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Riccio A, Brannon A, Krahn J, Bouvette J, Williams J, Borgnia M, Copeland W. Coordinated DNA polymerization by Polγ and the region of LonP1 regulated proteolysis. Nucleic Acids Res 2024; 52:7863-7875. [PMID: 38932681 PMCID: PMC11260448 DOI: 10.1093/nar/gkae539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 05/09/2024] [Accepted: 06/10/2024] [Indexed: 06/28/2024] Open
Abstract
The replicative mitochondrial DNA polymerase, Polγ, and its protein regulation are essential for the integrity of the mitochondrial genome. The intricacies of Polγ regulation and its interactions with regulatory proteins, which are essential for fine-tuning polymerase function, remain poorly understood. Misregulation of the Polγ heterotrimer, consisting of (i) PolG, the polymerase catalytic subunit and (ii) PolG2, the accessory subunit, ultimately results in mitochondrial diseases. Here, we used single particle cryo-electron microscopy to resolve the structure of PolG in its apoprotein state and we captured Polγ at three intermediates within the catalytic cycle: DNA bound, engaged, and an active polymerization state. Chemical crosslinking mass spectrometry, and site-directed mutagenesis uncovered the region of LonP1 engagement of PolG, which promoted proteolysis and regulation of PolG protein levels. PolG2 clinical variants, which disrupted a stable Polγ complex, led to enhanced LonP1-mediated PolG degradation. Overall, this insight into Polγ aids in an understanding of mitochondrial DNA replication and characterizes how machinery of the replication fork may be targeted for proteolytic degradation when improperly functioning.
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Affiliation(s)
- Amanda A Riccio
- Mitochondrial DNA Replication group, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Asia J Brannon
- Mitochondrial DNA Replication group, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Juno M Krahn
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Jonathan Bouvette
- Molecular Microscopy Consortium, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Jason G Williams
- Mass Spectrometry Research and Support Group, Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Mario J Borgnia
- Molecular Microscopy Consortium, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - William C Copeland
- Mitochondrial DNA Replication group, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
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2
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Yan W, Xie C, Sun S, Zheng Q, Wang J, Wang Z, Man CH, Wang H, Yang Y, Wang T, Shi L, Zhang S, Huang C, Xu S, Wang YP. SUCLG1 restricts POLRMT succinylation to enhance mitochondrial biogenesis and leukemia progression. EMBO J 2024; 43:2337-2367. [PMID: 38649537 PMCID: PMC11183053 DOI: 10.1038/s44318-024-00101-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 03/21/2024] [Accepted: 03/22/2024] [Indexed: 04/25/2024] Open
Abstract
Mitochondria are cellular powerhouses that generate energy through the electron transport chain (ETC). The mitochondrial genome (mtDNA) encodes essential ETC proteins in a compartmentalized manner, however, the mechanism underlying metabolic regulation of mtDNA function remains unknown. Here, we report that expression of tricarboxylic acid cycle enzyme succinate-CoA ligase SUCLG1 strongly correlates with ETC genes across various TCGA cancer transcriptomes. Mechanistically, SUCLG1 restricts succinyl-CoA levels to suppress the succinylation of mitochondrial RNA polymerase (POLRMT). Lysine 622 succinylation disrupts the interaction of POLRMT with mtDNA and mitochondrial transcription factors. SUCLG1-mediated POLRMT hyposuccinylation maintains mtDNA transcription, mitochondrial biogenesis, and leukemia cell proliferation. Specifically, leukemia-promoting FMS-like tyrosine kinase 3 (FLT3) mutations modulate nuclear transcription and upregulate SUCLG1 expression to reduce succinyl-CoA and POLRMT succinylation, resulting in enhanced mitobiogenesis. In line, genetic depletion of POLRMT or SUCLG1 significantly delays disease progression in mouse and humanized leukemia models. Importantly, succinyl-CoA level and POLRMT succinylation are downregulated in FLT3-mutated clinical leukemia samples, linking enhanced mitobiogenesis to cancer progression. Together, SUCLG1 connects succinyl-CoA with POLRMT succinylation to modulate mitochondrial function and cancer development.
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Affiliation(s)
- Weiwei Yan
- Precision Research Center for Refractory Diseases, Institute for Clinical Research, Shanghai Key Laboratory of Pancreatic Disease, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, 200080, Shanghai, China
| | - Chengmei Xie
- Precision Research Center for Refractory Diseases, Institute for Clinical Research, Shanghai Key Laboratory of Pancreatic Disease, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, 200080, Shanghai, China
| | - Sijun Sun
- Precision Research Center for Refractory Diseases, Institute for Clinical Research, Shanghai Key Laboratory of Pancreatic Disease, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, 200080, Shanghai, China
- Department of Gastrointestinal Surgery, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, 200080, Shanghai, China
| | - Quan Zheng
- Center for Single-Cell Omics, School of Public Health, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Jingyi Wang
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, 200080, Shanghai, China
| | - Zihao Wang
- Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, 200032, Shanghai, China
| | - Cheuk-Him Man
- Division of Haematology, Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Haiyan Wang
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, 200080, Shanghai, China
| | - Yunfan Yang
- Department of Cell Biology, School of Basic Medical Sciences, Cheeloo College of Medicine, Shandong University, 250012, Jinan, China
| | - Tianshi Wang
- Department of Biochemistry and Molecular Cell Biology, Shanghai Jiao Tong University School of Medicine, 200025, Shanghai, China
| | - Leilei Shi
- Precision Research Center for Refractory Diseases, Institute for Clinical Research, Shanghai Key Laboratory of Pancreatic Disease, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, 200080, Shanghai, China
| | - Shengjie Zhang
- Precision Research Center for Refractory Diseases, Institute for Clinical Research, Shanghai Key Laboratory of Pancreatic Disease, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, 200080, Shanghai, China.
| | - Chen Huang
- Department of Gastrointestinal Surgery, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, 200080, Shanghai, China.
| | - Shuangnian Xu
- Department of Hematology, Southwest Hospital, Army Medical University, 400038, Chongqing, China.
| | - Yi-Ping Wang
- Precision Research Center for Refractory Diseases, Institute for Clinical Research, Shanghai Key Laboratory of Pancreatic Disease, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, 200080, Shanghai, China.
- Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, 200032, Shanghai, China.
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Zong Y, Li H, Liao P, Chen L, Pan Y, Zheng Y, Zhang C, Liu D, Zheng M, Gao J. Mitochondrial dysfunction: mechanisms and advances in therapy. Signal Transduct Target Ther 2024; 9:124. [PMID: 38744846 PMCID: PMC11094169 DOI: 10.1038/s41392-024-01839-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 12/05/2023] [Accepted: 04/21/2024] [Indexed: 05/16/2024] Open
Abstract
Mitochondria, with their intricate networks of functions and information processing, are pivotal in both health regulation and disease progression. Particularly, mitochondrial dysfunctions are identified in many common pathologies, including cardiovascular diseases, neurodegeneration, metabolic syndrome, and cancer. However, the multifaceted nature and elusive phenotypic threshold of mitochondrial dysfunction complicate our understanding of their contributions to diseases. Nonetheless, these complexities do not prevent mitochondria from being among the most important therapeutic targets. In recent years, strategies targeting mitochondrial dysfunction have continuously emerged and transitioned to clinical trials. Advanced intervention such as using healthy mitochondria to replenish or replace damaged mitochondria, has shown promise in preclinical trials of various diseases. Mitochondrial components, including mtDNA, mitochondria-located microRNA, and associated proteins can be potential therapeutic agents to augment mitochondrial function in immunometabolic diseases and tissue injuries. Here, we review current knowledge of mitochondrial pathophysiology in concrete examples of common diseases. We also summarize current strategies to treat mitochondrial dysfunction from the perspective of dietary supplements and targeted therapies, as well as the clinical translational situation of related pharmacology agents. Finally, this review discusses the innovations and potential applications of mitochondrial transplantation as an advanced and promising treatment.
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Affiliation(s)
- Yao Zong
- Centre for Orthopaedic Research, Medical School, The University of Western Australia, Nedlands, WA, 6009, Australia
| | - Hao Li
- Department of Orthopaedics, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
- Institute of Microsurgery on Extremities, and Department of Orthopedic Surgery, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
| | - Peng Liao
- Department of Orthopaedics, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
- Institute of Microsurgery on Extremities, and Department of Orthopedic Surgery, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
| | - Long Chen
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, 200031, China
| | - Yao Pan
- Department of Orthopaedics, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
| | - Yongqiang Zheng
- Sixth People's Hospital Fujian, No. 16, Luoshan Section, Jinguang Road, Luoshan Street, Jinjiang City, Quanzhou, Fujian, China
| | - Changqing Zhang
- Department of Orthopaedics, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
| | - Delin Liu
- Department of Orthopaedics, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China.
- Institute of Microsurgery on Extremities, and Department of Orthopedic Surgery, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China.
| | - Minghao Zheng
- Centre for Orthopaedic Research, Medical School, The University of Western Australia, Nedlands, WA, 6009, Australia.
| | - Junjie Gao
- Department of Orthopaedics, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China.
- Institute of Microsurgery on Extremities, and Department of Orthopedic Surgery, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China.
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Wu C, Zhu H, Zhang Y, Ding L, Wang J. Interference with mitochondrial metabolism could serve as a potential therapeutic strategy for advanced prostate cancer. PLoS One 2024; 19:e0290753. [PMID: 38598542 PMCID: PMC11006138 DOI: 10.1371/journal.pone.0290753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 08/15/2023] [Indexed: 04/12/2024] Open
Abstract
Metabolic reprogramming has been defined as a hallmark of malignancies. Prior studies have focused on the single nucleotide polymorphism (SNP) of POLG2 gene, which is reportedly responsible for encoding mitochondrial DNA genes and is implicated in the material and energy metabolism of tumor cells, whereas its function in prostate cancer has been elusive. Gene expression profile matrix and clinical information were downloaded from TCGA (The Cancer Genome Atlas) data portal, and GSE3325 and GSE8511 were retrieved from GEO (Gene Expression Omnibus) database. We conducted analysis of the relative expression of POLG2, clinical characterization, survival analysis, GO / KEGG and GSEA (Gene Set Enrichment Analysis) enrichment analysis in R and employed STRING portal to acquaint ourselves with the protein-protein interaction (PPI). IHC (Immunohistochemical) profiles of POLG2 protein between normal and cancerous tissues were consulted via HPA (Human protein atlas) database and the immunohistochemical POLG2 were verified between para-cancerous and cancerous tissues in tissue array. At the cellular level, Mitochondrial dysfunction assay, DNA synthesis test, wound healing assay, and invasion assay were implemented to further validate the phenotype of POLG2 knockdown in PCa cell lines. RT-qPCR and western blotting were routinely adopted to verify variations of molecular expression within epithelial mesenchymal transition (EMT). Results showed that POLG2 was over-expressed in most cancer types, and the over-expression of POLG2 was correlated with PCa progression and suggested poor OS (Overall Survival) and PFI (Progress Free Interval). Multivariate analysis showed that POLG2 might be an independent prognostic factor of prostate cancer. We also performed GO/KEGG, GSEA analysis, co-expression genes, and PPI, and observed the metabolism-related gene alterations in PCa. Furthermore, we verified that POLG2 knockdown had an inhibitory effect on mitochondrial function, proliferation, cell motility, and invasion, we affirmed POLG2 could affect the prognosis of advanced prostate cancer via EMT. In summary, our findings indicate that over-expressed POLG2 renders poor prognosis in advanced prostate cancer. This disadvantageous factor can serve as a potential indicator, making it possible to target mitochondrial metabolism to treat advanced prostate cancer.
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Affiliation(s)
- Chuang Wu
- Department of Urology, Jiangsu Province Geriatric Hospital, Nanjing, Jiangsu, China
| | - Huihuang Zhu
- Department of Urology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Yang Zhang
- Department of Urology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Li Ding
- Department of Urology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Junqi Wang
- Department of Urology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
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Dombi E, Marinaki T, Spingardi P, Millar V, Hadjichristou N, Carver J, Johnston IG, Fratter C, Poulton J. Nucleoside supplements as treatments for mitochondrial DNA depletion syndrome. Front Cell Dev Biol 2024; 12:1260496. [PMID: 38665433 PMCID: PMC11043827 DOI: 10.3389/fcell.2024.1260496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 03/11/2024] [Indexed: 04/28/2024] Open
Abstract
Introduction: In mitochondrial DNA (mtDNA) depletion syndrome (MDS), patients cannot maintain sufficient mtDNA for their energy needs. MDS presentations range from infantile encephalopathy with hepatopathy (Alpers syndrome) to adult chronic progressive external ophthalmoplegia. Most are caused by nucleotide imbalance or by defects in the mtDNA replisome. There is currently no curative treatment available. Nucleoside therapy is a promising experimental treatment for TK2 deficiency, where patients are supplemented with exogenous deoxypyrimidines. We aimed to explore the benefits of nucleoside supplementation in POLG and TWNK deficient fibroblasts. Methods: We used high-content fluorescence microscopy with software-based image analysis to assay mtDNA content and membrane potential quantitatively, using vital dyes PicoGreen and MitoTracker Red CMXRos respectively. We tested the effect of 15 combinations (A, T, G, C, AT, AC, AG, CT, CG, GT, ATC, ATG, AGC, TGC, ATGC) of deoxynucleoside supplements on mtDNA content of fibroblasts derived from four patients with MDS (POLG1, POLG2, DGUOK, TWNK) in both a replicating (10% dialysed FCS) and quiescent (0.1% dialysed FCS) state. We used qPCR to measure mtDNA content of supplemented and non-supplemented fibroblasts following mtDNA depletion using 20 µM ddC and after 14- and 21-day recovery in a quiescent state. Results: Nucleoside treatments at 200 µM that significantly increased mtDNA content also significantly reduced the number of cells remaining in culture after 7 days of treatment, as well as mitochondrial membrane potential. These toxic effects were abolished by reducing the concentration of nucleosides to 50 µM. In POLG1 and TWNK cells the combination of ATGC treatment increased mtDNA content the most after 7 days in non-replicating cells. ATGC nucleoside combination significantly increased the rate of mtDNA recovery in quiescent POLG1 cells following mtDNA depletion by ddC. Conclusion: High-content imaging enabled us to link mtDNA copy number with key read-outs linked to patient wellbeing. Elevated G increased mtDNA copy number but severely impaired fibroblast growth, potentially by inhibiting purine synthesis and/or causing replication stress. Combinations of nucleosides ATGC, T, or TC, benefited growth of cells harbouring POLG mutations. These combinations, one of which reflects a commercially available preparation, could be explored further for treatment of POLG patients.
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Affiliation(s)
- Eszter Dombi
- Nuffield Department of Women’s and Reproductive Health, University of Oxford, Oxford, United Kingdom
| | - Tony Marinaki
- Purine Research Laboratory, Department of Biochemical Sciences, Guy’s and St Thomas’ Hospitals, London, United Kingdom
| | - Paolo Spingardi
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, Medical Sciences Division, University of Oxford, Oxford, United Kingdom
| | - Val Millar
- Target Discovery Institute, Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | | | - Janet Carver
- Nuffield Department of Women’s and Reproductive Health, University of Oxford, Oxford, United Kingdom
| | - Iain G. Johnston
- Department of Mathematics, University of Bergen, Bergen, Norway
- Computational Biology Unit, University of Bergen, Bergen, Norway
| | - Carl Fratter
- Oxford Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom
| | - Joanna Poulton
- Nuffield Department of Women’s and Reproductive Health, University of Oxford, Oxford, United Kingdom
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Che L, Wu Y, Sheng M, Xu J, Yu W, Weng Y. Intraoperative management during liver transplantation in the child with mitochondrial depletion syndrome: A case report. Int J Surg Case Rep 2024; 116:109432. [PMID: 38432165 PMCID: PMC10944120 DOI: 10.1016/j.ijscr.2024.109432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 02/17/2024] [Accepted: 02/19/2024] [Indexed: 03/05/2024] Open
Abstract
INTRODUCTION Mitochondrial DNA depletion syndrome (MDS) is a kind of autosomal recessive genetic disorder associated with a reduction in mitochondrial DNA (mtDNA) copy number caused by mutations in nuclear genes during nucleotide synthesis, which affects the energy production of tissues and organs. Changes in hemodynamics during liver transplantation may lead to high energy-demanding organs and tissues being vulnerable. This report described the intraoperative management during liver transplantation in a child with MDS. Ultimately, the child was discharged smoothly without any complications. PRESENTATION OF THE CASE A five-year-old boy was diagnosed with mitochondrial depletion syndrome preoperatively and scheduled for living donor liver transplantation. The incidence of postreperfusion syndrome (PRS) could not be avoided for 30 min after opening, despite our best efforts to aggressively prevent it before opening. While ensuring hemodynamic stability, we actively prevented and adopted high-energy-demand organ protection strategies to reduce the incidence of postoperative complications. Finally, the child was discharged 28 days after the operation, and no other complications were found. DISCUSSION Liver transplantation can be performed for liver failure in this disease to improve the quality of life and prolong the life of patients. As this child has mitochondrial DNA depletion syndrome, the disruption of cellular energy generation caused by mitochondrial malfunction puts high-energy-demanding organs and tissues at risk during surgery. It motivates us to pay closer attention to the prevention and treatment of PRS in anesthetic management to minimize damage to the child's organs and tissues with high energy demands. CONCLUSIONS This report describes the intraoperative management during liver transplantation in a child with mitochondrial depletion syndrome. To increase the safety of perioperative anesthesia and reduce mortality in patients with mitochondrial disease, for such patients, maintaining an acid-base balance and a stable internal environment is essential. We should also pay attention to protecting body temperature, using vasoactive drugs beforehand to lessen the incidence of PRS, and protecting high-energy-demanding organs afterward.
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Affiliation(s)
- Lu Che
- Department of Anesthesiology, Tianjin First Central Hospital, Tianjin, China
| | - Yuli Wu
- Tianjin Medical University First Central Clinical College, Tianjin, China
| | - Mingwei Sheng
- Department of Anesthesiology, Tianjin First Central Hospital, Tianjin, China
| | - Jiangang Xu
- Department of Anesthesiology, Tianjin First Central Hospital, Tianjin, China.
| | - Wenli Yu
- Department of Anesthesiology, Tianjin First Central Hospital, Tianjin, China.
| | - Yiqi Weng
- Department of Anesthesiology, Tianjin First Central Hospital, Tianjin, China.
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Wu S, Longley MJ, Lujan SA, Kunkel TA, Copeland WC. Mitochondrial DNA Enrichment for Sensitive Next-Generation Sequencing. Methods Mol Biol 2023; 2615:427-441. [PMID: 36807807 DOI: 10.1007/978-1-0716-2922-2_28] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Mitochondrial DNA (mtDNA) encodes components essential for cellular respiration. Low levels of point mutations and deletions accumulate in mtDNA during normal aging. However, improper maintenance of mtDNA results in mitochondrial diseases, stemming from progressive loss of mitochondrial function through the accelerated formation of deletions and mutations in mtDNA. To better understand the molecular mechanisms underlying the creation and propagation of mtDNA deletions, we developed the LostArc next-generation DNA sequencing pipeline to detect and quantify rare mtDNA species in small tissue samples. LostArc procedures are designed to minimize PCR amplification of mtDNA and instead achieve enrichment of mtDNA by selective destruction of nuclear DNA. This approach leads to cost-effective, high-depth sequencing of mtDNA with a sensitivity sufficient to identify one mtDNA deletion per million mtDNA circles. Here, we describe detailed protocols for isolation of genomic DNA from mouse tissues, enrichment of mtDNA through enzymatic destruction of linear nuclear DNA, and preparation of libraries for unbiased next-generation sequencing of mtDNA.
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Affiliation(s)
- Shilan Wu
- Genome Integrity and Structural Biology Laboratory, Mitochondrial DNA Replication Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Matthew J Longley
- Genome Integrity and Structural Biology Laboratory, Mitochondrial DNA Replication Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Scott A Lujan
- Genome Integrity and Structural Biology Laboratory, DNA Replication Fidelity Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Thomas A Kunkel
- Genome Integrity and Structural Biology Laboratory, DNA Replication Fidelity Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, Mitochondrial DNA Replication Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA.
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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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Chemotherapy Resistance: Role of Mitochondrial and Autophagic Components. Cancers (Basel) 2022; 14:cancers14061462. [PMID: 35326612 PMCID: PMC8945922 DOI: 10.3390/cancers14061462] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 03/10/2022] [Accepted: 03/10/2022] [Indexed: 11/16/2022] Open
Abstract
Simple Summary Chemotherapy resistance is a common occurrence during cancer treatment that cancer researchers are attempting to understand and overcome. Mitochondria are a crucial intracellular signaling core that are becoming important determinants of numerous aspects of cancer genesis and progression, such as metabolic reprogramming, metastatic capability, and chemotherapeutic resistance. Mitophagy, or selective autophagy of mitochondria, can influence both the efficacy of tumor chemotherapy and the degree of drug resistance. Regardless of the fact that mitochondria are well-known for coordinating ATP synthesis from cellular respiration in cellular bioenergetics, little is known its mitophagy regulation in chemoresistance. Recent advancements in mitochondrial research, mitophagy regulatory mechanisms, and their implications for our understanding of chemotherapy resistance are discussed in this review. Abstract Cancer chemotherapy resistance is one of the most critical obstacles in cancer therapy. One of the well-known mechanisms of chemotherapy resistance is the change in the mitochondrial death pathways which occur when cells are under stressful situations, such as chemotherapy. Mitophagy, or mitochondrial selective autophagy, is critical for cell quality control because it can efficiently break down, remove, and recycle defective or damaged mitochondria. As cancer cells use mitophagy to rapidly sweep away damaged mitochondria in order to mediate their own drug resistance, it influences the efficacy of tumor chemotherapy as well as the degree of drug resistance. Yet despite the importance of mitochondria and mitophagy in chemotherapy resistance, little is known about the precise mechanisms involved. As a consequence, identifying potential therapeutic targets by analyzing the signal pathways that govern mitophagy has become a vital research goal. In this paper, we review recent advances in mitochondrial research, mitophagy control mechanisms, and their implications for our understanding of chemotherapy resistance.
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Complex hereditary peripheral neuropathies caused by novel variants in mitochondrial-related nuclear genes. J Neurol 2022; 269:4129-4140. [PMID: 35235001 PMCID: PMC9293870 DOI: 10.1007/s00415-022-11026-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 02/05/2022] [Accepted: 02/11/2022] [Indexed: 11/04/2022]
Abstract
Mitochondrial disorders are a group of clinically and genetically heterogeneous multisystem disorders and peripheral neuropathy is frequently described in the context of mutations in mitochondrial-related nuclear genes. This study aimed to identify the causative mutations in mitochondrial-related nuclear genes in suspected hereditary peripheral neuropathy patients. We enrolled a large Japanese cohort of clinically suspected hereditary peripheral neuropathy patients who were mutation negative in the prescreening of the known Charcot–Marie–Tooth disease-causing genes. We performed whole-exome sequencing on 247 patients with autosomal recessive or sporadic inheritance for further analysis of 167 mitochondrial-related nuclear genes. We detected novel bi-allelic likely pathogenic/pathogenic variants in four patients, from four mitochondrial-related nuclear genes: pyruvate dehydrogenase beta-polypeptide (PDHB), mitochondrial poly(A) polymerase (MTPAP), hydroxyacyl-CoA dehydrogenase/3-ketoacyl-CoA thiolase/enoyl-CoA hydratase, beta subunit (HADHB), and succinate-CoA ligase ADP-forming beta subunit (SUCLA2). All these patients showed sensory and motor axonal polyneuropathy, combined with central nervous system or multisystem involvements. The pathological analysis of skeletal muscles revealed mild neurogenic changes without significant mitochondrial abnormalities. Targeted screening of mitochondria-related nuclear genes should be considered for patients with complex hereditary axonal polyneuropathy, accompanied by central nervous system dysfunctions, or with unexplainable multisystem disorders.
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Gustafson MA, Perera L, Shi M, Copeland WC. Mechanisms of SSBP1 variants in mitochondrial disease: Molecular dynamics simulations reveal stable tetramers with altered DNA binding surfaces. DNA Repair (Amst) 2021; 107:103212. [PMID: 34464898 PMCID: PMC8526412 DOI: 10.1016/j.dnarep.2021.103212] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 08/13/2021] [Indexed: 11/18/2022]
Abstract
Several mutations in the gene for the mitochondrial single stranded DNA binding protein (SSBP1) have recently been implicated in human disease, but initial reports are insufficient to explain the molecular mechanism of disease, including the possible role of SSBP1 heterotetramers in heterozygous patients. Here we employed molecular simulations to model the dynamics of wild type and 31 variant SSBP1 tetramer systems, including 7 variant homotetramer and 24 representative heterotetramer systems. Our simulations indicate that all variants are stable and most have stronger intermonomer interactions, reduced solvent accessible surface areas, and a net loss of positive surface charge. We then used structural alignments and phosphate binding simulations to predict DNA binding surfaces on SSBP1. Our models suggest that nearly the entire surface of SSBP1, excluding flexible loops and protruding helices, is available for DNA binding, and we observed several potential DNA binding hotspots. Changes to the protein surface in variant SSBP1 tetramers potentially alter anchor points or wrapping paths, rather than abolishing binding altogether. Overall, our findings disqualify tetramer destabilization or gross disruption of DNA binding as mechanisms of disease. Instead, they are consistent with subtle changes to DNA binding, wrapping, or release that cause rare but consequential failures of mtDNA maintenance, which, in turn, are consistent with the late onset of disease in most of the reported SSBP1 cases.
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Affiliation(s)
- Margaret A Gustafson
- Mitochondrial DNA Replication Group, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709, USA
| | - Lalith Perera
- Computational Chemistry and Molecular Modeling Support Group, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709, USA
| | - Min Shi
- Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709, USA
| | - William C Copeland
- Mitochondrial DNA Replication Group, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, 27709, USA.
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12
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Doğulu N, Tuna Kırsaçlıoğlu C, Köse E, Ünlüsoy Aksu A, Kuloğlu Z, Kansu A, Eminoğlu FT. The clinical variations and diagnostic challenges of deoxyguanosine kinase deficiency: a descriptive case series. J Pediatr Endocrinol Metab 2021; 34:1341-1347. [PMID: 34167177 DOI: 10.1515/jpem-2021-0108] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 05/03/2021] [Indexed: 11/15/2022]
Abstract
OBJECTIVES Deoxyguanosine kinase (DGUOK) deficiency is one of the leading causes of the mitochondrial DNA-depletion syndromes (MDDS) associated with hepatocerebral involvement. Herein, we present four cases of DGUOK deficiency to emphasize the clinical variability of disease and the challenges in the diagnosis of DGUOK deficiency. CASE PRESENTATION Hepatomegaly, hyperlactatemia, elevated alpha fetoprotein (AFP), alanine, and transaminase levels were detected in all patients, and cholestasis, coagulopathy, and hypotonia were common findings. All patients had a low birth weight, one patient underwent liver transplantation (LT). Clinical and laboratory findings of two patients and one patient suggested neonatal hemochromatosis and type 1 tyrosinemia, respectively. All patients were diagnosed with DGUOK deficiency by performing molecular genetic analysis. CONCLUSIONS Mitochondrial DNA-depletion syndromes should be kept in mind in cases in which hypotonicity, lactic acidosis, and neonatal cholestasis are observed. DGUOK deficiency may present in different clinics suggesting neonatal hemochromatosis or tyrosinemia type 1.
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Affiliation(s)
- Neslihan Doğulu
- Department of Pediatric Metabolism, Ankara University Faculty of Medicine, Ankara, Turkey
| | - Ceyda Tuna Kırsaçlıoğlu
- Department of Pediatric Gastroenterology, Hepatology and Nutrition, Ankara University Faculty of Medicine, Ankara, Turkey
| | - Engin Köse
- Department of Pediatric Metabolism, Ankara University Faculty of Medicine, Ankara, Turkey
| | - Aysel Ünlüsoy Aksu
- Department of Pediatric Gastroenterology, Hepatology and Nutrition, Ankara City Hospital, Ankara, Turkey
| | - Zarife Kuloğlu
- Department of Pediatric Gastroenterology, Hepatology and Nutrition, Ankara University Faculty of Medicine, Ankara, Turkey
| | - Aydan Kansu
- Department of Pediatric Gastroenterology, Hepatology and Nutrition, Ankara University Faculty of Medicine, Ankara, Turkey
| | - Fatma Tuba Eminoğlu
- Department of Pediatric Metabolism, Ankara University Faculty of Medicine, Ankara, Turkey
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13
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Sinsky J, Pichlerova K, Hanes J. Tau Protein Interaction Partners and Their Roles in Alzheimer's Disease and Other Tauopathies. Int J Mol Sci 2021; 22:9207. [PMID: 34502116 PMCID: PMC8431036 DOI: 10.3390/ijms22179207] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 08/23/2021] [Accepted: 08/25/2021] [Indexed: 02/06/2023] Open
Abstract
Tau protein plays a critical role in the assembly, stabilization, and modulation of microtubules, which are important for the normal function of neurons and the brain. In diseased conditions, several pathological modifications of tau protein manifest. These changes lead to tau protein aggregation and the formation of paired helical filaments (PHF) and neurofibrillary tangles (NFT), which are common hallmarks of Alzheimer's disease and other tauopathies. The accumulation of PHFs and NFTs results in impairment of physiological functions, apoptosis, and neuronal loss, which is reflected as cognitive impairment, and in the late stages of the disease, leads to death. The causes of this pathological transformation of tau protein haven't been fully understood yet. In both physiological and pathological conditions, tau interacts with several proteins which maintain their proper function or can participate in their pathological modifications. Interaction partners of tau protein and associated molecular pathways can either initiate and drive the tau pathology or can act neuroprotective, by reducing pathological tau proteins or inflammation. In this review, we focus on the tau as a multifunctional protein and its known interacting partners active in regulations of different processes and the roles of these proteins in Alzheimer's disease and tauopathies.
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Affiliation(s)
| | | | - Jozef Hanes
- Institute of Neuroimmunology, Slovak Academy of Sciences, Dubravska Cesta 9, 845 10 Bratislava, Slovakia; (J.S.); (K.P.)
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14
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Sullivan ED, Longley MJ, Copeland WC. Polymerase γ efficiently replicates through many natural template barriers but stalls at the HSP1 quadruplex. J Biol Chem 2021; 295:17802-17815. [PMID: 33454015 DOI: 10.1074/jbc.ra120.015390] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 10/05/2020] [Indexed: 12/27/2022] Open
Abstract
Faithful replication of the mitochondrial genome is carried out by a set of key nuclear-encoded proteins. DNA polymerase γ is a core component of the mtDNA replisome and the only replicative DNA polymerase localized to mitochondria. The asynchronous mechanism of mtDNA replication predicts that the replication machinery encounters dsDNA and unique physical barriers such as structured genes, G-quadruplexes, and other obstacles. In vitro experiments here provide evidence that the polymerase γ heterotrimer is well-adapted to efficiently synthesize DNA, despite the presence of many naturally occurring roadblocks. However, we identified a specific G-quadruplex-forming sequence at the heavy-strand promoter (HSP1) that has the potential to cause significant stalling of mtDNA replication. Furthermore, this structured region of DNA corresponds to the break site for a large (3,895 bp) deletion observed in mitochondrial disease patients. The presence of this deletion in humans correlates with UV exposure, and we have found that efficiency of polymerase γ DNA synthesis is reduced after this quadruplex is exposed to UV in vitro.
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Affiliation(s)
- Eric D Sullivan
- Mitochondrial DNA Replication Group, Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina, USA
| | - Matthew J Longley
- Mitochondrial DNA Replication Group, Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina, USA
| | - William C Copeland
- Mitochondrial DNA Replication Group, Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina, USA.
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15
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Moore TM, Zhou Z, Strumwasser AR, Cohn W, Lin AJ, Cory K, Whitney K, Ho T, Ho T, Lee JL, Rucker DH, Hoang AN, Widjaja K, Abrishami AD, Charugundla S, Stiles L, Whitelegge JP, Turcotte LP, Wanagat J, Hevener AL. Age-induced mitochondrial DNA point mutations are inadequate to alter metabolic homeostasis in response to nutrient challenge. Aging Cell 2020; 19:e13166. [PMID: 33049094 PMCID: PMC7681042 DOI: 10.1111/acel.13166] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 04/10/2020] [Accepted: 04/27/2020] [Indexed: 12/14/2022] Open
Abstract
Mitochondrial dysfunction is frequently associated with impairment in metabolic homeostasis and insulin action, and is thought to underlie cellular aging. However, it is unclear whether mitochondrial dysfunction is a cause or consequence of insulin resistance in humans. To determine the impact of intrinsic mitochondrial dysfunction on metabolism and insulin action, we performed comprehensive metabolic phenotyping of the polymerase gamma (PolG) D257A “mutator” mouse, a model known to accumulate supraphysiological mitochondrial DNA (mtDNA) point mutations. We utilized the heterozygous PolG mutator mouse (PolG+/mut) because it accumulates mtDNA point mutations ~ 500‐fold > wild‐type mice (WT), but fails to develop an overt progeria phenotype, unlike PolGmut/mut animals. To determine whether mtDNA point mutations induce metabolic dysfunction, we examined male PolG+/mut mice at 6 and 12 months of age during normal chow feeding, after 24‐hr starvation, and following high‐fat diet (HFD) feeding. No marked differences were observed in glucose homeostasis, adiposity, protein/gene markers of metabolism, or oxygen consumption in muscle between WT and PolG+/mut mice during any of the conditions or ages studied. However, proteomic analyses performed on isolated mitochondria from 12‐month‐old PolG+/mut mouse muscle revealed alterations in the expression of mitochondrial ribosomal proteins, electron transport chain components, and oxidative stress‐related factors compared with WT. These findings suggest that mtDNA point mutations at levels observed in mammalian aging are insufficient to disrupt metabolic homeostasis and insulin action in male mice.
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Affiliation(s)
- Timothy M. Moore
- Department of Biological Sciences Dana & David Dornsife College of Letters, Arts, and Sciences University of Southern California Los Angeles CA USA
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Zhenqi Zhou
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Alexander R. Strumwasser
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Whitaker Cohn
- Department of Psychiatry and Biobehavioral Sciences & The Semel Institute for Neuroscience and Human Behavior University of California Los Angeles CA USA
| | - Amanda J. Lin
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Kevin Cory
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Kate Whitney
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Theodore Ho
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Timothy Ho
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Joseph L. Lee
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Daniel H. Rucker
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Austin N. Hoang
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Kevin Widjaja
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Aaron D. Abrishami
- Division of Cardiology Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Sarada Charugundla
- Division of Cardiology Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Linsey Stiles
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Julian P. Whitelegge
- Department of Psychiatry and Biobehavioral Sciences & The Semel Institute for Neuroscience and Human Behavior University of California Los Angeles CA USA
| | - Lorraine P. Turcotte
- Department of Biological Sciences Dana & David Dornsife College of Letters, Arts, and Sciences University of Southern California Los Angeles CA USA
| | - Jonathan Wanagat
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
| | - Andrea L. Hevener
- Division of Endocrinology, Diabetes, and Hypertension Department of Medicine David Geffen School of Medicine University of California Los Angeles CA USA
- Iris Cantor‐UCLA Women's Health Center University of California Los Angeles CA USA
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16
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Lujan SA, Longley MJ, Humble MH, Lavender CA, Burkholder A, Blakely EL, Alston CL, Gorman GS, Turnbull DM, McFarland R, Taylor RW, Kunkel TA, Copeland WC. Ultrasensitive deletion detection links mitochondrial DNA replication, disease, and aging. Genome Biol 2020; 21:248. [PMID: 32943091 PMCID: PMC7500033 DOI: 10.1186/s13059-020-02138-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 08/07/2020] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Acquired human mitochondrial genome (mtDNA) deletions are symptoms and drivers of focal mitochondrial respiratory deficiency, a pathological hallmark of aging and late-onset mitochondrial disease. RESULTS To decipher connections between these processes, we create LostArc, an ultrasensitive method for quantifying deletions in circular mtDNA molecules. LostArc reveals 35 million deletions (~ 470,000 unique spans) in skeletal muscle from 22 individuals with and 19 individuals without pathogenic variants in POLG. This nuclear gene encodes the catalytic subunit of replicative mitochondrial DNA polymerase γ. Ablation, the deleted mtDNA fraction, suffices to explain skeletal muscle phenotypes of aging and POLG-derived disease. Unsupervised bioinformatic analyses reveal distinct age- and disease-correlated deletion patterns. CONCLUSIONS These patterns implicate replication by DNA polymerase γ as the deletion driver and suggest little purifying selection against mtDNA deletions by mitophagy in postmitotic muscle fibers. Observed deletion patterns are best modeled as mtDNA deletions initiated by replication fork stalling during strand displacement mtDNA synthesis.
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Affiliation(s)
- Scott A Lujan
- Genome Integrity and Structural Biology Laboratory, DNA Replication Fidelity Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA
| | - Matthew J Longley
- Genome Integrity and Structural Biology Laboratory, Mitochondrial DNA Replication Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA
| | - Margaret H Humble
- Genome Integrity and Structural Biology Laboratory, Mitochondrial DNA Replication Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA
| | - Christopher A Lavender
- Integrative Bioinformatics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA
| | - Adam Burkholder
- Integrative Bioinformatics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA
| | - Emma L Blakely
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- NHS Highly Specialised Mitochondrial Diagnostic Laboratory, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, NE1 4LP, UK
| | - Charlotte L Alston
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- NHS Highly Specialised Mitochondrial Diagnostic Laboratory, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, NE1 4LP, UK
| | - Grainne S Gorman
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Doug M Turnbull
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Robert McFarland
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- NHS Highly Specialised Mitochondrial Diagnostic Laboratory, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, NE1 4LP, UK
| | - Thomas A Kunkel
- Genome Integrity and Structural Biology Laboratory, DNA Replication Fidelity Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, Mitochondrial DNA Replication Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA.
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17
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Zhang H. Mechanisms of mutagenesis induced by DNA lesions: multiple factors affect mutations in translesion DNA synthesis. Crit Rev Biochem Mol Biol 2020; 55:219-251. [PMID: 32448001 DOI: 10.1080/10409238.2020.1768205] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Environmental mutagens lead to mutagenesis. However, the mechanisms are very complicated and not fully understood. Environmental mutagens produce various DNA lesions, including base-damaged or sugar-modified DNA lesions, as well as epigenetically modified DNA. DNA polymerases produce mutation spectra in translesion DNA synthesis (TLS) through misincorporation of incorrect nucleotides, frameshift deletions, blockage of DNA replication, imbalance of leading- and lagging-strand DNA synthesis, and genome instability. Motif or subunit in DNA polymerases further affects the mutations in TLS. Moreover, protein interactions and accessory proteins in DNA replisome also alter mutations in TLS, demonstrated by several representative DNA replisomes. Finally, in cells, multiple DNA polymerases or cellular proteins collaborate in TLS and reduce in vivo mutagenesis. Summaries and perspectives were listed. This review shows mechanisms of mutagenesis induced by DNA lesions and the effects of multiple factors on mutations in TLS in vitro and in vivo.
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Affiliation(s)
- Huidong Zhang
- Key Laboratory of Environment and Female Reproductive Health, West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China
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18
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Mahjoub G, Habibzadeh P, Dastsooz H, Mirzaei M, Kavosi A, Jamali L, Javanmardi H, Katibeh P, Faghihi MA, Dastgheib SA. Clinical and molecular characterization of three patients with Hepatocerebral form of mitochondrial DNA depletion syndrome: a case series. BMC MEDICAL GENETICS 2019; 20:167. [PMID: 31664948 PMCID: PMC6819644 DOI: 10.1186/s12881-019-0893-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 09/10/2019] [Indexed: 12/31/2022]
Abstract
Background Mitochondrial DNA depletion syndromes (MDS) are clinically and phenotypically heterogeneous disorders resulting from nuclear gene mutations. The affected individuals represent a notable reduction in mitochondrial DNA (mtDNA) content, which leads to malfunction of the components of the respiratory chain. MDS is classified according to the type of affected tissue; the most common type is hepatocerebral form, which is attributed to mutations in nuclear genes such as DGUOK and MPV17. These two genes encode mitochondrial proteins and play major roles in mtDNA synthesis. Case presentation In this investigation patients in three families affected by hepatocerebral form of MDS who were initially diagnosed with tyrosinemia underwent full clinical evaluation. Furthermore, the causative mutations were identified using next generation sequencing and were subsequently validated using sanger sequencing. The effect of the mutations on the gene expression was also studied using real-time PCR. A pathogenic heterozygous frameshift deletion mutation in DGUOK gene was identified in parents of two affected patients (c.706–707 + 2 del: p.k236 fs) presenting with jaundice, impaired fetal growth, low-birth weight, and failure to thrive who died at the age of 3 and 6 months in family I. Moreover, a novel splice site mutation in MPV17 gene (c.461 + 1G > C) was identified in a patient with jaundice, muscle weakness, and failure to thrive who died due to hepatic failure at the age of 4 months. A 5-month-old infant presenting with jaundice, dark urine, poor sucking, and feeding problems was also identified to have another novel mutation in MPV17 gene leading to stop gain mutation (c.277C > T: p.(Gln93*)). Conclusions These patients had overlapping clinical features with tyrosinemia. MDS should be considered a differential diagnosis in patients presenting with signs and symptoms of tyrosinemia.
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Affiliation(s)
- Ghazale Mahjoub
- Persian BayanGene Research and Training Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Parham Habibzadeh
- Persian BayanGene Research and Training Center, Shiraz University of Medical Sciences, Shiraz, Iran.,Student Research Committee, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Hassan Dastsooz
- Persian BayanGene Research and Training Center, Shiraz University of Medical Sciences, Shiraz, Iran.,Italian Institute for Genomic Medicine (IIGM), University of Turin, Turin, Italy
| | - Malihe Mirzaei
- Persian BayanGene Research and Training Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Arghavan Kavosi
- Persian BayanGene Research and Training Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Laila Jamali
- Persian BayanGene Research and Training Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Haniyeh Javanmardi
- Student Research Committee, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Pegah Katibeh
- Department of Pediatrics, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Mohammad Ali Faghihi
- Persian BayanGene Research and Training Center, Shiraz University of Medical Sciences, Shiraz, Iran.,Center for Therapeutic Innovation, Department of Psychiatry and Behavioral Sciences, University of Miami Miller School of Medicine, Miami, USA
| | - Seyed Alireza Dastgheib
- Department of Medical Genetics, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
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19
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Genomic Balance: Two Genomes Establishing Synchrony to Modulate Cellular Fate and Function. Cells 2019; 8:cells8111306. [PMID: 31652817 PMCID: PMC6912345 DOI: 10.3390/cells8111306] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 10/17/2019] [Accepted: 10/22/2019] [Indexed: 01/21/2023] Open
Abstract
It is becoming increasingly apparent that cells require cooperation between the nuclear and mitochondrial genomes to promote effective function. However, it was long thought that the mitochondrial genome was under the strict control of the nuclear genome and the mitochondrial genome had little influence on cell fate unless it was extensively mutated, as in the case of the mitochondrial DNA diseases. However, as our understanding of the roles that epigenetic regulators, including DNA methylation, and metabolism play in cell fate and function, the role of the mitochondrial genome appears to have a greater influence than previously thought. In this review, I draw on examples from tumorigenesis, stem cells, and oocyte pre- and post-fertilisation events to discuss how modulating one genome affects the other and that this results in a compromise to produce functional mature cells. I propose that, during development, both of the genomes interact with each other through intermediaries to establish genomic balance and that establishing genomic balance is a key facet in determining cell fate and viability.
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20
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Haroon S, Li A, Weinert JL, Fritsch C, Ericson NG, Alexander-Floyd J, Braeckman BP, Haynes CM, Bielas JH, Gidalevitz T, Vermulst M. Multiple Molecular Mechanisms Rescue mtDNA Disease in C. elegans. Cell Rep 2019; 22:3115-3125. [PMID: 29562168 PMCID: PMC6106782 DOI: 10.1016/j.celrep.2018.02.099] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 12/07/2017] [Accepted: 02/25/2018] [Indexed: 01/03/2023] Open
Abstract
Genetic instability of the mitochondrial genome (mtDNA) plays an important role in human aging and disease. Thus far, it has proven difficult to develop successful treatment strategies for diseases that are caused by mtDNA instability. To address this issue, we developed a model of mtDNA disease in the nematode C. elegans, an animal model that can rapidly be screened for genes and biological pathways that reduce mitochondrial pathology. These worms recapitulate all the major hallmarks of mtDNA disease in humans, including increased mtDNA instability, loss of respiration, reduced neuromuscular function, and a shortened lifespan. We found that these phenotypes could be rescued by intervening in numerous biological pathways, including IGF-1/insulin signaling, mitophagy, and the mitochondrial unfolded protein response, suggesting that it may be possible to ameliorate mtDNA disease through multiple molecular mechanisms.
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Affiliation(s)
- Suraiya Haroon
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, PA 19104, USA
| | - Annie Li
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, PA 19104, USA
| | - Jaye L Weinert
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, PA 19104, USA
| | - Clark Fritsch
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, PA 19104, USA
| | - Nolan G Ericson
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | | | - Bart P Braeckman
- Laboratory of Aging Physiology and Molecular Evolution, Biology Department, Ghent University, 9000 Ghent, Belgium
| | - Cole M Haynes
- Department of Molecular, Cell, and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Jason H Bielas
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Tali Gidalevitz
- Department of Biology, Drexel University, Philadelphia, PA 19104, USA
| | - Marc Vermulst
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, PA 19104, USA.
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21
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Mitochondria and Female Germline Stem Cells-A Mitochondrial DNA Perspective. Cells 2019; 8:cells8080852. [PMID: 31398797 PMCID: PMC6721711 DOI: 10.3390/cells8080852] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 08/06/2019] [Accepted: 08/06/2019] [Indexed: 02/06/2023] Open
Abstract
Mitochondria and mitochondrial DNA have important roles to play in development. In primordial germ cells, they progress from small numbers to populate the maturing oocyte with high numbers to support post-fertilization events. These processes take place under the control of significant changes in DNA methylation and other epigenetic modifiers, as well as changes to the DNA methylation status of the nuclear-encoded mitochondrial DNA replication factors. Consequently, the differentiating germ cell requires significant synchrony between the two genomes in order to ensure that they are fit for purpose. In this review, I examine these processes in the context of female germline stem cells that are isolated from the ovary and those derived from embryonic stem cells and reprogrammed somatic cells. Although our knowledge is limited in this respect, I provide predictions based on other cellular systems of what is expected and provide insight into how these cells could be used in clinical medicine.
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22
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Kaur P, Longley MJ, Pan H, Wang H, Copeland WC. Single-molecule DREEM imaging reveals DNA wrapping around human mitochondrial single-stranded DNA binding protein. Nucleic Acids Res 2019; 46:11287-11302. [PMID: 30256971 PMCID: PMC6265486 DOI: 10.1093/nar/gky875] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 09/18/2018] [Indexed: 01/01/2023] Open
Abstract
Improper maintenance of the mitochondrial genome progressively disrupts cellular respiration and causes severe metabolic disorders commonly termed mitochondrial diseases. Mitochondrial single-stranded DNA binding protein (mtSSB) is an essential component of the mtDNA replication machinery. We utilized single-molecule methods to examine the modes by which human mtSSB binds DNA to help define protein interactions at the mtDNA replication fork. Direct visualization of individual mtSSB molecules by atomic force microscopy (AFM) revealed a random distribution of mtSSB tetramers bound to extended regions of single-stranded DNA (ssDNA), strongly suggesting non-cooperative binding by mtSSB. Selective binding to ssDNA was confirmed by AFM imaging of individual mtSSB tetramers bound to gapped plasmid DNA substrates bearing defined single-stranded regions. Shortening of the contour length of gapped DNA upon binding mtSSB was attributed to DNA wrapping around mtSSB. Tracing the DNA path in mtSSB–ssDNA complexes with Dual-Resonance-frequency-Enhanced Electrostatic force Microscopy established a predominant binding mode with one DNA strand winding once around each mtSSB tetramer at physiological salt conditions. Single-molecule imaging suggests mtSSB may not saturate or fully protect single-stranded replication intermediates during mtDNA synthesis, leaving the mitochondrial genome vulnerable to chemical mutagenesis, deletions driven by primer relocation or other actions consistent with clinically observed deletion biases.
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Affiliation(s)
- Parminder Kaur
- Physics Department, North Carolina State University, Raleigh, North Carolina, NC 27695, USA.,Center for Human Health and the Environment, North Carolina State University, Raleigh, North Carolina, NC 27695, USA
| | - Matthew J Longley
- Genome Integrity and Structural Biology Laboratory, NIEHS, NIH, Research Triangle Park, NC 27709, USA
| | - Hai Pan
- Physics Department, North Carolina State University, Raleigh, North Carolina, NC 27695, USA
| | - Hong Wang
- Physics Department, North Carolina State University, Raleigh, North Carolina, NC 27695, USA.,Center for Human Health and the Environment, North Carolina State University, Raleigh, North Carolina, NC 27695, USA
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, NIEHS, NIH, Research Triangle Park, NC 27709, USA
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Khodour Y, Kaguni LS, Stiban J. Iron-sulfur clusters in nucleic acid metabolism: Varying roles of ancient cofactors. Enzymes 2019; 45:225-256. [PMID: 31627878 DOI: 10.1016/bs.enz.2019.08.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Despite their relative simplicity, iron-sulfur clusters have been omnipresent as cofactors in myriad cellular processes such as oxidative phosphorylation and other respiratory pathways. Recent research advances confirm the presence of different clusters in enzymes involved in nucleic acid metabolism. Iron-sulfur clusters can therefore be considered hallmarks of cellular metabolism. Helicases, nucleases, glycosylases, DNA polymerases and transcription factors, among others, incorporate various types of clusters that serve differing roles. In this chapter, we review our current understanding of the identity and functions of iron-sulfur clusters in DNA and RNA metabolizing enzymes, highlighting their importance as regulators of cellular function.
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Affiliation(s)
- Yara Khodour
- Department of Biology and Biochemistry, Birzeit University, West Bank, Palestine
| | - Laurie S Kaguni
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, United States
| | - Johnny Stiban
- Department of Biology and Biochemistry, Birzeit University, West Bank, Palestine.
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24
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Kuskovsky R, Buj R, Xu P, Hofbauer S, Doan MT, Jiang H, Bostwick A, Mesaros C, Aird KM, Snyder NW. Simultaneous isotope dilution quantification and metabolic tracing of deoxyribonucleotides by liquid chromatography high resolution mass spectrometry. Anal Biochem 2018; 568:65-72. [PMID: 30605633 DOI: 10.1016/j.ab.2018.12.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 12/26/2018] [Accepted: 12/29/2018] [Indexed: 12/21/2022]
Abstract
Quantification of cellular deoxyribonucleoside mono- (dNMP), di- (dNDP), triphosphates (dNTPs) and related nucleoside metabolites are difficult due to their physiochemical properties and widely varying abundance. Involvement of dNTP metabolism in cellular processes including senescence and pathophysiological processes including cancer and viral infection make dNTP metabolism an important bioanalytical target. We modified a previously developed ion pairing reversed phase chromatography-mass spectrometry method for the simultaneous quantification and 13C isotope tracing of dNTP metabolites. dNMPs, dNDPs, and dNTPs were chromatographically resolved to avoid mis-annotation of in-source fragmentation. We used commercially available 13C15N-stable isotope labeled analogs as internal standards and show that this isotope dilution approach improves analytical figures of merit. At sufficiently high mass resolution achievable on an Orbitrap mass analyzer, stable isotope resolved metabolomics allows simultaneous isotope dilution quantification and 13C isotope tracing from major substrates including 13C-glucose. As a proof of principle, we quantified dNMP, dNDP and dNTP pools from multiple cell lines. We also identified isotopologue enrichment from glucose corresponding to ribose from the pentose-phosphate pathway in dNTP metabolites.
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Affiliation(s)
- Rostislav Kuskovsky
- AJ Drexel Autism Institute, Drexel University, 3020 Market St Suite 560, Philadelphia, PA, 19104, USA
| | - Raquel Buj
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA, USA
| | - Peining Xu
- AJ Drexel Autism Institute, Drexel University, 3020 Market St Suite 560, Philadelphia, PA, 19104, USA
| | - Samuel Hofbauer
- Centers for Cancer Pharmacology and Excellence in Environmental Toxicology, Department of Pharmacology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Mary T Doan
- AJ Drexel Autism Institute, Drexel University, 3020 Market St Suite 560, Philadelphia, PA, 19104, USA
| | - Helen Jiang
- AJ Drexel Autism Institute, Drexel University, 3020 Market St Suite 560, Philadelphia, PA, 19104, USA
| | - Anna Bostwick
- AJ Drexel Autism Institute, Drexel University, 3020 Market St Suite 560, Philadelphia, PA, 19104, USA
| | - Clementina Mesaros
- Centers for Cancer Pharmacology and Excellence in Environmental Toxicology, Department of Pharmacology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Katherine M Aird
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA, USA
| | - Nathaniel W Snyder
- AJ Drexel Autism Institute, Drexel University, 3020 Market St Suite 560, Philadelphia, PA, 19104, USA.
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Hoff KE, DeBalsi KL, Sanchez-Quintero MJ, Longley MJ, Hirano M, Naini AB, Copeland WC. Characterization of the human homozygous R182W POLG2 mutation in mitochondrial DNA depletion syndrome. PLoS One 2018; 13:e0203198. [PMID: 30157269 PMCID: PMC6114919 DOI: 10.1371/journal.pone.0203198] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Accepted: 08/14/2018] [Indexed: 12/18/2022] Open
Abstract
Mutations in mitochondrial DNA (mtDNA) have been linked to a variety of metabolic, neurological and muscular diseases which can present at any time throughout life. MtDNA is replicated by DNA polymerase gamma (Pol γ), twinkle helicase and mitochondrial single-stranded binding protein (mtSSB). The Pol γ holoenzyme is a heterotrimer consisting of the p140 catalytic subunit and a p55 homodimeric accessory subunit encoded by the nuclear genes POLG and POLG2, respectively. The accessory subunits enhance DNA binding and promote processive DNA synthesis of the holoenzyme. Mutations in either POLG or POLG2 are linked to disease and adversely affect maintenance of the mitochondrial genome, resulting in depletion, deletions and/or point mutations in mtDNA. A homozygous mutation located at Chr17: 62492543G>A in POLG2, resulting in R182W substitution in p55, was previously identified to cause mtDNA depletion and fatal hepatic liver failure. Here we characterize this homozygous R182W p55 mutation using in vivo cultured cell models and in vitro biochemical assessments. Compared to control fibroblasts, homozygous R182W p55 primary dermal fibroblasts exhibit a two-fold slower doubling time, reduced mtDNA copy number and reduced levels of POLG and POLG2 transcripts correlating with the reported disease state. Expression of R182W p55 in HEK293 cells impairs oxidative-phosphorylation. Biochemically, R182W p55 displays DNA binding and association with p140 similar to WT p55. R182W p55 mimics the ability of WT p55 to stimulate primer extension, support steady-state nucleotide incorporation, and suppress the exonuclease function of Pol γin vitro. However, R182W p55 has severe defects in protein stability as determined by differential scanning fluorimetry and in stimulating function as determined by thermal inactivation. These data demonstrate that the Chr17: 62492543G>A mutation in POLG2, R182W p55, severely impairs stability of the accessory subunit and is the likely cause of the disease phenotype.
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Affiliation(s)
- Kirsten E. Hoff
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC, United States of America
| | - Karen L. DeBalsi
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC, United States of America
| | - Maria J. Sanchez-Quintero
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY, United States of America
| | - Matthew J. Longley
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC, United States of America
| | - Michio Hirano
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY, United States of America
| | - Ali B. Naini
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY, United States of America
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States of America
- Division of Personalized Genomic Medicine, Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY, United States of America
| | - William C. Copeland
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC, United States of America
- * E-mail:
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Mitochondrial DNA replication: clinical syndromes. Essays Biochem 2018; 62:297-308. [PMID: 29950321 DOI: 10.1042/ebc20170101] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 03/17/2018] [Accepted: 05/23/2018] [Indexed: 02/08/2023]
Abstract
Each nucleated cell contains several hundreds of mitochondria, which are unique organelles in being under dual genome control. The mitochondria contain their own DNA, the mtDNA, but most of mitochondrial proteins are encoded by nuclear genes, including all the proteins required for replication, transcription, and repair of mtDNA. MtDNA replication is a continuous process that requires coordinated action of several enzymes that are part of the mtDNA replisome. It also requires constant supply of deoxyribonucleotide triphosphates(dNTPs) and interaction with other mitochondria for mixing and unifying the mitochondrial compartment. MtDNA maintenance defects are a growing list of disorders caused by defects in nuclear genes involved in different aspects of mtDNA replication. As a result of defects in these genes, mtDNA depletion and/or multiple mtDNA deletions develop in affected tissues resulting in variable manifestations that range from adult-onset mild disease to lethal presentation early in life.
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Lattuada D, Alfonsi G, Roncati L, Pusiol T, Bulfoni A, Ferrero S, Lavezzi A. Mitochondrial DNA content: A new biomarker for sudden intrauterine unexplained death syndrome (SIUDS). Mitochondrion 2018; 40:13-15. [DOI: 10.1016/j.mito.2017.09.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 06/08/2017] [Accepted: 09/01/2017] [Indexed: 10/18/2022]
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Kasahara T, Kato T. What Can Mitochondrial DNA Analysis Tell Us About Mood Disorders? Biol Psychiatry 2018; 83:731-738. [PMID: 29102411 DOI: 10.1016/j.biopsych.2017.09.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 09/11/2017] [Accepted: 09/12/2017] [Indexed: 12/11/2022]
Abstract
Variants in mitochondrial DNA (mtDNA) and nuclear genes encoding mitochondrial proteins in bipolar disorder, depression, or other psychiatric disorders have been studied for decades, since mitochondrial dysfunction was first suggested in the brains of patients with these diseases. Candidate gene association studies initially resulted in findings compatible with the mitochondrial dysfunction hypothesis. Many of those studies, however, were conducted with modest sample sizes (N < 1000), which could cause false positive findings. Furthermore, the DNA samples examined in these studies, including genome-wide association studies, were generally derived from peripheral tissues. One key unanswered question is whether there is an association between mood disorders and somatic mtDNA mutations (deletions and point mutations) in brain regions that accumulate a high amount of mtDNA mutations and/or are involved in the regulation of mood. Two lines of robust evidence supporting the importance of mtDNA mutations in brain tissues for mood disorders have come from clinical observation of mitochondrial disease patients who carry primary mtDNA mutations or accumulate secondary mtDNA mutations due to nuclear mutations and an animal model study. More than half of mitochondrial disease patients have comorbid mood disorders, and mice with neuron-specific accumulation of mtDNA mutations show spontaneous depression-like episodes. In this review, we first summarize the current knowledge of mtDNA and its genetics and discuss what mtDNA analysis tells us about neuropsychiatric disorders based on an example of Parkinson's disease. We also discuss challenges and future directions beyond mtDNA analysis toward an understanding of the pathophysiology of "idiopathic" mood disorders.
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Affiliation(s)
- Takaoki Kasahara
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute, Wako-shi, Saitama, Japan
| | - Tadafumi Kato
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute, Wako-shi, Saitama, Japan.
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Buj R, Aird KM. Deoxyribonucleotide Triphosphate Metabolism in Cancer and Metabolic Disease. Front Endocrinol (Lausanne) 2018; 9:177. [PMID: 29720963 PMCID: PMC5915462 DOI: 10.3389/fendo.2018.00177] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 04/03/2018] [Indexed: 12/22/2022] Open
Abstract
The maintenance of a healthy deoxyribonucleotide triphosphate (dNTP) pool is critical for the proper replication and repair of both nuclear and mitochondrial DNA. Temporal, spatial, and ratio imbalances of the four dNTPs have been shown to have a mutagenic and cytotoxic effect. It is, therefore, essential for cell homeostasis to maintain the balance between the processes of dNTP biosynthesis and degradation. Multiple oncogenic signaling pathways, such as c-Myc, p53, and mTORC1 feed into dNTP metabolism, and there is a clear role for dNTP imbalances in cancer initiation and progression. Additionally, multiple chemotherapeutics target these pathways to inhibit nucleotide synthesis. Less is understood about the role for dNTP levels in metabolic disorders and syndromes and whether alterations in dNTP levels change cancer incidence in these patients. For instance, while deficiencies in some metabolic pathways known to play a role in nucleotide synthesis are pro-tumorigenic (e.g., p53 mutations), others confer an advantage against the onset of cancer (G6PD). More recent evidence indicates that there are changes in nucleotide metabolism in diabetes, obesity, and insulin resistance; however, whether these changes play a mechanistic role is unclear. In this review, we will address the complex network of metabolic pathways, whereby cells can fuel dNTP biosynthesis and catabolism in cancer, and we will discuss the potential role for this pathway in metabolic disease.
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Affiliation(s)
| | - Katherine M. Aird
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA, United States
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30
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Family A and B DNA Polymerases in Cancer: Opportunities for Therapeutic Interventions. BIOLOGY 2018; 7:biology7010005. [PMID: 29301327 PMCID: PMC5872031 DOI: 10.3390/biology7010005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 12/14/2017] [Accepted: 12/29/2017] [Indexed: 02/07/2023]
Abstract
DNA polymerases are essential for genome replication, DNA repair and translesion DNA synthesis (TLS). Broadly, these enzymes belong to two groups: replicative and non-replicative DNA polymerases. A considerable body of data suggests that both groups of DNA polymerases are associated with cancer. Many mutations in cancer cells are either the result of error-prone DNA synthesis by non-replicative polymerases, or the inability of replicative DNA polymerases to proofread mismatched nucleotides due to mutations in 3'-5' exonuclease activity. Moreover, non-replicative, TLS-capable DNA polymerases can negatively impact cancer treatment by synthesizing DNA past lesions generated from treatments such as cisplatin, oxaliplatin, etoposide, bleomycin, and radiotherapy. Hence, the inhibition of DNA polymerases in tumor cells has the potential to enhance treatment outcomes. Here, we review the association of DNA polymerases in cancer from the A and B families, which participate in lesion bypass, and conduct gene replication. We also discuss possible therapeutic interventions that could be used to maneuver the role of these enzymes in tumorigenesis.
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31
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de la Fuente-Herreruela D, Gónzalez-Charro V, Almendro-Vedia VG, Morán M, Martín MÁ, Lillo MP, Natale P, López-Montero I. Rhodamine-based sensor for real-time imaging of mitochondrial ATP in living fibroblasts. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:999-1006. [PMID: 28947254 PMCID: PMC5656571 DOI: 10.1016/j.bbabio.2017.09.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 09/05/2017] [Accepted: 09/20/2017] [Indexed: 11/24/2022]
Abstract
Mitochondria are essential for the production and maintenance of ATP in the eukaryotic cell. To image and monitor intracellular ATP level without cell breakage, biological and chemical sensors were developed in the last years. Here, we have internalized a rhodamine-based sensor RSL+ into living cells and monitored the mitochondrial ATP levels in cultured mouse embryonic fibroblasts. To evaluate the robustness of the sensor we imaged the changes of the mitochondrial ATP levels under non-physiological conditions upon incubation with FCCP, oligomycin, azide, deoxyglucose or phosphoenolpyruvate; all compounds that interfere with ATP homeostasis of the cell. The ATP sensor allowed us to determine the mitochondrial ATP levels in human skin fibroblasts where we observe a similar amount of ATP compared to mouse embryonic fibroblasts. We propose the RSL+ to be a valuable tool for the assessment of mitochondrial dysfunction in human cells derived from mitochondrial OXPHOS patients and for basic studies on bioenergetics metabolism. The rhodamine-based sensor RSL+ permeates efficiently eukaryotic plasma membrane and accumulates in mitochondria. RSL+ detects mitochondrial ATP levels in human and mouse skin fibroblasts. RSL+ detects real-time variations of mitochondrial ATP levels under non-physiological conditions.
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Affiliation(s)
- Diego de la Fuente-Herreruela
- Dto. Química Física I, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain; Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain
| | - Vicente Gónzalez-Charro
- Dto. Química Física I, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain; Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain
| | - Víctor G Almendro-Vedia
- Dto. Química Física I, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain; Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain
| | - María Morán
- Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain; U723, Centro de Investigación Biomédica en Red en Enfermedades Raras (CIBERER), Madrid, Spain
| | - Miguel Ángel Martín
- Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain; U723, Centro de Investigación Biomédica en Red en Enfermedades Raras (CIBERER), Madrid, Spain
| | - M Pilar Lillo
- Grupo de Fluorescencia y Biofísica Molecular, Instituto Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain
| | - Paolo Natale
- Dto. Química Física I, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain; Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain
| | - Iván López-Montero
- Dto. Química Física I, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain; Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain.
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Abstract
Mitochondria are intracellular organelles responsible for adenosine triphosphate production. The strict control of intracellular energy needs require proper mitochondrial functioning. The mitochondria are under dual controls of mitochondrial DNA (mtDNA) and nuclear DNA (nDNA). Mitochondrial dysfunction can arise from changes in either mtDNA or nDNA genes regulating function. There are an estimated ∼1500 proteins in the mitoproteome, whereas the mtDNA genome has 37 proteins. There are, to date, ∼275 genes shown to give rise to disease. The unique physiology of mitochondrial functioning contributes to diverse gene expression. The onset and range of phenotypic expression of disease is diverse, with onset from neonatal to seventh decade of life. The range of dysfunction is heterogeneous, ranging from single organ to multisystem involvement. The complexity of disease expression has severely limited gene discovery. Combining phenotypes with improvements in gene sequencing strategies are improving the diagnosis process. This chapter focuses on the interplay of the unique physiology and gene discovery in the current knowledge of genetically derived mitochondrial disease.
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Affiliation(s)
- Russell P Saneto
- Seattle Children's Hospital/University of Washington, Seattle, WA, United States.
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Mitochondrial Diseases as Model of Neurodegeneration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1007:129-155. [DOI: 10.1007/978-3-319-60733-7_8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Vasileiou PVS, Mourouzis I, Pantos C. Principal Aspects Regarding the Maintenance of Mammalian Mitochondrial Genome Integrity. Int J Mol Sci 2017; 18:E1821. [PMID: 28829360 PMCID: PMC5578207 DOI: 10.3390/ijms18081821] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 08/11/2017] [Accepted: 08/14/2017] [Indexed: 12/11/2022] Open
Abstract
Mitochondria have emerged as key players regarding cellular homeostasis not only due to their contribution regarding energy production through oxidative phosphorylation, but also due to their involvement in signaling, ion regulation, and programmed cell death. Indeed, current knowledge supports the notion that mitochondrial dysfunction is a hallmark in the pathogenesis of various diseases. Mitochondrial biogenesis and function require the coordinated action of two genomes: nuclear and mitochondrial. Unfortunately, both intrinsic and environmental genotoxic insults constantly threaten the integrity of nuclear as well as mitochondrial DNA. Despite the extensive research that has been made regarding nuclear genome instability, the importance of mitochondrial genome integrity has only recently begun to be elucidated. The specific architecture and repair mechanisms of mitochondrial DNA, as well as the dynamic behavior that mitochondria exert regarding fusion, fission, and autophagy participate in mitochondrial genome stability, and therefore, cell homeostasis.
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Affiliation(s)
- Panagiotis V S Vasileiou
- Department of Basic Medical Sciences, Laboratory of Histology & Embryology, School of Medicine, National and Kapodistrian University of Athens, 75 MikrasAsias Avenue, Goudi, Athens 11527, Greece.
| | - Iordanis Mourouzis
- Department of Pharmacology, School of Medicine, National and Kapodistrian University of Athens, 75 MikrasAsias Avenue, Goudi, Athens 11527, Greece.
| | - Constantinos Pantos
- Department of Pharmacology, School of Medicine, National and Kapodistrian University of Athens, 75 MikrasAsias Avenue, Goudi, Athens 11527, Greece.
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Abstract
Telbivudine (LdT) is an antiviral agent currently used in the treatment of chronic hepatitis B virus, which was first approved by the US FDA in 2006. The safety of LdT is of great importance for patients that receive long-term treatment for this condition. It has been confirmed that patients treated with LdT have significantly elevated creatine kinase levels. However, the mechanism responsible for this adverse reaction is unclear. This review summarizes the current literature of the adverse reactions of LdT and the possible mechanisms that are involved in chronic hepatitis B infection. Thus, we aim to provide guidance on best practices in using LdT and to provide evidence of the possible mechanisms of LdT-associated adverse reactions.
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Affiliation(s)
- Jianfei Long
- Department of Pharmacy, HuaShan Hospital, Fudan University, No. 12 Middle Wu Lu Mu Qi Road, Shanghai 200040, China
| | - Min Wang
- College of Pharmacy, Fudan University, Shanghai, China
| | - Bicui Chen
- Department of Pharmacy, HuaShan Hospital, Fudan University, No. 12 Middle Wu Lu Mu Qi Road, Shanghai 200040, China
| | - Jiming Zhang
- Department of Infectious Diseases, HuaShan Hospital, Fudan University, No.12 Middle Wu Lu Mu Qi Road, Shanghai 200040, China
| | - Bin Wang
- Department of Pharmacy, HuaShan Hospital, Fudan University, No. 12 Middle Wu Lu Mu Qi Road, Shanghai 200040, China
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36
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Someya S, Kujoth GC, Kim MJ, Hacker TA, Vermulst M, Weindruch R, Prolla TA. Effects of calorie restriction on the lifespan and healthspan of POLG mitochondrial mutator mice. PLoS One 2017; 12:e0171159. [PMID: 28158260 PMCID: PMC5291490 DOI: 10.1371/journal.pone.0171159] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 01/16/2017] [Indexed: 01/21/2023] Open
Abstract
Mitochondrial DNA (mtDNA) mutations are thought to have a causative role in age-related pathologies. We have shown previously that mitochondrial mutator mice (PolgD257A/D257A), harboring a proofreading-deficient version of the mtDNA polymerase gamma (POLG), accumulate mtDNA mutations in multiple tissues and display several features of accelerated aging. Calorie restriction (CR) is known to delay the onset of age-related diseases and to extend the lifespan of a variety of species, including rodents. In the current study we investigated the effects of CR on the lifespan and healthspan of mitochondrial mutator mice. Long-term CR did not increase the median or maximum lifespan of PolgD257A/D257A mice. Furthermore, CR did not reduce mtDNA deletions in the heart and muscle, accelerated sarcopenia, testicular atrophy, nor improve the alterations in cardiac parameters that are present in aged mitochondrial mutator mice. Therefore, our findings suggest that accumulation of mtDNA mutations may interfere with the beneficial action of CR in aging retardation.
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Affiliation(s)
- Shinichi Someya
- Department of Aging and Geriatric Research, University of Florida, Gainesville, Florida, United States of America
| | - Gregory C. Kujoth
- Department of Neurological Surgery, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Mi-Jung Kim
- Department of Aging and Geriatric Research, University of Florida, Gainesville, Florida, United States of America
| | - Timothy A. Hacker
- Department of Medicine, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Marc Vermulst
- Center for Mitochondrial and Epigenomic Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Richard Weindruch
- Veterans Administration Hospital, Geriatric Research, Education and Clinical Center, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Tomas A. Prolla
- Departments of Genetics & Medical Genetics, University of Wisconsin, Madison, Wisconsin, United States of America
- * E-mail:
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Da Pozzo P, Cardaioli E, Rubegni A, Gallus GN, Malandrini A, Rufa A, Battisti C, Carluccio MA, Rocchi R, Giannini F, Bianchi A, Mancuso M, Siciliano G, Dotti MT, Federico A. Novel POLG mutations and variable clinical phenotypes in 13 Italian patients. Neurol Sci 2017; 38:563-570. [DOI: 10.1007/s10072-016-2734-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 10/07/2016] [Indexed: 11/29/2022]
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Krasich R, Copeland WC. DNA polymerases in the mitochondria: A critical review of the evidence. FRONT BIOSCI-LANDMRK 2017; 22:692-709. [PMID: 27814640 PMCID: PMC5485829 DOI: 10.2741/4510] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Since 1970, the DNA polymerase gamma (PolG) has been known to be the DNA polymerase responsible for replication and repair of mitochondrial DNA, and until recently it was generally accepted that this was the only polymerase present in mitochondria. However, recent data has challenged that opinion, as several polymerases are now proposed to have activity in mitochondria. To date, their exact role of these other DNA polymerases is unclear and the amount of evidence supporting their role in mitochondria varies greatly. Further complicating matters, no universally accepted standards have been set for definitive proof of the mitochondrial localization of a protein. To gain an appreciation of these newly proposed DNA polymerases in the mitochondria, we review the evidence and standards needed to establish the role of a polymerase in the mitochondria. Employing PolG as an example, we established a list of criteria necessary to verify the existence and function of new mitochondrial proteins. We then apply this criteria towards several other putative mitochondrial polymerases. While there is still a lot left to be done in this exciting new direction, it is clear that PolG is not acting alone in mitochondria, opening new doors for potential replication and repair mechanisms.
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Affiliation(s)
- Rachel Krasich
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, 111 T.W. Alexander Dr., Bldg. 101, Rm. E316, Research Triangle Park, NC 27709,
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NEWS and VIEWS: mitochondrial encephalomyopathies. ACTA MYOLOGICA 2016. [PMCID: PMC5416741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In recent years, there has been a surge of interest in mitochondrial diseases, a group of metabolic conditions caused by impairment of the oxidative phosphorylation system. The ubiquitous presence of mitochondria in all the cells of the body, their role as cell powerhouse and their particular genetic characteristics explain the phenotypic complexity and the diagnostic difficulties, bridging from paediatrician to neurologist.
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Abstract
Mitochondrial DNA transfer has recently received attention from physicians. The transfer techniques place genetic material from the egg nucleus of a woman with a mitochondrial DNA mutation into a healthy donated egg from which the nuclear DNA was removed. This technology intends to reconstruct a mitochondria-competent egg to produce a baby. Three approaches: (1) pronuclear transfer; (2) metaphase II spindle transfer (ST); and (3) polar body (PB) transfer, have been proposed and applied in animal models with very low levels of heteroplasmy. Because there is no curative treatment for patients with mitochondrial dysfunction, the UK government has allowed the use of this pioneering technique to prevent the transmission of rare and devastating mitochondrial diseases. Despite general safety in the observation period, this technology involves germline modification, raising scientific and ethical questions in the public. In this review, we focus on this unprecedented technology and discuss its clinical application in the future.
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Affiliation(s)
- Liang Xu
- a Research Center for Translational Medicine , Shanghai East Hospital, Tongji University School of Medicine , Shanghai, China
| | - Rui Shi
- b Department of Obstetrics and Gynecology , Shanghai East Hospital, Tongji University School of Medicine , Shanghai, China
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Young MJ, Copeland WC. Human mitochondrial DNA replication machinery and disease. Curr Opin Genet Dev 2016; 38:52-62. [PMID: 27065468 DOI: 10.1016/j.gde.2016.03.005] [Citation(s) in RCA: 129] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 03/03/2016] [Accepted: 03/08/2016] [Indexed: 12/21/2022]
Abstract
The human mitochondrial genome is replicated by DNA polymerase γ in concert with key components of the mitochondrial DNA (mtDNA) replication machinery. Defects in mtDNA replication or nucleotide metabolism cause deletions, point mutations, or depletion of mtDNA. The resulting loss of cellular respiration ultimately induces mitochondrial genetic diseases, including mtDNA depletion syndromes (MDS) such as Alpers or early infantile hepatocerebral syndromes, and mtDNA deletion disorders such as progressive external ophthalmoplegia, ataxia-neuropathy, or mitochondrial neurogastrointestinal encephalomyopathy. Here we review the current literature regarding human mtDNA replication and heritable disorders caused by genetic changes of the POLG, POLG2, Twinkle, RNASEH1, DNA2, and MGME1 genes.
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Affiliation(s)
- Matthew J Young
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, P.O. Box 12233, Research Triangle Park, NC 27709, United States
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, P.O. Box 12233, Research Triangle Park, NC 27709, United States.
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Liu B, Xue Q, Tang Y, Cao J, Guengerich FP, Zhang H. Mechanisms of mutagenesis: DNA replication in the presence of DNA damage. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2016; 768:53-67. [PMID: 27234563 PMCID: PMC5237373 DOI: 10.1016/j.mrrev.2016.03.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 02/07/2016] [Accepted: 03/14/2016] [Indexed: 10/22/2022]
Abstract
Environmental mutagens cause DNA damage that disturbs replication and produces mutations, leading to cancer and other diseases. We discuss mechanisms of mutagenesis resulting from DNA damage, from the level of DNA replication by a single polymerase to the complex DNA replisome of some typical model organisms (including bacteriophage T7, T4, Sulfolobus solfataricus, Escherichia coli, yeast and human). For a single DNA polymerase, DNA damage can affect replication in three major ways: reducing replication fidelity, causing frameshift mutations, and blocking replication. For the DNA replisome, protein interactions and the functions of accessory proteins can yield rather different results even with a single DNA polymerase. The mechanism of mutation during replication performed by the DNA replisome is a long-standing question. Using new methods and techniques, the replisomes of certain organisms and human cell extracts can now be investigated with regard to the bypass of DNA damage. In this review, we consider the molecular mechanism of mutagenesis resulting from DNA damage in replication at the levels of single DNA polymerases and complex DNA replisomes, including translesion DNA synthesis.
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Affiliation(s)
- Binyan Liu
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China
| | - Qizhen Xue
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China
| | - Yong Tang
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China
| | - Jia Cao
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China
| | - F Peter Guengerich
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
| | - Huidong Zhang
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing, PR China.
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Bannwarth S, Berg-Alonso L, Augé G, Fragaki K, Kolesar JE, Lespinasse F, Lacas-Gervais S, Burel-Vandenbos F, Villa E, Belmonte F, Michiels JF, Ricci JE, Gherardi R, Harrington L, Kaufman BA, Paquis-Flucklinger V. Inactivation of Pif1 helicase causes a mitochondrial myopathy in mice. Mitochondrion 2016; 30:126-37. [PMID: 26923168 DOI: 10.1016/j.mito.2016.02.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 02/19/2016] [Accepted: 02/19/2016] [Indexed: 12/13/2022]
Abstract
Mutations in genes coding for mitochondrial helicases such as TWINKLE and DNA2 are involved in mitochondrial myopathies with mtDNA instability in both human and mouse. We show that inactivation of Pif1, a third member of the mitochondrial helicase family, causes a similar phenotype in mouse. pif1-/- animals develop a mitochondrial myopathy with respiratory chain deficiency. Pif1 inactivation is responsible for a deficiency to repair oxidative stress-induced mtDNA damage in mouse embryonic fibroblasts that is improved by complementation with mitochondrial isoform mPif1(67). These results open new perspectives for the exploration of patients with mtDNA instability disorders.
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Affiliation(s)
- Sylvie Bannwarth
- IRCAN, CNRS UMR 7284/INSERM U1081/UNS, Faculté de Médecine, Nice, France; Service de Génétique Médicale, Hôpital Archet 2, CHU de Nice, Nice, France
| | | | - Gaëlle Augé
- IRCAN, CNRS UMR 7284/INSERM U1081/UNS, Faculté de Médecine, Nice, France; Service de Génétique Médicale, Hôpital Archet 2, CHU de Nice, Nice, France
| | - Konstantina Fragaki
- IRCAN, CNRS UMR 7284/INSERM U1081/UNS, Faculté de Médecine, Nice, France; Service de Génétique Médicale, Hôpital Archet 2, CHU de Nice, Nice, France
| | - Jill E Kolesar
- Department of Medicine, Center for Metabolism and Mitochondrial Medicine, University of Pittsburgh, Pittsburgh, USA
| | | | - Sandra Lacas-Gervais
- Centre Commun de Microscopie Electronique Appliquée, Faculté des Sciences, Université de Nice Sophia Antipolis, Nice, France
| | | | - Elodie Villa
- INSERM U1065, Centre Méditerranéen de Médecine Moléculaire (C3M), équipe "contrôle métabolique des morts cellulaires", Nice Sophia-Antipolis University, France
| | - Frances Belmonte
- Department of Medicine, Center for Metabolism and Mitochondrial Medicine, University of Pittsburgh, Pittsburgh, USA
| | | | - Jean-Ehrland Ricci
- INSERM U1065, Centre Méditerranéen de Médecine Moléculaire (C3M), équipe "contrôle métabolique des morts cellulaires", Nice Sophia-Antipolis University, France
| | | | - Lea Harrington
- Université de Montréal, Institut de Recherche en Immunologie et en Cancérologie, 2950 chemin de Polytechnique, Montréal, Québec H3T 1J4, Canada
| | - Brett A Kaufman
- Department of Medicine, Center for Metabolism and Mitochondrial Medicine, University of Pittsburgh, Pittsburgh, USA
| | - Véronique Paquis-Flucklinger
- IRCAN, CNRS UMR 7284/INSERM U1081/UNS, Faculté de Médecine, Nice, France; Service de Génétique Médicale, Hôpital Archet 2, CHU de Nice, Nice, France.
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Safdar A, Khrapko K, Flynn JM, Saleem A, De Lisio M, Johnston APW, Kratysberg Y, Samjoo IA, Kitaoka Y, Ogborn DI, Little JP, Raha S, Parise G, Akhtar M, Hettinga BP, Rowe GC, Arany Z, Prolla TA, Tarnopolsky MA. Exercise-induced mitochondrial p53 repairs mtDNA mutations in mutator mice. Skelet Muscle 2016; 6:7. [PMID: 26834962 PMCID: PMC4733510 DOI: 10.1186/s13395-016-0075-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Accepted: 01/05/2016] [Indexed: 11/22/2022] Open
Abstract
Background Human genetic disorders and transgenic mouse models have shown that mitochondrial DNA (mtDNA) mutations and telomere dysfunction instigate the aging process. Epidemiologically, exercise is associated with greater life expectancy and reduced risk of chronic diseases. While the beneficial effects of exercise are well established, the molecular mechanisms instigating these observations remain unclear. Results Endurance exercise reduces mtDNA mutation burden, alleviates multisystem pathology, and increases lifespan of the mutator mice, with proofreading deficient mitochondrial polymerase gamma (POLG1). We report evidence for a POLG1-independent mtDNA repair pathway mediated by exercise, a surprising notion as POLG1 is canonically considered to be the sole mtDNA repair enzyme. Here, we show that the tumor suppressor protein p53 translocates to mitochondria and facilitates mtDNA mutation repair and mitochondrial biogenesis in response to endurance exercise. Indeed, in mutator mice with muscle-specific deletion of p53, exercise failed to prevent mtDNA mutations, induce mitochondrial biogenesis, preserve mitochondrial morphology, reverse sarcopenia, or mitigate premature mortality. Conclusions Our data establish a new role for p53 in exercise-mediated maintenance of the mtDNA genome and present mitochondrially targeted p53 as a novel therapeutic modality for diseases of mitochondrial etiology. Electronic supplementary material The online version of this article (doi:10.1186/s13395-016-0075-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Adeel Safdar
- Department of Kinesiology, McMaster University, Hamilton, ON L8N 3Z5 Canada ; Department of Pediatrics, McMaster University, Hamilton, ON L8N 3Z5 Canada ; Department of Medicine, McMaster University, Hamilton, ON L8N 3Z5 Canada
| | | | - James M Flynn
- Buck Institute for Research on Aging, Novato, CA 94945 USA
| | - Ayesha Saleem
- Department of Pediatrics, McMaster University, Hamilton, ON L8N 3Z5 Canada
| | - Michael De Lisio
- Department of Kinesiology, McMaster University, Hamilton, ON L8N 3Z5 Canada
| | - Adam P W Johnston
- Department of Kinesiology, McMaster University, Hamilton, ON L8N 3Z5 Canada
| | | | - Imtiaz A Samjoo
- Department of Medical Sciences, McMaster University, Hamilton, ON L8N 3Z5 Canada
| | - Yu Kitaoka
- Department of Pediatrics, McMaster University, Hamilton, ON L8N 3Z5 Canada
| | - Daniel I Ogborn
- Department of Medical Sciences, McMaster University, Hamilton, ON L8N 3Z5 Canada
| | - Jonathan P Little
- School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC V1V 1V7 Canada
| | - Sandeep Raha
- Department of Pediatrics, McMaster University, Hamilton, ON L8N 3Z5 Canada
| | - Gianni Parise
- Department of Kinesiology, McMaster University, Hamilton, ON L8N 3Z5 Canada ; Department of Medical Physics & Applied Radiation Sciences, McMaster University, Hamilton, ON L8N 3Z5 Canada
| | - Mahmood Akhtar
- Department of Medicine, McMaster University, Hamilton, ON L8N 3Z5 Canada
| | - Bart P Hettinga
- Department of Pediatrics, McMaster University, Hamilton, ON L8N 3Z5 Canada
| | - Glenn C Rowe
- Division of Cardiovascular Disease, University of Alabama, Birmingham, AL 35294 USA
| | - Zoltan Arany
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 USA
| | - Tomas A Prolla
- Departments of Genetics, University of Wisconsin, Madison, WI 53706 USA ; Departments of Medical Genetics, University of Wisconsin, Madison, WI 53706 USA
| | - Mark A Tarnopolsky
- Department of Pediatrics, McMaster University, Hamilton, ON L8N 3Z5 Canada ; Department of Medicine, McMaster University, Hamilton, ON L8N 3Z5 Canada
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45
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St John JC. Mitochondrial DNA copy number and replication in reprogramming and differentiation. Semin Cell Dev Biol 2016; 52:93-101. [PMID: 26827792 DOI: 10.1016/j.semcdb.2016.01.028] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 01/11/2016] [Accepted: 01/21/2016] [Indexed: 11/26/2022]
Abstract
Until recently, it was thought that the role of the mitochondrial genome was confined to encoding key proteins that generate ATP through the process of oxidative phosphorylation in the electron transfer chain. However, with increasing new evidence, it is apparent that the mitochondrial genome has a major role to play in a number of diseases and phenotypes. For example, mitochondrial variants and copy number have been implicated in the processes of fertilisation outcome and development and the onset of tumorigenesis. On the other hand, mitochondrial DNA (mtDNA) haplotypes have been implicated in a variety of diseases and most likely account for the adaptation that our ancestors achieved in order that they were fit for their environments. The mechanisms, which enable the mitochondrial genome to either protect or promote the disease phenotype, require further elucidation. However, there appears to be significant 'crosstalk' between the chromosomal and mitochondrial genomes that enable this to take place. One such mechanism is the regulation of DNA methylation by mitochondrial DNA, which is often perturbed in reprogrammed cells that have undergone dedifferentiation and affects mitochondrial DNA copy number. Furthermore, it appears that the mitochondrial genome interacts with the chromosomal genome to regulate the transcription of key genes at certain stages during development. Additionally, the mitochondrial genome can accumulate a series of mtDNA variants, which can lead to diseases such as cancer. It is likely that a combination of certain mitochondrial variants and aberrant patterns of mtDNA copy number could indeed account for many diseases that have previously been unaccounted for. This review focuses on the role that the mitochondrial genome plays especially during early stages of development and in cancer.
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Affiliation(s)
- Justin C St John
- Centre for Genetic Diseases, Hudson Institute of Medical Research, and the Department of Molecular and Translational Science, Monash University, 27-31 Wright Street, Clayton, VIC 3168, Australia.
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Singh B, Owens KM, Bajpai P, Desouki MM, Srinivasasainagendra V, Tiwari HK, Singh KK. Mitochondrial DNA Polymerase POLG1 Disease Mutations and Germline Variants Promote Tumorigenic Properties. PLoS One 2015; 10:e0139846. [PMID: 26468652 PMCID: PMC4607296 DOI: 10.1371/journal.pone.0139846] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 09/17/2015] [Indexed: 02/04/2023] Open
Abstract
Germline mutations in mitochondrial DNA polymerase gamma (POLG1) induce mitochondrial DNA (mtDNA) mutations, depletion, and decrease oxidative phosphorylation. Earlier, we identified somatic mutations in POLG1 and the contribution of these mutations in human cancer. However, a role for germline variations in POLG1 in human cancers is unknown. In this study, we examined a role for disease associated germline variants of POLG1, POLG1 gene expression, copy number variation and regulation in human cancers. We analyzed the mutations, expression and copy number variation in POLG1 in several cancer databases and validated the analyses in primary breast tumors and breast cancer cell lines. We discovered 5-aza-2'-deoxycytidine led epigenetic regulation of POLG1, mtDNA-encoded genes and increased mitochondrial respiration. We conducted comprehensive race based bioinformatics analyses of POLG1 gene in more than 33,000 European-Americans and 5,000 African-Americans. We identified a mitochondrial disease causing missense variation in polymerase domain of POLG1 protein at amino acid 1143 (E1143G) to be 25 times more prevalent in European-Americans (allele frequency 0.03777) when compared to African-American (allele frequency 0.00151) population. We identified T251I and P587L missense variations in exonuclease and linker region of POLG1 also to be more prevalent in European-Americans. Expression of these variants increased glucose consumption, decreased ATP production and increased matrigel invasion. Interestingly, conditional expression of these variants revealed that matrigel invasion properties conferred by these germline variants were reversible suggesting a role of epigenetic regulators. Indeed, we identified a set of miRNA whose expression was reversible after variant expression was turned off. Together, our studies demonstrate altered genetic and epigenetic regulation of POLG1 in human cancers and suggest a role for POLG1 germline variants in promoting tumorigenic properties.
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Affiliation(s)
- Bhupendra Singh
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Kjerstin M. Owens
- Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, NY, United States of America
| | - Prachi Bajpai
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Mohamed Mokhtar Desouki
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN, United States of America
| | - Vinodh Srinivasasainagendra
- Section on Statistical Genetics, Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Hemant K. Tiwari
- Section on Statistical Genetics, Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Keshav K. Singh
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
- Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Department of Environmental Health, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Center for Aging, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- UAB Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Birmingham Veterans Affairs Medical Center, Birmingham, AL, 35294, United States of America
- * E-mail:
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Abstract
The ultrastructure of the cardiac myocyte is remarkable for the high density of mitochondria tightly packed between sarcomeres. This structural organization is designed to provide energy in the form of ATP to fuel normal pump function of the heart. A complex system comprised of regulatory factors and energy metabolic machinery, encoded by both mitochondrial and nuclear genomes, is required for the coordinate control of cardiac mitochondrial biogenesis, maturation, and high-capacity function. This process involves the action of a transcriptional regulatory network that builds and maintains the mitochondrial genome and drives the expression of the energy transduction machinery. This finely tuned system is responsive to developmental and physiological cues, as well as changes in fuel substrate availability. Deficiency of components critical for mitochondrial energy production frequently manifests as a cardiomyopathic phenotype, underscoring the requirement to maintain high respiration rates in the heart. Although a precise causative role is not clear, there is increasing evidence that perturbations in this regulatory system occur in the hypertrophied and failing heart. This review summarizes current knowledge and highlights recent advances in our understanding of the transcriptional regulatory factors and signaling networks that serve to regulate mitochondrial biogenesis and function in the mammalian heart.
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Affiliation(s)
- Rick B Vega
- From the Diabetes and Obesity Research Center, Cardiovascular Pathobiology Program, Sanford-Burnham Medical Research Institute, Orlando, FL
| | - Julie L Horton
- From the Diabetes and Obesity Research Center, Cardiovascular Pathobiology Program, Sanford-Burnham Medical Research Institute, Orlando, FL
| | - Daniel P Kelly
- From the Diabetes and Obesity Research Center, Cardiovascular Pathobiology Program, Sanford-Burnham Medical Research Institute, Orlando, FL.
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48
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Mayr JA, Haack TB, Freisinger P, Karall D, Makowski C, Koch J, Feichtinger RG, Zimmermann FA, Rolinski B, Ahting U, Meitinger T, Prokisch H, Sperl W. Spectrum of combined respiratory chain defects. J Inherit Metab Dis 2015; 38:629-40. [PMID: 25778941 PMCID: PMC4493854 DOI: 10.1007/s10545-015-9831-y] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 02/20/2015] [Accepted: 02/23/2015] [Indexed: 01/22/2023]
Abstract
Inherited disorders of mitochondrial energy metabolism form a large and heterogeneous group of metabolic diseases. More than 250 gene defects have been reported to date and this number continues to grow. Mitochondrial diseases can be grouped into (1) disorders of oxidative phosphorylation (OXPHOS) subunits and their assembly factors, (2) defects of mitochondrial DNA, RNA and protein synthesis, (3) defects in the substrate-generating upstream reactions of OXPHOS, (4) defects in relevant cofactors and (5) defects in mitochondrial homeostasis. Deficiency of more than one respiratory chain enzyme is a common finding. Combined defects are found in 49 % of the known disease-causing genes of mitochondrial energy metabolism and in 57 % of patients with OXPHOS defects identified in our diagnostic centre. Combined defects of complexes I, III, IV and V are typically due to deficiency of mitochondrial DNA replication, RNA metabolism or translation. Defects in cofactors can result in combined defects of various combinations, and defects of mitochondrial homeostasis can result in a generalised decrease of all OXPHOS enzymes. Noteworthy, identification of combined defects can be complicated by different degrees of severity of each affected enzyme. Furthermore, even defects of single respiratory chain enzymes can result in combined defects due to aberrant formation of respiratory chain supercomplexes. Combined OXPHOS defects have a great variety of clinical manifestations in terms of onset, course severity and tissue involvement. They can present as classical encephalomyopathy but also with hepatopathy, nephropathy, haematologic findings and Perrault syndrome in a subset of disorders.
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Affiliation(s)
- Johannes A Mayr
- Department of Paediatrics, Paracelsus Medical University, SALK Salzburg, Salzburg, 5020, Austria,
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49
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Lee J, Wong SA, Li BUK, Boles RG. NextGen nuclear DNA sequencing in cyclic vomiting syndrome reveals a significant association with the stress-induced calcium channel (RYR2). Neurogastroenterol Motil 2015; 27:990-6. [PMID: 25925909 DOI: 10.1111/nmo.12575] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 03/30/2015] [Indexed: 12/13/2022]
Abstract
BACKGROUND Cyclic vomiting syndrome (CVS) is a common, frequently disabling, 'functional' condition characterized by recurring, stereotypical attacks of intense nausea, vomiting, and lethargy, with the essential absence of these symptoms between episodes. Although the pathogenesis of CVS is yet unexplained, evidence has accumulated which suggest pathogenic roles for stress-related, autonomic, neuroendocrine, and mitochondrial factors. The objective of this pilot study was to elucidate mechanism(s) by identifying genes involved in the presumed multifactorial pathogenesis of CVS. METHODS In this pilot study, DNA from 75 unrelated CVS cases and 60 healthy controls were assayed by Courtagen Life Science's next-generation sequencing platform (nucSEEK(™) ), including over 1100 nuclear-encoded genes involved with mitochondria, metabolism, or ion channels. Significant sequence variants were defined as evolutionary conservation at least to Xenopus (frog) per the UCSC Genome Browser. KEY RESULTS The RYR2 gene, encoding a stress-induced calcium channel present in many neurons, was the only gene demonstrating a statistically significant difference in the proportion of conserved sequence variants among the groups (18/75 CVS, 24%, vs 3/60 controls, 5%; p = 0.0018, OR = 6.0, 95% CI = 1.7-22). CONCLUSIONS & INFERENCES We propose a mechanism in which RYR2 sequence variants result in aberrant stress-induced calcium release into the mitochondria of autonomic neurons, resulting in an increased risk to develop autonomic/functional disease such as CVS, and related conditions such as migraine and gut dysmotility. This model incorporates the existing hypotheses regarding CVS pathogenesis into a cohesive mechanism, and might have treatment implications.
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Affiliation(s)
- J Lee
- Courtagen Life Sciences Inc., Woburn, MA, USA
| | - S A Wong
- Courtagen Life Sciences Inc., Woburn, MA, USA
| | - B U K Li
- Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI, USA
| | - R G Boles
- Courtagen Life Sciences Inc., Woburn, MA, USA.,Division of Medical Genetics, Children's Hospital Los Angeles, Los Angeles, CA, USA.,Department of Pediatrics, Keck School of Medicine at USC, Los Angeles, CA, USA
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50
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PCR based determination of mitochondrial DNA copy number in multiple species. Methods Mol Biol 2015; 1241:23-38. [PMID: 25308485 DOI: 10.1007/978-1-4939-1875-1_3] [Citation(s) in RCA: 270] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Mitochondrial DNA (mtDNA) copy number is a critical component of overall mitochondrial health. In this chapter, we describe methods for isolation of both mtDNA and nuclear DNA (nucDNA) and measurement of their respective copy numbers using quantitative PCR. Methods differ depending on the species and cell type of the starting material and availability of specific PCR reagents.
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