1
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Wang G, Vasquez KM. Dynamic alternative DNA structures in biology and disease. Nat Rev Genet 2023; 24:211-234. [PMID: 36316397 DOI: 10.1038/s41576-022-00539-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2022] [Indexed: 11/06/2022]
Abstract
Repetitive elements in the human genome, once considered 'junk DNA', are now known to adopt more than a dozen alternative (that is, non-B) DNA structures, such as self-annealed hairpins, left-handed Z-DNA, three-stranded triplexes (H-DNA) or four-stranded guanine quadruplex structures (G4 DNA). These dynamic conformations can act as functional genomic elements involved in DNA replication and transcription, chromatin organization and genome stability. In addition, recent studies have revealed a role for these alternative structures in triggering error-generating DNA repair processes, thereby actively enabling genome plasticity. As a driving force for genetic variation, non-B DNA structures thus contribute to both disease aetiology and evolution.
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Affiliation(s)
- Guliang Wang
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Paediatric Research Institute, Austin, TX, USA
| | - Karen M Vasquez
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Paediatric Research Institute, Austin, TX, USA.
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2
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Stein M, Hile SE, Weissensteiner MH, Lee M, Zhang S, Kejnovský E, Kejnovská I, Makova KD, Eckert KA. Variation in G-quadruplex sequence and topology differentially impacts human DNA polymerase fidelity. DNA Repair (Amst) 2022; 119:103402. [PMID: 36116264 PMCID: PMC9798401 DOI: 10.1016/j.dnarep.2022.103402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 08/12/2022] [Accepted: 09/02/2022] [Indexed: 12/31/2022]
Abstract
G-quadruplexes (G4s), a type of non-B DNA, play important roles in a wide range of molecular processes, including replication, transcription, and translation. Genome integrity relies on efficient and accurate DNA synthesis, and is compromised by various stressors, to which non-B DNA structures such as G4s can be particularly vulnerable. However, the impact of G4 structures on DNA polymerase fidelity is largely unknown. Using an in vitro forward mutation assay, we investigated the fidelity of human DNA polymerases delta (δ4, four-subunit), eta (η), and kappa (κ) during synthesis of G4 motifs representing those in the human genome. The motifs differ in sequence, topology, and stability, features that may affect DNA polymerase errors. Polymerase error rate hierarchy (δ4 < κ < η) is largely maintained during G4 synthesis. Importantly, we observed unique polymerase error signatures during synthesis of VEGF G4 motifs, stable G4s which form parallel topologies. These statistically significant errors occurred within, immediately flanking, and encompassing the G4 motif. For pol δ4, the errors were deletions, insertions and complex errors within the G4 or encompassing the G4 motif and surrounding sequence. For pol η, the errors occurred in 3' sequences flanking the G4 motif. For pol κ, the errors were frameshift mutations within G-tracts of the G4. Because these error signatures were not observed during synthesis of an antiparallel G4 and, to a lesser extent, a hybrid G4, we suggest that G4 topology and/or stability could influence polymerase fidelity. Using in silico analyses, we show that most polymerase errors are predicted to have minimal effects on predicted G4 stability. Our results provide a unique view of G4s not previously elucidated, showing that G4 motif heterogeneity differentially influences polymerase fidelity within the motif and flanking sequences. Thus, our study advances the understanding of how DNA polymerase errors contribute to G4 mutagenesis.
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Affiliation(s)
- MaryElizabeth Stein
- Department of Pathology, The Jake Gittlen Laboratories for Cancer Research, Penn State University College of Medicine, Hershey, PA, USA
| | - Suzanne E Hile
- Department of Pathology, The Jake Gittlen Laboratories for Cancer Research, Penn State University College of Medicine, Hershey, PA, USA
| | | | - Marietta Lee
- Department of Biochemistry & Molecular Biology, New York Medical College, Valhalla, NY, USA
| | - Sufang Zhang
- Department of Biochemistry & Molecular Biology, New York Medical College, Valhalla, NY, USA
| | - Eduard Kejnovský
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
| | - Iva Kejnovská
- Department of Biophysics of Nucleic Acids, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
| | - Kateryna D Makova
- Department of Biology, Penn State University Eberly College of Science, University Park, PA, USA
| | - Kristin A Eckert
- Department of Pathology, The Jake Gittlen Laboratories for Cancer Research, Penn State University College of Medicine, Hershey, PA, USA.
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3
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Dahl JM, Thomas N, Tracy MA, Hearn BL, Perera L, Kennedy SR, Herr AJ, Kunkel TA. Probing the mechanisms of two exonuclease domain mutators of DNA polymerase ϵ. Nucleic Acids Res 2022; 50:962-974. [PMID: 35037018 DOI: 10.1093/nar/gkab1255] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 11/21/2021] [Accepted: 12/08/2021] [Indexed: 11/15/2022] Open
Abstract
We report the properties of two mutations in the exonuclease domain of the Saccharomyces cerevisiae DNA polymerase ϵ. One, pol2-Y473F, increases the mutation rate by about 20-fold, similar to the catalytically dead pol2-D290A/E290A mutant. The other, pol2-N378K, is a stronger mutator. Both retain the ability to excise a nucleotide from double-stranded DNA, but with impaired activity. pol2-Y473F degrades DNA poorly, while pol2-N378K degrades single-stranded DNA at an elevated rate relative to double-stranded DNA. These data suggest that pol2-Y473F reduces the capacity of the enzyme to perform catalysis in the exonuclease active site, while pol2-N378K impairs partitioning to the exonuclease active site. Relative to wild-type Pol ϵ, both variants decrease the dNTP concentration required to elicit a switch between proofreading and polymerization by more than an order of magnitude. While neither mutation appears to alter the sequence specificity of polymerization, the N378K mutation stimulates polymerase activity, increasing the probability of incorporation and extension of a mismatch. Considered together, these data indicate that impairing the primer strand transfer pathway required for proofreading increases the probability of common mutations by Pol ϵ, elucidating the association of homologous mutations in human DNA polymerase ϵ with cancer.
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Affiliation(s)
- Joseph M Dahl
- Genome Integrity Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC 27709, USA
| | - Natalie Thomas
- Genome Integrity Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC 27709, USA
| | - Maxwell A Tracy
- Department of Laboratory Medicine and Pathology, UW Medicine, Seattle, WA 98195, USA
| | - Brady L Hearn
- Department of Laboratory Medicine and Pathology, UW Medicine, Seattle, WA 98195, USA
| | - Lalith Perera
- Genome Integrity Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC 27709, USA
| | - Scott R Kennedy
- Department of Laboratory Medicine and Pathology, UW Medicine, Seattle, WA 98195, USA
| | - Alan J Herr
- Department of Laboratory Medicine and Pathology, UW Medicine, Seattle, WA 98195, USA
| | - Thomas A Kunkel
- Genome Integrity Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC 27709, USA
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4
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Kiktev DA, Dominska M, Zhang T, Dahl J, Stepchenkova EI, Mieczkowski P, Burgers PM, Lujan S, Burkholder A, Kunkel TA, Petes TD. The fidelity of DNA replication, particularly on GC-rich templates, is reduced by defects of the Fe-S cluster in DNA polymerase δ. Nucleic Acids Res 2021; 49:5623-5636. [PMID: 34019669 PMCID: PMC8191807 DOI: 10.1093/nar/gkab371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/22/2021] [Accepted: 05/16/2021] [Indexed: 11/12/2022] Open
Abstract
Iron-sulfur clusters (4Fe–4S) exist in many enzymes concerned with DNA replication and repair. The contribution of these clusters to enzymatic activity is not fully understood. We identified the MET18 (MMS19) gene of Saccharomyces cerevisiae as a strong mutator on GC-rich genes. Met18p is required for the efficient insertion of iron-sulfur clusters into various proteins. met18 mutants have an elevated rate of deletions between short flanking repeats, consistent with increased DNA polymerase slippage. This phenotype is very similar to that observed in mutants of POL3 (encoding the catalytic subunit of Pol δ) that weaken binding of the iron-sulfur cluster. Comparable mutants of POL2 (Pol ϵ) do not elevate deletions. Further support for the conclusion that met18 strains result in impaired DNA synthesis by Pol δ are the observations that Pol δ isolated from met18 strains has less bound iron and is less processive in vitro than the wild-type holoenzyme.
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Affiliation(s)
- Denis A Kiktev
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Margaret Dominska
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Tony Zhang
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Joseph Dahl
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Elena I Stepchenkova
- Department of Genetics and Biotechnology, Saint-Petersburg State University, St. Petersburg, Russia.,Vavilov Institute of General Genetics, Saint-Petersburg Branch, Russian Academy of Sciences, St. Petersburg, Russia
| | - Piotr Mieczkowski
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7264, USA
| | - Peter M Burgers
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Scott Lujan
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Adam Burkholder
- Office of Environmental Science Cyberinfrastructure, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Thomas A Kunkel
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Thomas D Petes
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
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5
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Chung J, Maruvka YE, Sudhaman S, Kelly J, Haradhvala NJ, Bianchi V, Edwards M, Forster VJ, Nunes NM, Galati MA, Komosa M, Deshmukh S, Cabric V, Davidson S, Zatzman M, Light N, Hayes R, Brunga L, Anderson ND, Ho B, Hodel KP, Siddaway R, Morrissy AS, Bowers DC, Larouche V, Bronsema A, Osborn M, Cole KA, Opocher E, Mason G, Thomas GA, George B, Ziegler DS, Lindhorst S, Vanan M, Yalon-Oren M, Reddy AT, Massimino M, Tomboc P, Van Damme A, Lossos A, Durno C, Aronson M, Morgenstern DA, Bouffet E, Huang A, Taylor MD, Villani A, Malkin D, Hawkins CE, Pursell ZF, Shlien A, Kunkel TA, Getz G, Tabori U. DNA Polymerase and Mismatch Repair Exert Distinct Microsatellite Instability Signatures in Normal and Malignant Human Cells. Cancer Discov 2020; 11:1176-1191. [PMID: 33355208 DOI: 10.1158/2159-8290.cd-20-0790] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 09/23/2020] [Accepted: 12/15/2020] [Indexed: 12/11/2022]
Abstract
Although replication repair deficiency, either by mismatch repair deficiency (MMRD) and/or loss of DNA polymerase proofreading, can cause hypermutation in cancer, microsatellite instability (MSI) is considered a hallmark of MMRD alone. By genome-wide analysis of tumors with germline and somatic deficiencies in replication repair, we reveal a novel association between loss of polymerase proofreading and MSI, especially when both components are lost. Analysis of indels in microsatellites (MS-indels) identified five distinct signatures (MS-sigs). MMRD MS-sigs are dominated by multibase losses, whereas mutant-polymerase MS-sigs contain primarily single-base gains. MS deletions in MMRD tumors depend on the original size of the MS and converge to a preferred length, providing mechanistic insight. Finally, we demonstrate that MS-sigs can be a powerful clinical tool for managing individuals with germline MMRD and replication repair-deficient cancers, as they can detect the replication repair deficiency in normal cells and predict their response to immunotherapy. SIGNIFICANCE: Exome- and genome-wide MSI analysis reveals novel signatures that are uniquely attributed to mismatch repair and DNA polymerase. This provides new mechanistic insight into MS maintenance and can be applied clinically for diagnosis of replication repair deficiency and immunotherapy response prediction.This article is highlighted in the In This Issue feature, p. 995.
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Affiliation(s)
- Jiil Chung
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada.,Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Yosef E Maruvka
- Massachusetts General Hospital Center for Cancer Research, Charlestown, Massachusetts.,Broad Institute of Harvard and MIT, Cambridge, Massachusetts
| | - Sumedha Sudhaman
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Jacalyn Kelly
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Nicholas J Haradhvala
- Massachusetts General Hospital Center for Cancer Research, Charlestown, Massachusetts.,Broad Institute of Harvard and MIT, Cambridge, Massachusetts.,Harvard Graduate Program in Biophysics, Harvard University, Cambridge, Massachusetts
| | - Vanessa Bianchi
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Melissa Edwards
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Victoria J Forster
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Nuno M Nunes
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Melissa A Galati
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada.,Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Martin Komosa
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Shriya Deshmukh
- Department of Experimental Medicine, McGill University, Montreal, Quebec, Canada.,The Research Institute of the McGill University Health Center, Montreal, Quebec, Canada
| | - Vanja Cabric
- Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada
| | - Scott Davidson
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Matthew Zatzman
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Nicholas Light
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.,Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Reid Hayes
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Ledia Brunga
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Nathaniel D Anderson
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Ben Ho
- Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Karl P Hodel
- Department of Biochemistry and Molecular Biology, Tulane Cancer Center, Tulane University of Medicine, New Orleans, Louisiana
| | - Robert Siddaway
- The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - A Sorana Morrissy
- Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Charbonneau Cancer Institute and Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada
| | - Daniel C Bowers
- Department of Pediatrics and Harold C. Simmons Comprehensive Cancer Center, The University of Texas Southwestern Medical Center, Dallas, Texas.,Pauline Allen Gill Center for Cancer and Blood Disorders, Children's Health, Dallas, Texas
| | - Valérie Larouche
- Department of Pediatrics, Centre Mere-enfant Soleil du CHU de Quebec, CRCHU de Quebec, Universite Laval, Quebec City, Quebec, Canada
| | - Annika Bronsema
- Department of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Michael Osborn
- Department of Haematology and Oncology, Women's and Children's Hospital, North Adelaide, South Australia, Australia
| | - Kristina A Cole
- Division of Oncology and Center for Childhood Cancer Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.,Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Enrico Opocher
- Pediatric Oncology and Hematology, Azienda Ospedaliera-Universita' degli Studi di Padova, Padova, Italy
| | - Gary Mason
- Department of Pediatric Hematology-Oncology, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania
| | - Gregory A Thomas
- Division of Pediatric Hematology-Oncology, Oregon Health and Science University, Portland, Oregon
| | - Ben George
- Division of Hematology and Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - David S Ziegler
- Kids Cancer Centre, Sydney Children's Hospital, Randwick, New South Wales, Australia.,Children's Cancer Institute, Lowy Cancer Research Centre, University of New South Wales, Randwick, New South Wales, Australia
| | - Scott Lindhorst
- Neuro-Oncology, Department of Neurosurgery, and Department of Medicine, Division of Hematology/Medical Oncology, Medical University of South Carolina Charleston, South Carolina
| | - Magimairajan Vanan
- Department of Pediatric Hematology-Oncology, Cancer Care Manitoba; Research Institute in Oncology and Hematology (RIOH), University of Manitoba, Winnipeg, Manitoba, Canada
| | - Michal Yalon-Oren
- Pediatric Hemato-Oncology, Edmond and Lilly Safra Children's Hospital and Cancer Research Center, Sheba Medical Center, Tel Hashomer Affiliated to the Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Alyssa T Reddy
- Division of Pediatric Hematology and Oncology, Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama
| | - Maura Massimino
- Pediatric Unit, Fondazione IRCCS Istituto Nazionale dei Tumori (INT), Milano, Italy
| | - Patrick Tomboc
- Department of Pediatrics Section of Hematology-Oncology, WVU Medicine Children's, Morgantown, West Virginia
| | - An Van Damme
- Division of Hematology and Oncology, Department of Pediatrics, Cliniques Universitaires Saint-Luc, Brussels, Belgium
| | - Alexander Lossos
- Department of Neurology, Agnes Ginges Center for Human Neurogenetics, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Carol Durno
- Zane Cohen Centre for Digestive Diseases, Mount Sinai Hospital, Toronto, Ontario, Canada.,Division of Gastroenterology, Hepatology and Nutrition, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Melyssa Aronson
- Zane Cohen Centre for Digestive Diseases, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Daniel A Morgenstern
- Department of Paediatrics, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada
| | - Eric Bouffet
- Department of Hematology/Oncology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Annie Huang
- The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.,Department of Hematology/Oncology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Michael D Taylor
- The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Neurosurgery, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Anita Villani
- Department of Hematology/Oncology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - David Malkin
- Department of Hematology/Oncology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Cynthia E Hawkins
- The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.,Program in Cell Biology, The Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Zachary F Pursell
- Department of Biochemistry and Molecular Biology, Tulane Cancer Center, Tulane University of Medicine, New Orleans, Louisiana
| | - Adam Shlien
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Thomas A Kunkel
- Genome Integrity Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Durham, North Carolina
| | - Gad Getz
- Massachusetts General Hospital Center for Cancer Research, Charlestown, Massachusetts. .,Broad Institute of Harvard and MIT, Cambridge, Massachusetts.,Harvard Medical School, Boston, Massachusetts.,Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts
| | - Uri Tabori
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada. .,The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Hematology/Oncology, The Hospital for Sick Children, Toronto, Ontario, Canada
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Abstract
Gastrointestinal (GIT) tumors are extremely fatal and lethal tumors with limited therapeutic options. Antitumor immunity is new line of research in management of solid tumors. Immune check points are negative regulators of immune system and control the immune response. These checkpoints are exploited by cancer cells. Cancer cells causes early activation of checkpoints and suppress the immune response, and therefore have unchecked growth and metastasis of malignant cells. Immune checkpoint inhibitors (ICIs), downregulates these checkpoints and activate the proliferation of cytotoxic T cells which helps in lysis of tumor cells. ICIs have shown the promising results in management of melanoma, non-small cell lung cancer and renal cell carcinoma. Encouraged by their recent success in solid tumors many clinical trials are ongoing to evaluate their efficacy in GIT tumors. In this article we will try to explain rationale for use of ICIs in GIT tumors. We will summarize the ongoing research, preliminary results and future aspects of ICIs in GIT malignancies.
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Affiliation(s)
- Vishal Jindal
- Department of Internal Medicine, St. Vincent Hospital, Worcester, MA, USA
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7
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Li L, Fang Z, Zhou J, Chen H, Hu Z, Gao L, Chen L, Ren S, Ma H, Lu L, Zhang W, Peng H. An accurate and efficient method for large-scale SSR genotyping and applications. Nucleic Acids Res 2017; 45:e88. [PMID: 28184437 PMCID: PMC5449614 DOI: 10.1093/nar/gkx093] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 02/01/2017] [Indexed: 01/10/2023] Open
Abstract
Accurate and efficient genotyping of simple sequence repeats (SSRs) constitutes the basis of SSRs as an effective genetic marker with various applications. However, the existing methods for SSR genotyping suffer from low sensitivity, low accuracy, low efficiency and high cost. In order to fully exploit the potential of SSRs as genetic marker, we developed a novel method for SSR genotyping, named as AmpSeq-SSR, which combines multiplexing polymerase chain reaction (PCR), targeted deep sequencing and comprehensive analysis. AmpSeq-SSR is able to genotype potentially more than a million SSRs at once using the current sequencing techniques. In the current study, we simultaneously genotyped 3105 SSRs in eight rice varieties, which were further validated experimentally. The results showed that the accuracies of AmpSeq-SSR were nearly 100 and 94% with a single base resolution for homozygous and heterozygous samples, respectively. To demonstrate the power of AmpSeq-SSR, we adopted it in two applications. The first was to construct discriminative fingerprints of the rice varieties using 3105 SSRs, which offer much greater discriminative power than the 48 SSRs commonly used for rice. The second was to map Xa21, a gene that confers persistent resistance to rice bacterial blight. We demonstrated that genome-scale fingerprints of an organism can be efficiently constructed and candidate genes, such as Xa21 in rice, can be accurately and efficiently mapped using an innovative strategy consisting of multiplexing PCR, targeted sequencing and computational analysis. While the work we present focused on rice, AmpSeq-SSR can be readily extended to animals and micro-organisms.
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Affiliation(s)
- Lun Li
- Institute for Systems Biology, Jianghan University, Wuhan, Hubei 430056, China
| | - Zhiwei Fang
- Institute for Systems Biology, Jianghan University, Wuhan, Hubei 430056, China
| | - Junfei Zhou
- Institute for Systems Biology, Jianghan University, Wuhan, Hubei 430056, China
| | - Hong Chen
- Center for Development of Science and Technology, Ministry of Agriculture, P.R. China, Beijing 100122, China
| | - Zhangfeng Hu
- Institute for Systems Biology, Jianghan University, Wuhan, Hubei 430056, China
| | - Lifen Gao
- Institute for Systems Biology, Jianghan University, Wuhan, Hubei 430056, China
| | - Lihong Chen
- Institute for Systems Biology, Jianghan University, Wuhan, Hubei 430056, China
| | - Sheng Ren
- Division of Biomedical Informatics, Cincinnati Children's Hospital Research Foundation, 3333 Burnet Avenue, Cincinnati, OH 45229-3026, USA.,Department of Mathematical Sciences, McMicken College of Arts & Sciences, University of Cincinnati, 2815 Commons Way, Cincinnati, OH 45221-0025, USA
| | - Hongyu Ma
- Thermo Fisher Scientific, Building 6, No. 27, Xin Jinqiao Rd., Pudong, Shanghai 201206, China
| | - Long Lu
- Institute for Systems Biology, Jianghan University, Wuhan, Hubei 430056, China.,Division of Biomedical Informatics, Cincinnati Children's Hospital Research Foundation, 3333 Burnet Avenue, Cincinnati, OH 45229-3026, USA
| | - Weixiong Zhang
- Institute for Systems Biology, Jianghan University, Wuhan, Hubei 430056, China.,Department of Computer Science and Engineering, Washington University in St Louis, MO 63130, USA.,Department of Genetics, Washington University School of Medicine, St Louis, MO 63130, USA
| | - Hai Peng
- Institute for Systems Biology, Jianghan University, Wuhan, Hubei 430056, China
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8
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Bournique E, Dall'Osto M, Hoffmann JS, Bergoglio V. Role of specialized DNA polymerases in the limitation of replicative stress and DNA damage transmission. Mutat Res 2017; 808:62-73. [PMID: 28843435 DOI: 10.1016/j.mrfmmm.2017.08.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 08/08/2017] [Accepted: 08/09/2017] [Indexed: 01/31/2023]
Abstract
Replication stress is a strong and early driving force for genomic instability and tumor development. Beside replicative DNA polymerases, an emerging group of specialized DNA polymerases is involved in the technical assistance of the replication machinery in order to prevent replicative stress and its deleterious consequences. During S-phase, altered progression of the replication fork by endogenous or exogenous impediments induces replicative stress, causing cells to reach mitosis with genomic regions not fully duplicated. Recently, specific mechanisms to resolve replication intermediates during mitosis with the aim of limiting DNA damage transmission to daughter cells have been identified. In this review, we detail the two major actions of specialized DNA polymerases that limit DNA damage transmission: the prevention of replicative stress by non-B DNA replication and the recovery of stalled replication forks.
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Affiliation(s)
- Elodie Bournique
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037, Toulouse, France
| | - Marina Dall'Osto
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037, Toulouse, France
| | - Jean-Sébastien Hoffmann
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037, Toulouse, France
| | - Valérie Bergoglio
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037, Toulouse, France.
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9
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Abstract
Anti-tumor immunity is a new line of research for the treatment of patients with solid tumors. In this field, negative regulators of the immune system called immune checkpoints play a key role in limiting antitumor immunologic responses. For this reason, immune checkpoint-inhibiting agents, such as those directed against cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programmed death-1 receptor (PD1) and its ligand PD-L1, have been developed as antitumor drugs, producing interesting results in preclinical and clinical studies. We present an updated review of the biological background and clinical development of immune checkpoint inhibitors in colorectal cancer (CRC). Early trial results on PD1 and PD-L1 blockade appear promising, especially in CRC patients with microsatellite instability (MSI). Clinical trials are ongoing to confirm these preliminary results, evaluate combination strategies and identify biomarkers to predict which patients are most likely to benefit from, or show resistance to, the effects of checkpoint inhibition.
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10
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Opportunities for immunotherapy in microsatellite instable colorectal cancer. Cancer Immunol Immunother 2016; 65:1249-59. [PMID: 27060000 PMCID: PMC5035655 DOI: 10.1007/s00262-016-1832-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 03/23/2016] [Indexed: 12/22/2022]
Abstract
Microsatellite instability (MSI), the somatic accumulation of length variations in repetitive DNA sequences called microsatellites, is frequently observed in both hereditary and sporadic colorectal cancer (CRC). It has been established that defects in the DNA mismatch repair (MMR) pathway underlie the development of MSI in CRC. After the inactivation of the DNA MMR pathway, misincorporations, insertions and deletions introduced by DNA polymerase slippage are not properly recognized and corrected. Specific genomic regions, including microsatellites, are more prone for DNA polymerase slippage and, therefore, more susceptible for the introduction of these mutations if the DNA MMR capacity is lost. Some of these susceptible genomic regions are located within the coding regions of genes. Insertions and deletions in these regions may alter their reading frame, potentially resulting in the transcription and translation of frameshift peptides with c-terminally altered amino acid sequences. These frameshift peptides are called neoantigens and are highly immunogenic, which explains the enhanced immunogenicity of MSI CRC. Neoantigens contribute to increased infiltration of tumor tissue with activated neoantigen-specific cytotoxic T lymphocytes, a hallmark of MSI tumors. Currently, neoantigen-based vaccination is being studied in a clinical trial for Lynch syndrome and in a trial for sporadic MSI CRC of advanced stage. In this Focussed Research Review, we summarize current knowledge on molecular mechanisms and address immunological features of tumors with MSI. Finally, we describe their implications for immunotherapeutic approaches and provide an outlook on next-generation immunotherapy involving neoantigens and combinatorial therapies in the setting of MSI CRC.
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11
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Vaksman Z, Garner HR. Somatic microsatellite variability as a predictive marker for colorectal cancer and liver cancer progression. Oncotarget 2016; 6:5760-71. [PMID: 25691061 PMCID: PMC4467400 DOI: 10.18632/oncotarget.3306] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 01/02/2015] [Indexed: 12/13/2022] Open
Abstract
Microsatellites (MSTs) are short tandem repeated genetic motifs that comprise ~3% of the genome. MST instability (MSI), defined as acquired/lost primary alleles at a small subset of microsatellite loci (e.g. Bethesda markers), is a clinically relevant marker for colorectal cancer. However, these markers are not applicable to other types of cancers, specifically, for liver cancer which has a high mortality rate. Here we show that somatic MST variability (SMV), defined as the presence of additional, non-primary (aka minor) alleles at MST loci, is a complementary measure of MSI, and a genetic marker for colorectal and liver cancer. Re-analysis of Illumina sequenced exomes from The Cancer Genome Atlas indicates that SMV may distinguish a subpopulation of African American patients with colorectal cancer, which represents ~33% of the population in this study. Further, for liver cancer, a higher rate of SMV may be indicative of an earlier age of onset. The work presented here suggests that classical MSI should be expanded to include SMV, going beyond alterations of the primary alleles at a small number of microsatellite loci. This measure of SMV may represent a potential new diagnostic for a variety of cancers and may provide new information for colorectal cancer patients.
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Affiliation(s)
- Zalman Vaksman
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA, USA
| | - Harold R Garner
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA, USA
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12
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Fungtammasan A, Ananda G, Hile SE, Su MSW, Sun C, Harris R, Medvedev P, Eckert K, Makova KD. Accurate typing of short tandem repeats from genome-wide sequencing data and its applications. Genome Res 2015; 25:736-49. [PMID: 25823460 PMCID: PMC4417121 DOI: 10.1101/gr.185892.114] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 03/16/2015] [Indexed: 11/24/2022]
Abstract
Short tandem repeats (STRs) are implicated in dozens of human genetic diseases and contribute significantly to genome variation and instability. Yet profiling STRs from short-read sequencing data is challenging because of their high sequencing error rates. Here, we developed STR-FM, short tandem repeat profiling using flank-based mapping, a computational pipeline that can detect the full spectrum of STR alleles from short-read data, can adapt to emerging read-mapping algorithms, and can be applied to heterogeneous genetic samples (e.g., tumors, viruses, and genomes of organelles). We used STR-FM to study STR error rates and patterns in publicly available human and in-house generated ultradeep plasmid sequencing data sets. We discovered that STRs sequenced with a PCR-free protocol have up to ninefold fewer errors than those sequenced with a PCR-containing protocol. We constructed an error correction model for genotyping STRs that can distinguish heterozygous alleles containing STRs with consecutive repeat numbers. Applying our model and pipeline to Illumina sequencing data with 100-bp reads, we could confidently genotype several disease-related long trinucleotide STRs. Utilizing this pipeline, for the first time we determined the genome-wide STR germline mutation rate from a deeply sequenced human pedigree. Additionally, we built a tool that recommends minimal sequencing depth for accurate STR genotyping, depending on repeat length and sequencing read length. The required read depth increases with STR length and is lower for a PCR-free protocol. This suite of tools addresses the pressing challenges surrounding STR genotyping, and thus is of wide interest to researchers investigating disease-related STRs and STR evolution.
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Affiliation(s)
- Arkarachai Fungtammasan
- Integrative Biosciences, Bioinformatics and Genomics Option, Pennsylvania State University, University Park, Pennsylvania 16802, USA; Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA; Center for Medical Genomics, Pennsylvania State University, University Park, Pennsylvania 16802, USA; The Genome Science Institute at the Huck Institutes of Life Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Guruprasad Ananda
- Integrative Biosciences, Bioinformatics and Genomics Option, Pennsylvania State University, University Park, Pennsylvania 16802, USA; Center for Medical Genomics, Pennsylvania State University, University Park, Pennsylvania 16802, USA; The Genome Science Institute at the Huck Institutes of Life Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA; Department of Biochemistry and Molecular Biology, Pennsylvania State University, Pennsylvania 16802, USA
| | - Suzanne E Hile
- Center for Medical Genomics, Pennsylvania State University, University Park, Pennsylvania 16802, USA; Department of Pathology, The Jake Gittlen Laboratories for Cancer Research, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
| | - Marcia Shu-Wei Su
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA; Center for Medical Genomics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Chen Sun
- Department of Computer Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Robert Harris
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Paul Medvedev
- Center for Medical Genomics, Pennsylvania State University, University Park, Pennsylvania 16802, USA; The Genome Science Institute at the Huck Institutes of Life Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA; Department of Biochemistry and Molecular Biology, Pennsylvania State University, Pennsylvania 16802, USA; Department of Computer Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Kristin Eckert
- Center for Medical Genomics, Pennsylvania State University, University Park, Pennsylvania 16802, USA; Department of Pathology, The Jake Gittlen Laboratories for Cancer Research, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
| | - Kateryna D Makova
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA; Center for Medical Genomics, Pennsylvania State University, University Park, Pennsylvania 16802, USA; The Genome Science Institute at the Huck Institutes of Life Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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13
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Baptiste BA, Jacob KD, Eckert KA. Genetic evidence that both dNTP-stabilized and strand slippage mechanisms may dictate DNA polymerase errors within mononucleotide microsatellites. DNA Repair (Amst) 2015; 29:91-100. [PMID: 25758780 DOI: 10.1016/j.dnarep.2015.02.016] [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: 11/07/2014] [Revised: 02/15/2015] [Accepted: 02/16/2015] [Indexed: 12/19/2022]
Abstract
Mononucleotide microsatellites are tandem repeats of a single base pair, abundant within coding exons and frequent sites of mutation in the human genome. Because the repeated unit is one base pair, multiple mechanisms of insertion/deletion (indel) mutagenesis are possible, including strand-slippage, dNTP-stabilized, and misincorportion-misalignment. Here, we examine the effects of polymerase identity (mammalian Pols α, β, κ, and η), template sequence, dNTP pool size, and reaction temperature on indel errors during in vitro synthesis of mononucleotide microsatellites. We utilized the ratio of insertion to deletion errors as a genetic indicator of mechanism. Strikingly, we observed a statistically significant bias toward deletion errors within mononucleotide repeats for the majority of the 28 DNA template and polymerase combinations examined, with notable exceptions based on sequence and polymerase identity. Using mutator forms of Pol β did not substantially alter the error specificity, suggesting that mispairing-misalignment mechanism is not a primary mechanism. Based on our results for mammalian DNA polymerases representing three structurally distinct families, we suggest that dNTP-stabilized mutagenesis may be an alternative mechanism for mononucleotide microsatellite indel mutation. The change from a predominantly dNTP-stabilized mechanism to a strand-slippage mechanism with increasing microsatellite length may account for the differential rates of tandem repeat mutation that are observed genome-wide.
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Affiliation(s)
- Beverly A Baptiste
- The Jake Gittlen Laboratories for Cancer Research and the Department of Pathology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Kimberly D Jacob
- The Jake Gittlen Laboratories for Cancer Research and the Department of Pathology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Kristin A Eckert
- The Jake Gittlen Laboratories for Cancer Research and the Department of Pathology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
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14
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Ananda G, Hile SE, Breski A, Wang Y, Kelkar Y, Makova KD, Eckert KA. Microsatellite interruptions stabilize primate genomes and exist as population-specific single nucleotide polymorphisms within individual human genomes. PLoS Genet 2014; 10:e1004498. [PMID: 25033203 PMCID: PMC4102424 DOI: 10.1371/journal.pgen.1004498] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 05/28/2014] [Indexed: 01/01/2023] Open
Abstract
Interruptions of microsatellite sequences impact genome evolution and can alter disease manifestation. However, human polymorphism levels at interrupted microsatellites (iMSs) are not known at a genome-wide scale, and the pathways for gaining interruptions are poorly understood. Using the 1000 Genomes Phase-1 variant call set, we interrogated mono-, di-, tri-, and tetranucleotide repeats up to 10 units in length. We detected ∼26,000–40,000 iMSs within each of four human population groups (African, European, East Asian, and American). We identified population-specific iMSs within exonic regions, and discovered that known disease-associated iMSs contain alleles present at differing frequencies among the populations. By analyzing longer microsatellites in primate genomes, we demonstrate that single interruptions result in a genome-wide average two- to six-fold reduction in microsatellite mutability, as compared with perfect microsatellites. Centrally located interruptions lowered mutability dramatically, by two to three orders of magnitude. Using a biochemical approach, we tested directly whether the mutability of a specific iMS is lower because of decreased DNA polymerase strand slippage errors. Modeling the adenomatous polyposis coli tumor suppressor gene sequence, we observed that a single base substitution interruption reduced strand slippage error rates five- to 50-fold, relative to a perfect repeat, during synthesis by DNA polymerases α, β, or η. Computationally, we demonstrate that iMSs arise primarily by base substitution mutations within individual human genomes. Our biochemical survey of human DNA polymerase α, β, δ, κ, and η error rates within certain microsatellites suggests that interruptions are created most frequently by low fidelity polymerases. Our combined computational and biochemical results demonstrate that iMSs are abundant in human genomes and are sources of population-specific genetic variation that may affect genome stability. The genome-wide identification of iMSs in human populations presented here has important implications for current models describing the impact of microsatellite polymorphisms on gene expression. Microsatellites are short tandem repeat DNA sequences located throughout the human genome that display a high degree of inter-individual variation. This characteristic makes microsatellites an attractive tool for population genetics and forensics research. Some microsatellites affect gene expression, and mutations within such microsatellites can cause disease. Interruption mutations disrupt the perfect repeated array and are frequently associated with altered disease risk, but they have not been thoroughly studied in human genomes. We identified interrupted mono-, di-, tri- and tetranucleotide MSs (iMS) within individual genomes from African, European, Asian and American population groups. We show that many iMSs, including some within disease-associated genes, are unique to a single population group. By measuring the conservation of microsatellites between human and chimpanzee genomes, we demonstrate that interruptions decrease the probability of microsatellite mutations throughout the genome. We demonstrate that iMSs arise in the human genome by single base changes within the DNA, and provide biochemical data suggesting that these stabilizing changes may be created by error-prone DNA polymerases. Our genome-wide study supports the model in which iMSs act to stabilize individual genomes, and suggests that population-specific differences in microsatellite architecture may be an avenue by which genetic ancestry impacts individual disease risk.
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Affiliation(s)
- Guruprasad Ananda
- Department of Biology, Penn State University, University Park, Pennsylvania, United States of America
| | - Suzanne E. Hile
- Department of Pathology, Gittlen Cancer Research Foundation, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Amanda Breski
- Department of Pathology, Gittlen Cancer Research Foundation, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Yanli Wang
- Department of Biology, Penn State University, University Park, Pennsylvania, United States of America
| | - Yogeshwar Kelkar
- Department of Biology, Penn State University, University Park, Pennsylvania, United States of America
| | - Kateryna D. Makova
- Department of Biology, Penn State University, University Park, Pennsylvania, United States of America
- Center for Medical Genomics, Penn State University, University Park, Pennsylvania, United States of America
- * E-mail: (KDM); (KAE)
| | - Kristin A. Eckert
- Department of Pathology, Gittlen Cancer Research Foundation, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
- Center for Medical Genomics, Penn State University, University Park, Pennsylvania, United States of America
- * E-mail: (KDM); (KAE)
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15
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16
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Boyer AS, Grgurevic S, Cazaux C, Hoffmann JS. The Human Specialized DNA Polymerases and Non-B DNA: Vital Relationships to Preserve Genome Integrity. J Mol Biol 2013; 425:4767-81. [DOI: 10.1016/j.jmb.2013.09.022] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 09/17/2013] [Accepted: 09/19/2013] [Indexed: 12/26/2022]
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17
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Lormand JD, Buncher N, Murphy CT, Kaur P, Lee MY, Burgers P, Wang H, Kunkel TA, Opresko PL. DNA polymerase δ stalls on telomeric lagging strand templates independently from G-quadruplex formation. Nucleic Acids Res 2013; 41:10323-33. [PMID: 24038470 PMCID: PMC3905856 DOI: 10.1093/nar/gkt813] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Previous evidence indicates that telomeres resemble common fragile sites and present a challenge for DNA replication. The precise impediments to replication fork progression at telomeric TTAGGG repeats are unknown, but are proposed to include G-quadruplexes (G4) on the G-rich strand. Here we examined DNA synthesis and progression by the replicative DNA polymerase δ/proliferating cell nuclear antigen/replication factor C complex on telomeric templates that mimic the leading C-rich and lagging G-rich strands. Increased polymerase stalling occurred on the G-rich template, compared with the C-rich and nontelomeric templates. Suppression of G4 formation by substituting Li+ for K+ as the cation, or by using templates with 7-deaza-G residues, did not alleviate Pol δ pause sites within the G residues. Furthermore, we provide evidence that G4 folding is less stable on single-stranded circular TTAGGG templates where ends are constrained, compared with linear oligonucleotides. Artificially stabilizing G4 structures on the circular templates with the G4 ligand BRACO-19 inhibited Pol δ progression into the G-rich repeats. Similar results were obtained for yeast and human Pol δ complexes. Our data indicate that G4 formation is not required for polymerase stalling on telomeric lagging strands and suggest that an alternative mechanism, in addition to stable G4s, contributes to replication stalling at telomeres.
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Affiliation(s)
- Justin D Lormand
- Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, 100 Technology Drive, Pittsburgh, PA 15219, USA, Department of Physics, North Carolina State University, 2401 Stinson Drive, Raleigh, NC, 27695, USA, Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA, Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA and Laboratory of Molecular Genetics and Laboratory of Structural Biology, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, NC 27709, USA
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18
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Mutation rates, spectra, and genome-wide distribution of spontaneous mutations in mismatch repair deficient yeast. G3-GENES GENOMES GENETICS 2013; 3:1453-65. [PMID: 23821616 PMCID: PMC3755907 DOI: 10.1534/g3.113.006429] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
DNA mismatch repair is a highly conserved DNA repair pathway. In humans, germline mutations in hMSH2 or hMLH1, key components of mismatch repair, have been associated with Lynch syndrome, a leading cause of inherited cancer mortality. Current estimates of the mutation rate and the mutational spectra in mismatch repair defective cells are primarily limited to a small number of individual reporter loci. Here we use the yeast Saccharomyces cerevisiae to generate a genome-wide view of the rates, spectra, and distribution of mutation in the absence of mismatch repair. We performed mutation accumulation assays and next generation sequencing on 19 strains, including 16 msh2 missense variants implicated in Lynch cancer syndrome. The mutation rate for DNA mismatch repair null strains was approximately 1 mutation per genome per generation, 225-fold greater than the wild-type rate. The mutations were distributed randomly throughout the genome, independent of replication timing. The mutation spectra included insertions/deletions at homopolymeric runs (87.7%) and at larger microsatellites (5.9%), as well as transitions (4.5%) and transversions (1.9%). Additionally, repeat regions with proximal repeats are more likely to be mutated. A bias toward deletions at homopolymers and insertions at (AT)n microsatellites suggests a different mechanism for mismatch generation at these sites. Interestingly, 5% of the single base pair substitutions might represent double-slippage events that occurred at the junction of immediately adjacent repeats, resulting in a shift in the repeat boundary. These data suggest a closer scrutiny of tumor suppressors with homopolymeric runs with proximal repeats as the potential drivers of oncogenesis in mismatch repair defective cells.
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19
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Vasquez KM, Wang G. The yin and yang of repair mechanisms in DNA structure-induced genetic instability. Mutat Res 2013; 743-744:118-131. [PMID: 23219604 PMCID: PMC3661696 DOI: 10.1016/j.mrfmmm.2012.11.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 11/21/2012] [Accepted: 11/24/2012] [Indexed: 01/14/2023]
Abstract
DNA can adopt a variety of secondary structures that deviate from the canonical Watson-Crick B-DNA form. More than 10 types of non-canonical or non-B DNA secondary structures have been characterized, and the sequences that have the capacity to adopt such structures are very abundant in the human genome. Non-B DNA structures have been implicated in many important biological processes and can serve as sources of genetic instability, implicating them in disease and evolution. Non-B DNA conformations interact with a wide variety of proteins involved in replication, transcription, DNA repair, and chromatin architectural regulation. In this review, we will focus on the interactions of DNA repair proteins with non-B DNA and their roles in genetic instability, as the proteins and DNA involved in such interactions may represent plausible targets for selective therapeutic intervention.
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Affiliation(s)
- Karen M Vasquez
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Pediatric Research Institute, 1400 Barbara Jordan Blvd. R1800, Austin, TX 78723, United States.
| | - Guliang Wang
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Pediatric Research Institute, 1400 Barbara Jordan Blvd. R1800, Austin, TX 78723, United States
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20
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Prindle MJ, Loeb LA. DNA polymerase delta in DNA replication and genome maintenance. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2012; 53:666-82. [PMID: 23065663 PMCID: PMC3694620 DOI: 10.1002/em.21745] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Revised: 09/09/2012] [Accepted: 09/12/2012] [Indexed: 05/12/2023]
Abstract
The eukaryotic genome is in a constant state of modification and repair. Faithful transmission of the genomic information from parent to daughter cells depends upon an extensive system of surveillance, signaling, and DNA repair, as well as accurate synthesis of DNA during replication. Often, replicative synthesis occurs over regions of DNA that have not yet been repaired, presenting further challenges to genomic stability. DNA polymerase δ (pol δ) occupies a central role in all of these processes: catalyzing the accurate replication of a majority of the genome, participating in several DNA repair synthetic pathways, and contributing structurally to the accurate bypass of problematic lesions during translesion synthesis. The concerted actions of pol δ on the lagging strand, pol ϵ on the leading strand, associated replicative factors, and the mismatch repair (MMR) proteins results in a mutation rate of less than one misincorporation per genome per replication cycle. This low mutation rate provides a high level of protection against genetic defects during development and may prevent the initiation of malignancies in somatic cells. This review explores the role of pol δ in replication fidelity and genome maintenance.
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Affiliation(s)
- Marc J Prindle
- Department of Pathology, The Joseph Gottstien Memorial Cancer Research Laboratory, University of Washington, Seattle, WA 98195-7705, USA
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21
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Hile SE, Shabashev S, Eckert KA. Tumor-specific microsatellite instability: do distinct mechanisms underlie the MSI-L and EMAST phenotypes? Mutat Res 2012. [PMID: 23206442 DOI: 10.1016/j.mrfmmm.2012.11.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Microsatellite DNA sequences display allele length alterations or microsatellite instability (MSI) in tumor tissues, and MSI is used diagnostically for tumor detection and classification. We discuss the known types of tumor-specific MSI patterns and the relevant mechanisms underlying each pattern. Mutation rates of individual microsatellites vary greatly, and the intrinsic DNA features of motif size, sequence, and length contribute to this variation. MSI is used for detecting mismatch repair (MMR)-deficient tumors, which display an MSI-high phenotype due to genome-wide microsatellite destabilization. Because several pathways maintain microsatellite stability, tumors that have undergone other events associated with moderate genome instability may display diagnostic MSI only at specific di- or tetranucleotide markers. We summarize evidence for such alternative MSI forms (A-MSI) in sporadic cancers, also referred to as MSI-low and EMAST. While the existence of A-MSI is not disputed, there is disagreement about the origin and pathologic significance of this phenomenon. Although ambiguities due to PCR methods may be a source, evidence exists for other mechanisms to explain tumor-specific A-MSI. Some portion of A-MSI tumors may result from random mutational events arising during neoplastic cell evolution. However, this mechanism fails to explain the specificity of A-MSI for di- and tetranucleotide instability. We present evidence supporting the alternative argument that some A-MSI tumors arise by a distinct genetic pathway, and give examples of DNA metabolic pathways that, when altered, may be responsible for instability at specific microsatellite motifs. Finally, we suggest that A-MSI in tumors could be molecular signatures of environmental influences and DNA damage. Importantly, A-MSI occurs in several pre-neoplastic inflammatory states, including inflammatory bowel diseases, consistent with a role of oxidative stress in A-MSI. Understanding the biochemical basis of A-MSI tumor phenotypes will advance the development of new diagnostic tools and positively impact the clinical management of individual cancers.
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Affiliation(s)
- Suzanne E Hile
- Department of Pathology, Gittlen Cancer Research Foundation, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Samion Shabashev
- Department of Pathology, Gittlen Cancer Research Foundation, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Kristin A Eckert
- Department of Pathology, Gittlen Cancer Research Foundation, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
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22
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Baptiste BA, Eckert KA. DNA polymerase kappa microsatellite synthesis: two distinct mechanisms of slippage-mediated errors. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2012; 53:787-796. [PMID: 22965905 DOI: 10.1002/em.21721] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 06/29/2012] [Accepted: 07/03/2012] [Indexed: 06/01/2023]
Abstract
Microsatellite tandem repeats are frequent sites of strand slippage mutagenesis in the human genome. Microsatellite mutations often occur as insertion/deletion of a repeat motif (unit-based indels), and increase in frequency with increasing repeat length after a threshold is reached. We recently demonstrated that DNA polymerase κ (Pol κ) produces fewer unit-based indel errors within dinucleotide microsatellites than does polymerase δ. Here, we examined human Pol κ's error profile within microsatellite alleles of varying sequence composition and length, using an in vitro HSV-tk gap-filling assay. We observed that Pol κ displays relatively accurate synthesis for unit-based indels, using di- and tetranucleotide repeat templates longer than the threshold length. We observed an abrupt increase in the unit-based indel frequency when the total microsatellite length exceeds 28 nucleotides, suggesting that extended Pol κ protein-DNA interactions enhance fidelity of the enzyme when synthesizing these microsatellite alleles. In contrast, Pol κ is error-prone within the HSV-tk coding sequence, producing frequent single-base errors in a manner that is highly biased with regard to sequence context. Single-nucleotide errors are also created by Pol κ within di- and tetranucleotide repeats, independently of the microsatellite allele length and at a frequency per nucleotide similar to the frequency of single base errors within the coding sequence. These single-base errors represent the mutational signature of Pol κ, and we propose them a mechanism independent of homology-stabilized slippage. Pol κ's dual fidelity nature provides a unique research tool to explore the distinct mechanisms of slippage-mediated mutagenesis.
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Affiliation(s)
- Beverly A Baptiste
- Department of Pathology, Gittlen Cancer Research Foundation, Pennsylvania State University College of Medicine, Hershey, PA, USA
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Waisertreiger ISR, Liston VG, Menezes MR, Kim HM, Lobachev KS, Stepchenkova EI, Tahirov TH, Rogozin IB, Pavlov YI. Modulation of mutagenesis in eukaryotes by DNA replication fork dynamics and quality of nucleotide pools. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2012; 53:699-724. [PMID: 23055184 PMCID: PMC3893020 DOI: 10.1002/em.21735] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 08/13/2012] [Accepted: 08/15/2012] [Indexed: 06/01/2023]
Abstract
The rate of mutations in eukaryotes depends on a plethora of factors and is not immediately derived from the fidelity of DNA polymerases (Pols). Replication of chromosomes containing the anti-parallel strands of duplex DNA occurs through the copying of leading and lagging strand templates by a trio of Pols α, δ and ϵ, with the assistance of Pol ζ and Y-family Pols at difficult DNA template structures or sites of DNA damage. The parameters of the synthesis at a given location are dictated by the quality and quantity of nucleotides in the pools, replication fork architecture, transcription status, regulation of Pol switches, and structure of chromatin. The result of these transactions is a subject of survey and editing by DNA repair.
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Affiliation(s)
- Irina S.-R. Waisertreiger
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
| | - Victoria G. Liston
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
| | - Miriam R. Menezes
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
| | - Hyun-Min Kim
- School of Biology and Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, U.S.A
| | - Kirill S. Lobachev
- School of Biology and Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, U.S.A
| | - Elena I. Stepchenkova
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
- Saint Petersburg Branch of Vavilov Institute of General Genetics, Universitetskaya emb. 7/9, St Petersburg, 199034, Russia
- Department of Genetics, Saint Petersburg University, Universitetskaya emb. 7/9, St Petersburg, 199034, Russia
| | - Tahir H. Tahirov
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
| | - Igor B. Rogozin
- National Center for Biotechnology Information NLM, National Institutes of Health, Bethesda, MD 20894, U.S.A
- Institute of Cytology and Genetics, 630090 Novosibirsk, Russia
| | - Youri. I. Pavlov
- Eppley Institute for Research in Cancer and Allied Diseases, ESH 7009, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, U.S.A
- Department of Genetics, Saint Petersburg University, Universitetskaya emb. 7/9, St Petersburg, 199034, Russia
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Hile SE, Wang X, Lee MYWT, Eckert KA. Beyond translesion synthesis: polymerase κ fidelity as a potential determinant of microsatellite stability. Nucleic Acids Res 2011; 40:1636-47. [PMID: 22021378 PMCID: PMC3287198 DOI: 10.1093/nar/gkr889] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Microsatellite DNA synthesis represents a significant component of human genome replication that must occur faithfully. However, yeast replicative DNA polymerases do not possess high fidelity for microsatellite synthesis. We hypothesized that the structural features of Y-family polymerases that facilitate accurate translesion synthesis may promote accurate microsatellite synthesis. We compared human polymerases κ (Pol κ) and η (Pol η) fidelities to that of replicative human polymerase δ holoenzyme (Pol δ4), using the in vitro HSV-tk assay. Relative polymerase accuracy for insertion/deletion (indel) errors within 2-3 unit repeats internal to the HSV-tk gene concurred with the literature: Pol δ4 >> Pol κ or Pol η. In contrast, relative polymerase accuracy for unit-based indel errors within [GT](10) and [TC](11) microsatellites was: Pol κ ≥ Pol δ4 > Pol η. The magnitude of difference was greatest between Pols κ and δ4 with the [GT] template. Biochemically, Pol κ displayed less synthesis termination within the [GT] allele than did Pol δ4. In dual polymerase reactions, Pol κ competed with either a stalled or moving Pol δ4, thereby reducing termination. Our results challenge the ideology that pol κ is error prone, and suggest that DNA polymerases with complementary biochemical properties can function cooperatively at repetitive sequences.
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Affiliation(s)
- Suzanne E Hile
- Department of Pathology, Gittlen Cancer Research Foundation, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
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