1
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Isolating Mitochondria, Mitoplasts, and mtDNA from Cultured Mammalian Cells. Methods Mol Biol 2023; 2615:17-30. [PMID: 36807781 DOI: 10.1007/978-1-0716-2922-2_2] [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
Mitochondria are double membrane-bound eukaryotic organelles with roles in a range of cellular activities including energy conversion, apoptosis, cell signalling, and the biosynthesis of enzyme cofactors. Mitochondria contain their own genome, called mtDNA, which encodes subunits of the oxidative phosphorylation machinery as well as the rRNA and tRNA molecules required for their translation within mitochondria. The ability to isolate highly purified mitochondria from cells has been instrumental in a number of studies of mitochondrial function. Differential centrifugation is a long-established method for the isolation of mitochondria. Cells are subjected to osmotic swelling and disruption, followed by centrifugation in isotonic sucrose solutions to separate mitochondria from other cellular components. We present a method using this principle for the isolation of mitochondria from cultured mammalian cell lines. Mitochondria purified by this method can be further fractionated to investigate protein localization, or act as a starting point to purify mtDNA.
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2
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Menger KE, Chapman J, Díaz-Maldonado H, Khazeem M, Deen D, Erdinc D, Casement JW, Di Leo V, Pyle A, Rodríguez-Luis A, Cowell I, Falkenberg M, Austin C, Nicholls T. Two type I topoisomerases maintain DNA topology in human mitochondria. Nucleic Acids Res 2022; 50:11154-11174. [PMID: 36215039 PMCID: PMC9638942 DOI: 10.1093/nar/gkac857] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 09/03/2022] [Accepted: 09/26/2022] [Indexed: 11/12/2022] Open
Abstract
Genetic processes require the activity of multiple topoisomerases, essential enzymes that remove topological tension and intermolecular linkages in DNA. We have investigated the subcellular localisation and activity of the six human topoisomerases with a view to understanding the topological maintenance of human mitochondrial DNA. Our results indicate that mitochondria contain two topoisomerases, TOP1MT and TOP3A. Using molecular, genomic and biochemical methods we find that both proteins contribute to mtDNA replication, in addition to the decatenation role of TOP3A, and that TOP1MT is stimulated by mtSSB. Loss of TOP3A or TOP1MT also dysregulates mitochondrial gene expression, and both proteins promote transcription elongation in vitro. We find no evidence for TOP2 localisation to mitochondria, and TOP2B knockout does not affect mtDNA maintenance or expression. Our results suggest a division of labour between TOP3A and TOP1MT in mtDNA topology control that is required for the proper maintenance and expression of human mtDNA.
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Affiliation(s)
- Katja E Menger
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - James Chapman
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Héctor Díaz-Maldonado
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, 405 30 Gothenburg, Sweden
| | - Mushtaq M Khazeem
- Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Dasha Deen
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Direnis Erdinc
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, 405 30 Gothenburg, Sweden
| | - John W Casement
- Bioinformatics Support Unit, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Valeria Di Leo
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Angela Pyle
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Alejandro Rodríguez-Luis
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Ian G Cowell
- Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, 405 30 Gothenburg, Sweden
| | - Caroline A Austin
- Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Thomas J Nicholls
- Wellcome Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
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3
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Meng F, Jia Z, Zheng J, Ji Y, Wang J, Xiao Y, Fu Y, Wang M, Ling F, Guan MX. A deafness-associated mitochondrial DNA mutation caused pleiotropic effects on DNA replication and tRNA metabolism. Nucleic Acids Res 2022; 50:9453-9469. [PMID: 36039763 PMCID: PMC9458427 DOI: 10.1093/nar/gkac720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Accepted: 08/09/2022] [Indexed: 12/24/2022] Open
Abstract
In this report, we investigated the molecular mechanism underlying a deafness-associated m.5783C > T mutation that affects the canonical C50-G63 base-pairing of TΨC stem of tRNACys and immediately adjacent to 5' end of light-strand origin of mitochondrial DNA (mtDNA) replication (OriL). Two dimensional agarose gel electrophoresis revealed marked decreases in the replication intermediates including ascending arm of Y-fork arcs spanning OriL in the mutant cybrids bearing m.5783C > T mutation. mtDNA replication alterations were further evidenced by decreased levels of PolγA, Twinkle and SSBP1, newly synthesized mtDNA and mtDNA contents in the mutant cybrids. The m.5783C > T mutation altered tRNACys structure and function, including decreased melting temperature, conformational changes, instability and deficient aminoacylation of mutated tRNACys. The m.5783C > T mutation impaired the 5' end processing efficiency of tRNACys precursors and reduced the levels of tRNACys and downstream tRNATyr. The aberrant tRNA metabolism impaired mitochondrial translation, which was especially pronounced effects in the polypeptides harboring higher numbers of cysteine and tyrosine codons. These alterations led to deficient oxidative phosphorylation including instability and reduced activities of the respiratory chain enzyme complexes I, III, IV and intact supercomplexes overall. Our findings highlight the impact of mitochondrial dysfunction on deafness arising from defects in mitochondrial DNA replication and tRNA metabolism.
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Affiliation(s)
| | | | - Jing Zheng
- Division of Medical Genetics and Genomics, The Children's Hospital, Zhejiang University School of Medicine and National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China,Institute of Genetics, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China,Zhejiang Provincial Key Lab of Genetic and Developmental Disorder, Hangzhou, Zhejiang, China
| | - Yanchun Ji
- Division of Medical Genetics and Genomics, The Children's Hospital, Zhejiang University School of Medicine and National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China,Institute of Genetics, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China,Zhejiang Provincial Key Lab of Genetic and Developmental Disorder, Hangzhou, Zhejiang, China
| | - Jing Wang
- Institute of Genetics, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yun Xiao
- Institute of Genetics, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yong Fu
- Division of Otolaryngology-Head and Neck Surgery, The Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Meng Wang
- Division of Medical Genetics and Genomics, The Children's Hospital, Zhejiang University School of Medicine and National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China,Institute of Genetics, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China,Zhejiang Provincial Key Lab of Genetic and Developmental Disorder, Hangzhou, Zhejiang, China
| | - Feng Ling
- Chemical Genomics Research Group, RIKEN Center for Sustainable Resource Science, Hirosawa 2-1, Wako, Saitama, Japan
| | - Min-Xin Guan
- To whom correspondence should be addressed. Tel: +86 571 88206916; Fax: +86 571 88982377;
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4
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Hangas A, Kekäläinen NJ, Potter A, Michell C, Aho KJ, Rutanen C, Spelbrink JN, Pohjoismäki JL, Goffart S. Top3α is the replicative topoisomerase in mitochondrial DNA replication. Nucleic Acids Res 2022; 50:8733-8748. [PMID: 35904803 PMCID: PMC9410902 DOI: 10.1093/nar/gkac660] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/07/2022] [Accepted: 07/22/2022] [Indexed: 11/18/2022] Open
Abstract
Mitochondrial DNA has been investigated for nearly fifty years, but many aspects of the maintenance of this essential small genome remain unknown. Like any genome, mammalian mitochondrial DNA requires the function of topoisomerases to counter and regulate the topological tension arising during replication, transcription, segregation, and repair. However, the functions of the different mitochondrial topoisomerases are poorly understood. Here, we investigate the role of Topoisomerase 3α (Top3α) in mtDNA replication and transcription, providing evidence that this enzyme, previously reported to act in mtDNA segregation, also participates in mtDNA replication fork progression. Top3α knockdown caused replication fork stalling, increased mtDNA catenation and decreased mtDNA levels. Overexpression in contrast induced abundant double-strand breaks around the replication origin OH and abortion of early replication, while at the same time improving the resolution of mtDNA replication termination intermediates. Both Top3α knockdown and overexpression affected mitochondrial RNA transcription, leading to a decrease in steady-state levels of mitochondrial transcripts. Together, our results indicate that the mitochondrial isoform of Top3α is not only involved in mtDNA segregation, as reported previously, but also supports the progression of the replication fork. Mitochondrial Top3α is also influencing the progression of transcription, with its absence affecting downstream transcript levels.
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Affiliation(s)
- Anu Hangas
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Nina J Kekäläinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Alisa Potter
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland.,Radboud Center for Mitochondrial Medicine, Department of Paediatrics, Radboudumc, Nijmegen, The Netherlands
| | - Craig Michell
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Kauko J Aho
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Chiara Rutanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Johannes N Spelbrink
- Radboud Center for Mitochondrial Medicine, Department of Paediatrics, Radboudumc, Nijmegen, The Netherlands
| | - Jaakko L Pohjoismäki
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Steffi Goffart
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
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5
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Rahman MM, Young CKJ, Goffart S, Pohjoismäki JLO, Young MJ. Heterozygous p.Y955C mutation in DNA polymerase γ leads to alterations in bioenergetics, complex I subunit expression, and mtDNA replication. J Biol Chem 2022; 298:102196. [PMID: 35760101 PMCID: PMC9307957 DOI: 10.1016/j.jbc.2022.102196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 06/16/2022] [Accepted: 06/17/2022] [Indexed: 12/03/2022] Open
Abstract
In human cells, ATP is generated using oxidative phosphorylation machinery, which is inoperable without proteins encoded by mitochondrial DNA (mtDNA). The DNA polymerase gamma (Polγ) repairs and replicates the multicopy mtDNA genome in concert with additional factors. The Polγ catalytic subunit is encoded by the POLG gene, and mutations in this gene cause mtDNA genome instability and disease. Barriers to studying the molecular effects of disease mutations include scarcity of patient samples and a lack of available mutant models; therefore, we developed a human SJCRH30 myoblast cell line model with the most common autosomal dominant POLG mutation, c.2864A>G/p.Y955C, as individuals with this mutation can present with progressive skeletal muscle weakness. Using on-target sequencing, we detected a 50% conversion frequency of the mutation, confirming heterozygous Y955C substitution. We found mutated cells grew slowly in a glucose-containing medium and had reduced mitochondrial bioenergetics compared with the parental cell line. Furthermore, growing Y955C cells in a galactose-containing medium to obligate mitochondrial function enhanced these bioenergetic deficits. Also, we show complex I NDUFB8 and ND3 protein levels were decreased in the mutant cell line, and the maintenance of mtDNA was severely impaired (i.e., lower copy number, fewer nucleoids, and an accumulation of Y955C-specific replication intermediates). Finally, we show the mutant cells have increased sensitivity to the mitochondrial toxicant 2′-3′-dideoxycytidine. We expect this POLG Y955C cell line to be a robust system to identify new mitochondrial toxicants and therapeutics to treat mitochondrial dysfunction.
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Affiliation(s)
- Md Mostafijur Rahman
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901
| | - Carolyn K J Young
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901
| | - Steffi Goffart
- Department of Environmental and Biological Sciences, University of Eastern Finland, 80101 Joensuu, Finland
| | - Jaakko L O Pohjoismäki
- Department of Environmental and Biological Sciences, University of Eastern Finland, 80101 Joensuu, Finland
| | - Matthew J Young
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901.
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6
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Kosar M, Piccini D, Foiani M, Giannattasio M. A rapid method to visualize human mitochondrial DNA replication through rotary shadowing and transmission electron microscopy. Nucleic Acids Res 2021; 49:e121. [PMID: 34500456 PMCID: PMC8643652 DOI: 10.1093/nar/gkab770] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 08/15/2021] [Accepted: 08/26/2021] [Indexed: 11/21/2022] Open
Abstract
We report a rapid experimental procedure based on high-density in vivo psoralen inter-strand DNA cross-linking coupled to spreading of naked purified DNA, positive staining, low-angle rotary shadowing, and transmission electron microscopy (TEM) that allows quick visualization of the dynamic of heavy strand (HS) and light strand (LS) human mitochondrial DNA replication. Replication maps built on linearized mitochondrial genomes and optimized rotary shadowing conditions enable clear visualization of the progression of the mitochondrial DNA synthesis and visualization of replication intermediates carrying long single-strand DNA stretches. One variant of this technique, called denaturing spreading, allowed the inspection of the fine chromatin structure of the mitochondrial genome and was applied to visualize the in vivo three-strand DNA structure of the human mitochondrial D-loop intermediate with unprecedented clarity.
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Affiliation(s)
- Martin Kosar
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Milano, Italy
| | - Daniele Piccini
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Milano, Italy
| | - Marco Foiani
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Milano, Italy.,Dipartimento di Oncologia & Emato-Oncologia, Università degli Studi di Milano, Milano, Italy
| | - Michele Giannattasio
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Milano, Italy.,Dipartimento di Oncologia & Emato-Oncologia, Università degli Studi di Milano, Milano, Italy
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7
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Cheng L, Wang W, Yao Y, Sun Q. Mitochondrial RNase H1 activity regulates R-loop homeostasis to maintain genome integrity and enable early embryogenesis in Arabidopsis. PLoS Biol 2021; 19:e3001357. [PMID: 34343166 PMCID: PMC8330923 DOI: 10.1371/journal.pbio.3001357] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 07/08/2021] [Indexed: 11/24/2022] Open
Abstract
Plant mitochondrial genomes undergo frequent homologous recombination (HR). Ectopic HR activity is inhibited by the HR surveillance pathway, but the underlying regulatory mechanism is unclear. Here, we show that the mitochondrial RNase H1 AtRNH1B impairs the formation of RNA:DNA hybrids (R-loops) and participates in the HR surveillance pathway in Arabidopsis thaliana. AtRNH1B suppresses ectopic HR at intermediate-sized repeats (IRs) and thus maintains mitochondrial DNA (mtDNA) replication. The RNase H1 AtRNH1C is restricted to the chloroplast; however, when cells lack AtRNH1B, transport of chloroplast AtRNH1C into the mitochondria secures HR surveillance, thus ensuring the integrity of the mitochondrial genome and allowing embryogenesis to proceed. HR surveillance is further regulated by the single-stranded DNA-binding protein ORGANELLAR SINGLE-STRANDED DNA BINDING PROTEIN1 (OSB1), which decreases the formation of R-loops. This study uncovers a facultative dual targeting mechanism between organelles and sheds light on the roles of RNase H1 in organellar genome maintenance and embryogenesis. This study clarifies the function of mitochondrial RNase H1 in genome stability and early embryogenesis in plants, and shows that mitochondrial R-loops are involved in homologous recombination surveillance of mtDNA. Facultative re-targeting of the chloroplast RNase H1 protein to mitochondria, in response to cellular conditions, can help guarantee mitochondrial RNase H1 activity.
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Affiliation(s)
- Lingling Cheng
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Wenjie Wang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China.,Tsinghua-Peking Center for Life Sciences, Beijing, China
| | - Yao Yao
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China.,Tsinghua-Peking Center for Life Sciences, Beijing, China
| | - Qianwen Sun
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China.,Tsinghua-Peking Center for Life Sciences, Beijing, China
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8
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Oliveira MT, Pontes CDB, Ciesielski GL. Roles of the mitochondrial replisome in mitochondrial DNA deletion formation. Genet Mol Biol 2020; 43:e20190069. [PMID: 32141473 PMCID: PMC7197994 DOI: 10.1590/1678-4685-gmb-2019-0069] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Accepted: 08/12/2019] [Indexed: 01/07/2023] Open
Abstract
Mitochondrial DNA (mtDNA) deletions are a common cause of human mitochondrial
diseases. Mutations in the genes encoding components of the mitochondrial
replisome, such as DNA polymerase gamma (Pol γ) and the mtDNA helicase Twinkle,
have been associated with the accumulation of such deletions and the development
of pathological conditions in humans. Recently, we demonstrated that changes in
the level of wild-type Twinkle promote mtDNA deletions, which implies that not
only mutations in, but also dysregulation of the stoichiometry between the
replisome components is potentially pathogenic. The mechanism(s) by which
alterations to the replisome function generate mtDNA deletions is(are) currently
under debate. It is commonly accepted that stalling of the replication fork at
sites likely to form secondary structures precedes the deletion formation. The
secondary structural elements can be bypassed by the replication-slippage
mechanism. Otherwise, stalling of the replication fork can generate single- and
double-strand breaks, which can be repaired through recombination leading to the
elimination of segments between the recombination sites. Here, we discuss
aberrances of the replisome in the context of the two debated outcomes, and
suggest new mechanistic explanations based on replication restart and template
switching that could account for all the deletion types reported for
patients.
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Affiliation(s)
- Marcos T Oliveira
- Universidade Estadual Paulista Júlio de Mesquita Filho, Faculdade de Ciências Agrárias e Veterinárias, Departamento de Tecnologia, Jaboticabal, SP, Brazil
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9
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Bailey LJ, Bianchi J, Doherty AJ. PrimPol is required for the maintenance of efficient nuclear and mitochondrial DNA replication in human cells. Nucleic Acids Res 2019; 47:4026-4038. [PMID: 30715459 PMCID: PMC6486543 DOI: 10.1093/nar/gkz056] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 01/14/2019] [Accepted: 01/28/2019] [Indexed: 12/14/2022] Open
Abstract
Eukaryotic Primase-Polymerase (PrimPol) is an enzyme that maintains efficient DNA duplication by repriming replication restart downstream of replicase stalling lesions and structures. To elucidate the cellular requirements for PrimPol in human cells, we generated PrimPol-deleted cell lines and show that it plays key roles in maintaining active replication in both the nucleus and mitochondrion, even in the absence of exogenous damage. Human cells lacking PrimPol exhibit delayed recovery after UV-C damage and increased mutation frequency, micronuclei and sister chromatin exchanges but are not sensitive to genotoxins. PrimPol is also required during mitochondrial replication, with PrimPol-deficient cells having increased mtDNA copy number but displaying a significant decrease in replication. Deletion of PrimPol in XPV cells, lacking functional polymerase Eta, causes an increase in DNA damage sensitivity and pronounced fork stalling after UV-C treatment. We show that, unlike canonical TLS polymerases, PrimPol is important for allowing active replication to proceed, even in the absence of exogenous damage, thus preventing the accumulation of excessive fork stalling and genetic mutations. Together, these findings highlight the importance of PrimPol for maintaining efficient DNA replication in unperturbed cells and its complementary roles, with Pol Eta, in damage tolerance in human cells.
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Affiliation(s)
- Laura J Bailey
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, UK
| | - Julie Bianchi
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, UK
| | - Aidan J Doherty
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, UK
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10
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Silva J, Aivio S, Knobel PA, Bailey LJ, Casali A, Vinaixa M, Garcia-Cao I, Coyaud É, Jourdain AA, Pérez-Ferreros P, Rojas AM, Antolin-Fontes A, Samino-Gené S, Raught B, González-Reyes A, Ribas de Pouplana L, Doherty AJ, Yanes O, Stracker TH. EXD2 governs germ stem cell homeostasis and lifespan by promoting mitoribosome integrity and translation. Nat Cell Biol 2018; 20:162-174. [PMID: 29335528 DOI: 10.1038/s41556-017-0016-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 11/27/2017] [Indexed: 02/08/2023]
Abstract
Mitochondria are subcellular organelles that are critical for meeting the bioenergetic and biosynthetic needs of the cell. Mitochondrial function relies on genes and RNA species encoded both in the nucleus and mitochondria, and on their coordinated translation, import and respiratory complex assembly. Here, we characterize EXD2 (exonuclease 3'-5' domain-containing 2), a nuclear-encoded gene, and show that it is targeted to the mitochondria and prevents the aberrant association of messenger RNAs with the mitochondrial ribosome. Loss of EXD2 results in defective mitochondrial translation, impaired respiration, reduced ATP production, increased reactive oxygen species and widespread metabolic abnormalities. Depletion of the Drosophila melanogaster EXD2 orthologue (CG6744) causes developmental delays and premature female germline stem cell attrition, reduced fecundity and a dramatic extension of lifespan that is reversed with an antioxidant diet. Our results define a conserved role for EXD2 in mitochondrial translation that influences development and ageing.
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Affiliation(s)
- Joana Silva
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - Suvi Aivio
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,Department of Pathology, Brigham and Women's Hospital, Boston, MA, USA
| | - Philip A Knobel
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,Department for Radiation Oncology, University Hospital Zurich, Zurich, Switzerland
| | - Laura J Bailey
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, UK
| | - Andreu Casali
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - Maria Vinaixa
- Metabolomics Platform, Department of Electronic Engineering (DEEEA), Universitat Rovira i Virgili, Tarragona, Spain.,Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
| | - Isabel Garcia-Cao
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - Étienne Coyaud
- Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Alexis A Jourdain
- Department of Molecular Biology, Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA, USA.,Department of Systems Biology, Harvard Medical School, Boston, MA, USA.,Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Pablo Pérez-Ferreros
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,EMBL Australia, University of New South Wales, Lowy Cancer Research Center, Single Molecule Science Node, Sydney and Arc Center of Excellence in Advance Molecular Imaging, Sydney, New South Wales, Australia
| | - Ana M Rojas
- Computational Biology and Bioinformatics Group, Institute of Biomedicine of Seville (IBIS/CSIC/US/JA), Campus Hospital Universitario Virgen del Rocio, Seville, Spain
| | - Albert Antolin-Fontes
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - Sara Samino-Gené
- Metabolomics Platform, Department of Electronic Engineering (DEEEA), Universitat Rovira i Virgili, Tarragona, Spain.,Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
| | - Brian Raught
- Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Acaimo González-Reyes
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide/CSIC/JA, Seville, Spain
| | - Lluís Ribas de Pouplana
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
| | - Aidan J Doherty
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, UK
| | - Oscar Yanes
- Metabolomics Platform, Department of Electronic Engineering (DEEEA), Universitat Rovira i Virgili, Tarragona, Spain.,Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
| | - Travis H Stracker
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.
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11
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Nicholls TJ, Nadalutti CA, Motori E, Sommerville EW, Gorman GS, Basu S, Hoberg E, Turnbull DM, Chinnery PF, Larsson NG, Larsson E, Falkenberg M, Taylor RW, Griffith JD, Gustafsson CM. Topoisomerase 3α Is Required for Decatenation and Segregation of Human mtDNA. Mol Cell 2017; 69:9-23.e6. [PMID: 29290614 DOI: 10.1016/j.molcel.2017.11.033] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 10/26/2017] [Accepted: 11/26/2017] [Indexed: 01/01/2023]
Abstract
How mtDNA replication is terminated and the newly formed genomes are separated remain unknown. We here demonstrate that the mitochondrial isoform of topoisomerase 3α (Top3α) fulfills this function, acting independently of its nuclear role as a component of the Holliday junction-resolving BLM-Top3α-RMI1-RMI2 (BTR) complex. Our data indicate that mtDNA replication termination occurs via a hemicatenane formed at the origin of H-strand replication and that Top3α is essential for resolving this structure. Decatenation is a prerequisite for separation of the segregating unit of mtDNA, the nucleoid, within the mitochondrial network. The importance of this process is highlighted in a patient with mitochondrial disease caused by biallelic pathogenic variants in TOP3A, characterized by muscle-restricted mtDNA deletions and chronic progressive external ophthalmoplegia (CPEO) plus syndrome. Our work establishes Top3α as an essential component of the mtDNA replication machinery and as the first component of the mtDNA separation machinery.
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Affiliation(s)
- Thomas J Nicholls
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, 405 30 Gothenburg, Sweden
| | - Cristina A Nadalutti
- Lineberger Comprehensive Cancer Center, Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Elisa Motori
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Ewen W Sommerville
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Gráinne S Gorman
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Swaraj Basu
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, 405 30 Gothenburg, Sweden
| | - Emily Hoberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, 405 30 Gothenburg, Sweden
| | - Doug M Turnbull
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Patrick F Chinnery
- Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Nils-Göran Larsson
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany; Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Erik Larsson
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, 405 30 Gothenburg, Sweden
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, 405 30 Gothenburg, Sweden
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Jack D Griffith
- Lineberger Comprehensive Cancer Center, Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Claes M Gustafsson
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, 405 30 Gothenburg, Sweden.
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12
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Reyes A, Melchionda L, Nasca A, Carrara F, Lamantea E, Zanolini A, Lamperti C, Fang M, Zhang J, Ronchi D, Bonato S, Fagiolari G, Moggio M, Ghezzi D, Zeviani M. RNASEH1 Mutations Impair mtDNA Replication and Cause Adult-Onset Mitochondrial Encephalomyopathy. Am J Hum Genet 2015; 97:186-93. [PMID: 26094573 DOI: 10.1016/j.ajhg.2015.05.013] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 05/21/2015] [Indexed: 11/27/2022] Open
Abstract
Chronic progressive external ophthalmoplegia (CPEO) is common in mitochondrial disorders and is frequently associated with multiple mtDNA deletions. The onset is typically in adulthood, and affected subjects can also present with general muscle weakness. The underlying genetic defects comprise autosomal-dominant or recessive mutations in several nuclear genes, most of which play a role in mtDNA replication. Next-generation sequencing led to the identification of compound-heterozygous RNASEH1 mutations in two singleton subjects and a homozygous mutation in four siblings. RNASEH1, encoding ribonuclease H1 (RNase H1), is an endonuclease that is present in both the nucleus and mitochondria and digests the RNA component of RNA-DNA hybrids. Unlike mitochondria, the nucleus harbors a second ribonuclease (RNase H2). All affected individuals first presented with CPEO and exercise intolerance in their twenties, and these were followed by muscle weakness, dysphagia, and spino-cerebellar signs with impaired gait coordination, dysmetria, and dysarthria. Ragged-red and cytochrome c oxidase (COX)-negative fibers, together with impaired activity of various mitochondrial respiratory chain complexes, were observed in muscle biopsies of affected subjects. Western blot analysis showed the virtual absence of RNase H1 in total lysate from mutant fibroblasts. By an in vitro assay, we demonstrated that altered RNase H1 has a reduced capability to remove the RNA from RNA-DNA hybrids, confirming their pathogenic role. Given that an increasing amount of evidence indicates the presence of RNA primers during mtDNA replication, this result might also explain the accumulation of mtDNA deletions and underscores the importance of RNase H1 for mtDNA maintenance.
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Affiliation(s)
- Aurelio Reyes
- Mitochondrial Biology Unit, Medical Research Council, Cambridge CB2 0XY, UK
| | - Laura Melchionda
- Unit of Molecular Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan 20126, Italy
| | - Alessia Nasca
- Unit of Molecular Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan 20126, Italy
| | - Franco Carrara
- Unit of Molecular Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan 20126, Italy
| | - Eleonora Lamantea
- Unit of Molecular Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan 20126, Italy
| | - Alice Zanolini
- Unit of Molecular Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan 20126, Italy
| | - Costanza Lamperti
- Unit of Molecular Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan 20126, Italy
| | - Mingyan Fang
- Beijing Genomic Institute, Shenzhen 518083, China
| | | | - Dario Ronchi
- Neurology Unit, Neuroscience Section, Department of Pathophysiology and Transplantation, Dino Ferrari Center, IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan 20122, Italy
| | - Sara Bonato
- Neurology Unit, Neuroscience Section, Department of Pathophysiology and Transplantation, Dino Ferrari Center, IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan 20122, Italy
| | - Gigliola Fagiolari
- Neuromuscular Unit, Neuroscience Section, Department of Pathophysiology and Transplantation, Dino Ferrari Center, IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan 20122, Italy
| | - Maurizio Moggio
- Neuromuscular Unit, Neuroscience Section, Department of Pathophysiology and Transplantation, Dino Ferrari Center, IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan 20122, Italy
| | - Daniele Ghezzi
- Unit of Molecular Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan 20126, Italy.
| | - Massimo Zeviani
- Mitochondrial Biology Unit, Medical Research Council, Cambridge CB2 0XY, UK.
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13
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Jõers P, Lewis SC, Fukuoh A, Parhiala M, Ellilä S, Holt IJ, Jacobs HT. Mitochondrial transcription terminator family members mTTF and mTerf5 have opposing roles in coordination of mtDNA synthesis. PLoS Genet 2013; 9:e1003800. [PMID: 24068965 PMCID: PMC3778013 DOI: 10.1371/journal.pgen.1003800] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Accepted: 07/30/2013] [Indexed: 12/19/2022] Open
Abstract
All genomes require a system for avoidance or handling of collisions between the machineries of DNA replication and transcription. We have investigated the roles in this process of the mTERF (mitochondrial transcription termination factor) family members mTTF and mTerf5 in Drosophila melanogaster. The two mTTF binding sites in Drosophila mtDNA, which also bind mTerf5, were found to coincide with major sites of replication pausing. RNAi-mediated knockdown of either factor resulted in mtDNA depletion and developmental arrest. mTTF knockdown decreased site-specific replication pausing, but led to an increase in replication stalling and fork regression in broad zones around each mTTF binding site. Lagging-strand DNA synthesis was impaired, with extended RNA/DNA hybrid segments seen in replication intermediates. This was accompanied by the accumulation of recombination intermediates and nicked/broken mtDNA species. Conversely, mTerf5 knockdown led to enhanced replication pausing at mTTF binding sites, a decrease in fragile replication intermediates containing single-stranded segments, and the disappearance of species containing segments of RNA/DNA hybrid. These findings indicate an essential and previously undescribed role for proteins of the mTERF family in the integration of transcription and DNA replication, preventing unregulated collisions and facilitating productive interactions between the two machineries that are inferred to be essential for completion of lagging-strand DNA synthesis.
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Affiliation(s)
- Priit Jõers
- Institute of Biomedical Technology and Tampere University Hospital, Tampere, Finland
- Estonian Biocentre, Tartu, Estonia
| | - Samantha C. Lewis
- Institute of Biomedical Technology and Tampere University Hospital, Tampere, Finland
- Department of Biology, University of California, Riverside, California, United States of America
| | - Atsushi Fukuoh
- Institute of Biomedical Technology and Tampere University Hospital, Tampere, Finland
- Department of Clinical Chemistry and Laboratory Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan
- Department of Medical Laboratory Science, Junshin Gakuen University, Fukuoka, Japan
| | - Mikael Parhiala
- Institute of Biomedical Technology and Tampere University Hospital, Tampere, Finland
| | - Simo Ellilä
- Institute of Biomedical Technology and Tampere University Hospital, Tampere, Finland
| | - Ian J. Holt
- MRC National Institute of Medical Research, London, United Kingdom
| | - Howard T. Jacobs
- Institute of Biomedical Technology and Tampere University Hospital, Tampere, Finland
- Molecular Neurology Research Program, University of Helsinki, Helsinki, Finland
- * E-mail:
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14
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Reyes A, Kazak L, Wood SR, Yasukawa T, Jacobs HT, Holt IJ. Mitochondrial DNA replication proceeds via a 'bootlace' mechanism involving the incorporation of processed transcripts. Nucleic Acids Res 2013; 41:5837-50. [PMID: 23595151 PMCID: PMC3675460 DOI: 10.1093/nar/gkt196] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The observation that long tracts of RNA are associated with replicating molecules of mitochondrial DNA (mtDNA) suggests that the mitochondrial genome of mammals is copied by an unorthodox mechanism. Here we show that these RNA-containing species are present in living cells and tissue, based on interstrand cross-linking. Using DNA synthesis in organello, we demonstrate that isolated mitochondria incorporate radiolabeled RNA precursors, as well as DNA precursors, into replicating DNA molecules. RNA-containing replication intermediates are chased into mature mtDNA, to which they are thus in precursor-product relationship. While a DNA chain terminator rapidly blocks the labeling of mitochondrial replication intermediates, an RNA chain terminator does not. Furthermore, processed L-strand transcripts can be recovered from gel-extracted mtDNA replication intermediates. Therefore, instead of concurrent DNA and RNA synthesis, respectively, on the leading and lagging strands, preformed processed RNA is incorporated as a provisional lagging strand during mtDNA replication. These findings indicate that RITOLS is a physiological mechanism of mtDNA replication, and that it involves a 'bootlace' mechanism, in which processed transcripts are successively hybridized to the lagging-strand template, as the replication fork advances.
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Affiliation(s)
- Aurelio Reyes
- MRC-Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
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15
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Jõers P, Jacobs HT. Analysis of replication intermediates indicates that Drosophila melanogaster mitochondrial DNA replicates by a strand-coupled theta mechanism. PLoS One 2013; 8:e53249. [PMID: 23308172 PMCID: PMC3537619 DOI: 10.1371/journal.pone.0053249] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 11/28/2012] [Indexed: 11/18/2022] Open
Abstract
Mitochondrial DNA synthesis is necessary for the normal function of the organelle and for the eukaryotic organism as a whole. Here we demonstrate, using two-dimensional agarose gel electrophoresis to analyse replication intermediates, that unidirectional, strand-coupled DNA synthesis is the prevalent mode of mtDNA replication in Drosophila melanogaster. Commencing within the single, extended non-coding region (NCR), replication proceeds around the circular genome, manifesting an irregular rate of elongation, and pausing frequently in specific regions. Evidence for a limited contribution of strand-asynchronous DNA synthesis was found in a subset of mtDNA molecules, but confined to the ribosomal RNA gene region, just downstream of the NCR. Our findings imply that strand-coupled replication is widespread amongst metazoans, and should inform future research on mtDNA metabolism in D. melanogaster.
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Affiliation(s)
- Priit Jõers
- Institute of Biomedical Technology and Tampere University Hospital, University of Tampere, Tampere, Finland
| | - Howard T. Jacobs
- Institute of Biomedical Technology and Tampere University Hospital, University of Tampere, Tampere, Finland
- * E-mail:
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16
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Kolesar JE, Wang CY, Taguchi YV, Chou SH, Kaufman BA. Two-dimensional intact mitochondrial DNA agarose electrophoresis reveals the structural complexity of the mammalian mitochondrial genome. Nucleic Acids Res 2012; 41:e58. [PMID: 23275548 PMCID: PMC3575812 DOI: 10.1093/nar/gks1324] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The mitochondrial genome exists in numerous structural conformations, complicating the study of mitochondrial DNA (mtDNA) metabolism. Here, we describe the development of 2D intact mtDNA agarose gel electrophoresis (2D-IMAGE) for the separation and detection of approximately two-dozen distinct topoisomers. Although the major topoisomers were well conserved across many cell and tissue types, unique differences in certain cells and tissues were also observed. RNase treatment revealed that partially hybridized RNAs associated primarily with covalently closed circular DNA, consistent with this structure being the template for transcription. Circular structures composed of RNA:DNA hybrids contained only heavy-strand DNA sequences, implicating them as lagging-strand replication intermediates. During recovery from replicative arrest, 2D-IMAGE showed changes in both template selection and replication products. These studies suggest that discrete topoisomers are associated with specific mtDNA-directed processes. Because of the increased resolution, 2D-IMAGE has the potential to identify novel mtDNA intermediates involved in replication or transcription, or pathology including oxidative linearization, deletions or depletion.
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Affiliation(s)
- Jill E Kolesar
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street VET220E, Philadelphia, PA 19104, USA
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17
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Comte C, Tonin Y, Heckel-Mager AM, Boucheham A, Smirnov A, Auré K, Lombès A, Martin RP, Entelis N, Tarassov I. Mitochondrial targeting of recombinant RNAs modulates the level of a heteroplasmic mutation in human mitochondrial DNA associated with Kearns Sayre Syndrome. Nucleic Acids Res 2012; 41:418-33. [PMID: 23087375 PMCID: PMC3592399 DOI: 10.1093/nar/gks965] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mitochondrial mutations, an important cause of incurable human neuromuscular diseases, are mostly heteroplasmic: mutated mitochondrial DNA is present in cells simultaneously with wild-type genomes, the pathogenic threshold being generally >70% of mutant mtDNA. We studied whether heteroplasmy level could be decreased by specifically designed oligoribonucleotides, targeted into mitochondria by the pathway delivering RNA molecules in vivo. Using mitochondrially imported RNAs as vectors, we demonstrated that oligoribonucleotides complementary to mutant mtDNA region can specifically reduce the proportion of mtDNA bearing a large deletion associated with the Kearns Sayre Syndrome in cultured transmitochondrial cybrid cells. These findings may be relevant to developing of a new tool for therapy of mtDNA associated diseases.
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Affiliation(s)
- Caroline Comte
- Department of Molecular and Cellular Genetics, UMR Génétique Moléculaire, Génomique, Microbiologie, CNRS, Université de Strasbourg, Strasbourg, France
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18
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Wanrooij S, Falkenberg M. The human mitochondrial replication fork in health and disease. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1378-88. [PMID: 20417176 DOI: 10.1016/j.bbabio.2010.04.015] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 04/13/2010] [Accepted: 04/15/2010] [Indexed: 11/16/2022]
Abstract
Mitochondria are organelles whose main function is to generate power by oxidative phosphorylation. Some of the essential genes required for this energy production are encoded by the mitochondrial genome, a small circular double stranded DNA molecule. Human mtDNA is replicated by a specialized machinery distinct from the nuclear replisome. Defects in the mitochondrial replication machinery can lead to loss of genetic information by deletion and/or depletion of the mtDNA, which subsequently may cause disturbed oxidative phosphorylation and neuromuscular symptoms in patients. We discuss here the different components of the mitochondrial replication machinery and their role in disease. We also review the mode of mammalian mtDNA replication.
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Affiliation(s)
- Sjoerd Wanrooij
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-40530 Gothenburg, Sweden.
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