1
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King DE, Copeland WC. DNA repair pathways in the mitochondria. DNA Repair (Amst) 2025; 146:103814. [PMID: 39914164 PMCID: PMC11848857 DOI: 10.1016/j.dnarep.2025.103814] [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: 11/26/2024] [Revised: 01/14/2025] [Accepted: 01/28/2025] [Indexed: 02/24/2025]
Abstract
Mitochondria contain their own small, circular genome that is present in high copy number. The mitochondrial genome (mtDNA) encodes essential subunits of the electron transport chain. Mutations in the mitochondrial genome are associated with a wide range of mitochondrial diseases and the maintenance and replication of mtDNA is crucial to cellular health. Despite the importance of maintaining mtDNA genomic integrity, fewer DNA repair pathways exist in the mitochondria than in the nucleus. However, mitochondria have numerous pathways that allow for the removal and degradation of DNA damage that may prevent accumulation of mutations. Here, we briefly review the DNA repair pathways present in the mitochondria, sources of mtDNA mutations, and discuss the passive role that mtDNA mutagenesis may play in cancer progression.
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Affiliation(s)
- Dillon E King
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, United States
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, United States.
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2
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Li X, Cao G, Liu X, Tang TS, Guo C, Liu H. Polymerases and DNA Repair in Neurons: Implications in Neuronal Survival and Neurodegenerative Diseases. Front Cell Neurosci 2022; 16:852002. [PMID: 35846567 PMCID: PMC9279898 DOI: 10.3389/fncel.2022.852002] [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: 01/10/2022] [Accepted: 05/23/2022] [Indexed: 12/22/2022] Open
Abstract
Most of the neurodegenerative diseases and aging are associated with reactive oxygen species (ROS) or other intracellular damaging agents that challenge the genome integrity of the neurons. As most of the mature neurons stay in G0/G1 phase, replication-uncoupled DNA repair pathways including BER, NER, SSBR, and NHEJ, are pivotal, efficient, and economic mechanisms to maintain genomic stability without reactivating cell cycle. In these progresses, polymerases are prominent, not only because they are responsible for both sensing and repairing damages, but also for their more diversified roles depending on the cell cycle phase and damage types. In this review, we summarized recent knowledge on the structural and biochemical properties of distinct polymerases, including DNA and RNA polymerases, which are known to be expressed and active in nervous system; the biological relevance of these polymerases and their interactors with neuronal degeneration would be most graphically illustrated by the neurological abnormalities observed in patients with hereditary diseases associated with defects in DNA repair; furthermore, the vicious cycle of the trinucleotide repeat (TNR) and impaired DNA repair pathway is also discussed. Unraveling the mechanisms and contextual basis of the role of the polymerases in DNA damage response and repair will promote our understanding about how long-lived postmitotic cells cope with DNA lesions, and why disrupted DNA repair contributes to disease origin, despite the diversity of mutations in genes. This knowledge may lead to new insight into the development of targeted intervention for neurodegenerative diseases.
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Affiliation(s)
- Xiaoling Li
- Nano-Biotechnology Key Lab of Hebei Province, Yanshan University, Qinhuangdao, China
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China
- Xiaoling Li
| | - Guanghui Cao
- Nano-Biotechnology Key Lab of Hebei Province, Yanshan University, Qinhuangdao, China
| | - Xiaokang Liu
- Nano-Biotechnology Key Lab of Hebei Province, Yanshan University, Qinhuangdao, China
| | - Tie-Shan Tang
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- Beijing Institute for Stem Cell and Regenerative Medicine, Beijing, China
| | - Caixia Guo
- Beijing Institute of Genomics, University of Chinese Academy of Sciences, Chinese Academy of Sciences/China National Center for Bioinformation, Beijing, China
- *Correspondence: Caixia Guo
| | - Hongmei Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- Beijing Institute for Stem Cell and Regenerative Medicine, Beijing, China
- Hongmei Liu
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3
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Roy A, Kandettu A, Ray S, Chakrabarty S. Mitochondrial DNA replication and repair defects: Clinical phenotypes and therapeutic interventions. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148554. [PMID: 35341749 DOI: 10.1016/j.bbabio.2022.148554] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 03/06/2022] [Accepted: 03/16/2022] [Indexed: 12/15/2022]
Abstract
Mitochondria is a unique cellular organelle involved in multiple cellular processes and is critical for maintaining cellular homeostasis. This semi-autonomous organelle contains its circular genome - mtDNA (mitochondrial DNA), that undergoes continuous cycles of replication and repair to maintain the mitochondrial genome integrity. The majority of the mitochondrial genes, including mitochondrial replisome and repair genes, are nuclear-encoded. Although the repair machinery of mitochondria is quite efficient, the mitochondrial genome is highly susceptible to oxidative damage and other types of exogenous and endogenous agent-induced DNA damage, due to the absence of protective histones and their proximity to the main ROS production sites. Mutations in replication and repair genes of mitochondria can result in mtDNA depletion and deletions subsequently leading to mitochondrial genome instability. The combined action of mutations and deletions can result in compromised mitochondrial genome maintenance and lead to various mitochondrial disorders. Here, we review the mechanism of mitochondrial DNA replication and repair process, key proteins involved, and their altered function in mitochondrial disorders. The focus of this review will be on the key genes of mitochondrial DNA replication and repair machinery and the clinical phenotypes associated with mutations in these genes.
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Affiliation(s)
- Abhipsa Roy
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Amoolya Kandettu
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Swagat Ray
- Department of Life Sciences, School of Life and Environmental Sciences, University of Lincoln, Lincoln LN6 7TS, United Kingdom
| | - Sanjiban Chakrabarty
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India.
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4
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Sullivan ED, Longley MJ, Copeland WC. Polymerase γ efficiently replicates through many natural template barriers but stalls at the HSP1 quadruplex. J Biol Chem 2021; 295:17802-17815. [PMID: 33454015 DOI: 10.1074/jbc.ra120.015390] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 10/05/2020] [Indexed: 12/27/2022] Open
Abstract
Faithful replication of the mitochondrial genome is carried out by a set of key nuclear-encoded proteins. DNA polymerase γ is a core component of the mtDNA replisome and the only replicative DNA polymerase localized to mitochondria. The asynchronous mechanism of mtDNA replication predicts that the replication machinery encounters dsDNA and unique physical barriers such as structured genes, G-quadruplexes, and other obstacles. In vitro experiments here provide evidence that the polymerase γ heterotrimer is well-adapted to efficiently synthesize DNA, despite the presence of many naturally occurring roadblocks. However, we identified a specific G-quadruplex-forming sequence at the heavy-strand promoter (HSP1) that has the potential to cause significant stalling of mtDNA replication. Furthermore, this structured region of DNA corresponds to the break site for a large (3,895 bp) deletion observed in mitochondrial disease patients. The presence of this deletion in humans correlates with UV exposure, and we have found that efficiency of polymerase γ DNA synthesis is reduced after this quadruplex is exposed to UV in vitro.
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Affiliation(s)
- Eric D Sullivan
- Mitochondrial DNA Replication Group, Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina, USA
| | - Matthew J Longley
- Mitochondrial DNA Replication Group, Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina, USA
| | - William C Copeland
- Mitochondrial DNA Replication Group, Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina, USA.
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5
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Marco Antônio Salgado Martins T, de Figueiredo Peloso E, Costa-Silva HM, Rajão MA, Van Houten B, Machado CR, Ramos Gadelha F. Mitochondrial behavior during nuclear and mitochondrial DNA repair in Trypanosoma cruzi epimastigotes. Exp Parasitol 2020; 219:108016. [PMID: 33035543 DOI: 10.1016/j.exppara.2020.108016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 09/30/2020] [Accepted: 10/05/2020] [Indexed: 12/12/2022]
Abstract
Different genotoxic agents can lead to DNA single- and double-strand breaks, base modification and oxidation. As most living organisms, Trypanosoma cruzi is subjected to oxidative stress during its life cycle; thus, DNA repair is essential for parasite survival and establishment of infection. The mitochondrion plays important roles beyond the production of ATP. For example, it is a source of signaling molecules, such as the superoxide anion and H2O2. Since T. cruzi has only one mitochondrion, the integrity of this organelle is pivotal for parasite viability. H2O2 and methyl methanesulfonate cause DNA lesions in T. cruzi that are repaired by different DNA repair pathways. Herein, we evaluate mitochondrial involvement during the repair of nuclear and mitochondrial DNA in T. cruzi epimastigotes incubated with these two genotoxic agents under conditions that induce repairable DNA damage. Overall, in both treatments, an increase in oxygen consumption rates and in mitochondrial H2O2 release was observed, as well as maintenance of ATP levels compared to control. Interestingly, these changes coincided with DNA repair kinetics, suggesting the importance of the mitochondrion for this energy-consuming process.
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Affiliation(s)
| | | | | | - Matheus Andrade Rajão
- Departamento de Bioquímica e Imunologia, ICB - UFMG, Belo Horizonte, Minas Gerais, Brazil
| | - Bennet Van Houten
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine and the University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA, United States
| | - Carlos Renato Machado
- Departamento de Bioquímica e Imunologia, ICB - UFMG, Belo Horizonte, Minas Gerais, Brazil
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6
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Matkarimov BT, Saparbaev MK. DNA Repair and Mutagenesis in Vertebrate Mitochondria: Evidence for Asymmetric DNA Strand Inheritance. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1241:77-100. [DOI: 10.1007/978-3-030-41283-8_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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7
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Zhao L. Mitochondrial DNA degradation: A quality control measure for mitochondrial genome maintenance and stress response. Enzymes 2019; 45:311-341. [PMID: 31627882 DOI: 10.1016/bs.enz.2019.08.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mitochondria play a central role in bioenergetics, and fulfill a plethora of functions in cell signaling, programmed cell death, and biosynthesis of key protein cofactors. Mitochondria harbor their own genomic DNA, which encodes protein subunits of the electron transport chain and a full set of transfer and ribosomal RNAs. Mitochondrial DNA (mtDNA) is essential for cellular and organismal functions, and defects in mitochondrial genome maintenance have been implicated in common human diseases and mitochondrial disorders. mtDNA repair and degradation are known pathways to cope with mtDNA damage; however, molecular factors involved in this process have remained unclear. Such knowledge is fundamental to the understanding of mitochondrial genomic maintenance and pathology, because mtDNA degradation may contribute to the etiology of mtDNA depletion syndromes and to the activation of the innate immune response by fragmented mtDNA. This article reviews the current literature regarding the importance of mitochondrial DNA degradation in mtDNA maintenance and stress response, and the recent progress in uncovering molecular factors involved in mtDNA degradation. These factors include key components of the mtDNA replication machinery, such as DNA polymerase γ, helicase Twinkle, and exonuclease MGME1, as well as a major DNA-packaging protein, mitochondrial transcription factor A (TFAM).
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Affiliation(s)
- Linlin Zhao
- Department of Chemistry, University of California, Riverside, Riverside, CA, United States.
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8
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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: 5.1] [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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9
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Peeva V, Blei D, Trombly G, Corsi S, Szukszto MJ, Rebelo-Guiomar P, Gammage PA, Kudin AP, Becker C, Altmüller J, Minczuk M, Zsurka G, Kunz WS. Linear mitochondrial DNA is rapidly degraded by components of the replication machinery. Nat Commun 2018; 9:1727. [PMID: 29712893 PMCID: PMC5928156 DOI: 10.1038/s41467-018-04131-w] [Citation(s) in RCA: 147] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 04/04/2018] [Indexed: 02/02/2023] Open
Abstract
Emerging gene therapy approaches that aim to eliminate pathogenic mutations of mitochondrial DNA (mtDNA) rely on efficient degradation of linearized mtDNA, but the enzymatic machinery performing this task is presently unknown. Here, we show that, in cellular models of restriction endonuclease-induced mtDNA double-strand breaks, linear mtDNA is eliminated within hours by exonucleolytic activities. Inactivation of the mitochondrial 5'-3'exonuclease MGME1, elimination of the 3'-5'exonuclease activity of the mitochondrial DNA polymerase POLG by introducing the p.D274A mutation, or knockdown of the mitochondrial DNA helicase TWNK leads to severe impediment of mtDNA degradation. We do not observe similar effects when inactivating other known mitochondrial nucleases (EXOG, APEX2, ENDOG, FEN1, DNA2, MRE11, or RBBP8). Our data suggest that rapid degradation of linearized mtDNA is performed by the same machinery that is responsible for mtDNA replication, thus proposing novel roles for the participating enzymes POLG, TWNK, and MGME1.
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Affiliation(s)
- Viktoriya Peeva
- 0000 0001 2240 3300grid.10388.32Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany
| | - Daniel Blei
- 0000 0001 2240 3300grid.10388.32Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany
| | - Genevieve Trombly
- 0000 0001 2240 3300grid.10388.32Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany
| | - Sarah Corsi
- 0000 0001 2240 3300grid.10388.32Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany ,0000 0001 0462 7212grid.1006.7Present Address: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, NE2 4HH UK
| | - Maciej J. Szukszto
- 0000000121885934grid.5335.0MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY UK
| | - Pedro Rebelo-Guiomar
- 0000000121885934grid.5335.0MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY UK ,0000 0001 1503 7226grid.5808.5Graduate Program in Areas of Basic and Applied Biology (GABBA), University of Porto, Porto, 4200-135 Portugal
| | - Payam A. Gammage
- 0000000121885934grid.5335.0MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY UK
| | - Alexei P. Kudin
- 0000 0001 2240 3300grid.10388.32Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany
| | - Christian Becker
- 0000 0000 8580 3777grid.6190.eCologne Center for Genomics, Center for Molecular Medicine Cologne (CMMC), University of Cologne, Weyertal 115b, Cologne, D-50931 Germany
| | - Janine Altmüller
- 0000 0000 8580 3777grid.6190.eCologne Center for Genomics, Center for Molecular Medicine Cologne (CMMC), University of Cologne, Weyertal 115b, Cologne, D-50931 Germany ,0000 0000 8580 3777grid.6190.eInstitute of Human Genetics, University of Cologne, Kerpener Str. 34, Cologne, D-50931 Germany
| | - Michal Minczuk
- 0000000121885934grid.5335.0MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY UK
| | - Gábor Zsurka
- 0000 0001 2240 3300grid.10388.32Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany ,0000 0001 2240 3300grid.10388.32Department of Epileptology and Life & Brain Center, University of Bonn, Sigmund-Freud-Str. 25, Bonn, D-53105 Germany
| | - Wolfram S. Kunz
- 0000 0001 2240 3300grid.10388.32Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany ,0000 0001 2240 3300grid.10388.32Department of Epileptology and Life & Brain Center, University of Bonn, Sigmund-Freud-Str. 25, Bonn, D-53105 Germany
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10
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Van Houten B, Santa-Gonzalez GA, Camargo M. DNA repair after oxidative stress: current challenges. CURRENT OPINION IN TOXICOLOGY 2018; 7:9-16. [PMID: 29159324 PMCID: PMC5693256 DOI: 10.1016/j.cotox.2017.10.009] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Reactive oxygen and nitrogen species damage cellular macromolecules including DNA. Cells have a robust base excision repair pathway to deal with this damage in both nuclear and mitochondrial genomes. However, mitochondria lack nucleotide excision repair. Evidence suggests that chronic oxidative stress can induce protective pathways lowering genotoxicity. Understanding oxidant injury to DNA and its repair is critical for our understanding the pathophysiology of a wide range of human disorders.
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Affiliation(s)
- Bennett Van Houten
- Program in Molecular Biophysics and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
- The University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15213, USA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Gloria A Santa-Gonzalez
- University Research Center and Biology Institute, Genetics, Regeneration and Cancer Laboratory, SIU Lab 432, Universidad de Antioquia, Medellin, Colombia
| | - Mauricio Camargo
- University Research Center and Biology Institute, Genetics, Regeneration and Cancer Laboratory, SIU Lab 432, Universidad de Antioquia, Medellin, Colombia
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11
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Prasad R, Çağlayan M, Dai DP, Nadalutti CA, Zhao ML, Gassman NR, Janoshazi AK, Stefanick DF, Horton JK, Krasich R, Longley MJ, Copeland WC, Griffith JD, Wilson SH. DNA polymerase β: A missing link of the base excision repair machinery in mammalian mitochondria. DNA Repair (Amst) 2017; 60:77-88. [PMID: 29100041 PMCID: PMC5919216 DOI: 10.1016/j.dnarep.2017.10.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Mitochondrial genome integrity is fundamental to mammalian cell viability. Since mitochondrial DNA is constantly under attack from oxygen radicals released during ATP production, DNA repair is vital in removing oxidatively generated lesions in mitochondrial DNA, but the presence of a strong base excision repair system has not been demonstrated. Here, we addressed the presence of such a system in mammalian mitochondria involving the primary base lesion repair enzyme DNA polymerase (pol) β. Pol β was localized to mammalian mitochondria by electron microscopic-immunogold staining, immunofluorescence co-localization and biochemical experiments. Extracts from purified mitochondria exhibited base excision repair activity that was dependent on pol β. Mitochondria from pol β-deficient mouse fibroblasts had compromised DNA repair and showed elevated levels of superoxide radicals after hydrogen peroxide treatment. Mitochondria in pol β-deficient fibroblasts displayed altered morphology by electron microscopy. These results indicate that mammalian mitochondria contain an efficient base lesion repair system mediated in part by pol β and thus pol β plays a role in preserving mitochondrial genome stability.
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Affiliation(s)
- Rajendra Prasad
- Genome Integrity and Structural Biology Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA
| | - Melike Çağlayan
- Genome Integrity and Structural Biology Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA
| | - Da-Peng Dai
- Genome Integrity and Structural Biology Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA
| | - Cristina A Nadalutti
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ming-Lang Zhao
- Genome Integrity and Structural Biology Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA
| | - Natalie R Gassman
- Genome Integrity and Structural Biology Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA; University of South Alabama Mitchell Cancer Institute, 1660 Springhill Ave, Mobile, AL 36604, USA
| | - Agnes K Janoshazi
- Signal Transduction Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA
| | - Donna F Stefanick
- Genome Integrity and Structural Biology Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA
| | - Julie K Horton
- Genome Integrity and Structural Biology Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA
| | - Rachel Krasich
- Genome Integrity and Structural Biology Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA
| | - Matthew J Longley
- Genome Integrity and Structural Biology Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA
| | - Jack D Griffith
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Samuel H Wilson
- Genome Integrity and Structural Biology Laboratory, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA.
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12
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Jia PP, Junaid M, Ma YB, Ahmad F, Jia YF, Li WG, Pei DS. Role of human DNA2 (hDNA2) as a potential target for cancer and other diseases: A systematic review. DNA Repair (Amst) 2017; 59:9-19. [PMID: 28903076 DOI: 10.1016/j.dnarep.2017.09.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 08/29/2017] [Accepted: 09/01/2017] [Indexed: 11/28/2022]
Abstract
DNA nuclease/helicase 2 (DNA2), a multi-functional protein protecting the high fidelity of genomic transmission, plays critical roles in DNA replication and repair processes. In the maturation of Okazaki fragments, DNA2 acts synergistically with other enzymes to cleave the DNA-RNA primer flaps via different pathways. DNA2 is also involved in the stability of mitochondrial DNA and the maintenance of telomeres. Moreover, DNA2 potentially participates in controlling the cell cycle by repairing the DNA replication faults at main checkpoints. In addition, previous evidences demonstrated that DNA2 also functions in the repair process of DNA damages, such as base excision repair (BER). Currently, large studies revealed the structures and functions of DNA2 in prokaryotes and unicellular eukaryotes, such as bacteria and yeast. However, the studies that highlighted the functions of human DNA2 (hDNA2) and the relationships with other multifunctional proteins are still elusive, and more precise investigations are immensely needed. Therefore, this review mainly encompasses the key functions of DNA2 in human cells with various aspects, especially focusing on the genome integrity, and also generalizes the recent insights to the mechanisms related to the occurrence of cancer and other diseases potentially linked to the mutations in DNA2.
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Affiliation(s)
- Pan-Pan Jia
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 401122, China; College of Life Science, Henan Normal University, Xinxiang 453007, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Muhammad Junaid
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 401122, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yan-Bo Ma
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 401122, China
| | - Farooq Ahmad
- Sustainable Development Study Centre, GC University Lahore, Pakistan
| | - Yong-Fang Jia
- College of Life Science, Henan Normal University, Xinxiang 453007, China
| | - Wei-Guo Li
- College of Life Science, Henan Normal University, Xinxiang 453007, China.
| | - De-Sheng Pei
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 401122, China.
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13
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Pawłowska E, Szczepanska J, Blasiak J. DNA2-An Important Player in DNA Damage Response or Just Another DNA Maintenance Protein? Int J Mol Sci 2017; 18:ijms18071562. [PMID: 28718810 PMCID: PMC5536050 DOI: 10.3390/ijms18071562] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 07/13/2017] [Accepted: 07/17/2017] [Indexed: 02/01/2023] Open
Abstract
The human DNA2 (DNA replication helicase/nuclease 2) protein is expressed in both the nucleus and mitochondria, where it displays ATPase-dependent nuclease and helicase activities. DNA2 plays an important role in the removing of long flaps in DNA replication and long-patch base excision repair (LP-BER), interacting with the replication protein A (RPA) and the flap endonuclease 1 (FEN1). DNA2 can promote the restart of arrested replication fork along with Werner syndrome ATP-dependent helicase (WRN) and Bloom syndrome protein (BLM). In mitochondria, DNA2 can facilitate primer removal during strand-displacement replication. DNA2 is involved in DNA double strand (DSB) repair, in which it is complexed with BLM, RPA and MRN for DNA strand resection required for homologous recombination repair. DNA2 can be a major protein involved in the repair of complex DNA damage containing a DSB and a 5' adduct resulting from a chemical group bound to DNA 5' ends, created by ionizing radiation and several anticancer drugs, including etoposide, mitoxantrone and some anthracyclines. The role of DNA2 in telomere end maintenance and cell cycle regulation suggests its more general role in keeping genomic stability, which is impaired in cancer. Therefore DNA2 can be an attractive target in cancer therapy. This is supported by enhanced expression of DNA2 in many cancer cell lines with oncogene activation and premalignant cells. Therefore, DNA2 can be considered as a potential marker, useful in cancer therapy. DNA2, along with PARP1 inhibition, may be considered as a potential target for inducing synthetic lethality, a concept of killing tumor cells by targeting two essential genes.
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Affiliation(s)
- Elzbieta Pawłowska
- Department of Orthodontics, Medical University of Lodz, 92-216 Lodz, Poland.
| | - Joanna Szczepanska
- Department of Pediatric Dentistry, Medical University of Lodz, 92-216 Lodz, Poland.
| | - Janusz Blasiak
- Department of Molecular Genetics, Faculty of Biology and Environmental Protection, University of Lodz, 90-236 Lodz, Poland.
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14
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Saki M, Prakash A. DNA damage related crosstalk between the nucleus and mitochondria. Free Radic Biol Med 2017; 107:216-227. [PMID: 27915046 PMCID: PMC5449269 DOI: 10.1016/j.freeradbiomed.2016.11.050] [Citation(s) in RCA: 114] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 10/25/2016] [Accepted: 11/29/2016] [Indexed: 12/18/2022]
Abstract
The electron transport chain is the primary pathway by which a cell generates energy in the form of ATP. Byproducts of this process produce reactive oxygen species that can cause damage to mitochondrial DNA. If not properly repaired, the accumulation of DNA damage can lead to mitochondrial dysfunction linked to several human disorders including neurodegenerative diseases and cancer. Mitochondria are able to combat oxidative DNA damage via repair mechanisms that are analogous to those found in the nucleus. Of the repair pathways currently reported in the mitochondria, the base excision repair pathway is the most comprehensively described. Proteins that are involved with the maintenance of mtDNA are encoded by nuclear genes and translocate to the mitochondria making signaling between the nucleus and mitochondria imperative. In this review, we discuss the current understanding of mitochondrial DNA repair mechanisms and also highlight the sensors and signaling pathways that mediate crosstalk between the nucleus and mitochondria in the event of mitochondrial stress.
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Affiliation(s)
- Mohammad Saki
- Mitchell Cancer Institute, The University of South Alabama, 1660 Springhill Avenue, Mobile, AL 36604, United States
| | - Aishwarya Prakash
- Mitchell Cancer Institute, The University of South Alabama, 1660 Springhill Avenue, Mobile, AL 36604, United States.
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15
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Krasich R, Copeland WC. DNA polymerases in the mitochondria: A critical review of the evidence. FRONT BIOSCI-LANDMRK 2017; 22:692-709. [PMID: 27814640 PMCID: PMC5485829 DOI: 10.2741/4510] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Since 1970, the DNA polymerase gamma (PolG) has been known to be the DNA polymerase responsible for replication and repair of mitochondrial DNA, and until recently it was generally accepted that this was the only polymerase present in mitochondria. However, recent data has challenged that opinion, as several polymerases are now proposed to have activity in mitochondria. To date, their exact role of these other DNA polymerases is unclear and the amount of evidence supporting their role in mitochondria varies greatly. Further complicating matters, no universally accepted standards have been set for definitive proof of the mitochondrial localization of a protein. To gain an appreciation of these newly proposed DNA polymerases in the mitochondria, we review the evidence and standards needed to establish the role of a polymerase in the mitochondria. Employing PolG as an example, we established a list of criteria necessary to verify the existence and function of new mitochondrial proteins. We then apply this criteria towards several other putative mitochondrial polymerases. While there is still a lot left to be done in this exciting new direction, it is clear that PolG is not acting alone in mitochondria, opening new doors for potential replication and repair mechanisms.
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Affiliation(s)
- Rachel Krasich
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, 111 T.W. Alexander Dr., Bldg. 101, Rm. E316, Research Triangle Park, NC 27709,
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16
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Van Houten B, Hunter SE, Meyer JN. Mitochondrial DNA damage induced autophagy, cell death, and disease. Front Biosci (Landmark Ed) 2016; 21:42-54. [PMID: 26709760 DOI: 10.2741/4375] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Mammalian mitochondria contain multiple small genomes. While these organelles have efficient base excision removal of oxidative DNA lesions and alkylation damage, many DNA repair systems that work on nuclear DNA damage are not active in mitochondria. What is the fate of DNA damage in the mitochondria that cannot be repaired or that overwhelms the repair system? Some forms of mitochondrial DNA damage can apparently trigger mitochondrial DNA destruction, either via direct degradation or through specific forms of autophagy, such as mitophagy. However, accumulation of certain types of mitochondrial damage, in the absence of DNA ligase III (Lig3) or exonuclease G (EXOG), can directly trigger cell death. This review examines the cellular effects of persistent damage to mitochondrial genomes and discusses the very different cell fates that occur in response to different kinds of damage.
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Affiliation(s)
- Bennett Van Houten
- Department of Pharmacology Chemical Biology, University of Pittsburgh, 15213-1863,
| | - Senyene E Hunter
- School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27516
| | - Joel N Meyer
- Nicholas School of the Environment, Duke University, Durham, NC 27708-0328
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17
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Lodi T, Dallabona C, Nolli C, Goffrini P, Donnini C, Baruffini E. DNA polymerase γ and disease: what we have learned from yeast. Front Genet 2015; 6:106. [PMID: 25852747 PMCID: PMC4362329 DOI: 10.3389/fgene.2015.00106] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 03/02/2015] [Indexed: 11/16/2022] Open
Abstract
Mip1 is the Saccharomyces cerevisiae DNA polymerase γ (Pol γ), which is responsible for the replication of mitochondrial DNA (mtDNA). It belongs to the family A of the DNA polymerases and it is orthologs to human POLGA. In humans, mutations in POLG(1) cause many mitochondrial pathologies, such as progressive external ophthalmoplegia (PEO), Alpers' syndrome, and ataxia-neuropathy syndrome, all of which present instability of mtDNA, which results in impaired mitochondrial function in several tissues with variable degrees of severity. In this review, we summarize the genetic and biochemical knowledge published on yeast mitochondrial DNA polymerase from 1989, when the MIP1 gene was first cloned, up until now. The role of yeast is particularly emphasized in (i) validating the pathological mutations found in human POLG and modeled in MIP1, (ii) determining the molecular defects caused by these mutations and (iii) finding the correlation between mutations/polymorphisms in POLGA and mtDNA toxicity induced by specific drugs. We also describe recent findings regarding the discovery of molecules able to rescue the phenotypic defects caused by pathological mutations in Mip1, and the construction of a model system in which the human Pol γ holoenzyme is expressed in yeast and complements the loss of Mip1.
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Affiliation(s)
- Tiziana Lodi
- Department of Life Sciences, University of Parma Parma, Italy
| | | | - Cecilia Nolli
- Department of Life Sciences, University of Parma Parma, Italy
| | - Paola Goffrini
- Department of Life Sciences, University of Parma Parma, Italy
| | - Claudia Donnini
- Department of Life Sciences, University of Parma Parma, Italy
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18
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Krokan HE, Sætrom P, Aas PA, Pettersen HS, Kavli B, Slupphaug G. Error-free versus mutagenic processing of genomic uracil—Relevance to cancer. DNA Repair (Amst) 2014; 19:38-47. [DOI: 10.1016/j.dnarep.2014.03.028] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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19
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Abstract
Human mitochondria harbor an essential, high copy number, 16,569 base pair, circular DNA genome that encodes 13 gene products required for electron transport and oxidative phosphorylation. Mutation of this genome can compromise cellular respiration, ultimately resulting in a variety of progressive metabolic diseases collectively known as 'mitochondrial diseases'. Mutagenesis of mtDNA and the persistence of mtDNA mutations in cells and tissues is a complex topic, involving the interplay of DNA replication, DNA damage and repair, purifying selection, organelle dynamics, mitophagy, and aging. We briefly review these general elements that affect maintenance of mtDNA, and we focus on nuclear genes encoding the mtDNA replication machinery that can perturb the genetic integrity of the mitochondrial genome.
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Affiliation(s)
- William C Copeland
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, Durham, NC 27709, USA.
| | - Matthew J Longley
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, Durham, NC 27709, USA
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20
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Mechanism of homologous recombination and implications for aging-related deletions in mitochondrial DNA. Microbiol Mol Biol Rev 2014; 77:476-96. [PMID: 24006472 DOI: 10.1128/mmbr.00007-13] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Homologous recombination is a universal process, conserved from bacteriophage to human, which is important for the repair of double-strand DNA breaks. Recombination in mitochondrial DNA (mtDNA) was documented more than 4 decades ago, but the underlying molecular mechanism has remained elusive. Recent studies have revealed the presence of a Rad52-type recombination system of bacteriophage origin in mitochondria, which operates by a single-strand annealing mechanism independent of the canonical RecA/Rad51-type recombinases. Increasing evidence supports the notion that, like in bacteriophages, mtDNA inheritance is a coordinated interplay between recombination, repair, and replication. These findings could have profound implications for understanding the mechanism of mtDNA inheritance and the generation of mtDNA deletions in aging cells.
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21
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Alexeyev M, Shokolenko I, Wilson G, LeDoux S. The maintenance of mitochondrial DNA integrity--critical analysis and update. Cold Spring Harb Perspect Biol 2013; 5:a012641. [PMID: 23637283 DOI: 10.1101/cshperspect.a012641] [Citation(s) in RCA: 320] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
DNA molecules in mitochondria, just like those in the nucleus of eukaryotic cells, are constantly damaged by noxious agents. Eukaryotic cells have developed efficient mechanisms to deal with this assault. The process of DNA repair in mitochondria, initially believed nonexistent, has now evolved into a mature area of research. In recent years, it has become increasingly appreciated that mitochondria possess many of the same DNA repair pathways that the nucleus does. Moreover, a unique pathway that is enabled by high redundancy of the mitochondrial DNA and allows for the disposal of damaged DNA molecules operates in this organelle. In this review, we attempt to present a unified view of our current understanding of the process of DNA repair in mitochondria with an emphasis on issues that appear controversial.
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Affiliation(s)
- Mikhail Alexeyev
- Department of Cell Biology and Neuroscience, University of South Alabama, Mobile, AL 36688, USA
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22
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Ronchi D, Di Fonzo A, Lin W, Bordoni A, Liu C, Fassone E, Pagliarani S, Rizzuti M, Zheng L, Filosto M, Ferrò M, Ranieri M, Magri F, Peverelli L, Li H, Yuan YC, Corti S, Sciacco M, Moggio M, Bresolin N, Shen B, Comi G. Mutations in DNA2 link progressive myopathy to mitochondrial DNA instability. Am J Hum Genet 2013; 92:293-300. [PMID: 23352259 DOI: 10.1016/j.ajhg.2012.12.014] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2012] [Revised: 11/05/2012] [Accepted: 12/27/2012] [Indexed: 11/24/2022] Open
Abstract
Syndromes associated with multiple mtDNA deletions are due to different molecular defects that can result in a wide spectrum of predominantly adult-onset clinical presentations, ranging from progressive external ophthalmoplegia (PEO) to multisystemic disorders of variable severity. The autosomal-dominant form of PEO is genetically heterogeneous. Recently, causative mutations have been reported in several nuclear genes that encode proteins of the mtDNA replisome machinery (POLG, POLG2, and C10orf2) or that are involved in pathways for the synthesis of deoxyribonuclotides (ANT1 and RRM2B). Despite these findings, putative mutations remain unknown in half of the subjects with PEO. We report the identification, by exome sequencing, of mutations in DNA2 in adult-onset individuals with a form of mitochondrial myopathy featuring instability of muscle mtDNA. DNA2 encodes a helicase/nuclease family member that is most likely involved in mtDNA replication, as well as in the long-patch base-excision repair (LP-BER) pathway. In vitro biochemical analysis of purified mutant proteins revealed a severe impairment of nuclease, helicase, and ATPase activities. These results implicate human DNA2 and the LP-BER pathway in the pathogenesis of adult-onset disorders of mtDNA maintenance.
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23
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Mitochondrial and nuclear DNA damage and repair in age-related macular degeneration. Int J Mol Sci 2013; 14:2996-3010. [PMID: 23434654 PMCID: PMC3588027 DOI: 10.3390/ijms14022996] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 01/04/2013] [Accepted: 01/25/2013] [Indexed: 12/28/2022] Open
Abstract
Aging and oxidative stress seem to be the most important factors in the pathogenesis of age-related macular degeneration (AMD), a condition affecting many elderly people in the developed world. However, aging is associated with the accumulation of oxidative damage in many biomolecules, including DNA. Furthermore, mitochondria may be especially important in this process because the reactive oxygen species produced in their electron transport chain can damage cellular components. Therefore, the cellular response to DNA damage, expressed mainly through DNA repair, may play an important role in AMD etiology. In several studies the increase in mitochondrial DNA (mtDNA) damage and mutations, and the decrease in the efficacy of DNA repair have been correlated with the occurrence and the stage of AMD. It has also been shown that mitochondrial DNA accumulates more DNA lesions than nuclear DNA in AMD. However, the DNA damage response in mitochondria is executed by nucleus-encoded proteins, and thus mutagenesis in nuclear DNA (nDNA) may affect the ability to respond to mutagenesis in its mitochondrial counterpart. We reported that lymphocytes from AMD patients displayed a higher amount of total endogenous basal and oxidative DNA damage, exhibited a higher sensitivity to hydrogen peroxide and UV radiation, and repaired the lesions induced by these factors less effectively than did cells from control individuals. We postulate that poor efficacy of DNA repair (i.e., is impaired above average for a particular age) when combined with the enhanced sensitivity of retinal pigment epithelium cells to environmental stress factors, contributes to the pathogenesis of AMD. Collectively, these data suggest that the cellular response to both mitochondrial and nuclear DNA damage may play an important role in AMD pathogenesis.
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24
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Loss-of-function mutations in MGME1 impair mtDNA replication and cause multisystemic mitochondrial disease. Nat Genet 2013; 45:214-9. [PMID: 23313956 DOI: 10.1038/ng.2501] [Citation(s) in RCA: 170] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 11/28/2012] [Indexed: 12/17/2022]
Abstract
Known disease mechanisms in mitochondrial DNA (mtDNA) maintenance disorders alter either the mitochondrial replication machinery (POLG, POLG2 and C10orf2) or the biosynthesis pathways of deoxyribonucleoside 5'-triphosphates for mtDNA synthesis. However, in many of these disorders, the underlying genetic defect has yet to be discovered. Here, we identify homozygous nonsense and missense mutations in the orphan gene C20orf72 in three families with a mitochondrial syndrome characterized by external ophthalmoplegia, emaciation and respiratory failure. Muscle biopsies showed mtDNA depletion and multiple mtDNA deletions. C20orf72, hereafter MGME1 (mitochondrial genome maintenance exonuclease 1), encodes a mitochondrial RecB-type exonuclease belonging to the PD-(D/E)XK nuclease superfamily. We show that MGME1 cleaves single-stranded DNA and processes DNA flap substrates. Fibroblasts from affected individuals do not repopulate after chemically induced mtDNA depletion. They also accumulate intermediates of stalled replication and show increased levels of 7S DNA, as do MGME1-depleted cells. Thus, we show that MGME1-mediated mtDNA processing is essential for mitochondrial genome maintenance.
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25
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Mason PA, Cox LS. The role of DNA exonucleases in protecting genome stability and their impact on ageing. AGE (DORDRECHT, NETHERLANDS) 2012; 34:1317-1340. [PMID: 21948156 PMCID: PMC3528374 DOI: 10.1007/s11357-011-9306-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 08/19/2011] [Indexed: 05/30/2023]
Abstract
Exonucleases are key enzymes involved in many aspects of cellular metabolism and maintenance and are essential to genome stability, acting to cleave DNA from free ends. Exonucleases can act as proof-readers during DNA polymerisation in DNA replication, to remove unusual DNA structures that arise from problems with DNA replication fork progression, and they can be directly involved in repairing damaged DNA. Several exonucleases have been recently discovered, with potentially critical roles in genome stability and ageing. Here we discuss how both intrinsic and extrinsic exonuclease activities contribute to the fidelity of DNA polymerases in DNA replication. The action of exonucleases in processing DNA intermediates during normal and aberrant DNA replication is then assessed, as is the importance of exonucleases in repair of double-strand breaks and interstrand crosslinks. Finally we examine how exonucleases are involved in maintenance of mitochondrial genome stability. Throughout the review, we assess how nuclease mutation or loss predisposes to a range of clinical diseases and particularly ageing.
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Affiliation(s)
- Penelope A. Mason
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Lynne S. Cox
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
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26
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Nuclear and mitochondrial DNA repair in selected eukaryotic aging model systems. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2012; 2012:282438. [PMID: 23050036 PMCID: PMC3462412 DOI: 10.1155/2012/282438] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2012] [Accepted: 08/26/2012] [Indexed: 12/21/2022]
Abstract
Knowledge about the different mechanisms underlying the aging process has increased exponentially in the last decades. The fact that the basic mechanisms involved in the aging process are believed to be universal allows the use of different model systems, from the simplest eukaryotic cells such as fungi to the most complex organisms such as mice or human. As our knowledge on the aging mechanisms in those model systems increases, our understanding of human aging and the potential interventions that we could approach rise significantly. Among the different mechanisms that have been implicated in the aging process, DNA repair is one of the processes which have been suggested to play an important role. Here, we review the latest investigations supporting the role of these mechanisms in the aging process, stressing how beneficial the use of different model systems is. We discuss how human genetic studies as well as several investigations on mammalian models and simpler eukaryotic organisms have contributed to a better understanding of the involvement of DNA repair mechanisms in aging.
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27
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Kasiviswanathan R, Collins TRL, Copeland WC. The interface of transcription and DNA replication in the mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1819:970-8. [PMID: 22207204 DOI: 10.1016/j.bbagrm.2011.12.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2011] [Revised: 12/09/2011] [Accepted: 12/12/2011] [Indexed: 11/30/2022]
Abstract
DNA replication of the mitochondrial genome is unique in that replication is not primed by RNA derived from dedicated primases, but instead by extension of processed RNA transcripts laid down by the mitochondrial RNA polymerase. Thus, the RNA polymerase serves not only to generate the transcripts but also the primers needed for mitochondrial DNA replication. The interface between this transcription and DNA replication is not well understood but must be highly regulated and coordinated to carry out both mitochondrial DNA replication and transcription. This review focuses on the extension of RNA primers for DNA replication by the replication machinery and summarizes the current models of DNA replication in mitochondria as well as the proteins involved in mitochondrial DNA replication, namely, the DNA polymerase γ and its accessory subunit, the mitochondrial DNA helicase, the single-stranded DNA binding protein, topoisomerase I and IIIα and RNaseH1. This article is part of a Special Issue entitled: Mitochondrial Gene Expression.
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Affiliation(s)
- Rajesh Kasiviswanathan
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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28
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Sykora P, Wilson DM, Bohr VA. Repair of persistent strand breaks in the mitochondrial genome. Mech Ageing Dev 2011; 133:169-75. [PMID: 22138376 DOI: 10.1016/j.mad.2011.11.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 11/03/2011] [Accepted: 11/14/2011] [Indexed: 10/14/2022]
Abstract
Oxidative DNA damage has been attributed to increased cancer incidence and premature aging phenotypes. Reactive oxygen species (ROS) are unavoidable byproducts of oxidative phosphorylation and are the major contributors of endogenous oxidative damage. To prevent the negative effects of ROS, cells have developed DNA repair mechanisms designed to specifically combat endogenous DNA modifications. The base excision repair (BER) pathway is primarily responsible for the repair of small non-helix distorting lesions and DNA single strand breaks. This repair pathway is found in all organisms, and in mammalian cells, consists of three related sub-pathways: short patch (SP-BER), long patch (LP-BER) and single strand break repair (SSBR). While much is known about nuclear BER, comparatively little is known about this pathway in the mitochondria, particularly the LP-BER and SSBR sub-pathways. There are a number of proteins that have recently been found to be involved in mitochondrial BER, including Cockayne syndrome proteins A and B (CSA and CSB), aprataxin (APTX), tryosyl-DNA phosphodiesterase 1 (TDP1), flap endonuclease 1 (FEN-1) and exonuclease G (EXOG). These significant advances in mitochondrial DNA repair may open new avenues in the management and treatment of a number of neurological disorders associated with mitochondrial dysfunction, and will be reviewed in further detail herein.
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Affiliation(s)
- Peter Sykora
- NIH Biomedical Research Center, 251 Bayview Boulevard, Baltimore, MD 21224, USA.
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29
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Abstract
Completion of lagging strand DNA synthesis requires processing of up to 50 million Okazaki fragments per cell cycle in mammalian cells. Even in yeast, the Okazaki fragment maturation happens approximately a million times during a single round of DNA replication. Therefore, efficient processing of Okazaki fragments is vital for DNA replication and cell proliferation. During this process, primase-synthesized RNA/DNA primers are removed, and Okazaki fragments are joined into an intact lagging strand DNA. The processing of RNA/DNA primers requires a group of structure-specific nucleases typified by flap endonuclease 1 (FEN1). Here, we summarize the distinct roles of these nucleases in different pathways for removal of RNA/DNA primers. Recent findings reveal that Okazaki fragment maturation is highly coordinated. The dynamic interactions of polymerase δ, FEN1 and DNA ligase I with proliferating cell nuclear antigen allow these enzymes to act sequentially during Okazaki fragment maturation. Such protein-protein interactions may be regulated by post-translational modifications. We also discuss studies using mutant mouse models that suggest two distinct cancer etiological mechanisms arising from defects in different steps of Okazaki fragment maturation. Mutations that affect the efficiency of RNA primer removal may result in accumulation of unligated nicks and DNA double-strand breaks. These DNA strand breaks can cause varying forms of chromosome aberrations, contributing to development of cancer that associates with aneuploidy and gross chromosomal rearrangement. On the other hand, mutations that impair editing out of polymerase α incorporation errors result in cancer displaying a strong mutator phenotype.
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Affiliation(s)
- Li Zheng
- Department of Cancer Biology, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA 91010, USA
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30
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Fortini BK, Pokharel S, Polaczek P, Balakrishnan L, Bambara RA, Campbell JL. Characterization of the endonuclease and ATP-dependent flap endo/exonuclease of Dna2. J Biol Chem 2011; 286:23763-70. [PMID: 21572043 DOI: 10.1074/jbc.m111.243071] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two processes, DNA replication and DNA damage repair, are key to maintaining genomic fidelity. The Dna2 enzyme lies at the heart of both of these processes, acting in conjunction with flap endonuclease 1 and replication protein A in DNA lagging strand replication and with BLM/Sgs1 and MRN/X in double strand break repair. In vitro, Dna2 helicase and flap endo/exonuclease activities require an unblocked 5' single-stranded DNA end to unwind or cleave DNA. In this study we characterize a Dna2 nuclease activity that does not require, and in fact can create, 5' single-stranded DNA ends. Both endonuclease and flap endo/exonuclease are abolished by the Dna2-K677R mutation, implicating the same active site in catalysis. In addition, we define a novel ATP-dependent flap endo/exonuclease activity, which is observed only in the presence of Mn(2+). The endonuclease is blocked by ATP and is thus experimentally distinguishable from the flap endo/exonuclease function. Thus, Dna2 activities resemble those of RecB and AddAB nucleases even more closely than previously appreciated. This work has important implications for understanding the mechanism of action of Dna2 in multiprotein complexes, where dissection of enzymatic activities and cofactor requirements of individual components contributing to orderly and precise execution of multistep replication/repair processes depends on detailed characterization of each individual activity.
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Affiliation(s)
- Barbara K Fortini
- Braun Laboratories, California Institute of Technology, Pasadena, California 91125, USA
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Stumpf JD, Copeland WC. Mitochondrial DNA replication and disease: insights from DNA polymerase γ mutations. Cell Mol Life Sci 2011; 68:219-33. [PMID: 20927567 PMCID: PMC3046768 DOI: 10.1007/s00018-010-0530-4] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 08/31/2010] [Accepted: 09/02/2010] [Indexed: 10/19/2022]
Abstract
DNA polymerase γ (pol γ), encoded by POLG, is responsible for replicating human mitochondrial DNA. About 150 mutations in the human POLG have been identified in patients with mitochondrial diseases such as Alpers syndrome, progressive external ophthalmoplegia, and ataxia-neuropathy syndromes. Because many of the mutations are described in single citations with no genotypic family history, it is important to ascertain which mutations cause or contribute to mitochondrial disease. The vast majority of data about POLG mutations has been generated from biochemical characterizations of recombinant pol γ. However, recently, the study of mitochondrial dysfunction in Saccharomyces cerevisiae and mouse models provides important in vivo evidence for the role of POLG mutations in disease. Also, the published 3D-structure of the human pol γ assists in explaining some of the biochemical and genetic properties of the mutants. This review summarizes the current evidence that identifies and explains disease-causing POLG mutations.
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Affiliation(s)
- Jeffrey D. Stumpf
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, 111 T.W. Alexander Dr., Bldg. 101, Rm. E316, Research Triangle Park, NC 27709 USA
| | - William C. Copeland
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, 111 T.W. Alexander Dr., Bldg. 101, Rm. E316, Research Triangle Park, NC 27709 USA
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Abstract
Human tyrosyl-DNA phosphodiesterase (TDP1) hydrolyzes the phosphodiester bond at a DNA 3'-end linked to a tyrosyl moiety and has been implicated in the repair of topoisomerase I (Top1)-DNA covalent complexes. TDP1 can also hydrolyze other 3'-end DNA alterations including 3'-phosphoglycolate and 3'-abasic sites, and exhibits 3'-nucleosidase activity indicating it may function as a general 3'-end-processing DNA repair enzyme. Here, using laser confocal microscopy, subcellular fractionation and biochemical analyses we demonstrate that a fraction of the TDP1 encoded by the nuclear TDP1 gene localizes to mitochondria. We also show that mitochondrial base excision repair depends on TDP1 activity and provide evidence that TDP1 is required for efficient repair of oxidative damage in mitochondrial DNA. Together, our findings provide evidence for TDP1 as a novel mitochondrial enzyme.
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Balakrishnan L, Polaczek P, Pokharel S, Campbell JL, Bambara RA. Dna2 exhibits a unique strand end-dependent helicase function. J Biol Chem 2010; 285:38861-8. [PMID: 20929864 DOI: 10.1074/jbc.m110.165191] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dna2 endonuclease/helicase participates in eukaryotic DNA transactions including cleavage of long flaps generated during Okazaki fragment processing. Its unusual substrate interaction consists of recognition and binding of the flap base, then threading over the 5'-end of the flap, and cleaving periodically to produce a terminal product ∼5 nt in length. Blocking the 5'-end prevents cleavage. The Dna2 ATP-driven 5' to 3' DNA helicase function promotes motion of Dna2 on the flap, presumably aiding its nuclease function. Here we demonstrate using two different nuclease-dead Dna2 mutants that on substrates simulating Okazaki fragments, Dna2 must thread onto an unblocked 5' flap to display helicase activity. This requirement is maintained on substrates with single-stranded regions thousands of nucleotides in length. To our knowledge this is the first description of a eukaryotic helicase that cannot load onto its tracking strand internally but instead must enter from the end. Biologically, the loading requirement likely helps the helicase to coordinate with the Dna2 nuclease function to prevent creation of undesirably long flaps during DNA transactions.
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Affiliation(s)
- Lata Balakrishnan
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
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de Souza-Pinto NC, Aamann MD, Kulikowicz T, Stevnsner TV, Bohr VA. Mitochondrial helicases and mitochondrial genome maintenance. Mech Ageing Dev 2010; 131:503-10. [PMID: 20576512 PMCID: PMC2933315 DOI: 10.1016/j.mad.2010.04.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Revised: 04/26/2010] [Accepted: 04/28/2010] [Indexed: 12/28/2022]
Abstract
Helicases are essential enzymes that utilize the energy of nucleotide hydrolysis to drive unwinding of nucleic acid duplexes. Helicases play roles in all aspects of DNA metabolism including DNA repair, DNA replication and transcription. The subcellular locations and functions of several helicases have been studied in detail; however, the roles of specific helicases in mitochondrial biology remain poorly characterized. This review presents important recent advances in identifying and characterizing mitochondrial helicases, some of which also operate in the nucleus.
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Affiliation(s)
- Nadja C de Souza-Pinto
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
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Kang YH, Lee CH, Seo YS. Dna2 on the road to Okazaki fragment processing and genome stability in eukaryotes. Crit Rev Biochem Mol Biol 2010; 45:71-96. [PMID: 20131965 DOI: 10.3109/10409230903578593] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
DNA replication is a primary mechanism for maintaining genome integrity, but it serves this purpose best by cooperating with other proteins involved in DNA repair and recombination. Unlike leading strand synthesis, lagging strand synthesis has a greater risk of faulty replication for several reasons: First, a significant part of DNA is synthesized by polymerase alpha, which lacks a proofreading function. Second, a great number of Okazaki fragments are synthesized, processed and ligated per cell division. Third, the principal mechanism of Okazaki fragment processing is via generation of flaps, which have the potential to form a variety of structures in their sequence context. Finally, many proteins for the lagging strand interact with factors involved in repair and recombination. Thus, lagging strand DNA synthesis could be the best example of a converging place of both replication and repair proteins. To achieve the risky task with extraordinary fidelity, Okazaki fragment processing may depend on multiple layers of redundant, but connected pathways. An essential Dna2 endonuclease/helicase plays a pivotal role in processing common structural intermediates that occur during diverse DNA metabolisms (e.g. lagging strand synthesis and telomere maintenance). Many roles of Dna2 suggest that the preemptive removal of long or structured flaps ultimately contributes to genome maintenance in eukaryotes. In this review, we describe the function of Dna2 in Okazaki fragment processing, and discuss its role in the maintenance of genome integrity with an emphasis on its functional interactions with other factors required for genome maintenance.
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Affiliation(s)
- Young-Hoon Kang
- Center for DNA Replication and Genome Instability, Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Korea
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Liu P, Demple B. DNA repair in mammalian mitochondria: Much more than we thought? ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2010; 51:417-426. [PMID: 20544882 DOI: 10.1002/em.20576] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
For many years, the repair of most damage in mitochondrial DNA (mtDNA) was thought limited to short-patch base excision repair (SP-BER), which replaces a single nucleotide by the sequential action of DNA glycosylases, an apurinic/apyrimidinic (AP) endonuclease, the mitochondrial DNA polymerase gamma, an abasic lyase activity, and mitochondrial DNA ligase. However, the likely array of lesions inflicted on mtDNA by oxygen radicals and the possibility of replication errors and disruptions indicated that such a restricted repair repertoire would be inadequate. Recent studies have considerably expanded our knowledge of mtDNA repair to include long-patch base excision repair (LP-BER), mismatch repair, and homologous recombination and nonhomologous end-joining. In addition, elimination of mutagenic 8-oxodeoxyguanosine triphosphate (8-oxodGTP) helps prevent cell death due to the accumulation of this oxidation product in mtDNA. Although it was suspected for many years that irreparably damaged mtDNA might be targeted for degradation, only recently was clear evidence provided for this hypothesis. Therefore, multiple DNA repair pathways and controlled degradation of mtDNA function together to maintain the integrity of mitochondrial genome.
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Affiliation(s)
- Pingfang Liu
- Department of Radiation Oncology, Dana Farber Cancer Institute, Boston, Massachusetts, USA
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Chung WH, Zhu Z, Papusha A, Malkova A, Ira G. Defective resection at DNA double-strand breaks leads to de novo telomere formation and enhances gene targeting. PLoS Genet 2010; 6:e1000948. [PMID: 20485519 PMCID: PMC2869328 DOI: 10.1371/journal.pgen.1000948] [Citation(s) in RCA: 143] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Accepted: 04/12/2010] [Indexed: 11/19/2022] Open
Abstract
The formation of single-stranded DNA (ssDNA) at double-strand break (DSB) ends is essential in repair by homologous recombination and is mediated by DNA helicases and nucleases. Here we estimated the length of ssDNA generated during DSB repair and analyzed the consequences of elimination of processive resection pathways mediated by Sgs1 helicase and Exo1 nuclease on DSB repair fidelity. In wild-type cells during allelic gene conversion, an average of 2-4 kb of ssDNA accumulates at each side of the break. Longer ssDNA is formed during ectopic recombination or break-induced replication (BIR), reflecting much slower repair kinetics. This relatively extensive resection may help determine sequences involved in homology search and prevent recombination within short DNA repeats next to the break. In sgs1Delta exo1Delta mutants that form only very short ssDNA, allelic gene conversion decreases 5-fold and DSBs are repaired by BIR or de novo telomere formation resulting in loss of heterozygosity. The absence of the telomerase inhibitor, PIF1, increases de novo telomere pathway usage to about 50%. Accumulation of Cdc13, a protein recruiting telomerase, at the break site increases in sgs1Delta exo1Delta, and the requirement of the Ku complex for new telomere formation is partially bypassed. In contrast to this decreased and alternative DSB repair, the efficiency and accuracy of gene targeting increases dramatically in sgs1Delta exo1Delta cells, suggesting that transformed DNA is very stable in these mutants. Altogether these data establish a new role for processive resection in the fidelity of DSB repair.
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Affiliation(s)
- Woo-Hyun Chung
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Zhu Zhu
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Alma Papusha
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Anna Malkova
- Department of Biology, School of Science, Indiana University–Purdue University Indianapolis, Indianapolis, Indiana, United States of America
| | - Grzegorz Ira
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
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Abstract
Since mutations in mitochondrial DNA (mtDNA) have been shown to be a cause of many mitochondrial diseases as well as aging, it is important to understand the origin of these mutations and how replication proteins modulate this process. DNA polymerase gamma (pol gamma) is the polymerase that is responsible for replication and repair of mtDNA. Pol gamma has three main roles in mtDNA maintenance and mutagenesis. As the only known DNA polymerase in mitochondria, pol gamma is required for all replication and repair functions and is the main source of errors produced in human mtDNA. Pol gamma is also sensitive to a host of antiviral nucleoside analogs used to treat HIV-1 infections, which can cause an induced mitochondrial toxicity. Finally, the gene for pol gamma, POLG, is a genetic locus for several mitochondrial disease with over 150 genetic mutations currently identified.
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Balakrishnan L, Stewart J, Polaczek P, Campbell JL, Bambara RA. Acetylation of Dna2 endonuclease/helicase and flap endonuclease 1 by p300 promotes DNA stability by creating long flap intermediates. J Biol Chem 2009; 285:4398-404. [PMID: 20019387 DOI: 10.1074/jbc.m109.086397] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Flap endonuclease 1 (FEN1) and Dna2 endonuclease/helicase (Dna2) sequentially coordinate their nuclease activities for efficient resolution of flap structures that are created during the maturation of Okazaki fragments and repair of DNA damage. Acetylation of FEN1 by p300 inhibits its endonuclease activity, impairing flap cleavage, a seemingly undesirable effect. We now show that p300 also acetylates Dna2, stimulating its 5'-3' endonuclease, the 5'-3' helicase, and DNA-dependent ATPase activities. Furthermore, acetylated Dna2 binds its DNA substrates with higher affinity. Differential regulation of the activities of the two endonucleases by p300 indicates a mechanism in which the acetylase promotes formation of longer flaps in the cell at the same time as ensuring correct processing. Intentional formation of longer flaps mediated by p300 in an active chromatin environment would increase the resynthesis patch size, providing increased opportunity for incorrect nucleotide removal during DNA replication and damaged nucleotide removal during DNA repair. For example, altering the ratio between short and long flap Okazaki fragment processing would be a mechanism for better correction of the error-prone synthesis catalyzed by DNA polymerase alpha.
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Affiliation(s)
- Lata Balakrishnan
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
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Holt IJ. Mitochondrial DNA replication and repair: all a flap. Trends Biochem Sci 2009; 34:358-65. [PMID: 19559620 DOI: 10.1016/j.tibs.2009.03.007] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 03/04/2009] [Accepted: 03/10/2009] [Indexed: 10/20/2022]
Abstract
The mitochondrial genome is dwarfed by its neighbour in the nucleus, and, thus, it has been sensible for far more resources to be invested in the study of nuclear, rather than mitochondrial, DNA metabolism. Furthermore, few researchers have considered using mitochondrial DNA (mtDNA) as a model system for nuclear DNA metabolism. A quick look into the history of mtDNA provides ready answers as to why this was the case; however, recently mitochondria have been found to contain several nuclear replication and repair factors, so is there any potential to adopt the mitochondrion as a tool to unravel some of the intricacies of replication and repair in higher-order eukaryotes? Perhaps it is now time to invite the Cinderella genome to the ball.
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Affiliation(s)
- Ian J Holt
- MRC Mitochondrial Biology Unit, Cambridge, UK.
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