1
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Hua AB, Sweasy JB. Functional roles and cancer variants of the bifunctional glycosylase NEIL2. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2024; 65 Suppl 1:40-56. [PMID: 37310399 DOI: 10.1002/em.22555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 05/23/2023] [Accepted: 06/08/2023] [Indexed: 06/14/2023]
Abstract
Over 70,000 DNA lesions occur in the cell every day, and the inability to properly repair them can lead to mutations and destabilize the genome, resulting in carcinogenesis. The base excision repair (BER) pathway is critical for maintaining genomic integrity by repairing small base lesions, abasic sites and single-stranded breaks. Monofunctional and bifunctional glycosylases initiate the first step of BER by recognizing and excising specific base lesions, followed by DNA end processing, gap filling, and finally nick sealing. The Nei-like 2 (NEIL2) enzyme is a critical bifunctional DNA glycosylase in BER that preferentially excises cytosine oxidation products and abasic sites from single-stranded, double-stranded, and bubble-structured DNA. NEIL2 has been implicated to have important roles in several cellular functions, including genome maintenance, participation in active demethylation, and modulation of the immune response. Several germline and somatic variants of NEIL2 with altered expression and enzymatic activity have been reported in the literature linking them to cancers. In this review, we provide an overview of NEIL2 cellular functions and summarize current findings on NEIL2 variants and their relationship to cancer.
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Affiliation(s)
- Anh B Hua
- Department of Cellular and Molecular Medicine, University of Arizona Cancer Center, Tucson, Arizona, USA
| | - Joann B Sweasy
- Department of Cellular and Molecular Medicine, University of Arizona Cancer Center, Tucson, Arizona, USA
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2
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Yu Y, Wang X, Fox J, Li Q, Yu Y, Hastings PJ, Chen K, Ira G. RPA and Rad27 limit templated and inverted insertions at DNA breaks. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.07.583931. [PMID: 38496432 PMCID: PMC10942419 DOI: 10.1101/2024.03.07.583931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
Formation of templated insertions at DNA double-strand breaks (DSBs) is very common in cancer cells. The mechanisms and enzymes regulating these events are largely unknown. Here, we investigated templated insertions in yeast at DSBs using amplicon sequencing across a repaired locus. We document very short (most ∼5-34 bp), templated inverted duplications at DSBs. They are generated through a foldback mechanism that utilizes microhomologies adjacent to the DSB. Enzymatic requirements suggest a hybrid mechanism wherein one end requires Polδ-mediated synthesis while the other end is captured by nonhomologous end joining (NHEJ). This process is exacerbated in mutants with low levels or mutated RPA ( rtt105 Δ; rfa1 -t33) or extensive resection mutant ( sgs1 Δ exo1 Δ). Templated insertions from various distant genomic locations also increase in these mutants as well as in rad27 Δ and originate from fragile regions of the genome. Among complex insertions, common events are insertions of two sequences, originating from the same locus and with inverted orientation. We propose that these inversions are also formed by microhomology-mediated template switching. Taken together, we propose that a shortage of RPA typical in cancer cells is one possible factor stimulating the formation of templated insertions.
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3
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Martins DJ, Di Lazzaro Filho R, Bertola DR, Hoch NC. Rothmund-Thomson syndrome, a disorder far from solved. FRONTIERS IN AGING 2023; 4:1296409. [PMID: 38021400 PMCID: PMC10676203 DOI: 10.3389/fragi.2023.1296409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 10/17/2023] [Indexed: 12/01/2023]
Abstract
Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive disorder characterized by a range of clinical symptoms, including poikiloderma, juvenile cataracts, short stature, sparse hair, eyebrows/eyelashes, nail dysplasia, and skeletal abnormalities. While classically associated with mutations in the RECQL4 gene, which encodes a DNA helicase involved in DNA replication and repair, three additional genes have been recently identified in RTS: ANAPC1, encoding a subunit of the APC/C complex; DNA2, which encodes a nuclease/helicase involved in DNA repair; and CRIPT, encoding a poorly characterized protein implicated in excitatory synapse formation and splicing. Here, we review the clinical spectrum of RTS patients, analyze the genetic basis of the disease, and discuss molecular functions of the affected genes, drawing some novel genotype-phenotype correlations and proposing avenues for future studies into this enigmatic disorder.
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Affiliation(s)
- Davi Jardim Martins
- Genomic Stability Unit, Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Ricardo Di Lazzaro Filho
- Center for Human Genome Studies, Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil
- Dasa Genômica/Genera, Genômica, São Paulo, Brazil
| | - Debora Romeo Bertola
- Center for Human Genome Studies, Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil
- Genetics Unit, Department of Pediatrics, Faculty of Medicine, Children’s Institute, Hospital das Clínicas, University of São Paulo, São Paulo, Brazil
| | - Nícolas Carlos Hoch
- Genomic Stability Unit, Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
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4
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Gan X, Zhang Y, Jiang D, Shi J, Zhao H, Xie C, Wang Y, Xu J, Zhang X, Cai G, Wang H, Huang J, Chen X. Proper RPA acetylation promotes accurate DNA replication and repair. Nucleic Acids Res 2023; 51:5565-5583. [PMID: 37140030 PMCID: PMC10287905 DOI: 10.1093/nar/gkad291] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Revised: 04/06/2023] [Accepted: 04/12/2023] [Indexed: 05/05/2023] Open
Abstract
The single-stranded DNA (ssDNA) binding protein complex RPA plays a critical role in promoting DNA replication and multiple DNA repair pathways. However, how RPA is regulated to achieve its functions precisely in these processes remains elusive. Here, we found that proper acetylation and deacetylation of RPA are required to regulate RPA function in promoting high-fidelity DNA replication and repair. We show that yeast RPA is acetylated on multiple conserved lysines by the acetyltransferase NuA4 upon DNA damage. Mimicking constitutive RPA acetylation or blocking its acetylation causes spontaneous mutations with the signature of micro-homology-mediated large deletions or insertions. In parallel, improper RPA acetylation/deacetylation impairs DNA double-strand break (DSB) repair by the accurate gene conversion or break-induced replication while increasing the error-prone repair by single-strand annealing or alternative end joining. Mechanistically, we show that proper acetylation and deacetylation of RPA ensure its normal nuclear localization and ssDNA binding ability. Importantly, mutation of the equivalent residues in human RPA1 also impairs RPA binding on ssDNA, leading to attenuated RAD51 loading and homologous recombination repair. Thus, timely RPA acetylation and deacetylation likely represent a conserved mechanism promoting high-fidelity replication and repair while discriminating the error-prone repair mechanisms in eukaryotes.
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Affiliation(s)
- Xiaoli Gan
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Yueyue Zhang
- The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Donghao Jiang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Jingyao Shi
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Han Zhao
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Chengyu Xie
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Yanyan Wang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Jingyan Xu
- Department of Hematology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China
| | - Xinghua Zhang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Gang Cai
- The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Hailong Wang
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Jun Huang
- The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Xuefeng Chen
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
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5
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Sun H, Ma L, Tsai YF, Abeywardana T, Shen B, Zheng L. Okazaki fragment maturation: DNA flap dynamics for cell proliferation and survival. Trends Cell Biol 2023; 33:221-234. [PMID: 35879148 PMCID: PMC9867784 DOI: 10.1016/j.tcb.2022.06.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 06/28/2022] [Accepted: 06/30/2022] [Indexed: 01/24/2023]
Abstract
Unsuccessful processing of Okazaki fragments leads to the accumulation of DNA breaks which are associated with many human diseases including cancer and neurodegenerative disorders. Recently, Okazaki fragment maturation (OFM) has received renewed attention regarding how unprocessed Okazaki fragments are sensed and repaired, and how inappropriate OFM impacts on genome stability and cell viability, especially in cancer cells. We provide an overview of the highly efficient and faithful canonical OFM pathways and their regulation of genomic integrity and cell survival. We also discuss how cells induce alternative error-prone OFM processes to promote cell survival in response to environmental stresses. Such stress-induced OFM processes may be important mechanisms driving mutagenesis, cellular evolution, and resistance to radio/chemotherapy and targeted therapeutics in human cancers.
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Affiliation(s)
- Haitao Sun
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, 1500 East Duarte Road, Duarte, CA 91010, USA
| | - Lingzi Ma
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, 1500 East Duarte Road, Duarte, CA 91010, USA
| | - Ya-Fang Tsai
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, 1500 East Duarte Road, Duarte, CA 91010, USA
| | - Tharindu Abeywardana
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, 1500 East Duarte Road, Duarte, CA 91010, USA
| | - Binghui Shen
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, 1500 East Duarte Road, Duarte, CA 91010, USA.
| | - Li Zheng
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, 1500 East Duarte Road, Duarte, CA 91010, USA.
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6
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Salinero AC, Emerson S, Cormier TC, Yin J, Morse RH, Curcio MJ. Reliance of Host-Encoded Regulators of Retromobility on Ty1 Promoter Activity or Architecture. Front Mol Biosci 2022; 9:896215. [PMID: 35847981 PMCID: PMC9283973 DOI: 10.3389/fmolb.2022.896215] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 06/10/2022] [Indexed: 11/13/2022] Open
Abstract
The Ty1 retrotransposon family is maintained in a functional but dormant state by its host, Saccharomyces cerevisiae. Several hundred RHF and RTT genes encoding co-factors and restrictors of Ty1 retromobility, respectively, have been identified. Well-characterized examples include MED3 and MED15, encoding subunits of the Mediator transcriptional co-activator complex; control of retromobility by Med3 and Med15 requires the Ty1 promoter in the U3 region of the long terminal repeat. To characterize the U3-dependence of other Ty1 regulators, we screened a library of 188 known rhf and rtt mutants for altered retromobility of Ty1his3AI expressed from the strong, TATA-less TEF1 promoter or the weak, TATA-containing U3 promoter. Two classes of genes, each including both RHFs and RTTs, were identified. The first class comprising 82 genes that regulated Ty1his3AI retromobility independently of U3 is enriched for RHF genes that restrict the G1 phase of the cell cycle and those involved in transcriptional elongation and mRNA catabolism. The second class of 51 genes regulated retromobility of Ty1his3AI driven only from the U3 promoter. Nineteen U3-dependent regulators (U3DRs) also controlled retromobility of Ty1his3AI driven by the weak, TATA-less PSP2 promoter, suggesting reliance on the low activity of U3. Thirty-one U3DRs failed to modulate PPSP2-Ty1his3AI retromobility, suggesting dependence on the architecture of U3. To further investigate the U3-dependency of Ty1 regulators, we developed a novel fluorescence-based assay to monitor expression of p22-Gag, a restriction factor expressed from the internal Ty1i promoter. Many U3DRs had minimal effects on levels of Ty1 RNA, Ty1i RNA or p22-Gag. These findings uncover a role for the Ty1 promoter in integrating signals from diverse host factors to modulate Ty1 RNA biogenesis or fate.
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Affiliation(s)
- Alicia C. Salinero
- Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, NY, United States
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, NY, United States
| | - Simey Emerson
- Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, NY, United States
| | - Tayla C. Cormier
- Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, NY, United States
| | - John Yin
- Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, NY, United States
| | - Randall H. Morse
- Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, NY, United States
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, NY, United States
| | - M. Joan Curcio
- Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, NY, United States
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, NY, United States
- *Correspondence: M. Joan Curcio,
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7
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Miller AK, Mao G, Knicely BG, Daniels HG, Rahal C, Putnam CD, Kolodner RD, Goellner EM. Rad5 and Its Human Homologs, HLTF and SHPRH, Are Novel Interactors of Mismatch Repair. Front Cell Dev Biol 2022; 10:843121. [PMID: 35784486 PMCID: PMC9243396 DOI: 10.3389/fcell.2022.843121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 05/16/2022] [Indexed: 12/02/2022] Open
Abstract
DNA mismatch repair (MMR) repairs replication errors, and MMR defects play a role in both inherited cancer predisposition syndromes and in sporadic cancers. MMR also recognizes mispairs caused by environmental and chemotherapeutic agents; however, in these cases mispair recognition leads to apoptosis and not repair. Although mutation avoidance by MMR is fairly well understood, MMR-associated proteins are still being identified. We performed a bioinformatic analysis that implicated Saccharomyces cerevisiae Rad5 as a candidate for interacting with the MMR proteins Msh2 and Mlh1. Rad5 is a DNA helicase and E3 ubiquitin ligase involved in post-replicative repair and damage tolerance. We confirmed both interactions and found that the Mlh1 interaction is mediated by a conserved Mlh1-interacting motif (MIP box). Despite this, we did not find a clear role for Rad5 in the canonical MMR mutation avoidance pathway. The interaction of Rad5 with Msh2 and Mlh1 is conserved in humans, although each of the Rad5 human homologs, HLTF and SHPRH, shared only one of the interactions: HLTF interacts with MSH2, and SHPRH interacts with MLH1. Moreover, depletion of SHPRH, but not HLTF, results in a mild increase in resistance to alkylating agents although not as strong as loss of MMR, suggesting gene duplication led to specialization of the MMR-protein associated roles of the human Rad5 homologs. These results provide insights into how MMR accessory factors involved in the MMR-dependent apoptotic response interact with the core MMR machinery and have important health implications into how human cells respond to environmental toxins, tumor development, and treatment choices of tumors with defects in Rad5 homologs.
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Affiliation(s)
- Anna K. Miller
- College of Medicine Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, KY, United States
| | - Guogen Mao
- College of Medicine Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, KY, United States
| | - Breanna G. Knicely
- College of Medicine Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, KY, United States
| | - Hannah G. Daniels
- College of Medicine Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, KY, United States
| | - Christine Rahal
- Ludiwg Institute for Cancer Research San Diego, San Diego, CA, United States
| | - Christopher D. Putnam
- Ludiwg Institute for Cancer Research San Diego, San Diego, CA, United States
- Department of Medicine, University of California San Diego, San Diego, CA, United States
| | - Richard D. Kolodner
- Ludiwg Institute for Cancer Research San Diego, San Diego, CA, United States
- Moores-UCSD Cancer Center, San Diego, CA, United States
- Institute of Genomic Medicine, San Diego, CA, United States
- Department of Cellular and Molecular Medicine, University of California San Diego, San Diego, CA, United States
| | - Eva M. Goellner
- College of Medicine Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, KY, United States
- Markey Cancer Center, University of Kentucky, Lexington, KY, United States
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8
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Ma L, Sun H, Abeywardana T, Zheng L, Shen B. Structure-specific nucleases: role in Okazaki fragment maturation. Trends Genet 2022; 38:793-796. [PMID: 35491358 DOI: 10.1016/j.tig.2022.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/25/2022] [Accepted: 04/01/2022] [Indexed: 10/18/2022]
Abstract
Proper function of structure-specific nucleases is key for faithful Okazaki fragment maturation (OFM) process completion. Deregulation of such nucleases leads to aberrant OFM and causes a spectrum of mutations, some of which may confer survival outcomes under specific stresses and serve as attractive targets for therapeutic intervention in human cancers.
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Affiliation(s)
- Lingzi Ma
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, CA 91010, USA
| | - Haitao Sun
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, CA 91010, USA
| | - Tharindumala Abeywardana
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, CA 91010, USA
| | - Li Zheng
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, CA 91010, USA.
| | - Binghui Shen
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, CA 91010, USA.
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9
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Yang YS, Ning SK, Lyu XH, Suo F, Jia GS, Li W, Du LL. Canavanine resistance mutation can1-1 in Schizosaccharomyces pombe is a missense mutation in the ubiquitin ligase adaptor gene any1. MICROPUBLICATION BIOLOGY 2022; 2022:10.17912/micropub.biology.000538. [PMID: 35300005 PMCID: PMC8922049 DOI: 10.17912/micropub.biology.000538] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 03/05/2022] [Accepted: 03/09/2022] [Indexed: 11/18/2022]
Abstract
In Schizosaccharomyces pombe, the can1-1 mutation confers resistance to the toxic arginine analog canavanine. This mutation has been assumed to disrupt a gene encoding an arginine transporter. In PomBase, the gene SPBC18H10.16 is currently designated can1. Here, we sequenced the genomes of three can1-1 strains. No mutations were found in SPBC18H10.16. Instead, these strains harbor an R175C mutation in the gene any1 (SPBC18H10.20c). any1 encodes an α-arrestin that acts as a ubiquitin ligase adaptor to downregulate plasma membrane amino acid transporters. Our findings indicate that can1-1 is not a loss-of-function mutation in an amino acid transporter gene, but a possible gain-of-function mutation in a gene encoding a negative regulator of amino acid transporters.
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Affiliation(s)
- Yu-Sheng Yang
- National Institute of Biological Sciences, Beijing, China
| | - Shao-Kai Ning
- National Institute of Biological Sciences, Beijing, China
| | - Xiao-Hui Lyu
- National Institute of Biological Sciences, Beijing, China
| | - Fang Suo
- National Institute of Biological Sciences, Beijing, China
| | - Guo-Song Jia
- National Institute of Biological Sciences, Beijing, China
| | - Wen Li
- National Institute of Biological Sciences, Beijing, China
| | - Li-Lin Du
- National Institute of Biological Sciences, Beijing, China
,
Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing, China
,
Correspondence to: Li-Lin Du (
)
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10
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Sun H, Lu Z, Singh A, Zhou Y, Zheng E, Zhou M, Wang J, Wu X, Hu Z, Gu Z, Campbell JL, Zheng L, Shen B. Error-prone, stress-induced 3' flap-based Okazaki fragment maturation supports cell survival. Science 2021; 374:1252-1258. [PMID: 34855483 PMCID: PMC8852821 DOI: 10.1126/science.abj1013] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
How cells with DNA replication defects acquire mutations that allow them to escape apoptosis under environmental stress is a long-standing question. Here, we report that an error-prone Okazaki fragment maturation (OFM) pathway is activated at restrictive temperatures in rad27Δ yeast cells. Restrictive temperature stress activated Dun1, facilitating transformation of unprocessed 5′ flaps into 3′ flaps, which were removed by 3′ nucleases, including DNA polymerase δ (Polδ). However, at certain regions, 3′ flaps formed secondary structures that facilitated 3′ end extension rather than degradation, producing alternative duplications with short spacer sequences, such as pol3 internal tandem duplications. Consequently, little 5′ flap was formed, suppressing rad27Δ-induced lethality at restrictive temperatures. We define a stress-induced, error-prone OFM pathway that generates mutations that counteract replication defects and drive cellular evolution and survival.
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Affiliation(s)
- Haitao Sun
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
| | - Zhaoning Lu
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
| | - Amanpreet Singh
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
| | - Yajing Zhou
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
| | - Eric Zheng
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
- Department of Molecular, Cellular, and Developmental Biology, University of California at Santa Barbara, Santa Barbara, CA 93106
| | - Mian Zhou
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
| | - Jinhui Wang
- Department of Molecular and Cellular Biology, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
| | - Xiwei Wu
- Department of Molecular and Cellular Biology, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
| | - Zunsong Hu
- Department of Computational and Quantitative Medicine, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
| | - Zhaohui Gu
- Department of Computational and Quantitative Medicine, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
| | - Judith L. Campbell
- Divisions of Chemistry and Chemical Engineering and Biology and Biological Engineering California Institute of Technology, Pasadena, CA 91125, USA
| | - Li Zheng
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
| | - Binghui Shen
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, 1500 East Duarte Road, Duarte, CA 91010
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11
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A rapidly reversible mutation generates subclonal genetic diversity and unstable drug resistance. Proc Natl Acad Sci U S A 2021; 118:2019060118. [PMID: 34675074 PMCID: PMC8639346 DOI: 10.1073/pnas.2019060118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/11/2021] [Indexed: 11/18/2022] Open
Abstract
Most genetic changes have negligible reversion rates. As most mutations that confer resistance to an adverse condition (e.g., drug treatment) also confer a growth defect in its absence, it is challenging for cells to genetically adapt to transient environmental changes. Here, we identify a set of rapidly reversible drug-resistance mutations in Schizosaccharomyces pombe that are caused by microhomology-mediated tandem duplication (MTD) and reversion back to the wild-type sequence. Using 10,000× coverage whole-genome sequencing, we identify nearly 6,000 subclonal MTDs in a single clonal population and determine, using machine learning, how MTD frequency is encoded in the genome. We find that sequences with the highest-predicted MTD rates tend to generate insertions that maintain the correct reading frame, suggesting that MTD formation has shaped the evolution of coding sequences. Our study reveals a common mechanism of reversible genetic variation that is beneficial for adaptation to environmental fluctuations and facilitates evolutionary divergence.
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12
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Rad27 and Exo1 function in different excision pathways for mismatch repair in Saccharomyces cerevisiae. Nat Commun 2021; 12:5568. [PMID: 34552065 PMCID: PMC8458276 DOI: 10.1038/s41467-021-25866-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 08/31/2021] [Indexed: 11/20/2022] Open
Abstract
Eukaryotic DNA Mismatch Repair (MMR) involves redundant exonuclease 1 (Exo1)-dependent and Exo1-independent pathways, of which the Exo1-independent pathway(s) is not well understood. The exo1Δ440-702 mutation, which deletes the MutS Homolog 2 (Msh2) and MutL Homolog 1 (Mlh1) interacting peptides (SHIP and MIP boxes, respectively), eliminates the Exo1 MMR functions but is not lethal in combination with rad27Δ mutations. Analyzing the effect of different combinations of the exo1Δ440-702 mutation, a rad27Δ mutation and the pms1-A99V mutation, which inactivates an Exo1-independent MMR pathway, demonstrated that each of these mutations inactivates a different MMR pathway. Furthermore, it was possible to reconstitute a Rad27- and Msh2-Msh6-dependent MMR reaction in vitro using a mispaired DNA substrate and other MMR proteins. Our results demonstrate Rad27 defines an Exo1-independent eukaryotic MMR pathway that is redundant with at least two other MMR pathways. Defects in DNA mismatch repair (MMR) have been linked to inherited and sporadic cancers. Here the authors demonstrate that the DNA repair protein Rad27 (human FEN1) functions in one of three redundant mispair excision pathways, where its flap endonuclease activity catalyzes mispair excision.
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Strand discrimination in DNA mismatch repair. DNA Repair (Amst) 2021; 105:103161. [PMID: 34171627 DOI: 10.1016/j.dnarep.2021.103161] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 06/15/2021] [Accepted: 06/16/2021] [Indexed: 11/24/2022]
Abstract
DNA mismatch repair (MMR) corrects non-Watson-Crick basepairs generated by replication errors, recombination intermediates, and some forms of chemical damage to DNA. In MutS and MutL homolog-dependent MMR, damaged bases do not identify the error-containing daughter strand that must be excised and resynthesized. In organisms like Escherichia coli that use methyl-directed MMR, transient undermethylation identifies the daughter strand. For other organisms, growing in vitro and in vivo evidence suggest that strand discrimination is mediated by DNA replication-associated daughter strand nicks that direct asymmetric loading of the replicative clamp (the β-clamp in bacteria and the proliferating cell nuclear antigen, PCNA, in eukaryotes). Structural modeling suggests that replicative clamps mediate strand specificity either through the ability of MutL homologs to recognize the fixed orientation of the daughter strand relative to one face of the replicative clamps or through parental strand-specific diffusion of replicative clamps on DNA, which places the daughter strand in the MutL homolog endonuclease active site. Finally, identification of bacteria that appear to lack strand discrimination mediated by a replicative clamp and a pre-existing nick suggest that other strand discrimination mechanisms exist or that these organisms perform MMR by generating a double-stranded DNA break intermediate, which may be analogous to NucS-mediated MMR.
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Rtt105 promotes high-fidelity DNA replication and repair by regulating the single-stranded DNA-binding factor RPA. Proc Natl Acad Sci U S A 2021; 118:2106393118. [PMID: 34140406 DOI: 10.1073/pnas.2106393118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Single-stranded DNA (ssDNA) covered with the heterotrimeric Replication Protein A (RPA) complex is a central intermediate of DNA replication and repair. How RPA is regulated to ensure the fidelity of DNA replication and repair remains poorly understood. Yeast Rtt105 is an RPA-interacting protein required for RPA nuclear import and efficient ssDNA binding. Here, we describe an important role of Rtt105 in high-fidelity DNA replication and recombination and demonstrate that these functions of Rtt105 primarily depend on its regulation of RPA. The deletion of RTT105 causes elevated spontaneous DNA mutations with large duplications or deletions mediated by microhomologies. Rtt105 is recruited to DNA double-stranded break (DSB) ends where it promotes RPA assembly and homologous recombination repair by gene conversion or break-induced replication. In contrast, Rtt105 attenuates DSB repair by the mutagenic single-strand annealing or alternative end joining pathway. Thus, Rtt105-mediated regulation of RPA promotes high-fidelity replication and recombination while suppressing repair by deleterious pathways. Finally, we show that the human RPA-interacting protein hRIP-α, a putative functional homolog of Rtt105, also stimulates RPA assembly on ssDNA, suggesting the conservation of an Rtt105-mediated mechanism.
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Williams JS, Tumbale PP, Arana ME, Rana JA, Williams RS, Kunkel TA. High-fidelity DNA ligation enforces accurate Okazaki fragment maturation during DNA replication. Nat Commun 2021; 12:482. [PMID: 33473124 PMCID: PMC7817679 DOI: 10.1038/s41467-020-20800-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 12/08/2020] [Indexed: 01/29/2023] Open
Abstract
DNA ligase 1 (LIG1, Cdc9 in yeast) finalizes eukaryotic nuclear DNA replication by sealing Okazaki fragments using DNA end-joining reactions that strongly discriminate against incorrectly paired DNA substrates. Whether intrinsic ligation fidelity contributes to the accuracy of replication of the nuclear genome is unknown. Here, we show that an engineered low-fidelity LIG1Cdc9 variant confers a novel mutator phenotype in yeast typified by the accumulation of single base insertion mutations in homonucleotide runs. The rate at which these additions are generated increases upon concomitant inactivation of DNA mismatch repair, or by inactivation of the Fen1Rad27 Okazaki fragment maturation (OFM) nuclease. Biochemical and structural data establish that LIG1Cdc9 normally avoids erroneous ligation of DNA polymerase slippage products, and this protection is compromised by mutation of a LIG1Cdc9 high-fidelity metal binding site. Collectively, our data indicate that high-fidelity DNA ligation is required to prevent insertion mutations, and that this may be particularly critical following strand displacement synthesis during the completion of OFM.
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Affiliation(s)
- Jessica S Williams
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, 111 TW Alexander Drive, Research Triangle Park, NC, 27709, USA
| | - Percy P Tumbale
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, 111 TW Alexander Drive, Research Triangle Park, NC, 27709, USA
| | - Mercedes E Arana
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, 111 TW Alexander Drive, Research Triangle Park, NC, 27709, USA
| | - Julian A Rana
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, 111 TW Alexander Drive, Research Triangle Park, NC, 27709, USA
| | - R Scott Williams
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, 111 TW Alexander Drive, Research Triangle Park, NC, 27709, USA.
| | - Thomas A Kunkel
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, 111 TW Alexander Drive, Research Triangle Park, NC, 27709, USA.
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16
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Reyes GX, Kolodziejczak A, Devakumar LJPS, Kubota T, Kolodner RD, Putnam CD, Hombauer H. Ligation of newly replicated DNA controls the timing of DNA mismatch repair. Curr Biol 2021; 31:1268-1276.e6. [PMID: 33417883 PMCID: PMC8281387 DOI: 10.1016/j.cub.2020.12.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 11/10/2020] [Accepted: 12/14/2020] [Indexed: 11/23/2022]
Abstract
Mismatch repair (MMR) safeguards genome stability through recognition and excision of DNA replication errors.1–4 How eukaryotic MMR targets the newly replicated strand in vivo has not been established. MMR reactions reconstituted in vitro are directed to the strand containing a preexisting nick or gap,5–8 suggesting that strand discontinuities could act as discrimination signals. Another candidate is the proliferating cell nuclear antigen (PCNA) that is loaded at replication forks and is required for the activation of Mlh1-Pms1 endonuclease.7–9 Here, we discovered that overexpression of DNA ligase I (Cdc9) in Saccharomyces cerevisiae causes elevated mutation rates and increased chromatin-bound PCNA levels and accumulation of Pms1 foci that are MMR intermediates, suggesting that premature ligation of replication-associated nicks interferes with MMR. We showed that yeast Pms1 expression is mainly restricted to S phase, in agreement with the temporal coupling between MMR and DNA replication.10 Restricting Pms1 expression to the G2/M phase caused a mutator phenotype that was exacerbated in the absence of the exonuclease Exo1. This mutator phenotype was largely suppressed by increasing the lifetime of replication-associated DNA nicks, either by reducing or delaying Cdc9 ligase activity in vivo. Therefore, Cdc9 dictates a window of time for MMR determined by transient DNA nicks that direct the Mlh1-Pms1 in a strand-specific manner. Because DNA nicks occur on both newly synthesized leading and lagging strands,11 these results establish a general mechanism for targeting MMR to the newly synthesized DNA, thus preventing the accumulation of mutations that underlie the development of human cancer. The correction of DNA replication errors by the mismatch repair (MMR) machinery requires the discrimination between parental and daughter DNA strands. Reyes et al. provide evidence that DNA replication-associated nicks are used as MMR strand discrimination signals and that DNA ligase I (Cdc9) activity dictates a window of time for MMR.
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Affiliation(s)
- Gloria X Reyes
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg 69120, Germany
| | - Anna Kolodziejczak
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg 69120, Germany; Faculty of Bioscience, Heidelberg University, Heidelberg 69120, Germany
| | - Lovely Jael Paul Solomon Devakumar
- Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Foresterhill, Aberdeen, Scotland AB25 2ZD, UK
| | - Takashi Kubota
- Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Foresterhill, Aberdeen, Scotland AB25 2ZD, UK
| | - Richard D Kolodner
- Ludwig Institute for Cancer Research, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA; Department of Cellular and Molecular Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA; Moores Cancer Center at UC San Diego Health, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA; Institute of Genomic Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA
| | - Christopher D Putnam
- Ludwig Institute for Cancer Research, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA; Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA
| | - Hans Hombauer
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg 69120, Germany; Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Heidelberg 69120, Germany.
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Flap endonuclease 1 (FEN1) as a novel diagnostic and prognostic biomarker for gastric cancer. Clin Res Hepatol Gastroenterol 2021; 45:101455. [PMID: 32505732 DOI: 10.1016/j.clinre.2020.04.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 04/16/2020] [Accepted: 04/20/2020] [Indexed: 02/04/2023]
Abstract
OBJECTIVE Flap endonuclease 1 (FEN1) overexpression has been reported to be closely associated with cancer prognosis. However, its diagnostic and prognostic significance in gastric cancer (GC) has not yet been explored. METHODS FEN1 expression, its correlation with clinical parameters, and prognostic significance were investigated by data mining of The Cancer Genome Atlas (TCGA) datasets. Patients were divided into low- and high-expression groups using the median value of FEN1 expression as the cut-off. The diagnostic value of FEN1 expression in GC tissues was determined via receiver operating characteristic (ROC) curve analysis. Univariate and multivariate Cox regression analyses were used to identify the prognostic indicators. Gene set enrichment analysis (GSEA) was used to explore FEN1-related signalling pathways in GC. Furthermore, the Human Protein Atlas (HPA) database and GSE62254 dataset were used for further external validation. RESULTS FEN1 was expressed at a higher level in GC tissues than in normal gastric tissues with high diagnostic accuracy (area under the ROC=0.909). Higher FEN1 expression was also validated at the protein level using the HPA database. High FEN1 expression in GC was correlated with older age (P<0.05). Patients with high FEN1 expression had a favourable prognosis compared to patients with low FEN1 expression (P=0.0048). Univariate and multivariate analyses revealed that FEN1 was an independent predictive factor associated with overall survival in both the TCGA cohort and the GSE62254 dataset (P=0.0004 and P=0.011, respectively). GSEA identified that the FEN1 expression was related to DNA replication, cell cycle, cytosolic and sensing pathways, oocyte meiosis, and the P53 signalling pathway. CONCLUSION The results revealed high expression of FEN1 in GC; thus, it could be a promising early diagnostic and independent prognostic biomarker for GC.
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Kontizas E, Tastsoglou S, Karamitros T, Karayiannis Y, Kollia P, Hatzigeorgiou AG, Sgouras DN. Impact of Helicobacter pylori Infection and Its Major Virulence Factor CagA on DNA Damage Repair. Microorganisms 2020; 8:microorganisms8122007. [PMID: 33339161 PMCID: PMC7765595 DOI: 10.3390/microorganisms8122007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 12/11/2020] [Accepted: 12/14/2020] [Indexed: 01/10/2023] Open
Abstract
Helicobacter pylori infection induces a plethora of DNA damages. Gastric epithelial cells, in order to maintain genomic integrity, require an integrous DNA damage repair (DDR) machinery, which, however, is reported to be modulated by the infection. CagA is a major H. pylori virulence factor, associated with increased risk for gastric carcinogenesis. Its pathogenic activity is partly regulated by phosphorylation on EPIYA motifs. Our aim was to identify effects of H. pylori infection and CagA on DDR, investigating the transcriptome of AGS cells, infected with wild-type, ΔCagA and EPIYA-phosphorylation-defective strains. Upon RNA-Seq-based transcriptomic analysis, we observed that a notable number of DDR genes were found deregulated during the infection, potentially resulting to base excision repair and mismatch repair compromise and an intricate deregulation of nucleotide excision repair, homologous recombination and non-homologous end-joining. Transcriptome observations were further investigated on the protein expression level, utilizing infections of AGS and GES-1 cells. We observed that CagA contributed to the downregulation of Nth Like DNA Glycosylase 1 (NTHL1), MutY DNA Glycosylase (MUTYH), Flap Structure-Specific Endonuclease 1 (FEN1), RAD51 Recombinase, DNA Polymerase Delta Catalytic Subunit (POLD1), and DNA Ligase 1 (LIG1) and, contrary to transcriptome results, Apurinic/Apyrimidinic Endodeoxyribonuclease 1 (APE1) upregulation. Our study accentuates the role of CagA as a significant contributor of H. pylori infection-mediated DDR modulation, potentially disrupting the balance between DNA damage and repair, thus favoring genomic instability and carcinogenesis.
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Affiliation(s)
- Eleftherios Kontizas
- Laboratory of Medical Microbiology, Hellenic Pasteur Institute, 11521 Athens, Greece;
- Department of Genetics and Biotechnology, Faculty of Biology, National and Kapodistrian University of Athens, 15772 Athens, Greece;
- Correspondence: (E.K.); (D.N.S.); Tel.: +30-210-647-8812 (E.K.); +30-210-647-8824 (D.N.S.)
| | - Spyros Tastsoglou
- Department of Electrical and Computer Engineering, University of Thessaly, 38221 Volos, Greece;
- DIANA-Lab, Hellenic Pasteur Institute, 11521 Athens, Greece;
| | - Timokratis Karamitros
- Bioinformatics and Applied Genomics Unit, Hellenic Pasteur Institute, 11521 Athens, Greece;
| | - Yiannis Karayiannis
- Laboratory of Medical Microbiology, Hellenic Pasteur Institute, 11521 Athens, Greece;
- Department of Genetics and Biotechnology, Faculty of Biology, National and Kapodistrian University of Athens, 15772 Athens, Greece;
| | - Panagoula Kollia
- Department of Genetics and Biotechnology, Faculty of Biology, National and Kapodistrian University of Athens, 15772 Athens, Greece;
| | - Artemis G. Hatzigeorgiou
- DIANA-Lab, Hellenic Pasteur Institute, 11521 Athens, Greece;
- DIANA-Lab, Department of Computer Science and Biomedical Informatics, University of Thessaly, 35131 Lamia, Greece
| | - Dionyssios N. Sgouras
- Laboratory of Medical Microbiology, Hellenic Pasteur Institute, 11521 Athens, Greece;
- Correspondence: (E.K.); (D.N.S.); Tel.: +30-210-647-8812 (E.K.); +30-210-647-8824 (D.N.S.)
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Identification of MLH2/hPMS1 dominant mutations that prevent DNA mismatch repair function. Commun Biol 2020; 3:751. [PMID: 33303966 PMCID: PMC7730388 DOI: 10.1038/s42003-020-01481-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 11/11/2020] [Indexed: 12/27/2022] Open
Abstract
Inactivating mutations affecting key mismatch repair (MMR) components lead to microsatellite instability (MSI) and cancer. However, a number of patients with MSI-tumors do not present alterations in classical MMR genes. Here we discovered that specific missense mutations in the MutL homolog MLH2, which is dispensable for MMR, confer a dominant mutator phenotype in S. cerevisiae. MLH2 mutations elevated frameshift mutation rates, and caused accumulation of long-lasting nuclear MMR foci. Both aspects of this phenotype were suppressed by mutations predicted to prevent the binding of Mlh2 to DNA. Genetic analysis revealed that mlh2 dominant mutations interfere with both Exonuclease 1 (Exo1)-dependent and Exo1-independent MMR. Lastly, we demonstrate that a homolog mutation in human hPMS1 results in a dominant mutator phenotype. Our data support a model in which yeast Mlh1-Mlh2 or hMLH1-hPMS1 mutant complexes act as roadblocks on DNA preventing MMR, unraveling a novel mechanism that can account for MSI in human cancer.
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FEN1 endonuclease as a therapeutic target for human cancers with defects in homologous recombination. Proc Natl Acad Sci U S A 2020; 117:19415-19424. [PMID: 32719125 PMCID: PMC7431096 DOI: 10.1073/pnas.2009237117] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Synthetic lethality strategies for cancer therapy exploit cancer-specific genetic defects to identify targets that are uniquely essential to the survival of tumor cells. Here we show RAD27/FEN1, which encodes flap endonuclease 1 (FEN1), a structure-specific nuclease with roles in DNA replication and repair, and has the greatest number of synthetic lethal interactions with Saccharomyces cerevisiae genome instability genes, is a druggable target for an inhibitor-based approach to kill cancers with defects in homologous recombination (HR). The vulnerability of cancers with HR defects to FEN1 loss was validated by studies showing that small-molecule FEN1 inhibitors and FEN1 small interfering RNAs (siRNAs) selectively killed BRCA1- and BRCA2-defective human cell lines. Furthermore, the differential sensitivity to FEN1 inhibition was recapitulated in mice, where a small-molecule FEN1 inhibitor reduced the growth of tumors established from drug-sensitive but not drug-resistant cancer cell lines. FEN1 inhibition induced a DNA damage response in both sensitive and resistant cell lines; however, sensitive cell lines were unable to recover and replicate DNA even when the inhibitor was removed. Although FEN1 inhibition activated caspase to higher levels in sensitive cells, this apoptotic response occurred in p53-defective cells and cell killing was not blocked by a pan-caspase inhibitor. These results suggest that FEN1 inhibitors have the potential for therapeutically targeting HR-defective cancers such as those resulting from BRCA1 and BRCA2 mutations, and other genetic defects.
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Witkin AE, Banerji J, Bullock PA. A model for the formation of the duplicated enhancers found in polyomavirus regulatory regions. Virology 2020; 543:27-33. [PMID: 32056844 DOI: 10.1016/j.virol.2020.01.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 01/27/2020] [Accepted: 01/27/2020] [Indexed: 12/14/2022]
Abstract
When purified from persistent infections, the genomes of most human polyomaviruses contain single enhancers. However, when isolated from productively infected cells from immunocompromised individuals, the genomes of several polyomaviruses contain duplicated enhancers that promote a number of polyoma-based diseases. The mechanism(s) that gives rise to the duplicated enhancers in the polyomaviruses is, however, not known. Herein we propose a model for the duplication of the enhancers that is based on recent advances in our understanding of; 1) the initiation of polyomavirus DNA replication, 2) the formation of long flaps via displacement synthesis and 3) the subsequent generation of duplicated enhancers via double stranded break repair. Finally, we discuss the possibility that the polyomavirus based replication dependent enhancer duplication model may be relevant to the enhancer-associated rearrangements detected in human genomes that are associated with various diseases, including cancers.
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Affiliation(s)
- Anna E Witkin
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA, 02111, USA
| | - Julian Banerji
- Center for Computational and Integrative Biology, Simches Research Center, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA, 02114, USA
| | - Peter A Bullock
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA, 02111, USA.
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22
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Williams GM, Petrides AK, Balakrishnan L, Surtees JA. Tracking Expansions of Stable and Threshold Length Trinucleotide Repeat Tracts In Vivo and In Vitro Using Saccharomyces cerevisiae. Methods Mol Biol 2020; 2056:25-68. [PMID: 31586340 DOI: 10.1007/978-1-4939-9784-8_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Trinucleotide repeat (TNR) tracts are inherently unstable during DNA replication, leading to repeat expansions and/or contractions. Expanded tracts are the cause of over 40 neurodegenerative and neuromuscular diseases. In this chapter, we focus on the (CAG)n and (CTG)n repeat sequences that, when expanded, lead to Huntington's disease (HD) and myotonic dystrophy type 1 (DM1), respectively, as well as a number of other neurodegenerative diseases. TNR tracts in most individuals are relatively small and stable in terms of length. However, TNR tracts become increasingly prone to expansion as tract length increases, eventually leading to very long tracts that disrupt coding (e.g. HD) or noncoding (e.g., DM1) regions of the genome. It is important to understand the early stages in TNR expansions, that is, the transition from small, stable lengths to susceptible threshold lengths. We describe PCR-based in vivo assays, using the model system Saccharomyces cerevisiae, to determine and characterize the dynamic behavior of TNR tracts in the stable and threshold ranges. We also describe a simple in vitro system to assess tract dynamics during 5' single-stranded DNA (ssDNA) flap processing and to assess the role of different DNA metabolism proteins in these dynamics. These assays can ultimately be used to determine factors that influence the early stages of TNR tract expansion.
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Affiliation(s)
- Gregory M Williams
- Centre for Chromosome Biology, National University of Ireland, Galway, Galway, Ireland
- Galway Neuroscience Centre, National Universityof Ireland, Galway, Galway, Ireland
| | | | - Lata Balakrishnan
- Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN, USA
| | - Jennifer A Surtees
- Department of Biochemistry, JacobsSchool of Medicine and BiomedicalSciences, State University of New York atBuffalo, Buffalo, NY, USA.
- Genetics, Genomics and Bioinformatics Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA.
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Otálora-Otálora BA, Florez M, López-Kleine L, Canas Arboleda A, Grajales Urrego DM, Rojas A. Joint Transcriptomic Analysis of Lung Cancer and Other Lung Diseases. Front Genet 2019; 10:1260. [PMID: 31867044 PMCID: PMC6908522 DOI: 10.3389/fgene.2019.01260] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 11/14/2019] [Indexed: 12/09/2022] Open
Abstract
Background: Epidemiological and clinical evidence points cancer comorbidity with pulmonary chronic disease. The acquisition of some hallmarks of cancer by cells affected with lung pathologies as a cell adaptive mechanism to a shear stress, suggests that could be associated with the establishment of tumoral processes. Objective: To propose a bioinformatic pipeline for the identification of all deregulated genes and the transcriptional regulators (TFs) that are coexpressed during lung cancer establishment, and therefore could be important for the acquisition of the hallmarks of cancer. Methods: Ten microarray datasets (six of lung cancer, four of lung diseases) comparing normal and diseases-related lung tissue were selected to identify hub differentiated expressed genes (DEGs) in common between lung pathologies and lung cancer, along with transcriptional regulators through the utilization of specialized libraries from R language. DAVID bioinformatics tool for gene enrichment analyses was used to identify genes with experimental evidence associated to tumoral processes and signaling pathways. Coexpression networks of DEGs and TFs in lung cancer establishment were created with Coexnet library, and a survival analysis of the main hub genes was made. Results: Two hundred ten DEGs were identified in common between lung cancer and other lung diseases related to the acquisition of tumoral characteristics, which are coexpressed in a lung cancer network with TFs, suggesting that could be related to the establishment of the tumoral pathology in lung. The comparison of the coexpression networks of lung cancer and other lung diseases allowed the identification of common connectivity patterns (CCPs) with DEGs and TFs correlated to important tumoral processes and signaling pathways, that haven´t been studied to experimentally validate their role in the early stages of lung cancer. Some of the TFs identified showed a correlation between its expression levels and the survival of lung cancer patients. Conclusion: Our findings indicate that lung diseases share genes with lung cancer which are coexpressed in lung cancer, and might be able to explain the epidemiological observations that point to direct and inverse comorbid associations between some chronic lung diseases and lung cancer and represent a complex transcriptomic scenario.
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Affiliation(s)
| | - Mauro Florez
- Departamento de Estadística, Grupo de Investigación en Bioinformática y Biología de sistemas – GiBBS, Facultad de Ciencias, Universidad Nacional de Colombia, Bogotá, Colombia
| | - Liliana López-Kleine
- Departamento de Estadística, Grupo de Investigación en Bioinformática y Biología de sistemas – GiBBS, Facultad de Ciencias, Universidad Nacional de Colombia, Bogotá, Colombia
| | | | | | - Adriana Rojas
- Instituto de Genética Humana, Facultad de Medicina, Pontificia Universidad Javeriana, Bogotá, Colombia
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Xu X, Shi R, Zheng L, Guo Z, Wang L, Zhou M, Zhao Y, Tian B, Truong K, Chen Y, Shen B, Hua Y, Xu H. SUMO-1 modification of FEN1 facilitates its interaction with Rad9-Rad1-Hus1 to counteract DNA replication stress. J Mol Cell Biol 2019; 10:460-474. [PMID: 30184152 PMCID: PMC6231531 DOI: 10.1093/jmcb/mjy047] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 09/03/2018] [Indexed: 01/25/2023] Open
Abstract
Human flap endonuclease 1 (FEN1) is a structure-specific, multi-functional endonuclease essential for DNA replication and repair. We and others have shown that during DNA replication, FEN1 processes Okazaki fragments via its interaction with the proliferating cell nuclear antigen (PCNA). Alternatively, in response to DNA damage, FEN1 interacts with the PCNA-like Rad9–Rad1–Hus1 complex instead of PCNA to engage in DNA repair activities, such as homology-directed repair of stalled DNA replication forks. However, it is unclear how FEN1 is able to switch between these interactions and its roles in DNA replication and DNA repair. Here, we report that FEN1 undergoes SUMOylation by SUMO-1 in response to DNA replication fork-stalling agents, such as UV irradiation, hydroxyurea, and mitomycin C. This DNA damage-induced SUMO-1 modification promotes the interaction of FEN1 with the Rad9–Rad1–Hus1 complex. Furthermore, we found that FEN1 mutations that prevent its SUMO-1 modification also impair its ability to interact with HUS1 and to rescue stalled replication forks. These impairments lead to the accumulation of DNA damage and heightened sensitivity to fork-stalling agents. Altogether, our findings suggest an important role of the SUMO-1 modification of FEN1 in regulating its roles in DNA replication and repair.
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Affiliation(s)
- Xiaoli Xu
- Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China
| | - Rongyi Shi
- Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China
| | - Li Zheng
- Department of Cancer Genetics and Epigenetics, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA, USA
| | - Zhigang Guo
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology and College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Liangyan Wang
- Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China
| | - Mian Zhou
- Department of Cancer Genetics and Epigenetics, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA, USA
| | - Ye Zhao
- Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China
| | - Bing Tian
- Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China
| | - Khue Truong
- Department of Molecular Medicine, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA, USA
| | - Yuan Chen
- Department of Molecular Medicine, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA, USA
| | - Binghui Shen
- Department of Cancer Genetics and Epigenetics, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA, USA
| | - Yuejin Hua
- Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China
| | - Hong Xu
- Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China
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25
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Hoffert KM, Higginbotham KSP, Gibson JT, Oehrle S, Strome ED. Mutations in the S-Adenosylmethionine Synthetase Genes SAM1 and SAM2 Differentially Affect Genome Stability in Saccharomyces cerevisiae. Genetics 2019; 213:97-112. [PMID: 31320408 PMCID: PMC6727793 DOI: 10.1534/genetics.119.302435] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 07/15/2019] [Indexed: 12/20/2022] Open
Abstract
Maintenance of genome integrity is a crucial cellular focus that involves a wide variety of proteins functioning in multiple processes. Defects in many different pathways can result in genome instability, a hallmark of cancer. Utilizing a diploid Saccharomyces cerevisiae model, we previously reported a collection of gene mutations that affect genome stability in a haploinsufficient state. In this work we explore the effect of gene dosage on genome instability for one of these genes and its paralog; SAM1 and SAM2 These genes encode S-Adenosylmethionine (AdoMet) synthetases, responsible for the creation of AdoMet from methionine and ATP. AdoMet is the universal methyl donor for methylation reactions and is essential for cell viability. It is the second most used cellular enzyme substrate and is exceptionally well-conserved through evolution. Mammalian cells express three genes, MAT1A, MAT2A, and MAT2B, with distinct expression profiles and functions. Alterations to these AdoMet synthetase genes, and AdoMet levels, are found in many cancers, making them a popular target for therapeutic intervention. However, significant variance in these alterations are found in different tumor types, with the cellular consequences of the variation still unknown. By studying this pathway in the yeast system, we demonstrate that losses of SAM1 and SAM2 have different effects on genome stability through distinctive effects on gene expression and AdoMet levels, and ultimately separate effects on the methyl cycle. Thus, this study provides insight into the mechanisms by which differential expression of the SAM genes have cellular consequences that affect genome instability.
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Affiliation(s)
- Kellyn M Hoffert
- Department of Biological Sciences, Northern Kentucky University, Highland Heights, Kentucky 41099
| | - Kathryn S P Higginbotham
- Department of Biological Sciences, Northern Kentucky University, Highland Heights, Kentucky 41099
| | - Justin T Gibson
- Department of Biological Sciences, Northern Kentucky University, Highland Heights, Kentucky 41099
| | - Stuart Oehrle
- Waters Field Laboratory, Chemistry Department, Northern Kentucky University, Highland Heights, Kentucky 41099
| | - Erin D Strome
- Department of Biological Sciences, Northern Kentucky University, Highland Heights, Kentucky 41099
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26
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Zaher MS, Rashid F, Song B, Joudeh LI, Sobhy MA, Tehseen M, Hingorani MM, Hamdan SM. Missed cleavage opportunities by FEN1 lead to Okazaki fragment maturation via the long-flap pathway. Nucleic Acids Res 2019; 46:2956-2974. [PMID: 29420814 PMCID: PMC5888579 DOI: 10.1093/nar/gky082] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 01/27/2018] [Indexed: 12/11/2022] Open
Abstract
RNA–DNA hybrid primers synthesized by low fidelity DNA polymerase α to initiate eukaryotic lagging strand synthesis must be removed efficiently during Okazaki fragment (OF) maturation to complete DNA replication. In this process, each OF primer is displaced and the resulting 5′-single-stranded flap is cleaved by structure-specific 5′-nucleases, mainly Flap Endonuclease 1 (FEN1), to generate a ligatable nick. At least two models have been proposed to describe primer removal, namely short- and long-flap pathways that involve FEN1 or FEN1 along with Replication Protein A (RPA) and Dna2 helicase/nuclease, respectively. We addressed the question of pathway choice by studying the kinetic mechanism of FEN1 action on short- and long-flap DNA substrates. Using single molecule FRET and rapid quench-flow bulk cleavage assays, we showed that unlike short-flap substrates, which are bound, bent and cleaved within the first encounter between FEN1 and DNA, long-flap substrates can escape cleavage even after DNA binding and bending. Notably, FEN1 can access both substrates in the presence of RPA, but bending and cleavage of long-flap DNA is specifically inhibited. We propose that FEN1 attempts to process both short and long flaps, but occasional missed cleavage of the latter allows RPA binding and triggers the long-flap OF maturation pathway.
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Affiliation(s)
- Manal S Zaher
- King Abdullah University of Science and Technology, Division of Biological and Environmental Science and Engineering, Thuwal 23955, Saudi Arabia
| | - Fahad Rashid
- King Abdullah University of Science and Technology, Division of Biological and Environmental Science and Engineering, Thuwal 23955, Saudi Arabia
| | - Bo Song
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06459, USA
| | - Luay I Joudeh
- King Abdullah University of Science and Technology, Division of Biological and Environmental Science and Engineering, Thuwal 23955, Saudi Arabia
| | - Mohamed A Sobhy
- King Abdullah University of Science and Technology, Division of Biological and Environmental Science and Engineering, Thuwal 23955, Saudi Arabia
| | - Muhammad Tehseen
- King Abdullah University of Science and Technology, Division of Biological and Environmental Science and Engineering, Thuwal 23955, Saudi Arabia
| | - Manju M Hingorani
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06459, USA
| | - Samir M Hamdan
- King Abdullah University of Science and Technology, Division of Biological and Environmental Science and Engineering, Thuwal 23955, Saudi Arabia
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27
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Becker JR, Gallo D, Leung W, Croissant T, Thu YM, Nguyen HD, Starr TK, Brown GW, Bielinsky AK. Flap endonuclease overexpression drives genome instability and DNA damage hypersensitivity in a PCNA-dependent manner. Nucleic Acids Res 2019; 46:5634-5650. [PMID: 29741650 PMCID: PMC6009675 DOI: 10.1093/nar/gky313] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 04/16/2018] [Indexed: 12/31/2022] Open
Abstract
Overexpression of the flap endonuclease FEN1 has been observed in a variety of cancer types and is a marker for poor prognosis. To better understand the cellular consequences of FEN1 overexpression we utilized a model of its Saccharomyces cerevisiae homolog, RAD27. In this system, we discovered that flap endonuclease overexpression impedes replication fork progression and leads to an accumulation of cells in mid-S phase. This was accompanied by increased phosphorylation of the checkpoint kinase Rad53 and histone H2A-S129. RAD27 overexpressing cells were hypersensitive to treatment with DNA damaging agents, and defective in ubiquitinating the replication clamp proliferating cell nuclear antigen (PCNA) at lysine 164. These effects were reversed when the interaction between overexpressed Rad27 and PCNA was ablated, suggesting that the observed phenotypes were linked to problems in DNA replication. RAD27 overexpressing cells also exhibited an unexpected dependence on the SUMO ligases SIZ1 and MMS21 for viability. Importantly, we found that overexpression of FEN1 in human cells also led to phosphorylation of CHK1, CHK2, RPA32 and histone H2AX, all markers of genome instability. Our data indicate that flap endonuclease overexpression is a driver of genome instability in yeast and human cells that impairs DNA replication in a manner dependent on its interaction with PCNA.
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Affiliation(s)
- Jordan R Becker
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - David Gallo
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON M5S 3E2, Canada
| | - Wendy Leung
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Taylor Croissant
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Yee Mon Thu
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Hai Dang Nguyen
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Timothy K Starr
- Department of Obstetrics, Gynecology, and Women's Health, University of Minnesota, Minneapolis, MN 55455, USA
| | - Grant W Brown
- Department of Biochemistry and Donnelly Centre, University of Toronto, Toronto, ON M5S 3E2, Canada
| | - Anja-Katrin Bielinsky
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
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28
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Liu J, François JM, Capp JP. Gene Expression Noise Produces Cell-to-Cell Heterogeneity in Eukaryotic Homologous Recombination Rate. Front Genet 2019; 10:475. [PMID: 31164905 PMCID: PMC6536703 DOI: 10.3389/fgene.2019.00475] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 05/03/2019] [Indexed: 11/13/2022] Open
Abstract
Variation in gene expression among genetically identical individual cells (called gene expression noise) directly contributes to phenotypic diversity. Whether such variation can impact genome stability and lead to variation in genotype remains poorly explored. We addressed this question by investigating whether noise in the expression of genes affecting homologous recombination (HR) activity either directly (RAD52) or indirectly (RAD27) confers cell-to-cell heterogeneity in HR rate in Saccharomyces cerevisiae. Using cell sorting to isolate subpopulations with various expression levels, we show that spontaneous HR rate is highly heterogeneous from cell-to-cell in clonal populations depending on the cellular amount of proteins affecting HR activity. Phleomycin-induced HR is even more heterogeneous, showing that RAD27 expression variation strongly affects the rate of recombination from cell-to-cell. Strong variations in HR rate between subpopulations are not correlated to strong changes in cell cycle stage. Moreover, this heterogeneity occurs even when simultaneously sorting cells at equal expression level of another gene involved in DNA damage response (BMH1) that is upregulated by DNA damage, showing that the initiating DNA damage is not responsible for the observed heterogeneity in HR rate. Thus gene expression noise seems mainly responsible for this phenomenon. Finally, HR rate non-linearly scales with Rad27 levels showing that total amount of HR cannot be explained solely by the time- or population-averaged Rad27 expression. Altogether, our data reveal interplay between heterogeneity at the gene expression and genetic levels in the production of phenotypic diversity with evolutionary consequences from microbial to cancer cell populations.
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Affiliation(s)
- Jian Liu
- Laboratoire d'Ingénierie des Systèmes Biologiques et des Procédés, Institut National des Sciences Appliquées de Toulouse, UMR CNRS 5504, UMR INRA 792, Université de Toulouse, Toulouse, France
| | - Jean-Marie François
- Laboratoire d'Ingénierie des Systèmes Biologiques et des Procédés, Institut National des Sciences Appliquées de Toulouse, UMR CNRS 5504, UMR INRA 792, Université de Toulouse, Toulouse, France
| | - Jean-Pascal Capp
- Laboratoire d'Ingénierie des Systèmes Biologiques et des Procédés, Institut National des Sciences Appliquées de Toulouse, UMR CNRS 5504, UMR INRA 792, Université de Toulouse, Toulouse, France
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29
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DNA Replication Through Strand Displacement During Lagging Strand DNA Synthesis in Saccharomyces cerevisiae. Genes (Basel) 2019; 10:genes10020167. [PMID: 30795600 PMCID: PMC6409922 DOI: 10.3390/genes10020167] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 02/14/2019] [Accepted: 02/18/2019] [Indexed: 01/21/2023] Open
Abstract
This review discusses a set of experimental results that support the existence of extended strand displacement events during budding yeast lagging strand DNA synthesis. Starting from introducing the mechanisms and factors involved in leading and lagging strand DNA synthesis and some aspects of the architecture of the eukaryotic replisome, we discuss studies on bacterial, bacteriophage and viral DNA polymerases with potent strand displacement activities. We describe proposed pathways of Okazaki fragment processing via short and long flaps, with a focus on experimental results obtained in Saccharomyces cerevisiae that suggest the existence of frequent and extended strand displacement events during eukaryotic lagging strand DNA synthesis, and comment on their implications for genome integrity.
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30
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Human Exonuclease 1 (EXO1) Regulatory Functions in DNA Replication with Putative Roles in Cancer. Int J Mol Sci 2018; 20:ijms20010074. [PMID: 30585186 PMCID: PMC6337416 DOI: 10.3390/ijms20010074] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 12/12/2018] [Accepted: 12/19/2018] [Indexed: 12/11/2022] Open
Abstract
Human exonuclease 1 (EXO1), a 5'→3' exonuclease, contributes to the regulation of the cell cycle checkpoints, replication fork maintenance, and post replicative DNA repair pathways. These processes are required for the resolution of stalled or blocked DNA replication that can lead to replication stress and potential collapse of the replication fork. Failure to restart the DNA replication process can result in double-strand breaks, cell-cycle arrest, cell death, or cellular transformation. In this review, we summarize the involvement of EXO1 in the replication, DNA repair pathways, cell cycle checkpoints, and the link between EXO1 and cancer.
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31
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Uncoupling Sae2 Functions in Downregulation of Tel1 and Rad53 Signaling Activities. Genetics 2018; 211:515-530. [PMID: 30538107 DOI: 10.1534/genetics.118.301830] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 12/09/2018] [Indexed: 11/18/2022] Open
Abstract
The Mre11-Rad50-Xrs2 (MRX) complex acts together with the Sae2 protein to initiate resection of DNA double-strand breaks (DSBs) and to regulate a checkpoint response that couples cell cycle progression with DSB repair. Sae2 supports resistance to DNA damage and downregulates the signaling activities of MRX, Tel1, and Rad53 checkpoint proteins at the sites of damage. How these functions are connected to each other is not known. Here, we describe the separation-of-function sae2-ms mutant that, similar to SAE2 deletion, upregulates MRX and Tel1 signaling activities at DSBs by reducing Mre11 endonuclease activity. However, unlike SAE2 deletion, Sae2-ms causes neither DNA damage sensitivity nor enhanced Rad53 activation, indicating that DNA damage resistance depends mainly on Sae2-mediated Rad53 inhibition. The lack of Sae2, but not the presence of Sae2-ms, impairs long-range resection and increases both Rad9 accumulation at DSBs and Rad53-Rad9 interaction independently of Mre11 nuclease activity. Altogether, these data lead to a model whereby Sae2 plays distinct functions in limiting MRX-Tel1 and Rad9 abundance at DSBs, with the control on Rad9 association playing the major role in supporting DNA damage resistance and in regulating long-range resection and checkpoint activation.
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32
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Stodola JL, Burgers PM. Mechanism of Lagging-Strand DNA Replication in Eukaryotes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1042:117-133. [PMID: 29357056 DOI: 10.1007/978-981-10-6955-0_6] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This chapter focuses on the enzymes and mechanisms involved in lagging-strand DNA replication in eukaryotic cells. Recent structural and biochemical progress with DNA polymerase α-primase (Pol α) provides insights how each of the millions of Okazaki fragments in a mammalian cell is primed by the primase subunit and further extended by its polymerase subunit. Rapid kinetic studies of Okazaki fragment elongation by Pol δ illuminate events when the polymerase encounters the double-stranded RNA-DNA block of the preceding Okazaki fragment. This block acts as a progressive molecular break that provides both time and opportunity for the flap endonuclease 1 (FEN1) to access the nascent flap and cut it. The iterative action of Pol δ and FEN1 is coordinated by the replication clamp PCNA and produces a regulated degradation of the RNA primer, thereby preventing the formation of long-strand displacement flaps. Occasional long flaps are further processed by backup nucleases including Dna2.
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Affiliation(s)
- Joseph L Stodola
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO, USA
| | - Peter M Burgers
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO, USA.
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33
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Li Z, Liu B, Jin W, Wu X, Zhou M, Liu VZ, Goel A, Shen Z, Zheng L, Shen B. hDNA2 nuclease/helicase promotes centromeric DNA replication and genome stability. EMBO J 2018; 37:embj.201796729. [PMID: 29773570 PMCID: PMC6043852 DOI: 10.15252/embj.201796729] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 04/16/2018] [Accepted: 04/25/2018] [Indexed: 11/18/2022] Open
Abstract
DNA2 is a nuclease/helicase that is involved in Okazaki fragment maturation, replication fork processing, and end resection of DNA double‐strand breaks. Similar such helicase activity for resolving secondary structures and structure‐specific nuclease activity are needed during DNA replication to process the chromosome‐specific higher order repeat units present in the centromeres of human chromosomes. Here, we show that DNA2 binds preferentially to centromeric DNA. The nuclease and helicase activities of DNA2 are both essential for resolution of DNA structural obstacles to facilitate DNA replication fork movement. Loss of DNA2‐mediated clean‐up mechanisms impairs centromeric DNA replication and CENP‐A deposition, leading to activation of the ATR DNA damage checkpoints at centromeric DNA regions and late‐S/G2 cell cycle arrest. Cells that escape arrest show impaired metaphase plate formation and abnormal chromosomal segregation. Furthermore, the DNA2 inhibitor C5 mimics DNA2 knockout and synergistically kills cancer cells when combined with an ATR inhibitor. These findings provide mechanistic insights into how DNA2 supports replication of centromeric DNA and give further insights into new therapeutic strategies.
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Affiliation(s)
- Zhengke Li
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, Duarte, CA, USA
| | - Bochao Liu
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers Robert Wood Johnson Medical School, Rutgers, the State University of New Jersey, New Brunswick, NJ, USA
| | - Weiwei Jin
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, Duarte, CA, USA.,Department of Gastroenterology & Pancreatic Surgery, Zhejiang Provincial People's Hospital, Hangzhou, Zhejiang, China
| | - Xiwei Wu
- Department of Molecular and Cellular Biology, Beckman Research Institute, City of Hope, Duarte, CA, USA
| | - Mian Zhou
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, Duarte, CA, USA
| | - Vincent Zewen Liu
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, Duarte, CA, USA.,Department of Computer Science, Columbia University, New York, NY, USA
| | - Ajay Goel
- Center for Gastrointestinal Research, Center for Translational Genomics and Oncology, Baylor Scott and White Research Institute and Charles A. Sammons Cancer Center, Baylor University Medical Center, Dallas, TX, USA
| | - Zhiyuan Shen
- Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers Robert Wood Johnson Medical School, Rutgers, the State University of New Jersey, New Brunswick, NJ, USA
| | - Li Zheng
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, Duarte, CA, USA
| | - Binghui Shen
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, Duarte, CA, USA
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34
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Chou AK, Shen MY, Chen FY, Hsiao CL, Shih LC, Chang WS, Tsai CW, Ying TH, Wu MH, Huang CY, Bau DAT. The Association of Flap Endonuclease 1 Genotypes with the Susceptibility of Endometriosis. Cancer Genomics Proteomics 2017; 14:455-460. [PMID: 29109095 DOI: 10.21873/cgp.20055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 09/05/2017] [Accepted: 10/06/2017] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND/AIM Flap endonuclease 1 (FEN1), a protein with multiple functions in genome stability maintenance, is important in cancer prevention. The two functional germline variants of FEN1, rs174538 and rs4246215, regarding cancer susceptibility have been reported in lung, breast, liver, esophageal, gastric, colorectal cancer, glioma and leukemia, but not endometriosis. In this study, we firstly aimed at evaluating the contribution of FEN1 genotypes to endometriosis risk in a representative Taiwan population. MATERIALS AND METHODS In total, 153 patients with endometriosis and 636 non-cancer healthy controls were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methodology. RESULTS The genotypes of FEN1 rs174538, but not those of rs4246215, were differently distributed between the endometriosis and control groups. In detail, the AA of FEN1 rs174538 genotypes were significantly less frequently found among endometriosis patients than among controls (odds ratio [OR]=0.43, 95% confidence interval [CI]=0.24-0.78, p=0.0125). The A allele at FEN1 rs174538 was also significantly less frequent among cases than controls (OR=0.65, 95%CI=0.50-0.86, p=0.0021). As for age of first menarche, those with first menarche at the age >12.8 carrying the FEN1 rs174538 AA genotype conferred lower OR of 0.29 (95%CI=0.11-0.78, p=0.0381) for endometriosis. Regarding the full pregnancy status, those without having had a full-term pregnancy carrying the FEN1 rs174538 AA genotype were of lower risk (ORs=0.12, 95%CI=0.03-0.53, p=0.0050). CONCLUSION The FEN1 rs174538 A allele is a novel protective biomarker for endometriosis and this genotype may have interactions with age- and hormone-related factors on the development of endometriosis.
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Affiliation(s)
- An-Kuo Chou
- Department of Anesthesiology, China Medical University Hospital, Taichung, Taiwan, R.O.C
| | - Ming-Yi Shen
- Department of Medical Research, China Medical University Hospital, Taichung, Taiwan Hospital, Taichung, Taiwan, R.O.C.,Graduate Institute of Biomedical Sciences, China Medical University, Taichung, Taiwan, R.O.C
| | - Fang-Yu Chen
- Department of Medical Research, China Medical University Hospital, Taichung, Taiwan Hospital, Taichung, Taiwan, R.O.C
| | - Chieh-Lun Hsiao
- Graduate Institute of Biomedical Sciences, China Medical University, Taichung, Taiwan, R.O.C.,Terry Fox Cancer Research Laboratory, China Medical University Hospital, Taichung, Taiwan, R.O.C
| | - Liang-Chun Shih
- Terry Fox Cancer Research Laboratory, China Medical University Hospital, Taichung, Taiwan, R.O.C
| | - Wen-Shin Chang
- Terry Fox Cancer Research Laboratory, China Medical University Hospital, Taichung, Taiwan, R.O.C
| | - Chia-Wen Tsai
- Terry Fox Cancer Research Laboratory, China Medical University Hospital, Taichung, Taiwan, R.O.C
| | - Tsung-Ho Ying
- Department of Obstetrics and Gynecology, Chung Shan Medical University Hospital, Taichung, Taiwan, R.O.C
| | - Ming-Hsien Wu
- Taichung Armed Forces General Hospital, Taichung, Taiwan, R.O.C
| | - Chung-Yu Huang
- Taoyuan Armed Forces General Hospital, Taoyuan, Taiwan, R.O.C
| | - DA-Tian Bau
- Graduate Institute of Biomedical Sciences, China Medical University, Taichung, Taiwan, R.O.C. .,Terry Fox Cancer Research Laboratory, China Medical University Hospital, Taichung, Taiwan, R.O.C.,Department of Bioinformatics and Medical Engineering, Asia University, Taichung, Taiwan, R.O.C
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35
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Whole Genome Sequence Analysis of Mutations Accumulated in rad27Δ Yeast Strains with Defects in the Processing of Okazaki Fragments Indicates Template-Switching Events. G3-GENES GENOMES GENETICS 2017; 7:3775-3787. [PMID: 28974572 PMCID: PMC5677150 DOI: 10.1534/g3.117.300262] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Okazaki fragments that are formed during lagging strand DNA synthesis include an initiating primer consisting of both RNA and DNA. The RNA fragment must be removed before the fragments are joined. In Saccharomyces cerevisiae, a key player in this process is the structure-specific flap endonuclease, Rad27p (human homolog FEN1). To obtain a genomic view of the mutational consequence of loss of RAD27, a S. cerevisiae rad27Δ strain was subcultured for 25 generations and sequenced using Illumina paired-end sequencing. Out of the 455 changes observed in 10 colonies isolated the two most common types of events were insertions or deletions (INDELs) in simple sequence repeats (SSRs) and INDELs mediated by short direct repeats. Surprisingly, we also detected a previously neglected class of 21 template-switching events. These events were presumably generated by quasi-palindrome to palindrome correction, as well as palindrome elongation. The formation of these events is best explained by folding back of the stalled nascent strand and resumption of DNA synthesis using the same nascent strand as a template. Evidence of quasi-palindrome to palindrome correction that could be generated by template switching appears also in yeast genome evolution. Out of the 455 events, 55 events appeared in multiple isolates; further analysis indicates that these loci are mutational hotspots. Since Rad27 acts on the lagging strand when the leading strand should not contain any gaps, we propose a mechanism favoring intramolecular strand switching over an intermolecular mechanism. We note that our results open new ways of understanding template switching that occurs during genome instability and evolution.
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Pathways and Mechanisms that Prevent Genome Instability in Saccharomyces cerevisiae. Genetics 2017; 206:1187-1225. [PMID: 28684602 PMCID: PMC5500125 DOI: 10.1534/genetics.112.145805] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 04/26/2017] [Indexed: 12/13/2022] Open
Abstract
Genome rearrangements result in mutations that underlie many human diseases, and ongoing genome instability likely contributes to the development of many cancers. The tools for studying genome instability in mammalian cells are limited, whereas model organisms such as Saccharomyces cerevisiae are more amenable to these studies. Here, we discuss the many genetic assays developed to measure the rate of occurrence of Gross Chromosomal Rearrangements (called GCRs) in S. cerevisiae. These genetic assays have been used to identify many types of GCRs, including translocations, interstitial deletions, and broken chromosomes healed by de novo telomere addition, and have identified genes that act in the suppression and formation of GCRs. Insights from these studies have contributed to the understanding of pathways and mechanisms that suppress genome instability and how these pathways cooperate with each other. Integrated models for the formation and suppression of GCRs are discussed.
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Activation of Dun1 in response to nuclear DNA instability accounts for the increase in mitochondrial point mutations in Rad27/FEN1 deficient S. cerevisiae. PLoS One 2017; 12:e0180153. [PMID: 28678842 PMCID: PMC5497989 DOI: 10.1371/journal.pone.0180153] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 06/09/2017] [Indexed: 11/25/2022] Open
Abstract
Rad27/FEN1 nuclease that plays important roles in the maintenance of DNA stability in the nucleus has recently been shown to reside in mitochondria. Accordingly, it has been established that Rad27 deficiency causes increased mutagenesis, but decreased microsatellite instability and homologous recombination in mitochondria. Our current analysis of mutations leading to erythromycin resistance indicates that only some of them arise in mitochondrial DNA and that the GC→AT transition is a hallmark of the mitochondrial mutagenesis in rad27 null background. We also show that the mitochondrial mutator phenotype resulting from Rad27 deficiency entirely depends on the DNA damage checkpoint kinase Dun1. DUN1 inactivation suppresses the mitochondrial mutator phenotype caused by Rad27 deficiency and this suppression is eliminated at least in part by subsequent deletion of SML1 encoding a repressor of ribonucleotide reductase. We conclude that Rad27 deficiency causes a mitochondrial mutator phenotype via activation of DNA damage checkpoint kinase Dun1 and that a Dun1-mediated increase of dNTP pools contributes to this phenomenon. These results point to the nuclear DNA instability as the source of mitochondrial mutagenesis. Consistently, we show that mitochondrial mutations occurring more frequently in yeast devoid of Rrm3, a DNA helicase involved in rDNA replication, are also dependent on Dun1. In addition, we have established that overproduction of Exo1, which suppresses DNA damage sensitivity and replication stress in nuclei of Rad27 deficient cells, but does not enter mitochondria, suppresses the mitochondrial mutagenesis. Exo1 overproduction restores also a great part of allelic recombination and microsatellite instability in mitochondria of Rad27 deficient cells. In contrast, the overproduction of Exo1 does not influence mitochondrial direct-repeat mediated deletions in rad27 null background, pointing to this homologous recombination pathway as the direct target of Rad27 activity in mitochondria.
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Phosphate steering by Flap Endonuclease 1 promotes 5'-flap specificity and incision to prevent genome instability. Nat Commun 2017; 8:15855. [PMID: 28653660 PMCID: PMC5490271 DOI: 10.1038/ncomms15855] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 05/05/2017] [Indexed: 12/13/2022] Open
Abstract
DNA replication and repair enzyme Flap Endonuclease 1 (FEN1) is vital for genome integrity, and FEN1 mutations arise in multiple cancers. FEN1 precisely cleaves single-stranded (ss) 5′-flaps one nucleotide into duplex (ds) DNA. Yet, how FEN1 selects for but does not incise the ss 5′-flap was enigmatic. Here we combine crystallographic, biochemical and genetic analyses to show that two dsDNA binding sites set the 5′polarity and to reveal unexpected control of the DNA phosphodiester backbone by electrostatic interactions. Via ‘phosphate steering’, basic residues energetically steer an inverted ss 5′-flap through a gateway over FEN1’s active site and shift dsDNA for catalysis. Mutations of these residues cause an 18,000-fold reduction in catalytic rate in vitro and large-scale trinucleotide (GAA)n repeat expansions in vivo, implying failed phosphate-steering promotes an unanticipated lagging-strand template-switch mechanism during replication. Thus, phosphate steering is an unappreciated FEN1 function that enforces 5′-flap specificity and catalysis, preventing genomic instability. Flap Endonuclease 1 is a DNA replication and repair enzyme indispensable for maintaining genomic stability. Here the authors provide mechanistic details on how FEN1 selects for 5′-flaps and promotes catalysis to avoid large-scale repeat expansion by a process termed ‘phosphate steering’.
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Schizosaccharomyces pombe MutSα and MutLα Maintain Stability of Tetra-Nucleotide Repeats and Msh3 of Hepta-Nucleotide Repeats. G3-GENES GENOMES GENETICS 2017; 7:1463-1473. [PMID: 28341698 PMCID: PMC5427490 DOI: 10.1534/g3.117.040816] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Defective mismatch repair (MMR) in humans is associated with colon cancer and instability of microsatellites, that is, DNA sequences with one or several nucleotides repeated. Key factors of eukaryotic MMR are the heterodimers MutSα (Msh2-Msh6), which recognizes base-base mismatches and unpaired nucleotides in DNA, and MutLα (Mlh1-Pms1), which facilitates downstream steps. In addition, MutSβ (Msh2-Msh3) recognizes DNA loops of various sizes, although our previous data and the data presented here suggest that Msh3 of Schizosaccharomyces pombe does not play a role in MMR. To test microsatellite stability in S. pombe and hence DNA loop repair, we have inserted tetra-, penta-, and hepta-nucleotide repeats in the ade6 gene and determined their Ade+ reversion rates and spectra in wild type and various mutants. Our data indicate that loops with four unpaired nucleotides in the nascent and the template strand are the upper limit of MutSα- and MutLα-mediated MMR in S. pombe Stability of hepta-nucleotide repeats requires Msh3 and Exo1 in MMR-independent processes as well as the DNA repair proteins Rad50, Rad51, and Rad2FEN1 Most strikingly, mutation rates in the double mutants msh3 exo1 and msh3 rad51 were decreased when compared to respective single mutants, indicating that Msh3 prevents error prone processes carried out by Exo1 and Rad51. We conclude that Msh3 has no obvious function in MMR in S. pombe, but contributes to DNA repeat stability in MMR-independent processes.
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40
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Roles for the Rad27 Flap Endonuclease in Mitochondrial Mutagenesis and Double-Strand Break Repair in Saccharomyces cerevisiae. Genetics 2017; 206:843-857. [PMID: 28450457 DOI: 10.1534/genetics.116.195149] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 04/18/2017] [Indexed: 01/07/2023] Open
Abstract
The structure-specific nuclease, Rad27p/FEN1, plays a crucial role in DNA repair and replication mechanisms in the nucleus. Genetic assays using the rad27-∆ mutant have shown altered rates of DNA recombination, microsatellite instability, and point mutation in mitochondria. In this study, we examined the role of Rad27p in mitochondrial mutagenesis and double-strand break (DSB) repair in Saccharomyces cerevisiae Our findings show that Rad27p is essential for efficient mitochondrial DSB repair by a pathway that generates deletions at a region flanked by direct repeat sequences. Mutant analysis suggests that both exonuclease and endonuclease activities of Rad27p are required for its role in mitochondrial DSB repair. In addition, we found that the nuclease activities of Rad27p are required for the prevention of mitochondrial DNA (mtDNA) point mutations, and in the generation of spontaneous mtDNA rearrangements. Overall, our findings underscore the importance of Rad27p in the maintenance of mtDNA, and demonstrate that it participates in multiple DNA repair pathways in mitochondria, unlinked to nuclear phenotypes.
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41
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Sang Y, Bo L, Gu H, Yang W, Chen Y. Flap endonuclease-1 rs174538 G>A polymorphisms are associated with the risk of esophageal cancer in a Chinese population. Thorac Cancer 2017; 8:192-196. [PMID: 28319330 PMCID: PMC5415465 DOI: 10.1111/1759-7714.12422] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 01/01/2017] [Accepted: 01/07/2017] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND Esophageal cancer has a high mortality rate, particularly in Asia, and there are obvious racial differences in regard to incidence. The purpose of our study was to assess the genetic susceptibility of functional single nucleotide polymorphisms in flap endonuclease-1 (FEN1) in esophageal squamous cell carcinoma ESCC. METHODS Clinical blood samples of 629 ESCC cases and 686 control samples were collected. The ligation detection reaction method was used to determine FEN 1 rs174538 G>A genotypes. RESULTS A significantly decreased risk of ESCC was associated with FEN1 rs174538 GA genotypes among patients under 63 years old. CONCLUSIONS Our results suggest that functional polymorphism FEN1 rs174538 G>A might affect personal susceptibility to ESCC. This result provides a solid theoretical foundation for further clinical study using larger sample sizes.
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Affiliation(s)
- Yonghua Sang
- Department of Cardiothoracic Surgery, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Lin Bo
- Department of Rheumatology, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Haiyong Gu
- Department of Cardiothoracic Surgery, Shanghai Chest Hospital, Shanghai, China.,Department of Cardiothoracic Surgery, Affiliated People's Hospital of Jiangsu University, Zhenjiang, China
| | - Wengtao Yang
- Department of Cardiothoracic Surgery, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Yongbing Chen
- Department of Cardiothoracic Surgery, The Second Affiliated Hospital of Soochow University, Suzhou, China
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42
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Prado F, Maya D. Regulation of Replication Fork Advance and Stability by Nucleosome Assembly. Genes (Basel) 2017; 8:genes8020049. [PMID: 28125036 PMCID: PMC5333038 DOI: 10.3390/genes8020049] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 01/04/2017] [Accepted: 01/16/2017] [Indexed: 12/13/2022] Open
Abstract
The advance of replication forks to duplicate chromosomes in dividing cells requires the disassembly of nucleosomes ahead of the fork and the rapid assembly of parental and de novo histones at the newly synthesized strands behind the fork. Replication-coupled chromatin assembly provides a unique opportunity to regulate fork advance and stability. Through post-translational histone modifications and tightly regulated physical and genetic interactions between chromatin assembly factors and replisome components, chromatin assembly: (1) controls the rate of DNA synthesis and adjusts it to histone availability; (2) provides a mechanism to protect the integrity of the advancing fork; and (3) regulates the mechanisms of DNA damage tolerance in response to replication-blocking lesions. Uncoupling DNA synthesis from nucleosome assembly has deleterious effects on genome integrity and cell cycle progression and is linked to genetic diseases, cancer, and aging.
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Affiliation(s)
- Felix Prado
- Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), Spanish National Research Council (CSIC), Seville 41092, Spain.
| | - Douglas Maya
- Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), Spanish National Research Council (CSIC), Seville 41092, Spain.
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43
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Kwon B, Munashingha PR, Shin YK, Lee CH, Li B, Seo YS. Physical and functional interactions between nucleosomes and Rad27, a critical component of DNA processing during DNA metabolism. FEBS J 2016; 283:4247-4262. [DOI: 10.1111/febs.13934] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 09/22/2016] [Accepted: 10/17/2016] [Indexed: 11/26/2022]
Affiliation(s)
- Buki Kwon
- Department of Biological Sciences; Korea Advanced Institute of Science and Technology; Yuseong-gu Daejeon Korea
| | - Palinda Ruvan Munashingha
- Department of Biological Sciences; Korea Advanced Institute of Science and Technology; Yuseong-gu Daejeon Korea
| | - Yong-Keol Shin
- Department of Biological Sciences; Korea Advanced Institute of Science and Technology; Yuseong-gu Daejeon Korea
| | - Chul-Hwan Lee
- Department of Molecular Biology; UT Southwestern Medical Center; Dallas TX USA
| | - Bing Li
- Department of Molecular Biology; UT Southwestern Medical Center; Dallas TX USA
| | - Yeon-Soo Seo
- Department of Biological Sciences; Korea Advanced Institute of Science and Technology; Yuseong-gu Daejeon Korea
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44
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Dosage Mutator Genes in Saccharomyces cerevisiae: A Novel Mutator Mode-of-Action of the Mph1 DNA Helicase. Genetics 2016; 204:975-986. [PMID: 27585847 PMCID: PMC5105872 DOI: 10.1534/genetics.116.192211] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 08/25/2016] [Indexed: 01/25/2023] Open
Abstract
Mutations that cause genome instability are considered important predisposing events that contribute to initiation and progression of cancer. Genome instability arises either due to defects in genes that cause an increased mutation rate (mutator phenotype), or defects in genes that cause chromosome instability (CIN). To extend the catalog of genome instability genes, we systematically explored the effects of gene overexpression on mutation rate, using a forward-mutation screen in budding yeast. We screened ∼5100 plasmids, each overexpressing a unique single gene, and characterized the five strongest mutators, MPH1 (mutator phenotype 1), RRM3, UBP12, PIF1, and DNA2 We show that, for MPH1, the yeast homolog of Fanconi Anemia complementation group M (FANCM), the overexpression mutator phenotype is distinct from that of mph1Δ. Moreover, while four of our top hits encode DNA helicases, the overexpression of 48 other DNA helicases did not cause a mutator phenotype, suggesting this is not a general property of helicases. For Mph1 overexpression, helicase activity was not required for the mutator phenotype; in contrast Mph1 DEAH-box function was required for hypermutation. Mutagenesis by MPH1 overexpression was independent of translesion synthesis (TLS), but was suppressed by overexpression of RAD27, a conserved flap endonuclease. We propose that binding of DNA flap structures by excess Mph1 may block Rad27 action, creating a mutator phenotype that phenocopies rad27Δ. We believe this represents a novel mutator mode-of-action and opens up new prospects to understand how upregulation of DNA repair proteins may contribute to mutagenesis.
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45
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The FEN1 L209P mutation interferes with long-patch base excision repair and induces cellular transformation. Oncogene 2016; 36:194-207. [PMID: 27270424 PMCID: PMC5140775 DOI: 10.1038/onc.2016.188] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Revised: 04/12/2016] [Accepted: 04/12/2016] [Indexed: 12/20/2022]
Abstract
Flap endonuclease-1 (FEN1) is a multifunctional, structure-specific nuclease that has a critical role in maintaining human genome stability. FEN1 mutations have been detected in human cancer specimens and have been suggested to cause genomic instability and cancer predisposition. However, the exact relationship between FEN1 deficiency and cancer susceptibility remains unclear. In the current work, we report a novel colorectal cancer-associated FEN1 mutation, L209P. This mutant protein lacks the FEN, exonuclease (EXO) and gap endonuclease (GEN) activities of FEN1 but retains DNA-binding affinity. The L209P FEN1 variant interferes with the function of the wild-type FEN1 enzyme in a dominant-negative manner and impairs long-patch base excision repair in vitro and in vivo. Expression of L209P FEN1 sensitizes cells to DNA damage, resulting in endogenous genomic instability and cellular transformation, as well as tumor growth in a mouse xenograft model. These data indicate that human cancer-associated genetic alterations in the FEN1 gene can contribute substantially to cancer development.
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46
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Stodola JL, Stith CM, Burgers PM. Proficient Replication of the Yeast Genome by a Viral DNA Polymerase. J Biol Chem 2016; 291:11698-705. [PMID: 27072134 DOI: 10.1074/jbc.m116.728741] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Indexed: 11/06/2022] Open
Abstract
DNA replication in eukaryotic cells requires minimally three B-family DNA polymerases: Pol α, Pol δ, and Pol ϵ. Pol δ replicates and matures Okazaki fragments on the lagging strand of the replication fork. Saccharomyces cerevisiae Pol δ is a three-subunit enzyme (Pol3-Pol31-Pol32). A small C-terminal domain of the catalytic subunit Pol3 carries both iron-sulfur cluster and zinc-binding motifs, which mediate interactions with Pol31, and processive replication with the replication clamp proliferating cell nuclear antigen (PCNA), respectively. We show that the entire N-terminal domain of Pol3, containing polymerase and proofreading activities, could be effectively replaced by those from bacteriophage RB69, and could carry out chromosomal DNA replication in yeast with remarkable high fidelity, provided that adaptive mutations in the replication clamp PCNA were introduced. This result is consistent with the model that all essential interactions for DNA replication in yeast are mediated through the small C-terminal domain of Pol3. The chimeric polymerase carries out processive replication with PCNA in vitro; however, in yeast, it requires an increased involvement of the mutagenic translesion DNA polymerase ζ during DNA replication.
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Affiliation(s)
- Joseph L Stodola
- From the Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Carrie M Stith
- From the Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Peter M Burgers
- From the Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110
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47
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Koc KN, Singh SP, Stodola JL, Burgers PM, Galletto R. Pif1 removes a Rap1-dependent barrier to the strand displacement activity of DNA polymerase δ. Nucleic Acids Res 2016; 44:3811-9. [PMID: 27001517 PMCID: PMC4856994 DOI: 10.1093/nar/gkw181] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 03/08/2016] [Indexed: 11/13/2022] Open
Abstract
Using an in vitro reconstituted system in this work we provide direct evidence that the yeast repressor/activator protein 1 (Rap1), tightly bound to its consensus site, forms a strong non-polar barrier for the strand displacement activity of DNA polymerase δ. We propose that relief of inhibition may be mediated by the activity of an accessory helicase. To this end, we show that Pif1, a 5'-3' helicase, not only stimulates the strand displacement activity of Pol δ but it also allows efficient replication through the block, by removing bound Rap1 in front of the polymerase. This stimulatory activity of Pif1 is not limited to the displacement of a single Rap1 molecule; Pif1 also allows Pol δ to carry out DNA synthesis across an array of bound Rap1 molecules that mimics a telomeric DNA-protein assembly. This activity of Pif1 represents a novel function of this helicase during DNA replication.
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Affiliation(s)
- Katrina N Koc
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Saurabh P Singh
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Joseph L Stodola
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Peter M Burgers
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Roberto Galletto
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63110, USA
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48
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Becker JR, Pons C, Nguyen HD, Costanzo M, Boone C, Myers CL, Bielinsky AK. Genetic Interactions Implicating Postreplicative Repair in Okazaki Fragment Processing. PLoS Genet 2015; 11:e1005659. [PMID: 26545110 PMCID: PMC4636136 DOI: 10.1371/journal.pgen.1005659] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 10/19/2015] [Indexed: 01/28/2023] Open
Abstract
Ubiquitination of the replication clamp proliferating cell nuclear antigen (PCNA) at the conserved residue lysine (K)164 triggers postreplicative repair (PRR) to fill single-stranded gaps that result from stalled DNA polymerases. However, it has remained elusive as to whether cells engage PRR in response to replication defects that do not directly impair DNA synthesis. To experimentally address this question, we performed synthetic genetic array (SGA) analysis with a ubiquitination-deficient K164 to arginine (K164R) mutant of PCNA against a library of S. cerevisiae temperature-sensitive alleles. The SGA signature of the K164R allele showed a striking correlation with profiles of mutants deficient in various aspects of lagging strand replication, including rad27Δ and elg1Δ. Rad27 is the primary flap endonuclease that processes 5' flaps generated during lagging strand replication, whereas Elg1 has been implicated in unloading PCNA from chromatin. We observed chronic ubiquitination of PCNA at K164 in both rad27Δ and elg1Δ mutants. Notably, only rad27Δ cells exhibited a decline in cell viability upon elimination of PRR pathways, whereas elg1Δ mutants were not affected. We further provide evidence that K164 ubiquitination suppresses replication stress resulting from defective flap processing during Okazaki fragment maturation. Accordingly, ablation of PCNA ubiquitination increased S phase checkpoint activation, indicated by hyperphosphorylation of the Rad53 kinase. Furthermore, we demonstrate that alternative flap processing by overexpression of catalytically active exonuclease 1 eliminates PCNA ubiquitination. This suggests a model in which unprocessed flaps may directly participate in PRR signaling. Our findings demonstrate that PCNA ubiquitination at K164 in response to replication stress is not limited to DNA synthesis defects but extends to DNA processing during lagging strand replication.
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Affiliation(s)
- Jordan R. Becker
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Carles Pons
- Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Hai Dang Nguyen
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Michael Costanzo
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Charles Boone
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Chad L. Myers
- Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Anja-Katrin Bielinsky
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
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49
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Abstract
DNA exonucleases, enzymes that hydrolyze phosphodiester bonds in DNA from a free end, play important cellular roles in DNA repair, genetic recombination and mutation avoidance in all organisms. This article reviews the structure, biochemistry, and biological functions of the 17 exonucleases currently identified in the bacterium Escherichia coli. These include the exonucleases associated with DNA polymerases I (polA), II (polB), and III (dnaQ/mutD); Exonucleases I (xonA/sbcB), III (xthA), IV, VII (xseAB), IX (xni/xgdG), and X (exoX); the RecBCD, RecJ, and RecE exonucleases; SbcCD endo/exonucleases; the DNA exonuclease activities of RNase T (rnt) and Endonuclease IV (nfo); and TatD. These enzymes are diverse in terms of substrate specificity and biochemical properties and have specialized biological roles. Most of these enzymes fall into structural families with characteristic sequence motifs, and members of many of these families can be found in all domains of life.
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50
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Ren H, Ma H, Ke Y, Ma X, Xu D, Lin S, Wang X, Dai ZJ. Flap endonuclease 1 polymorphisms (rs174538 and rs4246215) contribute to an increased cancer risk: Evidence from a meta-analysis. Mol Clin Oncol 2015; 3:1347-1352. [PMID: 26807246 DOI: 10.3892/mco.2015.617] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 02/26/2015] [Indexed: 11/05/2022] Open
Abstract
Flap endonuclease-1 (FEN1) is a key factor during the maintenance of genomic stability and protection against tumorigenesis. Since the identification of functional polymorphisms of FEN1 (rs174538 and rs4246215), numerous studies have evaluated the association between the two single-nucleotide polymorphisms and cancer risk. To derive a more precise estimation, a meta-analysis was performed on the association between the FEN1 polymorphisms (rs174538 and rs4246215) and cancer risk. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to estimate the strength of the associations. Thirteen case-control studies, including 5,108 cases and 6,382 case-free controls, were identified. For rs174538, individuals with the GG or GA genotype had an increased risk of cancer when compared to the -69AA genotype (AA vs. GG: OR, 1.85; 95% CI, 1.65-2.08; P<0.00001; AA vs. GA: OR, 1.43; 95% CI, 1.27-1.60; P<0.00001; AA vs. GG+GA: OR, 1.28; 95% CI, 1.16-1.42; P<0.00001). For rs4246215, similar results were identified, as the GG or GT genotype was significantly associated with the increased cancer risk when compared to TT (TT vs. GG: OR, 1.71; 95% CI, 1.52-1.92; P<0.00001; TT vs. GT: OR, 1.34; 95% CI, 1.20-1.50; P<0.00001; TT vs. GG+GT: OR, 1.50; 95% CI, 1.35-1.67; P<0.00001). The present meta-analysis indicated that FEN1 rs174538 and rs4246215 polymorphisms may contribute to an increased risk of cancer.
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Affiliation(s)
- Hongtao Ren
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Hongbing Ma
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Yue Ke
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Xiaobin Ma
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Dan Xu
- Center for Translational Medicine, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710028, P.R. China
| | - Shuai Lin
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Xijing Wang
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China
| | - Zhi-Jun Dai
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, P.R. China; Center for Translational Medicine, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710028, P.R. China
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