62% of clones from a p53-deficient tumor cell line (PC3) and 33% of the clones from a primary cell line (HPS-19I) were within 5 kb of a G-quadruplex forming sequence. Analyses of a RACK7 gene sequence, that was cloned multiple times from the PC3 line, revealed multiple deletions in region about 1 kb from the cloned region that was present in a non-B conformation. Sequences from the region formed G-quadruplex and i-motif structures under physiological conditions. CONCLUSION Defects in components of non-B structure suppression systems (e.g. p53 helicase targeting) promote replication-linked damage selectively targeted to sequences prone to G-quadruplex and i-motif formation.
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Affiliation(s)
- Camille Amparo
- Division of Urology, City of Hope National Medical Center, Duarte, CA, U.S.A.,Beckman Research Institute, City of Hope, Duarte, CA, U.S.A
| | - Jarrod Clark
- Division of Urology, City of Hope National Medical Center, Duarte, CA, U.S.A.,Beckman Research Institute, City of Hope, Duarte, CA, U.S.A
| | - Victoria Bedell
- Division of Cytogenetics, City of Hope National Medical Center, Duarte, CA, U.S.A
| | | | - Marianna Martella
- Judy and Bernard Briskin Center for Multiple Myeloma Research, City of Hope National Medical Center, Duarte, CA, U.S.A.,Hematological Malignancies and Translational Science, City of Hope National Medical Center, Duarte, CA, U.S.A
| | - Flavia Pichiorri
- Judy and Bernard Briskin Center for Multiple Myeloma Research, City of Hope National Medical Center, Duarte, CA, U.S.A.,Hematological Malignancies and Translational Science, City of Hope National Medical Center, Duarte, CA, U.S.A
| | - Emily F Warner
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, U.K
| | | | - Zoë A E Waller
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, U.K
| | - Steven S Smith
- Beckman Research Institute, City of Hope, Duarte, CA, U.S.A. .,Hematological Malignancies and Translational Science, City of Hope National Medical Center, Duarte, CA, U.S.A
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8
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Zhang YX, Pan WY, Chen J. p53 and its isoforms in DNA double-stranded break repair. J Zhejiang Univ Sci B 2019; 20:457-466. [PMID: 31090271 DOI: 10.1631/jzus.b1900167] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
DNA double-stranded break (DSB) is one of the most catastrophic damages of genotoxic insult. Inappropriate repair of DNA DSBs results in the loss of genetic information, mutation, and the generation of harmful genomic rearrangements, which predisposes an organism to immunodeficiency, neurological damage, and cancer. The tumor repressor p53 plays a key role in DNA damage response, and has been found to be mutated in 50% of human cancer. p53, p63, and p73 are three members of the p53 gene family. Recent discoveries have shown that human p53 gene encodes at least 12 isoforms. Different p53 members and isoforms play various roles in orchestrating DNA damage response to maintain genomic integrity. This review briefly explores the functions of p53 and its isoforms in DNA DSB repair.
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Affiliation(s)
- Yu-Xi Zhang
- MOE Key Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Wen-Ya Pan
- MOE Key Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Jun Chen
- MOE Key Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
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9
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Gargallo P, Yáñez Y, Segura V, Juan A, Torres B, Balaguer J, Oltra S, Castel V, Cañete A. Li-Fraumeni syndrome heterogeneity. Clin Transl Oncol 2019; 22:978-988. [PMID: 31691207 DOI: 10.1007/s12094-019-02236-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 10/21/2019] [Indexed: 02/07/2023]
Abstract
Clinical variability is commonly seen in Li-Fraumeni syndrome. Phenotypic heterogeneity is present among different families affected by the same pathogenic variant in TP53 gene and among members of the same family. However, causes of this huge clinical spectrum have not been studied in depth. TP53 type mutation, polymorphic variants in TP53 gene or in TP53-related genes, copy number variations in particular regions, and/or epigenetic deregulation of TP53 expression might be responsible for clinical heterogeneity. In this review, recent advances in the understanding of genetic and epigenetic aspects influencing Li-Fraumeni phenotype are discussed.
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Affiliation(s)
- P Gargallo
- Pediatric Oncology, La Fe Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain.
| | - Y Yáñez
- Clinical and Translational Oncology Research Group, La Fe Hospital, Valencia, Spain
| | - V Segura
- Clinical and Translational Oncology Research Group, La Fe Hospital, Valencia, Spain
| | - A Juan
- Pediatric Oncology, La Fe Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
| | - B Torres
- Pediatric Oncology, La Fe Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
| | - J Balaguer
- Pediatric Oncology, La Fe Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
| | - S Oltra
- Genetics Unit, La Fe Hospital, Valencia, Spain.,Genetics Department, Valencia University, Valencia, Spain
| | - V Castel
- Pediatric Oncology, La Fe Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
| | - A Cañete
- Pediatric Oncology, La Fe Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
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10
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Lebel M, Monnat RJ. Werner syndrome (WRN) gene variants and their association with altered function and age-associated diseases. Ageing Res Rev 2018; 41:82-97. [PMID: 29146545 DOI: 10.1016/j.arr.2017.11.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 11/07/2017] [Accepted: 11/09/2017] [Indexed: 01/14/2023]
Abstract
Werner syndrome (WS) is a heritable autosomal recessive human disorder characterized by the premature onset of several age-associated pathologies including cancer. The protein defective in WS patients, WRN, is encoded by a member of the human RECQ gene family that contains both a DNA exonuclease and a helicase domain. WRN has been shown to participate in several DNA metabolic pathways including DNA replication, recombination and repair, as well as telomere maintenance and transcription modulation. Here we review base pair-level genetic variation that has been documented in WRN, with an emphasis on non-synonymous coding single nucleotide polymorphisms (SNPs) and their associations with anthropomorphic features, longevity and disease risk. These associations have been challenging to identify, as many reported WRN SNP associations appear to be further conditioned upon ethnic, age, gender or other environmental co-variables. The WRN variant phenotypic associations identified to date are intriguing, and several are of clear clinical import. Consequently, it will be important to extend these initial associations and to identify the mechanisms and conditions under which specific WRN variants may compromise WRN function to drive cellular and organismal phenotypes as well as disease risk.
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Affiliation(s)
- Michel Lebel
- Centre de recherche du CHU de Québec, Pavillon CHUL Université Laval, Faculté de Médecine, Québec City, Québec, G1V 4G2, Canada.
| | - Raymond J Monnat
- Departments of Pathology and Genome Sciences, University of Washington, Seattle, WA 98195, USA
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11
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Lin YH, Jewell BE, Gingold J, Lu L, Zhao R, Wang LL, Lee DF. Osteosarcoma: Molecular Pathogenesis and iPSC Modeling. Trends Mol Med 2017; 23:737-755. [PMID: 28735817 DOI: 10.1016/j.molmed.2017.06.004] [Citation(s) in RCA: 107] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 06/13/2017] [Accepted: 06/15/2017] [Indexed: 12/17/2022]
Abstract
Rare hereditary disorders provide unequivocal evidence of the importance of genes in human disease pathogenesis. Familial syndromes that predispose to osteosarcomagenesis are invaluable in understanding the underlying genetics of this malignancy. Recently, patient-derived induced pluripotent stem cells (iPSCs) have been successfully utilized to model Li-Fraumeni syndrome (LFS)-associated bone malignancy, demonstrating that iPSCs can serve as an in vitro disease model to elucidate osteosarcoma etiology. We provide here an overview of osteosarcoma predisposition syndromes and review recently established iPSC disease models for these familial syndromes. Merging molecular information gathered from these models with the current knowledge of osteosarcoma biology will help us to gain a deeper understanding of the pathological mechanisms underlying osteosarcomagenesis and will potentially aid in the development of future patient therapies.
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Affiliation(s)
- Yu-Hsuan Lin
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX 77030, USA; These authors contributed equally to this work
| | - Brittany E Jewell
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX 77030, USA; The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX 77030, USA; These authors contributed equally to this work
| | - Julian Gingold
- Women's Health Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, USA; These authors contributed equally to this work
| | - Linchao Lu
- Texas Children's Cancer Center, Department of Pediatrics, Section of Hematology/Oncology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Ruiying Zhao
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Lisa L Wang
- Texas Children's Cancer Center, Department of Pediatrics, Section of Hematology/Oncology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Dung-Fang Lee
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX 77030, USA; The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX 77030, USA; Center for Stem Cell and Regenerative Medicine, The Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; Center for Precision Health, School of Biomedical Informatics and School of Public Health, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA.
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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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Abstract
The cells in the human body are continuously challenged by a variety of genotoxic attacks. Erroneous repair of the DNA can lead to mutations and chromosomal aberrations that can alter the functions of tumor suppressor genes or oncogenes, thus causing cancer development. As a central tumor suppressor, p53 guards the genome by orchestrating a variety of DNA-damage-response (DDR) mechanisms. Already early in metazoan evolution, p53 started controlling the apoptotic demise of genomically compromised cells. p53 plays a prominent role as a facilitator of DNA repair by halting the cell cycle to allow time for the repair machineries to restore genome stability. In addition, p53 took on diverse roles to also directly impact the activity of various DNA-repair systems. It thus appears as if p53 is multitasking in providing protection from cancer development by maintaining genome stability.
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Affiliation(s)
- Ashley B Williams
- Medical Faculty, Institute for Genome Stability in Ageing and Disease, University of Cologne, 50931 Cologne, Germany Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne (CMMC) and Systems Biology of Ageing Cologne, University of Cologne, 50931 Cologne, Germany
| | - Björn Schumacher
- Medical Faculty, Institute for Genome Stability in Ageing and Disease, University of Cologne, 50931 Cologne, Germany Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), Center for Molecular Medicine Cologne (CMMC) and Systems Biology of Ageing Cologne, University of Cologne, 50931 Cologne, Germany
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14
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Keijzers G, Maynard S, Shamanna RA, Rasmussen LJ, Croteau DL, Bohr VA. The role of RecQ helicases in non-homologous end-joining. Crit Rev Biochem Mol Biol 2014; 49:463-72. [PMID: 25048400 DOI: 10.3109/10409238.2014.942450] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
DNA double-strand breaks are highly toxic DNA lesions that cause genomic instability, if not efficiently repaired. RecQ helicases are a family of highly conserved proteins that maintain genomic stability through their important roles in several DNA repair pathways, including DNA double-strand break repair. Double-strand breaks can be repaired by homologous recombination (HR) using sister chromatids as templates to facilitate precise DNA repair, or by an HR-independent mechanism known as non-homologous end-joining (NHEJ) (error-prone). NHEJ is a non-templated DNA repair process, in which DNA termini are directly ligated. Canonical NHEJ requires DNA-PKcs and Ku70/80, while alternative NHEJ pathways are DNA-PKcs and Ku70/80 independent. This review discusses the role of RecQ helicases in NHEJ, alternative (or back-up) NHEJ (B-NHEJ) and microhomology-mediated end-joining (MMEJ) in V(D)J recombination, class switch recombination and telomere maintenance.
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Affiliation(s)
- Guido Keijzers
- Department of Cellular and Molecular Medicine, Center for Healthy Aging, University of Copenhagen , Copenhagen , Denmark and
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15
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Tikoo S, Madhavan V, Hussain M, Miller ES, Arora P, Zlatanou A, Modi P, Townsend K, Stewart GS, Sengupta S. Ubiquitin-dependent recruitment of the Bloom syndrome helicase upon replication stress is required to suppress homologous recombination. EMBO J 2013; 32:1778-92. [PMID: 23708797 DOI: 10.1038/emboj.2013.117] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Accepted: 05/02/2013] [Indexed: 12/25/2022] Open
Abstract
Limiting the levels of homologous recombination (HR) that occur at sites of DNA damage is a major role of BLM helicase. However, very little is known about the mechanisms dictating its relocalization to these sites. Here, we demonstrate that the ubiquitin/SUMO-dependent DNA damage response (UbS-DDR), controlled by the E3 ligases RNF8/RNF168, triggers BLM recruitment to sites of replication fork stalling via ubiquitylation in the N-terminal region of BLM and subsequent BLM binding to the ubiquitin-interacting motifs of RAP80. Furthermore, we show that this mechanism of BLM relocalization is essential for BLM's ability to suppress excessive/uncontrolled HR at stalled replication forks. Unexpectedly, we also uncovered a requirement for RNF8-dependent ubiquitylation of BLM and PML for maintaining the integrity of PML-associated nuclear bodies and as a consequence the localization of BLM to these structures. Lastly, we identified a novel role for RAP80 in preventing proteasomal degradation of BLM in unstressed cells. Taken together, these data highlight an important biochemical link between the UbS-DDR and BLM-dependent pathways involved in maintaining genome stability.
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Affiliation(s)
- Shweta Tikoo
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India
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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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17
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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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18
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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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19
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Rezazadeh S. On BLM helicase in recombination-mediated telomere maintenance. Mol Biol Rep 2012; 40:3049-64. [DOI: 10.1007/s11033-012-2379-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 12/17/2012] [Indexed: 11/29/2022]
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20
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De S, Kumari J, Mudgal R, Modi P, Gupta S, Futami K, Goto H, Lindor NM, Furuichi Y, Mohanty D, Sengupta S. RECQL4 is essential for the transport of p53 to mitochondria in normal human cells in the absence of exogenous stress. J Cell Sci 2012; 125:2509-22. [PMID: 22357944 DOI: 10.1242/jcs.101501] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Mutations in RECQL4 helicase are associated with Rothmund-Thomson syndrome (RTS). A subset of RTS patients is predisposed to cancer and is sensitive to DNA damaging agents. The enhanced sensitivity of cells from RTS patients correlates with the accumulation of transcriptionally active nuclear p53. We found that in untreated normal human cells these two nuclear proteins, p53 and RECQL4, instead colocalize in the mitochondrial nucleoids. RECQL4 accumulates in mitochondria in all phases of the cell cycle except S phase and physically interacts with p53 only in the absence of DNA damage. p53-RECQL4 binding leads to the masking of the nuclear localization signal of p53. The N-terminal 84 amino acids of RECQL4 contain a mitochondrial localization signal, which causes the localization of RECQL4-p53 complex to the mitochondria. RECQL4-p53 interaction is disrupted after stress, allowing p53 translocation to the nucleus. In untreated normal cells RECQL4 optimizes de novo replication of mtDNA, which is consequently decreased in fibroblasts from RTS patients. Wild-type RECQL4-complemented RTS cells show relocalization of both RECQL4 and p53 to the mitochondria, loss of p53 activation, restoration of de novo mtDNA replication and resistance to different types of DNA damage. In cells expressing Δ84 RECQL4, which cannot translocate to mitochondria, all the above functions are compromised. The recruitment of p53 to the sites of de novo mtDNA replication is also regulated by RECQL4. Thus these findings elucidate the mechanism by which p53 is regulated by RECQL4 in unstressed normal cells and also delineates the mitochondrial functions of the helicase.
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Affiliation(s)
- Siddharth De
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India
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21
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Wiktor-Brown DM, Sukup-Jackson MR, Fakhraldeen SA, Hendricks CA, Engelward BP. p53 null fluorescent yellow direct repeat (FYDR) mice have normal levels of homologous recombination. DNA Repair (Amst) 2011; 10:1294-9. [PMID: 21993421 DOI: 10.1016/j.dnarep.2011.09.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 09/07/2011] [Accepted: 09/11/2011] [Indexed: 01/16/2023]
Abstract
The tumor suppressor p53 is a transcription factor whose function is critical for maintaining genomic stability in mammalian cells. In response to DNA damage, p53 initiates a signaling cascade that results in cell cycle arrest, DNA repair or, if the damage is severe, programmed cell death. In addition, p53 interacts with repair proteins involved in homologous recombination. Mitotic homologous recombination (HR) plays an essential role in the repair of double-strand breaks (DSBs) and broken replication forks. Loss of function of either p53 or HR leads to an increased risk of cancer. Given the importance of both p53 and HR in maintaining genomic integrity, we analyzed the effect of p53 on HR in vivo using Fluorescent Yellow Direct Repeat (FYDR) mice as well as with the sister chromatid exchange (SCE) assay. FYDR mice carry a direct repeat substrate in which an HR event can yield a fluorescent phenotype. Here, we show that p53 status does not significantly affect spontaneous HR in adult pancreatic cells in vivo or in primary fibroblasts in vitro when assessed using the FYDR substrate and SCEs. In addition, primary fibroblasts from p53 null mice do not show increased susceptibility to DNA damage-induced HR when challenged with mitomycin C. Taken together, the FYDR assay and SCE analysis indicate that, for some tissues and cell types, p53 status does not greatly impact HR.
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Affiliation(s)
- Dominika M Wiktor-Brown
- Massachusetts Institute of Technology, Department of Biological Engineering, 77 Massachusetts Avenue, 16-743, Cambridge, MA 02139, United States
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22
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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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23
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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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24
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Abstract
The RecQ helicases are conserved from bacteria to humans and play a critical role in genome stability. In humans, loss of RecQ gene function is associated with cancer predisposition and/or premature aging. Recent experiments have shown that the RecQ helicases function during distinct steps during DNA repair; DNA end resection, displacement-loop (D-loop) processing, branch migration, and resolution of double Holliday junctions (dHJs). RecQ function in these different processing steps has important implications for its role in repair of double-strand breaks (DSBs) that occur during DNA replication and meiosis, as well as at specific genomic loci such as telomeres.
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Affiliation(s)
- Kara A Bernstein
- Columbia University Medical Center, Department of Genetics & Development, New York, New York 10032, USA.
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25
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Vinciguerra P, Godinho SA, Parmar K, Pellman D, D'Andrea AD. Cytokinesis failure occurs in Fanconi anemia pathway-deficient murine and human bone marrow hematopoietic cells. J Clin Invest 2010; 120:3834-42. [PMID: 20921626 DOI: 10.1172/jci43391] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2010] [Accepted: 08/18/2010] [Indexed: 01/18/2023] Open
Abstract
Fanconi anemia (FA) is a genomic instability disorder characterized by bone marrow failure and cancer predisposition. FA is caused by mutations in any one of several genes that encode proteins cooperating in a repair pathway and is required for cellular resistance to DNA crosslinking agents. Recent studies suggest that the FA pathway may also play a role in mitosis, since FANCD2 and FANCI, the 2 key FA proteins, are localized to the extremities of ultrafine DNA bridges (UFBs), which link sister chromatids during cell division. However, whether FA proteins regulate cell division remains unclear. Here we have shown that FA pathway-deficient cells display an increased number of UFBs compared with FA pathway-proficient cells. The UFBs were coated by BLM (the RecQ helicase mutated in Bloom syndrome) in early mitosis. In contrast, the FA protein FANCM was recruited to the UFBs at a later stage. The increased number of bridges in FA pathway-deficient cells correlated with a higher rate of cytokinesis failure resulting in binucleated cells. Binucleated cells were also detectable in primary murine FA pathway-deficient hematopoietic stem cells (HSCs) and bone marrow stromal cells from human patients with FA. Based on these observations, we suggest that cytokinesis failure followed by apoptosis may contribute to bone marrow failure in patients with FA.
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Affiliation(s)
- Patrizia Vinciguerra
- Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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26
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Wyllie AH. "Where, O death, is thy sting?" A brief review of apoptosis biology. Mol Neurobiol 2010; 42:4-9. [PMID: 20552413 PMCID: PMC2894370 DOI: 10.1007/s12035-010-8125-5] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Accepted: 04/05/2010] [Indexed: 02/07/2023]
Abstract
Apoptosis was a term introduced in 1972 to distinguish a mode of cell death with characteristic morphology and apparently regulated, endogenously driven mechanisms. The effector processes responsible for apoptosis are now mostly well known, involving activation of caspases and Bcl2 family members in response to a wide variety of physiological and injury-induced signals. The factors that lead of the decision to activate apoptosis as opposed to adaptive responses to such signals (e.g. autophagy, cycle arrest, protein synthesis shutoff) are less well understood, but the intranuclear Promyelocytic Leukaemia Body (PML body) may create a local microenvironment in which the audit of DNA damage may occur, informed by the extent of the damage, the adequacy of its repair and other aspects of cell status.
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Affiliation(s)
- Andrew H Wyllie
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB21QP, UK.
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27
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Lee MS, Yaar M, Eller MS, Rünger TM, Gao Y, Gilchrest BA. Telomeric DNA induces p53-dependent reactive oxygen species and protects against oxidative damage. J Dermatol Sci 2009; 56:154-62. [PMID: 19906512 DOI: 10.1016/j.jdermsci.2009.08.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Revised: 07/20/2009] [Accepted: 08/24/2009] [Indexed: 01/12/2023]
Abstract
BACKGROUND Reactive oxygen species (ROS) are generated by cellular metabolism as well as by exogenous agents. While ROS can promote cellular senescence, they can also act as signaling molecules for processes that do not lead to senescence. Telomere homolog oligonucleotides (T-oligos) induce adaptive DNA damage responses including increased DNA repair capacity and these effects are mediated, at least in part, through p53. OBJECTIVE Studies were undertaken to determine whether such p53-mediated protective responses include enhanced antioxidant defenses. METHODS Normal human fibroblasts as well as R2F fibroblasts expressing wild type or dominant negative p53 were treated with an 11-base T-oligo, a complementary control oligo or diluents alone and then examined by western blot analysis, immunofluorescence microscopy and various biochemical assays. RESULTS We now report that T-oligo increases the level of the antioxidant enzymes superoxide dismutase 1 and 2 and protects cells from oxidative damage; and that telomere-based gammaH2AX (DNA damage) foci that form in response to T-oligos contain phosphorylated ATM and Chk2, proteins known to activate p53 and to mediate cell cycle arrest in response to oxidative stress. Further, T-oligo increases cellular ROS levels via a p53-dependent pathway, and these increases are abrogated by the NAD(P)H oxidase inhibitor diphenyliodonium chloride. CONCLUSION These results suggest the existence of innate telomere-based protective responses that act to reduce oxidative damage to cells. T-oligo treatment induces the same responses and offers a new model for studying intracellular ROS signaling and the relationships between DNA damage, ROS, oxidative stress, and cellular defense mechanisms.
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Affiliation(s)
- Margaret S Lee
- Department of Dermatology, Boston University School of Medicine, Boston, MA 02118, USA
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28
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Ahn J, Poyurovsky MV, Baptiste N, Beckerman R, Cain C, Mattia M, McKinney K, Zhou J, Zupnick A, Gottifredi V, Prives C. Dissection of the sequence-specific DNA binding and exonuclease activities reveals a superactive yet apoptotically impaired mutant p53 protein. Cell Cycle 2009; 8:1603-15. [PMID: 19462533 DOI: 10.4161/cc.8.10.8548] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Both sequence-specific DNA binding and exonuclease activities have been mapped to the central conserved core domain of p53. To gain more information about these two activities a series of mutants were generated that changed core domain histidine residues. Of these mutants, only one, H115N p53, showed markedly reduced exonuclease activity (ca. 15% of wild-type). Surprisingly, purified H115N p53 protein was found to be significantly more potent than wild-type p53 in binding to DNA by several criteria including gel mobility shift assay, filter binding and DNase I footprinting. Interestingly as well, non-specific DNA binding by the core domain of H115N p53 is superior to that of wild-type p53. To study H115N p53 in vivo, clones of H1299 cells expressing tetracycline regulated wild-type or H115N p53 were generated. H115N was both more potent than wild-type p53 in inducing p53 target genes such as p21 and PIG3 and was also more effective in arresting cells in G1. Unexpectedly, in contrast to wild-type p53, H115N p53 was markedly impaired in causing apoptosis when cells were subjected to DNA damage. Our results indicate that the exonuclease activity and transcriptional activation functions of p53 can be separated. They also extend previous findings showing that cell cycle arrest and apoptosis are separable functions of p53. Finally, these experiments confirm that DNA binding and xonuclease activities are distinct features of the p53 core domain.
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Affiliation(s)
- Jinwoo Ahn
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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29
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Babbe H, McMenamin J, Hobeika E, Wang J, Rodig SJ, Reth M, Leder P. Genomic instability resulting from Blm deficiency compromises development, maintenance, and function of the B cell lineage. THE JOURNAL OF IMMUNOLOGY 2009; 182:347-60. [PMID: 19109166 DOI: 10.4049/jimmunol.182.1.347] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The RecQ family helicase BLM is critically involved in the maintenance of genomic stability, and BLM mutation causes the heritable disorder Bloom's syndrome. Affected individuals suffer from a predisposition to a multitude of cancer types and an ill-defined immunodeficiency involving low serum Ab titers. To investigate its role in B cell biology, we inactivated murine Blm specifically in B lymphocytes in vivo. Numbers of developing B lymphoid cells in the bone marrow and mature B cells in the periphery were drastically reduced upon Blm inactivation. Of the major peripheral B cell subsets, B1a cells were most prominently affected. In the sera of Blm-deficient naive mice, concentrations of all Ig isotypes were low, particularly IgG3. Specific IgG Ab responses upon immunization were poor and mutant B cells exhibited a generally reduced Ab class switch capacity in vitro. We did not find evidence for a crucial role of Blm in the mechanism of class switch recombination. However, a modest shift toward microhomology-mediated switch junction formation was observed in Blm-deficient B cells. Finally, a cohort of p53-deficient, conditional Blm knockout mice revealed an increased propensity for B cell lymphoma development. Impaired cell cycle progression and survival as well as high rates of chromosomal structural abnormalities in mutant B cell blasts were identified as the basis for the observed effects. Collectively, our data highlight the importance of BLM-dependent genome surveillance for B cell immunity by ensuring proper development and function of the various B cell subsets while counteracting lymphomagenesis.
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Affiliation(s)
- Holger Babbe
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
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30
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Ding SL, Shen CY. Model of human aging: recent findings on Werner's and Hutchinson-Gilford progeria syndromes. Clin Interv Aging 2008; 3:431-44. [PMID: 18982914 PMCID: PMC2682376 DOI: 10.2147/cia.s1957] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The molecular mechanisms involved in human aging are complicated. Two progeria syndromes, Werner's syndrome (WS) and Hutchinson-Gilford progeria syndrome (HGPS), characterized by clinical features mimicking physiological aging at an early age, provide insights into the mechanisms of natural aging. Based on recent findings on WS and HGPS, we suggest a model of human aging. Human aging can be triggered by two main mechanisms, telomere shortening and DNA damage. In telomere-dependent aging, telomere shortening and dysfunction may lead to DNA damage responses which induce cellular senescence. In DNA damage-initiated aging, DNA damage accumulates, along with DNA repair deficiencies, resulting in genomic instability and accelerated cellular senescence. In addition, aging due to both mechanisms (DNA damage and telomere shortening) is strongly dependent on p53 status. These two mechanisms can also act cooperatively to increase the overall level ofgenomic instability, triggering the onset of human aging phenotypes.
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Affiliation(s)
- Shian-Ling Ding
- Department of Nursing, Kang-Ning Junior College of Medical Care and Management,Taipei,Taiwan.
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31
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Singh TR, Ali AM, Busygina V, Raynard S, Fan Q, Du CH, Andreassen PR, Sung P, Meetei AR. BLAP18/RMI2, a novel OB-fold-containing protein, is an essential component of the Bloom helicase-double Holliday junction dissolvasome. Genes Dev 2008; 22:2856-68. [PMID: 18923083 DOI: 10.1101/gad.1725108] [Citation(s) in RCA: 182] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Bloom Syndrome is an autosomal recessive cancer-prone disorder caused by mutations in the BLM gene. BLM encodes a DNA helicase of the RECQ family, and associates with Topo IIIalpha and BLAP75/RMI1 (BLAP for BLM-associated polypeptide/RecQ-mediated genome instability) to form the BTB (BLM-Topo IIIalpha-BLAP75/RMI1) complex. This complex can resolve the double Holliday junction (dHJ), a DNA intermediate generated during homologous recombination, to yield noncrossover recombinants exclusively. This attribute of the BTB complex likely serves to prevent chromosomal aberrations and rearrangements. Here we report the isolation and characterization of a novel member of the BTB complex termed BLAP18/RMI2. BLAP18/RMI2 contains a putative OB-fold domain, and several lines of evidence suggest that it is essential for BTB complex function. First, the majority of BLAP18/RMI2 exists in complex with Topo IIIalpha and BLAP75/RMI1. Second, depletion of BLAP18/RMI2 results in the destabilization of the BTB complex. Third, BLAP18/RMI2-depleted cells show spontaneous chromosomal breaks and are sensitive to methyl methanesulfonate treatment. Fourth, BLAP18/RMI2 is required to target BLM to chromatin and for the assembly of BLM foci upon hydroxyurea treatment. Finally, BLAP18/RMI2 stimulates the dHJ resolution capability of the BTB complex. Together, these results establish BLAP18/RMI2 as an essential member of the BTB dHJ dissolvasome that is required for the maintenance of a stable genome.
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Affiliation(s)
- Thiyam Ramsing Singh
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Research Foundation, University of Cincinnati College of Medicine, Cincinnati, Ohio 45229, USA
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32
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Association of human DNA helicase RecQ5beta with RNA polymerase II and its possible role in transcription. Biochem J 2008; 413:505-16. [PMID: 18419580 DOI: 10.1042/bj20071392] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Although RecQ5beta is a ssDNA (single-stranded DNA)-stimulated ATPase and an ATP-dependent DNA helicase with strand-annealing activities, its cellular function remains to be explored. In the present paper, we used immunopurification and MS-based analyses to show that human DNA helicase RecQ5beta is associated with at least four RNAP II (RNA polymerase II) subunits. RecQ5beta was also present in complexes immunoprecipitated using three different antibodies against the large subunit of RNAP II, or in complexes immunoprecipitated using an anti-FLAG antibody against either FLAG-RNAP II 33 kDa subunit or FLAG-Pin1. Different regions of the non-helicase domain of the RecQ5beta molecule were associated with hypophosphorylated and hyperphosphorylated forms of the RNAP II large subunit independently of DNA and RNA. RecQ5beta was also found in nuclear chromatin fractions and associated with the coding regions of the LDL (low-density lipoprotein) receptor and beta-actin genes. Knockdown of the RecQ5beta transcript increased the transcription of those genes. The results of the present study suggest that RecQ5beta has suppressive roles in events associated with RNAP II-dependent transcription.
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33
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Cabral REC, Queille S, Bodemer C, de Prost Y, Neto JBC, Sarasin A, Daya-Grosjean L. Identification of new RECQL4 mutations in Caucasian Rothmund-Thomson patients and analysis of sensitivity to a wide range of genotoxic agents. Mutat Res 2008; 643:41-7. [PMID: 18616953 DOI: 10.1016/j.mrfmmm.2008.06.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Revised: 04/18/2008] [Accepted: 06/13/2008] [Indexed: 12/17/2022]
Abstract
Rothmund-Thomson syndrome (RTS), a rare recessive autosomal disorder, presents genome instability and clinical heterogeneity with growth deficiency, skin and bone defects, premature aging symptoms and cancer susceptibility. A subset of RTS patients presents mutations of the RECQL4 gene, member of the RecQ family of DNA helicases, including the RECQL2 (BLM) and RECQL3 (WRN) genes, defective in the cancer prone Bloom and Werner syndromes, respectively. Analysis of the RECQL4 gene in six clinically diagnosed RTS patients shows five patients, including two siblings, with eight mutations mainly located in the helicase domain, three patients presenting two mutations. The alterations include four missense mutations, one nonsense mutation and the same frameshift deletion, g.2881delG in exon 9 found in three patients. Seven RECQL4 polymorphisms, two being new, have also been identified. Primary RTS fibroblasts from these RTS patients show no sensitivity to a wide variety of genotoxic agents including ionizing or ultraviolet irradiation, nitrogen mustard, 4NQO, 8-MOP, Cis-Pt, MMC, H2O2, HU, or UV plus caffeine which could be related to the RECQL4 alterations identified here. This is in contrast with the DNA damage sensitive Bloom and Werner cells and highlights the complexity of the numerous RecQ protein functions implicated in the different cellular pathways required for maintaining genomic integrity.
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Affiliation(s)
- Rosa Estela Caseira Cabral
- Laboratoire Génomes et Cancers, FRE2939 CNRS, Institut Gustave-Roussy, Université Paris-Sud, PRII, 39 Rue Camille Desmoulins, 94805 Villejuif, France
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34
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Bernardi R, Pandolfi PP. Structure, dynamics and functions of promyelocytic leukaemia nuclear bodies. Nat Rev Mol Cell Biol 2007; 8:1006-16. [PMID: 17928811 DOI: 10.1038/nrm2277] [Citation(s) in RCA: 698] [Impact Index Per Article: 41.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The promyelocytic leukaemia (PML) tumour suppressor protein epitomizes the PML-nuclear body (PML-NB) and is crucially required for the proper assembly of this macromolecular nuclear structure. Unlike other, more specialized subnuclear structures such as Cajal and Polycomb group bodies, PML-NBs are functionally promiscuous and have been implicated in the regulation of diverse cellular functions. PML-NBs are dynamic structures that favour the sequestration and release of proteins, mediate their post-translational modifications and promote specific nuclear events in response to various cellular stresses. Recent data suggest that PML-NBs may be heterogeneous in composition, mobility and function.
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Affiliation(s)
- Rosa Bernardi
- Cancer Genetics Program, Beth Israel Deaconess Cancer Center and Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA
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So S, Adachi N, Koyama H. Absence of p53 enhances growth defects and etoposide sensitivity of human cells lacking the Bloom syndrome helicase BLM. DNA Cell Biol 2007; 26:517-25. [PMID: 17630856 DOI: 10.1089/dna.2007.0578] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The Bloom syndrome helicase BLM and the tumor-suppressor protein p53 play important roles in preserving genome integrity. Here, we knock out the genes for BLM and p53 in a human pre-B-cell line, Nalm-6. We show that p53 plays an important role in cell proliferation, but not apoptosis, when BLM is absent. Intriguingly, despite the apoptotic function of p53, BLM(/)TP53(/) cells were more sensitive than either single mutant to etoposide, an anticancer agent that poisons DNA topoisomerase II. Our results suggest a direct, BLM-independent role for p53 in etoposide-induced, topoisomerase II-mediated DNA damage in human cells.
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Affiliation(s)
- Sairei So
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Japan
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Abstract
Convergent studies demonstrated that p53 regulates homologous recombination (HR) independently of its classic tumour-suppressor functions in transcriptionally transactivating cellular target genes that are implicated in growth control and apoptosis. In this review, we summarise the analyses of the involvement of p53 in spontaneous and double-strand break (DSB)-triggered HR and in alternative DSB repair routes. Molecular characterisation indicated that p53 controls the fidelity of Rad51-dependent HR and represses aberrant processing of replication forks after stalling at unrepaired DNA lesions. These findings established a genome stabilising role of p53 in counteracting error-prone DSB repair. However, recent work has also unveiled a stimulatory role for p53 in topoisomerase I-induced recombinative repair events that may have implications for a gain-of-function phenotype of cancer-related p53 mutants. Additional evidence will be discussed which suggests that p53 and/or p53-regulated gene products also contribute to nucleotide excision, base excision, and mismatch repair.
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Affiliation(s)
- S A Gatz
- Universitätsklinik für Kinder- und Jugendmedizin, Eythstr. 24, 89075 Ulm, Germany
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37
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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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38
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Coiteux V, Onclercq-Delic R, Fenaux P, Amor-Guéret M. Predisposition to therapy-related acute leukemia with balanced chromosomal translocations does not result from a major constitutive defect in DNA double-strand break end joining. Leuk Res 2007; 31:353-8. [PMID: 16890283 DOI: 10.1016/j.leukres.2006.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Revised: 02/08/2006] [Accepted: 06/02/2006] [Indexed: 12/28/2022]
Abstract
The frequency of acute myeloid leukemia (AML) with balanced chromosomal translocations arising after anticancer therapy with DNA-damaging agents such as DNA topoisomerase II inhibitors has increased over the last two decades. However, factors that predispose to these therapy-related disorders are still poorly defined. It has been reported that DNA double-strand break (DSB) repair by the non-homologous end-joining (NHEJ) pathway is impaired in myeloid leukemia cells. This led us to hypothesize that therapy-related AML (t-AML) may result from individual differences in the repair of DSBs generated by the treatment. We show here that DSB repair is accurate, in vivo, in non-tumoral cells derived from patients who developed t-AML with t(9;11) or t(15;17) translocation after treatment for a first cancer with DNA topoisomerase II inhibitors. These results indicate that a major constitutive defect in the NHEJ pathway is unlikely to predispose to t-AML with balanced chromosomal translocations.
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MESH Headings
- Acute Disease
- Adult
- Aged
- Antineoplastic Combined Chemotherapy Protocols/adverse effects
- Cell Line, Tumor
- Chromosomes, Human, Pair 11/genetics
- Chromosomes, Human, Pair 15/genetics
- Chromosomes, Human, Pair 17/genetics
- Chromosomes, Human, Pair 9/genetics
- DNA Breaks, Double-Stranded/drug effects
- DNA Repair/drug effects
- DNA Topoisomerases, Type II
- Enzyme Inhibitors/pharmacology
- Female
- Humans
- Leukemia, Myeloid/drug therapy
- Leukemia, Myeloid/genetics
- Male
- Middle Aged
- Neoplasms, Second Primary/drug therapy
- Neoplasms, Second Primary/genetics
- Structure-Activity Relationship
- Topoisomerase II Inhibitors
- Translocation, Genetic/genetics
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Affiliation(s)
- Valérie Coiteux
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8126, Institut Gustave Roussy, 39 Rue Camille Desmoulins, 94 805 Villejuif Cedex, France
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39
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Abstract
Osteosarcoma is a devastating but rare disease, whose study has illuminated both the basic biology and clinical management of cancer over the past 30 years. These contributions have included insight into the roles of key cancer genes such as the retinoblastoma tumor suppressor gene and TP53, the identification of familial cancer syndromes implicating DNA helicases, and dramatic improvements in survival by the use of adjuvant chemotherapy. This review provides a synoptic overview of our current understanding of the molecular causes of osteosarcoma, and suggests future directions for study.
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Affiliation(s)
- Maya Kansara
- Ian Potter Foundation Centre for Cancer Genomics and Predictive Medicine and Research Division, Peter MacCallum Cancer Centre, Melbourne, Australia
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40
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Babbe H, Chester N, Leder P, Reizis B. The Bloom's syndrome helicase is critical for development and function of the alphabeta T-cell lineage. Mol Cell Biol 2007; 27:1947-59. [PMID: 17210642 PMCID: PMC1820471 DOI: 10.1128/mcb.01402-06] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bloom's syndrome is a genetic disorder characterized by increased incidence of cancer and an immunodeficiency of unknown origin. The BLM gene mutated in Bloom's syndrome encodes a DNA helicase involved in the maintenance of genomic integrity. To explore the role of BLM in the immune system, we ablated murine Blm in the T-cell lineage. In the absence of Blm, thymocytes were severely reduced in numbers and displayed a developmental block at the beta-selection checkpoint that was partially p53 dependent. Blm-deficient thymocytes rearranged their T-cell receptor (TCR) beta genes normally yet failed to survive and proliferate in response to pre-TCR signaling. Furthermore, peripheral T cells were reduced in numbers, manifested defective homeostatic and TCR-induced proliferation, and produced extensive chromosomal damage. Finally, CD4(+) and CD8(+) T-cell responses were impaired upon antigen challenge. Thus, by ensuring genomic stability, Blm serves a vital role for development, maintenance, and function of T lymphocytes, suggesting a basis for the immune deficiency in Bloom's syndrome.
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Affiliation(s)
- Holger Babbe
- Department of Microbiology, Columbia University Medical Center, 701 W. 168th St., New York, NY 10032, USA.
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41
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Reliene R, Bishop AJR, Schiestl RH. Involvement of homologous recombination in carcinogenesis. ADVANCES IN GENETICS 2007; 58:67-87. [PMID: 17452246 DOI: 10.1016/s0065-2660(06)58003-4] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
DNA alterations of every type are associated with the incidence of carcinogenesis, often on the genomic scale. Although homologous recombination (HR) is an important pathway of DNA repair, evidence is accumulating that deleterious genomic rearrangements can result from HR. It therefore follows that HR events may play a causative role in carcinogenesis. HR is elevated in response to carcinogens. HR may also be increased or decreased when its upstream regulation is perturbed or components of the HR machinery itself are not fully functional. This chapter summarizes research findings that demonstrate an association between HR and carcinogenesis. Increased or decreased frequencies of HR have been found in cancer cells and cancer-prone hereditary human disorders characterized by mutations in genes playing a role in HR, such as ATM, Tp53, BRCA, BLM, and WRN genes. Another evidence linking perturbations in HR and carcinogenesis is provided by studies showing that exposure to carcinogens results in an increased frequency of HR resulting in DNA deletions in yeast, human cells, or mice.
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Affiliation(s)
- Ramune Reliene
- Department of Pathology, Geffen School of Medicine, UCLA, Los Angeles, CA 90024, USA
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42
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Jiao R, Harrigan JA, Shevelev I, Dietschy T, Selak N, Indig FE, Piotrowski J, Janscak P, Bohr VA, Stagljar I. The Werner syndrome protein is required for recruitment of chromatin assembly factor 1 following DNA damage. Oncogene 2006; 26:3811-22. [PMID: 17173071 DOI: 10.1038/sj.onc.1210150] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The Werner syndrome protein (WRN) and chromatin assembly factor 1 (CAF-1) are both involved in the maintenance of genome stability. In response to DNA-damaging signals, both of these proteins relocate to sites where DNA synthesis occurs. However, the interaction between WRN and CAF-1 has not yet been investigated. In this report, we show that WRN interacts physically with the largest subunit of CAF-1, hp150, in vitro and in vivo. Although hp150 does not alter WRN catalytic activities in vitro, and the chromatin assembly activity of CAF-1 is not affected in the absence of WRN in vivo, this interaction may have an important role during the cellular response to DNA replication fork blockage and/or DNA damage signals. In hp150 RNA-mediated interference (RNAi) knockdown cells, WRN partially formed foci following hydroxyurea (HU) treatment. However, in the absence of WRN, hp150 did not relocate to form foci following exposure to HU and ultraviolet light. Thus, our results demonstrate that WRN responds to DNA damage before CAF-1 and suggest that WRN may recruit CAF-1, via interaction with hp150, to DNA damage sites during DNA synthesis.
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Affiliation(s)
- R Jiao
- National Laboratory of Biomacromolecules and State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, The Chinese Academy of Sciences, Beijing, China.
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43
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Tronnersjö S, Hanefalk C, Balciunas D, Hu GZ, Nordberg N, Murén E, Ronne H. The jmjN and jmjC domains of the yeast zinc finger protein Gis1 interact with 19 proteins involved in transcription, sumoylation and DNA repair. Mol Genet Genomics 2006; 277:57-70. [PMID: 17043893 DOI: 10.1007/s00438-006-0171-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2006] [Accepted: 09/14/2006] [Indexed: 11/25/2022]
Abstract
The jumonji domain is a highly conserved bipartite domain made up of two subdomains, jmjN and jmjC, which is found in many eukaryotic transcription factors. The jmjC domain was recently shown to possess the histone demethylase activity. Here we show that the jmjN and jmjC domains of the yeast zinc finger protein Gis1 interact in a two-hybrid system with 19 yeast proteins that include the RecQ helicase Sgs1, the silencing factors Esc1 and Sir4, the URI-type prefoldin Bud27 and the PIAS type SUMO ligase Nfi1/Siz2. Extensive interaction cross dependencies further suggest that the proteins form a larger complex. Consistent with this, 16 of the proteins also interact with a Bud27 two-hybrid bait, and three of them co-precipitate with TAP-tagged Gis1. The Gis1 jumonji domain can repress transcription when recruited to a promoter as a lexA fusion. This effect is dependent on both the jmjN and jmjC subdomains, as were all 19 two-hybrid interactions, indicating that the two subdomains form a single functional unit. The human Sgs1 homolog WRN also interacts with the Gis1 jumonji domain. Finally, we note that several jumonji domain interactors are related to proteins that are found in mammalian PML nuclear bodies.
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Affiliation(s)
- Susanna Tronnersjö
- Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, P.O. Box 7080, 75007, Uppsala, Sweden
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44
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Marple T, Kim TM, Hasty P. Embryonic stem cells deficient for Brca2 or Blm exhibit divergent genotoxic profiles that support opposing activities during homologous recombination. Mutat Res 2006; 602:110-20. [PMID: 16997331 DOI: 10.1016/j.mrfmmm.2006.08.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Revised: 08/11/2006] [Accepted: 08/12/2006] [Indexed: 11/21/2022]
Abstract
The breast cancer susceptibility protein, Brca2 and the RecQ helicase, Blm (Bloom syndrome mutated) are tumor suppressors that maintain genome integrity, at least in part, through homologous recombination (HR). Brca2 facilitates HR by interacting with Rad51 in multiple regions, the BRC motifs encoded by exon 11 and a single domain encoded by exon 27; however, the exact importance of these regions is not fully understood. Blm also interacts with Rad51 and appears to suppress HR in most circumstances; however, its yeast homologue Sgs1 facilitates HR in response to some genotoxins. To better understand the biological importance of these two proteins, we performed a genotoxic screen on mouse embryonic stem (ES) cells impaired for either Brca2 or Blm to establish their genotoxic profiles (a cellular dose-response to a wide range of agents). This is the first side-by-side comparison of these two proteins in an identical genetic background. We compared cells deleted for Brca2 exon 27 to cells reduced for Blm expression and find that the Brca2- and Blm-impaired cells exhibit genotoxic profiles that reflect opposing activities during HR. Cells deleted for Brca2 exon 27 are hypersensitive to gamma-radiation, streptonigrin, mitomycin C and camptothecin and mildly resistant to ICRF-193 which is similar to HR defective cells null for Rad54. By contrast, Blm-impaired cells are hypersensitive to ICRF-193, mildly resistant to camptothecin and mitomycin C and more strongly resistant to hydroxyurea. These divergent profiles support the notion that Brca2 and Blm perform opposing functions during HR in mouse ES cells.
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Affiliation(s)
- Teresa Marple
- The Department of Molecular Medicine and Institute of Biotechnology, The University of Texas Health Science Center at San Antonio, 15355 Lambda Drive San Antonio, TX 78245-3207, USA
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45
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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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46
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Miao ZH, Rao VA, Agama K, Antony S, Kohn KW, Pommier Y. 4-nitroquinoline-1-oxide induces the formation of cellular topoisomerase I-DNA cleavage complexes. Cancer Res 2006; 66:6540-5. [PMID: 16818625 DOI: 10.1158/0008-5472.can-05-4471] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RecQ helicase BLM-deficient cells are characteristically hypersensitive to 4-nitroquinoline-1-oxide (4NQO). We recently reported that isogenic BLM-deficient cells (PNSG13) are more sensitive than BLM-complemented cells (PNSF5) to camptothecin, which specifically traps topoisomerase I cleavage complexes (Top1cc). We now report that PNSG13 are also 3.5-fold more sensitive to 4NQO compared with PNSF5 and that 4NQO induces higher levels of Top1cc and reduced histone gamma-H2AX in PSNG13 than in PNSF5. Similarly, 4NQO induces more Top1cc in primary fibroblasts from a patient with Bloom syndrome than in normal human fibroblasts. 4NQO also induces Top1cc in colon cancer HCT116 and HT29 cells in a time- and concentration-dependent fashion. Of note, distinct from camptothecin, the Top1cc produced by 4NQO accumulate progressively after 4NQO addition and persist following 4NQO removal. The Top1cc induced by 4NQO are detectable by alkaline elution. To examine the functional relevance of the Top1cc induced by 4NQO, we used two stable topoisomerase I small interfering RNA (siRNA) cell lines derived from HCT116 and MCF7 cells. Both topoisomerase I siRNA cell lines are resistant to 4NQO, indicating that Top1cc contribute to the cellular activity of 4NQO. Collectively, these data show that 4NQO is an effective inducer of cellular Top1cc. Because 4NQO does not directly trap Top1cc in biochemical assays, we propose that active metabolites of 4NQO trap Top1cc by forming DNA adducts. Induction of Top1cc and histone gamma-H2AX by 4NQO may contribute to the cellular effects of 4NQO, including its selective activity toward RecQ helicase BLM-deficient cells.
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Affiliation(s)
- Ze-Hong Miao
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute/NIH, Bethesda, MD 20892, USA
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47
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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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48
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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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49
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Amor-Guéret M. Bloom syndrome, genomic instability and cancer: the SOS-like hypothesis. Cancer Lett 2006; 236:1-12. [PMID: 15950375 DOI: 10.1016/j.canlet.2005.04.023] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2005] [Accepted: 04/12/2005] [Indexed: 12/15/2022]
Abstract
Bloom syndrome (BS) displays one of the strongest known correlations between chromosomal instability and an increased risk of malignancy at an early age. The prevention of genomic instability and cancer depends on a complex network of pathways induced in response to DNA damage and stalled replication forks, including cell-cycle checkpoints, DNA repair, and apoptosis. Several studies have demonstrated that BLM is involved in the cellular response to DNA damage and stalled replication forks. BLM interacts physically and functionally with several proteins involved in the maintenance of genome integrity and BLM is redistributed and/or phosphorylated in response to several genotoxic stresses. The data concerning the relationship between BLM and these cellular pathways are summarized and the role of BLM in the rescue of arrested replication forks is discussed. Moreover, I speculate that BLM deficiency is lethal, and that BLM-deficient cells escaping apoptotic death do so by constitutively inducing a bacterial SOS-like response including the induction of alternative replication pathway(s) dependent on recombination, contributing to the mutator and hyper-Rec phenotypes characteristic of BS cells. This mechanism may be dependent on the RAD51 gene family, and involved in carcinogenesis in the general population.
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Affiliation(s)
- Mounira Amor-Guéret
- UMR 2027 CNRS, Institut Curie, Group Instabilité Génétique et Cancérogenèse, Bâtiment 110, Centre Universitaire, 91405 Orsay Cedex, France.
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Dellaire G, Ching RW, Dehghani H, Ren Y, Bazett-Jones DP. The number of PML nuclear bodies increases in early S phase by a fission mechanism. J Cell Sci 2006; 119:1026-33. [PMID: 16492708 DOI: 10.1242/jcs.02816] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Promyelocytic leukemia (PML) nuclear bodies have been implicated in a variety of cellular processes including apoptosis, tumour suppression, anti-viral response, DNA repair and transcriptional regulation. PML nuclear bodies are both positionally and structurally stable over extended periods of interphase. As demonstrated in this study, the structural stability is lost as cells enter S phase, evidenced both by distortions in shape and by fission and fusion events. At the end of this period of structural instability, the number of PML nuclear bodies has increased by a factor of twofold. Association of the fission products with chromatin implies that the PML nuclear bodies respond to changes in chromatin organisation or topology, and thus could play a role in monitoring genome integrity during DNA synthesis or in the continued maintenance of functional chromosomal domains prior to mitosis.
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Affiliation(s)
- Graham Dellaire
- Programme in Cell Biology, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, M5G 1X8 Canada
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