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Akbari M, Nilsen HL, Montaldo NP. Dynamic features of human mitochondrial DNA maintenance and transcription. Front Cell Dev Biol 2022; 10:984245. [PMID: 36158192 PMCID: PMC9491825 DOI: 10.3389/fcell.2022.984245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 08/02/2022] [Indexed: 12/03/2022] Open
Abstract
Mitochondria are the primary sites for cellular energy production and are required for many essential cellular processes. Mitochondrial DNA (mtDNA) is a 16.6 kb circular DNA molecule that encodes only 13 gene products of the approximately 90 different proteins of the respiratory chain complexes and an estimated 1,200 mitochondrial proteins. MtDNA is, however, crucial for organismal development, normal function, and survival. MtDNA maintenance requires mitochondrially targeted nuclear DNA repair enzymes, a mtDNA replisome that is unique to mitochondria, and systems that control mitochondrial morphology and quality control. Here, we provide an overview of the current literature on mtDNA repair and transcription machineries and discuss how dynamic functional interactions between the components of these systems regulate mtDNA maintenance and transcription. A profound understanding of the molecular mechanisms that control mtDNA maintenance and transcription is important as loss of mtDNA integrity is implicated in normal process of aging, inflammation, and the etiology and pathogenesis of a number of diseases.
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Affiliation(s)
- Mansour Akbari
- Department of Medical Biology, Faculty of Health Sciences, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Hilde Loge Nilsen
- Department of Clinical Molecular Biology, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Unit for precision medicine, Akershus University Hospital, Nordbyhagen, Norway
- Department of Microbiology, Oslo University Hospital, Oslo, Norway
| | - Nicola Pietro Montaldo
- Department of Clinical Molecular Biology, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- *Correspondence: Nicola Pietro Montaldo,
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2
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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: 8] [Impact Index Per Article: 4.0] [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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3
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Tomkinson AE, Naila T, Khattri Bhandari S. Altered DNA ligase activity in human disease. Mutagenesis 2021; 35:51-60. [PMID: 31630206 DOI: 10.1093/mutage/gez026] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 09/09/2019] [Indexed: 12/18/2022] Open
Abstract
The joining of interruptions in the phosphodiester backbone of DNA is critical to maintain genome stability. These breaks, which are generated as part of normal DNA transactions, such as DNA replication, V(D)J recombination and meiotic recombination as well as directly by DNA damage or due to DNA damage removal, are ultimately sealed by one of three human DNA ligases. DNA ligases I, III and IV each function in the nucleus whereas DNA ligase III is the sole enzyme in mitochondria. While the identification of specific protein partners and the phenotypes caused either by genetic or chemical inactivation have provided insights into the cellular functions of the DNA ligases and evidence for significant functional overlap in nuclear DNA replication and repair, different results have been obtained with mouse and human cells, indicating species-specific differences in the relative contributions of the DNA ligases. Inherited mutations in the human LIG1 and LIG4 genes that result in the generation of polypeptides with partial activity have been identified as the causative factors in rare DNA ligase deficiency syndromes that share a common clinical symptom, immunodeficiency. In the case of DNA ligase IV, the immunodeficiency is due to a defect in V(D)J recombination whereas the cause of the immunodeficiency due to DNA ligase I deficiency is not known. Overexpression of each of the DNA ligases has been observed in cancers. For DNA ligase I, this reflects increased proliferation. Elevated levels of DNA ligase III indicate an increased dependence on an alternative non-homologous end-joining pathway for the repair of DNA double-strand breaks whereas elevated level of DNA ligase IV confer radioresistance due to increased repair of DNA double-strand breaks by the major non-homologous end-joining pathway. Efforts to determine the potential of DNA ligase inhibitors as cancer therapeutics are on-going in preclinical cancer models.
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Affiliation(s)
- Alan E Tomkinson
- Departments of Internal Medicine and Molecular Genetics and Microbiology, and the University of New Mexico Comprehensive Cancer Center, University of New Mexico, Albuquerque, NM, USA
| | - Tasmin Naila
- Departments of Internal Medicine and Molecular Genetics and Microbiology, and the University of New Mexico Comprehensive Cancer Center, University of New Mexico, Albuquerque, NM, USA
| | - Seema Khattri Bhandari
- Departments of Internal Medicine and Molecular Genetics and Microbiology, and the University of New Mexico Comprehensive Cancer Center, University of New Mexico, Albuquerque, NM, USA
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Caracciolo D, Di Martino MT, Amodio N, Morelli E, Montesano M, Botta C, Scionti F, Talarico D, Altomare E, Gallo Cantafio ME, Zuccalà V, Maltese L, Todoerti K, Rossi M, Arbitrio M, Neri A, Tagliaferri P, Tassone P. miR-22 suppresses DNA ligase III addiction in multiple myeloma. Leukemia 2019; 33:487-498. [PMID: 30120376 PMCID: PMC6365379 DOI: 10.1038/s41375-018-0238-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 07/04/2018] [Accepted: 07/13/2018] [Indexed: 12/15/2022]
Abstract
Multiple myeloma (MM) is a hematologic malignancy characterized by high genomic instability. Here we provide evidence that hyper-activation of DNA ligase III (LIG3) is crucial for genomic instability and survival of MM cells. LIG3 mRNA expression in MM patients correlates with shorter survival and even increases with more advanced stage of disease. Knockdown of LIG3 impairs MM cells viability in vitro and in vivo, suggesting that neoplastic plasmacells are dependent on LIG3-driven repair. To investigate the mechanisms involved in LIG3 expression, we investigated the post-transcriptional regulation. We identified miR-22-3p as effective negative regulator of LIG3 in MM. Enforced expression of miR-22 in MM cells downregulated LIG3 protein, which in turn increased DNA damage inhibiting in vitro and in vivo cell growth. Taken together, our findings demonstrate that myeloma cells are addicted to LIG3, which can be effectively inhibited by miR-22, promoting a novel axis of genome stability regulation.
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Affiliation(s)
- Daniele Caracciolo
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | - Maria Teresa Di Martino
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | - Nicola Amodio
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | - Eugenio Morelli
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | - Martina Montesano
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | - Cirino Botta
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | - Francesca Scionti
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | | | - Emanuela Altomare
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | - Maria Eugenia Gallo Cantafio
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | | | | | - Katia Todoerti
- Department of Oncology and Hemato-oncology, University of Milan, and Hematology, Fondazione Cà Granda IRCCS Policlinico, Milan, Italy
| | - Marco Rossi
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | - Mariamena Arbitrio
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | - Antonino Neri
- Department of Oncology and Hemato-oncology, University of Milan, and Hematology, Fondazione Cà Granda IRCCS Policlinico, Milan, Italy
| | - Pierosandro Tagliaferri
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy
| | - Pierfrancesco Tassone
- Department of Experimental and Clinical Medicine, Magna Græcia University, Campus Salvatore Venuta, Catanzaro, Italy.
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA, USA.
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Mitochondrial DNA Integrity: Role in Health and Disease. Cells 2019; 8:cells8020100. [PMID: 30700008 PMCID: PMC6406942 DOI: 10.3390/cells8020100] [Citation(s) in RCA: 131] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 01/25/2019] [Accepted: 01/28/2019] [Indexed: 01/06/2023] Open
Abstract
As the primary cellular location for respiration and energy production, mitochondria serve in a critical capacity to the cell. Yet, by virtue of this very function of respiration, mitochondria are subject to constant oxidative stress that can damage one of the unique features of this organelle, its distinct genome. Damage to mitochondrial DNA (mtDNA) and loss of mitochondrial genome integrity is increasingly understood to play a role in the development of both severe early-onset maladies and chronic age-related diseases. In this article, we review the processes by which mtDNA integrity is maintained, with an emphasis on the repair of oxidative DNA lesions, and the cellular consequences of diminished mitochondrial genome stability.
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Sallmyr A, Tomkinson AE. Repair of DNA double-strand breaks by mammalian alternative end-joining pathways. J Biol Chem 2018. [PMID: 29530982 DOI: 10.1074/jbc.tm117.000375] [Citation(s) in RCA: 161] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alternative end-joining (a-EJ) pathways, which repair DNA double-strand breaks (DSBs), are initiated by end resection that generates 3' single strands. This reaction is shared, at least in part, with homologous recombination but distinguishes a-EJ from the major nonhomologous end-joining pathway. Although the a-EJ pathways make only a minor and poorly understood contribution to DSB repair in nonmalignant cells, there is growing interest in these pathways, as they generate genomic rearrangements that are hallmarks of cancer cells. Here, we review and discuss the current understanding of the mechanisms and regulation of a-EJ pathways, the role of a-EJ in human disease, and the potential utility of a-EJ as a therapeutic target in cancer.
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Affiliation(s)
- Annahita Sallmyr
- From the Departments of Internal Medicine and Molecular Genetics and Microbiology, University of New Mexico Comprehensive Cancer Center, University of New Mexico, Albuquerque, New Mexico 87131
| | - Alan E Tomkinson
- From the Departments of Internal Medicine and Molecular Genetics and Microbiology, University of New Mexico Comprehensive Cancer Center, University of New Mexico, Albuquerque, New Mexico 87131
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Kwiatkowski D, Czarny P, Toma M, Korycinska A, Sowinska K, Galecki P, Bachurska A, Bielecka-Kowalska A, Szemraj J, Maes M, Sliwinski T. Association between Single-Nucleotide Polymorphisms of the hOGG1,NEIL1,APEX1, FEN1,LIG1, and LIG3 Genes and Alzheimer's Disease Risk. Neuropsychobiology 2016; 73:98-107. [PMID: 27010693 DOI: 10.1159/000444643] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 02/11/2016] [Indexed: 11/19/2022]
Abstract
BACKGROUND One of the factors that contribute to Alzheimer's disease (AD) is the DNA damage caused by oxidative stress and inflammation that occurs in nerve cells. It has been suggested that the risk of AD may be associated with an age-dependent reduction of the DNA repair efficiency. Base excision repair (BER) is, among other things, a main repair system of oxidative DNA damage. One of the reasons for the reduced efficiency of this system may be single-nucleotide polymorphisms (SNP) of the genes encoding its proteins. METHODS DNA for genotyping was obtained from the peripheral blood of 281 patients and 150 controls. In the present study, we evaluated the impact of 8 polymorphisms of 6 BER genes on the AD risk. We analyzed the following SNP: c.-468T>G and c.444T>G of APEX1, c.*50C>T and c.*83A>C of LIG3, c.977C>G of OGG1, c.*283C>G of NEIL1, c.-441G>A of FEN1, and c.-7C>T of LIG1. RESULTS We showed that the LIG1 c.-7C>T A/A and LIG3 c.*83A>C A/C variants increased, while the APEX1 c.444T>G G/T, LIG1 c.-7C>T G/, LIG3 c.*83A>C C/C variants reduced, the AD risk. We also evaluated the relation between gene-gene interactions and the AD risk. We showed that combinations of certain BER gene variants such as c.977C>G×c.*50C>T CC/CT, c.444T>G×c.*50C>T GG/CT, c.-468T>G×c.*50C>T GG/CT, c.-441G>Ac.*50C>T×c.*50C>T GG/CT, c.*83A>C× c.*50C>T CT/AC, and c.-7C>T×c.*50C>T CT/GG can substantially positively modulate the risk of AD. CONCLUSIONS In conclusion, we revealed that polymorphisms of BER genes may have a significant effect on the AD risk, and the presence of polymorphic variants may be an important marker for AD.
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Czarny P, Kwiatkowski D, Toma M, Gałecki P, Orzechowska A, Bobińska K, Bielecka-Kowalska A, Szemraj J, Berk M, Anderson G, Śliwiński T. Single-Nucleotide Polymorphisms of Genes Involved in Repair of Oxidative DNA Damage and the Risk of Recurrent Depressive Disorder. Med Sci Monit 2016; 22:4455-4474. [PMID: 27866211 PMCID: PMC5119689 DOI: 10.12659/msm.898091] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background Depressive disorder, including recurrent type (rDD), is accompanied by increased oxidative stress and activation of inflammatory pathways, which may induce DNA damage. This thesis is supported by the presence of increased levels of DNA damage in depressed patients. Such DNA damage is repaired by the base excision repair (BER) pathway. BER efficiency may be influenced by polymorphisms in BER-related genes. Therefore, we genotyped nine single-nucleotide polymorphisms (SNPs) in six genes encoding BER proteins. Material/Methods Using TaqMan, we selected and genotyped the following SNPs: c.-441G>A (rs174538) of FEN1, c.2285T>C (rs1136410) of PARP1, c.580C>T (rs1799782) and c.1196A>G (rs25487) of XRCC1, c.*83A>C (rs4796030) and c.*50C>T (rs1052536) of LIG3, c.-7C>T (rs20579) of LIG1, and c.-468T>G (rs1760944) and c.444T>G (rs1130409) of APEX1 in 599 samples (288 rDD patients and 311 controls). Results We found a strong correlation between rDD and both SNPs of LIG3, their haplotypes, as well as a weaker association with the c.-468T>G of APEXI which diminished after Nyholt correction. Polymorphisms of LIG3 were also associated with early onset versus late onset depression, whereas the c.-468T>G polymorphism showed the opposite association. Conclusions The SNPs of genes involved in the repair of oxidative DNA damage may modulate rDD risk. Since this is an exploratory study, the results should to be treated with caution and further work needs to be done to elucidate the exact involvement of DNA damage and repair mechanisms in the development of this disease.
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Affiliation(s)
- Piotr Czarny
- Department of Molecular Genetics, University of Łódź, Łódź, Poland
| | | | - Monika Toma
- Department of Molecular Genetics, University of Łódź, Łódź, Poland
| | - Piotr Gałecki
- Department of Adult Psychiatry, Medical University of Łódź, Łódź, Poland
| | - Agata Orzechowska
- Department of Adult Psychiatry, Medical University of Łódź, Łódź, Poland
| | - Kinga Bobińska
- Department of Adult Psychiatry, Medical University of Łódź, Łódź, Poland
| | | | - Janusz Szemraj
- Department of Medical Biochemistry, Medical University of Łódź, Łódź, Poland
| | - Michael Berk
- IMPACT Research Center, Deakin University, Geelong, Australia
| | - George Anderson
- Clinical Research Communications Centre, CRC Scotland & London, London, United Kingdom
| | - Tomasz Śliwiński
- Department of Molecular Genetics, University of Łódź, Łódź, Poland
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Sallmyr A, Matsumoto Y, Roginskaya V, Van Houten B, Tomkinson AE. Inhibiting Mitochondrial DNA Ligase IIIα Activates Caspase 1-Dependent Apoptosis in Cancer Cells. Cancer Res 2016; 76:5431-41. [PMID: 27503931 PMCID: PMC5036517 DOI: 10.1158/0008-5472.can-15-3243] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 06/30/2016] [Indexed: 01/09/2023]
Abstract
Elevated levels of DNA ligase IIIα (LigIIIα) have been identified as a biomarker of an alteration in DNA repair in cancer cells that confers hypersensitivity to a LigIIIα inhibitor, L67, in combination with a poly (ADP-ribose) polymerase inhibitor. Because LigIIIα functions in the nucleus and mitochondria, we examined the effect of L67 on these organelles. Here, we show that, although the DNA ligase inhibitor selectively targets mitochondria, cancer and nonmalignant cells respond differently to disruption of mitochondrial DNA metabolism. Inhibition of mitochondrial LigIIIα in cancer cells resulted in abnormal mitochondrial morphology, reduced levels of mitochondrial DNA, and increased levels of mitochondrially generated reactive oxygen species that caused nuclear DNA damage. In contrast, these effects did not occur in nonmalignant cells. Furthermore, inhibition of mitochondrial LigIIIα activated a caspase 1-dependent apoptotic pathway, which is known to be part of inflammatory responses induced by pathogenic microorganisms in cancer, but not nonmalignant cells. These results demonstrate that the disruption of mitochondrial DNA metabolism elicits different responses in nonmalignant and cancer cells and suggests that the abnormal response in cancer cells may be exploited in the development of novel therapeutic strategies that selectively target cancer cells. Cancer Res; 76(18); 5431-41. ©2016 AACR.
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Affiliation(s)
- Annahita Sallmyr
- Departments of Internal Medicine and Molecular Genetics and Microbiology, and University of New Mexico Cancer Center, University of New Mexico, Albuquerque, New Mexico
| | - Yoshihiro Matsumoto
- Departments of Internal Medicine and Molecular Genetics and Microbiology, and University of New Mexico Cancer Center, University of New Mexico, Albuquerque, New Mexico
| | - Vera Roginskaya
- Department of Pharmacology and Cell Biology, University of Pittsburgh School of Medicine and The University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, Pennsylvania
| | - Bennett Van Houten
- Department of Pharmacology and Cell Biology, University of Pittsburgh School of Medicine and The University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, Pennsylvania
| | - Alan E Tomkinson
- Departments of Internal Medicine and Molecular Genetics and Microbiology, and University of New Mexico Cancer Center, University of New Mexico, Albuquerque, New Mexico.
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Lysine Methyltransferase SETD7 (SET7/9) Regulates ROS Signaling through mitochondria and NFE2L2/ARE pathway. Sci Rep 2015; 5:14368. [PMID: 26435321 PMCID: PMC4593030 DOI: 10.1038/srep14368] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 08/20/2015] [Indexed: 01/07/2023] Open
Abstract
Reactive oxygen species (ROS) homeostasis requires stringent regulation. ROS imbalance, especially ROS accumulation, has profound implications in various disease pathogenesis. Lysine methylation of histone and non-histone proteins has been implicated in various cellular responses. The main objective of this study is to investigate the role of SET domain containing lysine methyltransferase SETD7 (SET7/9) in the regulation of ROS-mediated signaling. Here we report that inhibition of SETD7 with siRNA or a SETD7 small molecule inhibitor in both macrophages and a human bronchial epithelial cell line (Beas-2B) were able to counter NF-ĸB-induced oxidative stress and pro-inflammatory cytokine production. Meanwhile, inhibition of SETD7 elevates mitochondria antioxidant functions via negative regulation of PPARGC1A and NFE2L2. Using a co-expression system and purified proteins, we detected direct interaction between SETD7 and NFE2L2. These results indicate that lysine methylation by SETD7 is important for the fine-tuning of ROS signaling through its regulation on pro-inflammatory responses, mitochondrial function and the NFE2L2/ARE pathway. Up-regulation of multiple antioxidant genes and improved ROS clearance by inhibition of SETD7 suggests the potential benefit of targeting SETD7 in treating ROS-associated diseases.
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Akhmedov AT, Marín-García J. Mitochondrial DNA maintenance: an appraisal. Mol Cell Biochem 2015; 409:283-305. [DOI: 10.1007/s11010-015-2532-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 08/06/2015] [Indexed: 12/13/2022]
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12
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Primer removal during mammalian mitochondrial DNA replication. DNA Repair (Amst) 2015; 34:28-38. [PMID: 26303841 DOI: 10.1016/j.dnarep.2015.07.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 07/02/2015] [Indexed: 12/17/2022]
Abstract
The small circular mitochondrial genome in mammalian cells is replicated by a dedicated replisome, defects in which can cause mitochondrial disease in humans. A fundamental step in mitochondrial DNA (mtDNA) replication and maintenance is the removal of the RNA primers needed for replication initiation. The nucleases RNase H1, FEN1, DNA2, and MGME1 have been implicated in this process. Here we review the role of these nucleases in the light of primer removal pathways in mitochondria, highlight associations with disease, as well as consider the implications for mtDNA replication initiation.
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13
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Kukshal V, Kim IK, Hura GL, Tomkinson AE, Tainer JA, Ellenberger T. Human DNA ligase III bridges two DNA ends to promote specific intermolecular DNA end joining. Nucleic Acids Res 2015; 43:7021-31. [PMID: 26130724 PMCID: PMC4538836 DOI: 10.1093/nar/gkv652] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 06/15/2015] [Indexed: 12/14/2022] Open
Abstract
Mammalian DNA ligase III (LigIII) functions in both nuclear and mitochondrial DNA metabolism. In the nucleus, LigIII has functional redundancy with DNA ligase I whereas LigIII is the only mitochondrial DNA ligase and is essential for the survival of cells dependent upon oxidative respiration. The unique LigIII zinc finger (ZnF) domain is not required for catalytic activity but senses DNA strand breaks and stimulates intermolecular ligation of two DNAs by an unknown mechanism. Consistent with this activity, LigIII acts in an alternative pathway of DNA double strand break repair that buttresses canonical non-homologous end joining (NHEJ) and is manifest in NHEJ-defective cancer cells, but how LigIII acts in joining intermolecular DNA ends versus nick ligation is unclear. To investigate how LigIII efficiently joins two DNAs, we developed a real-time, fluorescence-based assay of DNA bridging suitable for high-throughput screening. On a nicked duplex DNA substrate, the results reveal binding competition between the ZnF and the oligonucleotide/oligosaccharide-binding domain, one of three domains constituting the LigIII catalytic core. In contrast, these domains collaborate and are essential for formation of a DNA-bridging intermediate by adenylated LigIII that positions a pair of blunt-ended duplex DNAs for efficient and specific intermolecular ligation.
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Affiliation(s)
- Vandna Kukshal
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - In-Kwon Kim
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Gregory L Hura
- Life Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Alan E Tomkinson
- Department of Internal Medicine and University of New Mexico Cancer Center, University of New Mexico, Albuquerque, NM 87131, USA
| | - John A Tainer
- Life Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Tom Ellenberger
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO 63110, USA
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14
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Szczepanowska K, Trifunovic A. Different faces of mitochondrial DNA mutators. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1847:1362-72. [PMID: 26014346 DOI: 10.1016/j.bbabio.2015.05.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Revised: 05/15/2015] [Accepted: 05/17/2015] [Indexed: 10/23/2022]
Abstract
A number of studies have shown that ageing is associated with increased amounts of mtDNA deletions and/or point mutations in a variety of species as diverse as Caenorhabditis elegans, Drosophila melanogaster, mice, rats, dogs, primates and humans. This detected vulnerability of mtDNA has led to the suggestion that the accumulation of somatic mtDNA mutations might arise from increased oxidative damage and could play an important role in the ageing process by producing cells with a decreased oxidative capacity. However, the vast majority of DNA polymorphisms and disease-causing base-substitution mutations and age-associated mutations that have been detected in human mtDNA are transition mutations. They are likely arising from the slight infidelity of the mitochondrial DNA polymerase. Indeed, transition mutations are also the predominant type of mutation found in mtDNA mutator mice, a model for premature ageing caused by increased mutation load due to the error prone mitochondrial DNA synthesis. These particular misincorporation events could also be exacerbated by dNTP pool imbalances. The role of different repair, replication and maintenance mechanisms that contribute to mtDNA integrity and mutagenesis will be discussed in details in this article. This article is part of a Special Issue entitled: Mitochondrial Dysfunction in Aging.
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Affiliation(s)
- Karolina Szczepanowska
- Cologne Excellence Cluster on Cellular Stress Responses in Ageing-Associated Diseases (CECAD) and Institute for Mitochondrial Diseases and Ageing, Medical Faculty, University of Cologne, D-50931 Cologne, Germany
| | - Aleksandra Trifunovic
- Cologne Excellence Cluster on Cellular Stress Responses in Ageing-Associated Diseases (CECAD) and Institute for Mitochondrial Diseases and Ageing, Medical Faculty, University of Cologne, D-50931 Cologne, Germany.
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15
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Overexpression of DNA ligase III in mitochondria protects cells against oxidative stress and improves mitochondrial DNA base excision repair. DNA Repair (Amst) 2014; 16:44-53. [PMID: 24674627 DOI: 10.1016/j.dnarep.2014.01.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 01/21/2014] [Accepted: 01/27/2014] [Indexed: 01/06/2023]
Abstract
Base excision repair (BER) is the most prominent DNA repair pathway in human mitochondria. BER also results in a temporary generation of AP-sites, single-strand breaks and nucleotide gaps. Thus, incomplete BER can result in the generation of DNA repair intermediates that can disrupt mitochondrial DNA replication and transcription and generate mutations. We carried out BER analysis in highly purified mitochondrial extracts from human cell lines U2OS and HeLa, and mouse brain using a circular DNA substrate containing a lesion at a specific position. We found that DNA ligation is significantly slower than the preceding mitochondrial BER steps. Overexpression of DNA ligase III in mitochondria improved the rate of overall BER, increased cell survival after menadione induced oxidative stress and reduced autophagy following the inhibition of the mitochondrial electron transport chain complex I by rotenone. Our results suggest that the amount of DNA ligase III in mitochondria may be critical for cell survival following prolonged oxidative stress, and demonstrate a functional link between mitochondrial DNA damage and repair, cell survival upon oxidative stress, and removal of dysfunctional mitochondria by autophagy.
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16
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Sharma NK, Lebedeva M, Thomas T, Kovalenko OA, Stumpf JD, Shadel GS, Santos JH. Intrinsic mitochondrial DNA repair defects in Ataxia Telangiectasia. DNA Repair (Amst) 2014; 13:22-31. [PMID: 24342190 PMCID: PMC6211587 DOI: 10.1016/j.dnarep.2013.11.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 11/12/2013] [Accepted: 11/26/2013] [Indexed: 12/28/2022]
Abstract
Ataxia Telangiectasia (A-T) is a progressive childhood disorder characterized most notably by cerebellar degeneration and predisposition to cancer. A-T is caused by mutations in the kinase ATM, a master regulator of the DNA double-strand break response. In addition to DNA-damage signaling defects, A-T cells display mitochondrial dysfunction that is thought to contribute to A-T pathogenesis. However, the molecular mechanism leading to mitochondrial dysfunction in A-T remains unclear. Here, we show that lack of ATM leads to reduced mitochondrial DNA (mtDNA) integrity and mitochondrial dysfunction, which are associated to defective mtDNA repair. While protein levels of mtDNA repair proteins are essentially normal, in the absence of ATM levels specifically of DNA ligase III (Lig3), the only DNA ligase working in mitochondria is reduced. The reduction of Lig3 is observed in different A-T patient cells, in brain and pre-B cells derived from ATM knockout mice as well as upon transient or stable knockdown of ATM. Furthermore, pharmacological inhibition of Lig3 in wild type cells phenocopies the mtDNA repair defects observed in A-T patient cells. As targeted deletion of LIG3 in the central nervous system causes debilitating ataxia in mice, reduced Lig3 protein levels and the consequent mtDNA repair defect may contribute to A-T neurodegeneration. A-T is thus the first disease characterized by diminished Lig3.
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Affiliation(s)
- Nilesh K Sharma
- Department of Pharmacology and Physiology, New Jersey Medical School of UMDNJ, 185 South Orange Avenue, Medical Sciences Building, Newark, NJ 07103, United States
| | - Maria Lebedeva
- Department of Genetics, Yale School of Medicine, 310 Cedar Street, BML 371, New Haven, CT 06520, United States
| | - Terace Thomas
- Department of Pharmacology and Physiology, New Jersey Medical School of UMDNJ, 185 South Orange Avenue, Medical Sciences Building, Newark, NJ 07103, United States
| | - Olga A Kovalenko
- Department of Pharmacology and Physiology, New Jersey Medical School of UMDNJ, 185 South Orange Avenue, Medical Sciences Building, Newark, NJ 07103, United States
| | - Jeffrey D Stumpf
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences (NIEHS), 111 TW Alexander Drive, Building 101, Durham, NC 27709, United States
| | - Gerald S Shadel
- Department of Genetics, Yale School of Medicine, 310 Cedar Street, BML 371, New Haven, CT 06520, United States; Department of Pathology, Yale School of Medicine, 310 Cedar Street, BML 371, New Haven, CT 06520, United States
| | - Janine H Santos
- Department of Pharmacology and Physiology, New Jersey Medical School of UMDNJ, 185 South Orange Avenue, Medical Sciences Building, Newark, NJ 07103, United States.
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17
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Tomkinson AE, Sallmyr A. Structure and function of the DNA ligases encoded by the mammalian LIG3 gene. Gene 2013; 531:150-7. [PMID: 24013086 DOI: 10.1016/j.gene.2013.08.061] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2012] [Revised: 08/15/2013] [Accepted: 08/20/2013] [Indexed: 11/30/2022]
Abstract
Among the mammalian genes encoding DNA ligases (LIG), the LIG3 gene is unique in that it encodes multiple DNA ligase polypeptides with different cellular functions. Notably, this nuclear gene encodes the only mitochondrial DNA ligase and so is essential for this organelle. In the nucleus, there is significant functional redundancy between DNA ligase IIIα and DNA ligase I in excision repair. In addition, DNA ligase IIIα is essential for DNA replication in the absence of the replicative DNA ligase, DNA ligase I. DNA ligase IIIα is a component of an alternative non-homologous end joining (NHEJ) pathway for DNA double-strand break (DSB) repair that is more active when the major DNA ligase IV-dependent pathway is defective. Unlike its other nuclear functions, the role of DNA ligase IIIα in alternative NHEJ is independent of its nuclear partner protein, X-ray repair cross-complementing protein 1 (XRCC1). DNA ligase IIIα is frequently overexpressed in cancer cells, acting as a biomarker for increased dependence upon alternative NHEJ for DSB repair and it is a promising novel therapeutic target.
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Affiliation(s)
- Alan E Tomkinson
- Department of Internal Medicine and University of New Mexico Cancer Center, University of New Mexico, Albuquerque, NM 87131, USA.
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18
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Shokolenko IN, Fayzulin RZ, Katyal S, McKinnon PJ, Wilson GL, Alexeyev MF. Mitochondrial DNA ligase is dispensable for the viability of cultured cells but essential for mtDNA maintenance. J Biol Chem 2013; 288:26594-605. [PMID: 23884459 DOI: 10.1074/jbc.m113.472977] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Multiple lines of evidence support the notion that DNA ligase III (LIG3), the only DNA ligase found in mitochondria, is essential for viability in both whole organisms and in cultured cells. Previous attempts to generate cells devoid of mitochondrial DNA ligase failed. Here, we report, for the first time, the derivation of viable LIG3-deficient mouse embryonic fibroblasts. These cells lack mtDNA and are auxotrophic for uridine and pyruvate, which may explain the apparent lethality of the Lig3 knock-out observed in cultured cells in previous studies. Cells with severely reduced expression of LIG3 maintain normal mtDNA copy number and respiration but show reduced viability in the face of alkylating and oxidative damage, increased mtDNA degradation in response to oxidative damage, and slow recovery from mtDNA depletion. Our findings clarify the cellular role of LIG3 and establish that the loss of viability in LIG3-deficient cells is conditional and secondary to the ρ(0) phenotype.
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19
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Tomkinson AE, Howes TR, Wiest NE. DNA ligases as therapeutic targets. Transl Cancer Res 2013; 2:1219. [PMID: 24224145 PMCID: PMC3819426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
During DNA replication, DNA joining events link Okazaki fragments on the lagging strand. In addition, they are required to repair DNA single- and double-strand breaks and to complete repair events initiated by the excision of mismatched and damaged bases. In human cells, there are three genes encoding DNA ligases. These enzymes are ATP-dependent and contain a conserved catalytic region. Biophysical studies have shown that the catalytic region contains three domains that, in the absence of DNA, are in an extended conformation. When the catalytic region engages a DNA nick, it adopts a compact, ring structure around the DNA nick with each of the three domains contacting the DNA. Protein-protein interactions involving the regions flanking the conserved catalytic regions of human DNA ligases play a major role in directing these enzymes to participate in specific DNA transactions. Among the human LIG genes, the LIG3 gene is unique in that it encodes multiple DNA ligase polypeptides with different N- and C-termini. One of these polypeptides is targeted to mitochondria where it plays an essential role in the maintenance of the mitochondrial genome. In the nucleus, DNA ligases I, III and IV have distinct but overlapping functions in DNA replication and repair. Small molecule inhibitors of human DNA ligases have been identified using structure-based approaches. As expected, these inhibitors are cytotoxic and also potentiate the cytotoxicity of DNA damaging agents. The results of preclinical studies with human cancer cell lines and mouse models of human cancer suggest that DNA ligase inhibitors may have utility as anti-cancer agents.
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Affiliation(s)
- Alan E. Tomkinson
- Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
- University of New Mexico Cancer Center, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
| | - Timothy R.L. Howes
- Biomedical Sciences Graduate Program, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
| | - Nathaniel E. Wiest
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
- Biomedical Sciences Graduate Program, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
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20
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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: 286] [Impact Index Per Article: 26.0] [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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21
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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: 48] [Impact Index Per Article: 3.7] [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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22
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Simsek D, Jasin M. DNA ligase III: a spotty presence in eukaryotes, but an essential function where tested. Cell Cycle 2011; 10:3636-44. [PMID: 22041657 DOI: 10.4161/cc.10.21.18094] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
DNA ligases are crucial for most DNA transactions, including DNA replication, repair, and recombination. Recently, DNA ligase III (Lig3) has been demonstrated to be crucial for cell survival due to its catalytic function in mitochondria. This review summarizes these recent results and reports on a hitherto unappreciated widespread phylogenetic presence of Lig3 in eukaryotes, including in some organisms before the divergence of metazoa. Analysis of these putative Lig3 homologs suggests that many of them are likely to be found in mitochondria and to be critical for mitochondrial function.
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Affiliation(s)
- Deniz Simsek
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, Weill Cornell Graduate School of Medical Sciences, New York, NY, USA
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23
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Ruhanen H, Ushakov K, Yasukawa T. Involvement of DNA ligase III and ribonuclease H1 in mitochondrial DNA replication in cultured human cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:2000-7. [PMID: 21878356 PMCID: PMC3223524 DOI: 10.1016/j.bbamcr.2011.08.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Revised: 07/29/2011] [Accepted: 08/01/2011] [Indexed: 12/05/2022]
Abstract
Recent evidence suggests that coupled leading and lagging strand DNA synthesis operates in mammalian mitochondrial DNA (mtDNA) replication, but the factors involved in lagging strand synthesis are largely uncharacterised. We investigated the effect of knockdown of the candidate proteins in cultured human cells under conditions where mtDNA appears to replicate chiefly via coupled leading and lagging strand DNA synthesis to restore the copy number of mtDNA to normal levels after transient mtDNA depletion. DNA ligase III knockdown attenuated the recovery of mtDNA copy number and appeared to cause single strand nicks in replicating mtDNA molecules, suggesting the involvement of DNA ligase III in Okazaki fragment ligation in human mitochondria. Knockdown of ribonuclease (RNase) H1 completely prevented the mtDNA copy number restoration, and replication intermediates with increased single strand nicks were readily observed. On the other hand, knockdown of neither flap endonuclease 1 (FEN1) nor DNA2 affected mtDNA replication. These findings imply that RNase H1 is indispensable for the progression of mtDNA synthesis through removing RNA primers from Okazaki fragments. In the nucleus, Okazaki fragments are ligated by DNA ligase I, and the RNase H2 is involved in Okazaki fragment processing. This study thus proposes that the mitochondrial replication system utilises distinct proteins, DNA ligase III and RNase H1, for Okazaki fragment maturation.
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Affiliation(s)
- Heini Ruhanen
- The Wolfson Institute for Biomedical Research, University College London, Gower Street, London, UK
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24
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Abstract
DNA strand break repair is essential for the prevention of multiple human diseases, particularly those which feature neuropathology. To further understand the pathogenesis of these syndromes, we recently developed animal models in which the DNA single-strand break repair (SSBR) components, XRCC1 and DNA Ligase III (LIG3), were inactivated in the developing nervous system. Although biochemical evidence suggests that inactivation of XRCC1 and LIG3 should share common biological defects, we found profound phenotypic differences between these two models, implying distinct biological roles for XRCC1 and LIG3 during DNA repair. Rather than a key role in nuclear DNA repair, we found LIG3 function was central to mitochondrial DNA maintenance. Instead, our data indicate that DNA Ligase 1 is the main DNA ligase for XRCC1-mediated DNA repair. These studies refine our understanding of DNA SSBR and the etiology of neurological disease.
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Affiliation(s)
- Sachin Katyal
- Department of Genetics, St. Jude Children's Research Hospital, Memphis, TN USA
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25
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DNA ligase III is critical for mtDNA integrity but not Xrcc1-mediated nuclear DNA repair. Nature 2011; 471:240-4. [PMID: 21390131 PMCID: PMC3079429 DOI: 10.1038/nature09773] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 12/22/2010] [Indexed: 01/20/2023]
Abstract
DNA replication and repair in mammalian cells involves three distinct DNA ligases; ligase I (Lig1), ligase III (Lig3) and ligase IV (Lig4)1. Lig3 is considered a key ligase during base excision repair because its stability depends upon its nuclear binding partner Xrcc1, a critical factor for this DNA repair pathway2,3. Lig3 is also present in the mitochondria where its role in mitochondrial DNA (mtDNA) maintenance is independent of Xrcc14. However, the biological role of Lig3 is unclear as inactivation of murine Lig3 results in early embryonic lethality5. Here we report that Lig3 is essential for mtDNA integrity but dispensable for nuclear DNA repair. Inactivation of Lig3 in the mouse nervous system resulted in mtDNA loss leading to profound mitochondrial dysfunction, disruption of cellular homeostasis and incapacitating ataxia. Similarly, inactivation of Lig3 in cardiac muscle resulted in mitochondrial dysfunction and defective heart pump function leading to heart failure. However, Lig3 inactivation did not result in nuclear DNA repair deficiency, indicating essential DNA repair functions of Xrcc1 can occur in the absence of Lig3. Instead, we found that Lig1 was critical for DNA repair, but in a cooperative manner with Lig3. Additionally, Lig3 deficiency did not recapitulate the hallmark features of neural Xrcc1 inactivation such as DNA damage-induced cerebellar interneuron loss6, further underscoring functional separation of these DNA repair factors. Therefore, our data reveal that the critical biological role of Lig3 is to maintain mtDNA integrity and not Xrcc1-dependent DNA repair.
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26
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DNA repair in organelles: Pathways, organization, regulation, relevance in disease and aging. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:186-200. [DOI: 10.1016/j.bbamcr.2010.10.002] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 10/01/2010] [Accepted: 10/05/2010] [Indexed: 12/20/2022]
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27
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Rassool FV, Tomkinson AE. Targeting abnormal DNA double strand break repair in cancer. Cell Mol Life Sci 2010; 67:3699-710. [PMID: 20697770 PMCID: PMC3014093 DOI: 10.1007/s00018-010-0493-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 07/28/2010] [Indexed: 12/19/2022]
Abstract
A major challenge in cancer treatment is the development of therapies that target cancer cells with little or no toxicity to normal tissues and cells. Alterations in DNA double strand break (DSB) repair in cancer cells include both elevated and reduced levels of key repair proteins and changes in the relative contributions of the various DSB repair pathways. These differences can result in increased sensitivity to DSB-inducing agents and increased genomic instability. The development of agents that selectively inhibit the DSB repair pathways that cancer cells are more dependent upon will facilitate the design of therapeutic strategies that exploit the differences in DSB repair between normal and cancer cells. Here, we discuss the pathways of DSB repair, alterations in DSB repair in cancer, inhibitors of DSB repair and future directions for cancer therapies that target DSB repair.
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Affiliation(s)
- Feyruz V. Rassool
- Department of Radiation Oncology, Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, 655 West Baltimore Street, BRB, Rm 7-025, Baltimore, MD 21201 USA
| | - Alan E. Tomkinson
- Department of Radiation Oncology, Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, 655 West Baltimore Street, BRB, Rm 7-025, Baltimore, MD 21201 USA
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28
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Animal models of mitochondrial DNA transactions in disease and ageing. Exp Gerontol 2010; 45:489-502. [PMID: 20123011 DOI: 10.1016/j.exger.2010.01.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2009] [Revised: 01/11/2010] [Accepted: 01/26/2010] [Indexed: 11/21/2022]
Abstract
Mitochondrial DNA (mtDNA) transactions, processes that include mtDNA replication, repair, recombination and transcription constitute the initial stages of mitochondrial biogenesis, and are at the core of understanding mitochondrial biology and medicine. All of the protein players are encoded in nuclear genes: some are proteins with well-known functions in the nucleus, others are well-known mitochondrial proteins now ascribed new functions, and still others are newly discovered factors. In this article we review recent advances in the field of mtDNA transactions with a special focus on physiological studies. In particular, we consider the expression of variant proteins, or altered expression of factors involved in these processes in powerful model organisms, such as Drosophila melanogaster and the mouse, which have promoted recognition of the broad relevance of oxidative phosphorylation defects resulting from improper maintenance of mtDNA. Furthermore, the animal models recapitulate many phenotypes related to human ageing and a variety of different diseases, a feature that has enhanced our understanding of, and inspired theories about, the molecular mechanisms of such biological processes.
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29
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Machado AMD, Figueiredo C, Seruca R, Rasmussen LJ. Helicobacter pylori infection generates genetic instability in gastric cells. Biochim Biophys Acta Rev Cancer 2010; 1806:58-65. [PMID: 20122996 DOI: 10.1016/j.bbcan.2010.01.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Revised: 01/16/2010] [Accepted: 01/24/2010] [Indexed: 01/02/2023]
Abstract
The discovery that Helicobacter pylori is associated with gastric cancer has led to numerous studies that investigate the mechanisms by which H. pylori induces carcinogenesis. Gastric cancer shows genetic instability both in nuclear and mitochondrial DNA, besides impairment of important DNA repair pathways. As such, this review highlights the consequences of H. pylori infection on the integrity of DNA in the host cells. By down-regulating major DNA repair pathways, H. pylori infection has the potential to generate mutations. In addition, H. pylori infection can induce direct changes on the DNA of the host, such as oxidative damage, methylation, chromosomal instability, microsatellite instability, and mutations. Interestingly, H. pylori infection generates genetic instability in nuclear and mitochondrial DNA. Based on the reviewed literature we conclude that H. pylori infection promotes gastric carcinogenesis by at least three different mechanisms: (1) a combination of increased endogenous DNA damage and decreased repair activities, (2) induction of mutations in the mitochondrial DNA, and (3) generation of a transient mutator phenotype that induces mutations in the nuclear genome.
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30
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Rossi MN, Carbone M, Mostocotto C, Mancone C, Tripodi M, Maione R, Amati P. Mitochondrial localization of PARP-1 requires interaction with mitofilin and is involved in the maintenance of mitochondrial DNA integrity. J Biol Chem 2009; 284:31616-24. [PMID: 19762472 DOI: 10.1074/jbc.m109.025882] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Poly(ADP-ribose)polymerase-1 (PARP-1) is a predominantly nuclear enzyme that exerts numerous functions in cellular physiology and pathology, from maintenance of DNA stability to transcriptional regulation. Through a proteomic analysis of PARP-1 co-immunoprecipitation complexes, we identified Mitofilin, a mitochondrial protein, as a new PARP-1 interactor. This result prompted us to further investigate the presence and the role of the enzyme in mitochondria. Using laser confocal microscopy and Western blot analysis of purified mitochondria, we demonstrated the mitochondrial localization of a fraction of PARP-1. Further, the effects of overexpressing or down-regulating Mitofilin showed that this protein promotes and is required for PARP-1 mitochondrial localization. We also report several lines of evidence suggesting that intramitochondrial PARP-1 plays a role in mitochondrial DNA (mtDNA) damage signaling and/or repair. First, we show that PARP-1 binds to different regions throughout the mtDNA. Moreover, we demonstrated that the depletion of either PARP-1 or Mitofilin, which abrogates the mitochondrial localization of the enzyme, leads to the accumulation of mtDNA damage. Finally, we show that DNA ligase III, known to be required for mtDNA repair, participates in a PARP-1-containing complex bound to mtDNA. This work highlights a new environment for PARP-1, opening the possibility that at least some of the nuclear functions of the enzyme can be also extended to mtDNA metabolism.
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Affiliation(s)
- Marianna N Rossi
- Pasteur Institute-Fondazione Cenci Bolognetti, Department of Cellular Biotechnologies and Hematology, University of Rome La Sapienza, Viale Regina Elena 324, 00161 Rome, Italy
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31
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HMGA1 levels influence mitochondrial function and mitochondrial DNA repair efficiency. Mol Cell Biol 2009; 29:5426-40. [PMID: 19687300 DOI: 10.1128/mcb.00105-09] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
HMGA chromatin proteins, a family of gene regulatory factors found at only low concentrations in normal cells, are almost universally overexpressed in cancer cells. HMGA proteins are located in the nuclei of normal cells except during the late S/G(2) phases of the cell cycle, when HMGA1, one of the members of the family, reversibly migrates to the mitochondria, where it binds to mitochondrial DNA (mtDNA). In many cancer cells, this controlled shuttling is lost and HMGA1 is found in mitochondria throughout the cell cycle. To investigate the effects of HMGA1 on mitochondria, we employed a genetically engineered line of human MCF-7 cells in which the levels of transgenic HMGA1 protein could be reversibly controlled. "Turn-ON" and "turn-OFF" time course experiments were performed with these cells to either increase or decrease intracellular HMGA1 levels, and various mitochondrial changes were monitored. Results demonstrated that changes in both mtDNA levels and mitochondrial mass inversely paralleled changes in HMGA1 concentrations, strongly implicating HMGA1 in the regulation of these parameters. Additionally, the level of cellular reactive oxygen species (ROS) increased and the efficiency of repair of oxidatively damaged mtDNA decreased as consequences of elevated HMGA1 expression. Increased ROS levels and reduced repair efficiency in HMGA1-overexpressing cells likely contribute to the increased occurrence of mutations in mtDNA frequently observed in cancer cells.
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32
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Bacman SR, Williams SL, Moraes CT. Intra- and inter-molecular recombination of mitochondrial DNA after in vivo induction of multiple double-strand breaks. Nucleic Acids Res 2009; 37:4218-26. [PMID: 19435881 PMCID: PMC2715231 DOI: 10.1093/nar/gkp348] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
To investigate mtDNA recombination induced by multiple double strand breaks (DSBs) we used a mitochondria-targeted form of the ScaI restriction endonuclease to introduce DSBs in heteroplasmic mice and cells in which we were able to utilize haplotype differences to trace the origin of recombined molecules. ScaI cleaves multiple sites in each haplotype of the heteroplasmic mice (five in NZB and three in BALB mtDNA) and prolonged expression causes severe mtDNA depletion. After a short pulse of restriction enzyme expression followed by a long period of recovery, mitochondrial genomes with large deletions were detected by PCR. Curiously, we found that some ScaI sites were more commonly involved in recombined molecules than others. In intra-molecular recombination events, deletion breakpoints were close to or upstream of ScaI cleavage sites, confirming the recombinogenic character of DSBs in mtDNA. A region adjacent to the D-loop was preferentially involved in recombination of all molecules. Sequencing through NZB and BALB haplotype markers in recombined molecules enabled us to show that in addition to intra-molecular mtDNA recombination, rare inter-molecular mtDNA recombination events can also occur. This study underscores the role of DSBs in the generation of mtDNA rearrangements and supports the existence of recombination hotspots.
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Affiliation(s)
- Sandra R Bacman
- Department of Neurology, University of Miami School of Medicine, Miami, FL 33136, USA
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33
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Abstract
DNA ligases are required for DNA replication, repair, and recombination. In eukaryotes, there are three families of ATP-dependent DNA ligases. Members of the DNA ligase I and IV families are found in all eukaryotes, whereas DNA ligase III family members are restricted to vertebrates. These enzymes share a common catalytic region comprising a DNA-binding domain, a nucleotidyltransferase (NTase) domain, and an oligonucleotide/oligosaccharide binding (OB)-fold domain. The catalytic region encircles nicked DNA with each of the domains contacting the DNA duplex. The unique segments adjacent to the catalytic region of eukaryotic DNA ligases are involved in specific protein-protein interactions with a growing number of DNA replication and repair proteins. These interactions determine the specific cellular functions of the DNA ligase isozymes. In mammals, defects in DNA ligation have been linked with an increased incidence of cancer and neurodegeneration.
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Affiliation(s)
- Tom Ellenberger
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
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34
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Abstract
Hereditary defects in the repair of DNA damage are implicated in a variety of diseases, many of which are typified by neurological dysfunction and/or increased genetic instability and cancer. Of the different types of DNA damage that arise in cells, single-strand breaks (SSBs) are the most common, arising at a frequency of tens of thousands per cell per day from direct attack by intracellular metabolites and from spontaneous DNA decay. Here, the molecular mechanisms and organization of the DNA-repair pathways that remove SSBs are reviewed and the connection between defects in these pathways and hereditary neurodegenerative disease are discussed.
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Affiliation(s)
- Keith W Caldecott
- Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton BN1 9RQ, UK.
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35
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Yang JL, Weissman L, Bohr VA, Mattson MP. Mitochondrial DNA damage and repair in neurodegenerative disorders. DNA Repair (Amst) 2008; 7:1110-20. [PMID: 18463003 DOI: 10.1016/j.dnarep.2008.03.012] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
By producing ATP and regulating intracellular calcium levels, mitochondria are vital for the function and survival of neurons. Oxidative stress and damage to mitochondrial DNA during the aging process can impair mitochondrial energy metabolism and ion homeostasis in neurons, thereby rendering them vulnerable to degeneration. Mitochondrial abnormalities have been documented in all of the major neurodegenerative disorders-Alzheimer's, Parkinson's and Huntington's diseases, and amyotrophic lateral sclerosis. Mitochondrial DNA damage and dysfunction may be downstream of primary disease processes such as accumulation of pathogenic proteins. However, recent experimental evidence demonstrates that mitochondrial DNA damage responses play important roles in aging and in the pathogenesis of neurodegenerative diseases. Therapeutic interventions that target mitochondrial regulatory systems have been shown effective in cell culture and animal models, but their efficacy in humans remains to be established.
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Affiliation(s)
- Jenq-Lin Yang
- Laboratory of Molecular Gerontology, National Institute on Aging Intramural Research Program, Baltimore, MD, USA
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36
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Cotner-Gohara E, Kim IK, Tomkinson AE, Ellenberger T. Two DNA-binding and nick recognition modules in human DNA ligase III. J Biol Chem 2008; 283:10764-72. [PMID: 18238776 DOI: 10.1074/jbc.m708175200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Human DNA ligase III contains an N-terminal zinc finger domain that binds to nicks and gaps in DNA. This small domain has been described as a DNA nick sensor, but it is not required for DNA nick joining activity in vitro. In light of new structural information for mammalian ligases, we measured the DNA binding affinity and specificity of each domain of DNA ligase III. These studies identified two separate, independent DNA-binding modules in DNA ligase III that each bind specifically to nicked DNA over intact duplex DNA. One of these modules comprises the zinc finger domain and DNA-binding domain, which function together as a single DNA binding unit. The catalytic core of ligase III is the second DNA nick-binding module. Both binding modules are required for ligation of blunt ended DNA substrates. Although the zinc finger increases the catalytic efficiency of nick ligation, it appears to occupy the same binding site as the DNA ligase III catalytic core. We present a jackknife model for ligase III that posits conformational changes during nick sensing and ligation to extend the versatility of the enzyme.
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Affiliation(s)
- Elizabeth Cotner-Gohara
- Biological and Biomedical Sciences Program, Harvard Medical School, Boston, Massachusetts 02115, USA
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37
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Mancuso M, Coppedè F, Murri L, Siciliano G. Mitochondrial cascade hypothesis of Alzheimer's disease: myth or reality? Antioxid Redox Signal 2007; 9:1631-46. [PMID: 17887917 DOI: 10.1089/ars.2007.1761] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mitochondria are recognized to play a pivotal role in neuronal cell survival or death because they are regulators of both energy metabolism and apoptotic pathways. Morphologic, biochemical, and molecular genetic studies suggest that mitochondria might be a convergence point for neurodegeneration, including Alzheimer's disease (AD). The functions and properties of mitochondria might render subsets of selectively vulnerable neurons intrinsically susceptible to cellular aging and stress. However, the question, "Is mitochondrial dysfunction a necessary step in neurodegeneration?" is still unanswered. This review presents the ways in which malfunctioning mitochondria and oxidative stress might contribute to neuronal death in AD.
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38
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Morel F, Renoux M, Lachaume P, Alziari S. Bleomycin-induced double-strand breaks in mitochondrial DNA of Drosophila cells are repaired. Mutat Res 2007; 637:111-7. [PMID: 17825327 DOI: 10.1016/j.mrfmmm.2007.07.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Revised: 06/28/2007] [Accepted: 07/17/2007] [Indexed: 11/23/2022]
Abstract
Mitochondrial DNA lesions cause numerous human diseases, and it is therefore important to identify the mechanisms whereby the mitochondrion repairs the damage. We have studied in cultured Drosophila cells the repair of bleomycin-induced double-strand breaks (DSBs) in mitochondrial DNA. Our results show that DSBs are repaired as rapidly and effectively in the mitochondria as in the nucleus. DNA repair is complete within 2h following bleomycin treatment, showing that Drosophila mitochondria have an effective system of DSB repair. The mechanism and mitochondrial proteins involved remain to be identified.
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Affiliation(s)
- Frederic Morel
- Equipe Genome Mitochondrial, UMR CNRS 6547, Université Blaise-Pascal, Clermont 2, 63177, Aubière-Cedex, France
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39
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Weissman L, de Souza-Pinto NC, Stevnsner T, Bohr VA. DNA repair, mitochondria, and neurodegeneration. Neuroscience 2007; 145:1318-29. [PMID: 17092652 DOI: 10.1016/j.neuroscience.2006.08.061] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Revised: 08/22/2006] [Accepted: 08/29/2006] [Indexed: 12/21/2022]
Abstract
Accumulation of nuclear and mitochondrial DNA damage is thought to be particularly deleterious in post-mitotic cells, which cannot be replaced through cell division. Recent experimental evidence demonstrates the importance of DNA damage responses for neuronal survival. Here, we summarize current literature on DNA damage responses in the mammalian CNS in aging and neurodegeneration. Base excision repair (BER) is the main pathway for the removal of small DNA base modifications, such as alkylation, deamination and oxidation, which are generated as by-products of normal metabolism and accumulate with age in various experimental models. Using neuronal cell cultures, human brain tissue and animal models, we and others have shown an active BER pathway functioning in the brain, both in the mitochondrial and nuclear compartments. Mitochondrial DNA repair may play a more essential role in neuronal cells because these cells depend largely on intact mitochondrial function for energy metabolism. We have characterized several BER enzymes in mammalian mitochondria and have shown that BER activities change with age in mitochondria from different brain regions. Together, the results reviewed here advocate that mitochondrial DNA damage response plays an important role in aging and in the pathogenesis of neurodegenerative diseases.
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Affiliation(s)
- L Weissman
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institute on Aging, IRP, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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40
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De A, Campbell C. A novel interaction between DNA ligase III and DNA polymerase gamma plays an essential role in mitochondrial DNA stability. Biochem J 2007; 402:175-86. [PMID: 17054425 PMCID: PMC1783996 DOI: 10.1042/bj20061004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The data in the present study show that DNA polymerase gamma and DNA ligase III interact in mitochondrial protein extracts from cultured HT1080 cells. An interaction was also observed between the two recombinant proteins in vitro. Expression of catalytically inert versions of DNA ligase III that bind DNA polymerase gamma was associated with reduced mitochondrial DNA copy number and integrity. In contrast, overexpression of wild-type DNA ligase III had no effect on mitochondrial DNA copy number or integrity. Experiments revealed that wild-type DNA ligase III facilitates the interaction of DNA polymerase gamma with a nicked DNA substrate in vitro, and that the zinc finger domain of DNA ligase III is required for this activity. Mitochondrial protein extracts prepared from cells overexpressing a DNA ligase III protein that lacked the zinc finger domain had reduced base excision repair activity compared with extracts from cells overexpressing the wild-type protein. These data support the interpretation that the interaction of DNA ligase III and DNA polymerase gamma is required for proper maintenance of the mammalian mitochondrial genome.
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Affiliation(s)
- Ananya De
- Department of Pharmacology, University of Minnesota Medical School, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis MN 55455, U.S.A
| | - Colin Campbell
- Department of Pharmacology, University of Minnesota Medical School, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis MN 55455, U.S.A
- To whom correspondences should be addressed (email )
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41
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Hudson G, Chinnery PF. Mitochondrial DNA polymerase-gamma and human disease. Hum Mol Genet 2006; 15 Spec No 2:R244-52. [PMID: 16987890 DOI: 10.1093/hmg/ddl233] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The maintenance of mitochondrial DNA (mtDNA) is critically dependent upon polymerase-gamma (pol-gamma), encoded by the nuclear gene POLG. Over the last 5 years, it has become clear that mutations of POLG are a major cause of human disease. Secondary mtDNA defects characterize these disorders, with mtDNA depletion, multiple mtDNA deletions or multiple point mutations of mtDNA in clinically affected tissues. The secondary mtDNA defects cause cell and tissue-specific deficiencies of mitochondrial oxidative phosphorylation, leading to organ dysfunction and human disease. Functional genetic variants of POLG are present in up to approximately 0.5% of the general population, and pathogenic mutations have been described in most exons of the gene. Clinically, POLG mutations can present from early neonatal life to late middle age, with a spectrum of phenotypes that includes common neurological disorders such as migraine, epilepsy and Parkinsonism. Transgenic mice and biochemical studies of recombinant mutated proteins are helping to unravel mechanisms of pathogenesis, and patterns are beginning to emerge relating genotype to phenotype.
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Affiliation(s)
- Gavin Hudson
- Mitochondrial Research Group and Institute of Human Genetics, M41014, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
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42
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Graziewicz MA, Longley MJ, Copeland WC. DNA polymerase gamma in mitochondrial DNA replication and repair. Chem Rev 2006; 106:383-405. [PMID: 16464011 DOI: 10.1021/cr040463d] [Citation(s) in RCA: 211] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Maria A Graziewicz
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
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43
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Tomkinson AE, Vijayakumar S, Pascal JM, Ellenberger T. DNA ligases: structure, reaction mechanism, and function. Chem Rev 2006; 106:687-99. [PMID: 16464020 DOI: 10.1021/cr040498d] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Alan E Tomkinson
- Radiation Oncology Research Laboratory and Marlene and Stewart Greenebaum Cancer Center, Molecular and Cellular Biology Graduate Program, University of Maryland School of Medicine, Baltimore, 21201, USA.
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44
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Larsen NB, Rasmussen M, Rasmussen LJ. Nuclear and mitochondrial DNA repair: similar pathways? Mitochondrion 2005; 5:89-108. [PMID: 16050976 DOI: 10.1016/j.mito.2005.02.002] [Citation(s) in RCA: 209] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2004] [Revised: 01/31/2005] [Accepted: 02/03/2005] [Indexed: 02/08/2023]
Abstract
Mitochondrial DNA (mtDNA) alterations are implicated in a broad range of human diseases and alterations of the mitochondrial genome are assumed to be a result of its high susceptibility to oxidative damage and its limited DNA repair compared to nuclear DNA (nDNA). Characterization of DNA repair mechanisms has generally focused on these processes in nDNA but increasing interest and research effort have contributed to our knowledge of the mechanisms underlying DNA repair in mitochondria. In this review, we make comparisons between nDNA and mtDNA repair pathways and propose a model for how these pathways interact in mitochondria.
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Affiliation(s)
- Nicolai Balle Larsen
- Department of Life Sciences and Chemistry, Roskilde University, Universitetsvej 1, 4000 Roskilde, Denmark
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45
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Taanman JW, Llewelyn Williams S. The Human Mitochondrial Genome. OXIDATIVE STRESS AND DISEASE 2005. [DOI: 10.1201/9781420028843.ch3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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46
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Wang H, Rosidi B, Perrault R, Wang M, Zhang L, Windhofer F, Iliakis G. DNA ligase III as a candidate component of backup pathways of nonhomologous end joining. Cancer Res 2005; 65:4020-30. [PMID: 15899791 DOI: 10.1158/0008-5472.can-04-3055] [Citation(s) in RCA: 260] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Biochemical and genetic studies support the view that the majority of DNA double-strand breaks induced in the genome of higher eukaryotes by ionizing radiation are removed by two pathways of nonhomologous end joining (NHEJ) termed D-NHEJ and B-NHEJ. Whereas D-NHEJ depends on the activities of the DNA-dependent protein kinase and DNA ligase IV/XRCC4, components of B-NHEJ have not been identified. Using extract fractionation, we show that the majority of DNA end joining activity in extracts of HeLa cells derives from DNA ligase III. DNA ligase III fractionates through two columns with the maximum in DNA end joining activity and its depletion from the extract causes loss of activity that can be recovered by the addition of purified enzyme. The same fractionation protocols provide evidence for an additional factor strongly enhancing DNA end joining and shifting the product spectrum from circles to multimers. An in vivo plasmid assay shows that DNA ligase IV-deficient mouse embryo fibroblasts retain significant DNA end joining activity that can be reduced by up to 80% by knocking down DNA ligase III using RNA interference. These in vivo and in vitro observations identify DNA ligase III as a candidate component for B-NHEJ and point to additional factors contributing to NHEJ efficiency.
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Affiliation(s)
- Huichen Wang
- Department of Radiation Oncology, Division of Experimental Radiation Oncology, Kimmel Cancer Center, Jefferson Medical College, Philadelphia, Pennsylvania 19122, USA
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47
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Sun D, Urrabaz R. Development of non-electrophoretic assay method for DNA ligases and its application to screening of chemical inhibitors of DNA ligase I. ACTA ACUST UNITED AC 2005; 59:49-59. [PMID: 15134906 DOI: 10.1016/s0165-022x(02)00071-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2002] [Revised: 05/13/2002] [Accepted: 08/02/2002] [Indexed: 11/24/2022]
Abstract
A new rapid assay method for DNA ligases has been developed, which allows direct quantification of enzyme activity without using the traditional polyacrylamide gel electrophoretic technique. In this method, the 5'-biotinylated nicked duplex was used as a substrate for the ligase reaction, in which the 5'-end of the first oligonucleotide (19-mer) on the nicked strand is biotinylated and the second oligonucleotide (20-mer) on the same strand is labeled with radioactive 32P at the 5'-end. After ligation of the biotinylated 19-mer oligonucleotide into the second oligonucleotide with the reaction of DNA ligases, the biotinylated 19-mer oligonucleotide is converted into the radioactive 39-mer oligonucleotide. The ligase reaction products were heat-denatured to release both ligated and unligated biotinylated oligonucleotides. The biotinylated oligonucleotides were then captured on a streptavidin-coated microtiter plate and counted. The results obtained using this method correlated very well with those from the standard assay method using electrophoresis. Using this assay method, we were able to screen a chemical library and identify new DNA ligase inhibitors structurally related to resorcinol, which has growth inhibitory effects on the human breast cancer cell, MCF-7. The method described here is anticipated to be very useful for screening DNA ligase inhibitors from chemical libraries.
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Affiliation(s)
- Daekyu Sun
- Institute for Drug Development, Cancer Therapy and Research Center, 14960 Omicron Drive, San Antonio, TX 78245-3217, USA.
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48
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Abstract
DNA polymerase (pol) gamma is the sole DNA polymerase in animal mitochondria. Biochemical and genetic evidence document a key role for pol gamma in mitochondrial DNA replication, and whereas DNA repair and recombination were thought to be limited or absent in animal mitochondria, both have been demonstrated in recent years. Thus, the mitochondrial replicase is also apparently responsible for the relevant DNA synthetic reactions in these processes. Pol gamma comprises a catalytic core in a heterodimeric complex with an accessory subunit. The two-subunit holoenzyme is an efficient and processive polymerase, which exhibits high fidelity in nucleotide selection and incorporation while proofreading errors with its intrinsic 3' 5' exonuclease. Incorporation of nucleotide analogs followed by proofreading failure leads to mitochondrial toxicity in antiviral therapy, and misincorporation during DNA replication leads to mitochondrial mutagenesis and dysfunction. This review describes our current understanding of pol gamma biochemistry and biology, and it introduces other key proteins that function at the mitochondrial DNA replication fork.
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Affiliation(s)
- Laurie S Kaguni
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1319, USA.
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49
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Stuart JA, Hashiguchi K, Wilson DM, Copeland WC, Souza-Pinto NC, Bohr VA. DNA base excision repair activities and pathway function in mitochondrial and cellular lysates from cells lacking mitochondrial DNA. Nucleic Acids Res 2004; 32:2181-92. [PMID: 15107486 PMCID: PMC407819 DOI: 10.1093/nar/gkh533] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2003] [Revised: 03/21/2004] [Accepted: 03/21/2004] [Indexed: 11/13/2022] Open
Abstract
Mitochondrial DNA (mtDNA) contains higher steady-state levels of oxidative damage and mutates at rates significantly greater than nuclear DNA. Oxidative lesions in mtDNA are removed by a base excision repair (BER) pathway. All mtDNA repair proteins are nuclear encoded and imported. Most mtDNA repair proteins so far discovered are either identical to nuclear DNA repair proteins or isoforms of nuclear proteins arising from differential splicing. Regulation of mitochondrial BER is therefore not expected to be independent of nuclear BER, though the extent to which mitochondrial BER is regulated with respect to mtDNA amount or damage is largely unknown. Here we have measured DNA BER activities in lysates of mitochondria isolated from human 143B TK(-) osteosarcoma cells that had been depleted of mtDNA (rho(0)) or not (wt). Despite the total absence of mtDNA in the rho(0) cells, a complete mitochondrial BER pathway was present, as demonstrated using an in vitro assay with synthetic oligonucleotides. Measurement of individual BER protein activities in mitochondrial lysates indicated that some BER activities are insensitive to the lack of mtDNA. Uracil and 8-oxoguanine DNA glycosylase activities were relatively insensitive to the absence of mtDNA, only about 25% reduced in rho(0) relative to wt cells. Apurinic/apyrimidinic (AP) endonuclease and polymerase gamma activities were more affected, 65 and 45% lower, respectively, in rho(0) mitochondria. Overall BER activity in lysates was also about 65% reduced in rho(0) mitochondria. To identify the limiting deficiencies in BER of rho(0) mitochondria we supplemented the BER assay of mitochondrial lysates with pure uracil DNA glycosylase, AP endonuclease and/or the catalytic subunit of polymerase gamma. BER activity was stimulated by addition of uracil DNA glycosylase and polymerase gamma. However, no addition or combination of additions stimulated BER activity to wt levels. This suggests that an unknown activity, factor or interaction important in BER is deficient in rho(0) mitochondria. While nuclear BER protein levels and activities were generally not altered in rho(0) cells, AP endonuclease activity was substantially reduced in nuclear and in whole cell extracts. This appeared to be due to reduced endogenous reactive oxygen species (ROS) production in rho(0) cells, and not a general dysfunction of rho(0) cells, as exposure of cells to ROS rapidly stimulated increases in AP endonuclease activities and APE1 protein levels.
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Affiliation(s)
- J A Stuart
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
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50
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Abstract
The mitochondrial electron transport chain plays an important role in energy production in aerobic organisms and is also a significant source of reactive oxygen species that damage DNA, RNA and proteins in the cell. Oxidative damage to the mitochondrial DNA is implicated in various degenerative diseases, cancer and aging. The importance of mitochondrial ROS in age-related degenerative diseases is further strengthened by studies using animal models, Caenorhabditis elegans, Drosophila and yeast. Research in the last several years shows that mitochondrial DNA is more susceptible to various carcinogens and ROS when compared to nuclear DNA. DNA damage in mammalian mitochondria is repaired by base excision repair (BER). Studies have shown that mitochondria contain all the enzymes required for BER. Mitochondrial DNA damage, if not repaired, leads to disruption of electron transport chain and production of more ROS. This vicious cycle of ROS production and mtDNA damage ultimately leads to energy depletion in the cell and apoptosis.
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Affiliation(s)
- Bhaskar S Mandavilli
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, 111 Alexander Drive, P.O. Box 12233, Research Triangle Park, NC 27709, USA
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