51
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Jemt E, Persson Ö, Shi Y, Mehmedovic M, Uhler JP, Dávila López M, Freyer C, Gustafsson CM, Samuelsson T, Falkenberg M. Regulation of DNA replication at the end of the mitochondrial D-loop involves the helicase TWINKLE and a conserved sequence element. Nucleic Acids Res 2015; 43:9262-75. [PMID: 26253742 PMCID: PMC4627069 DOI: 10.1093/nar/gkv804] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 07/28/2015] [Indexed: 11/12/2022] Open
Abstract
The majority of mitochondrial DNA replication events are terminated prematurely. The nascent DNA remains stably associated with the template, forming a triple-stranded displacement loop (D-loop) structure. However, the function of the D-loop region of the mitochondrial genome remains poorly understood. Using a comparative genomics approach we here identify two closely related 15 nt sequence motifs of the D-loop, strongly conserved among vertebrates. One motif is at the D-loop 5'-end and is part of the conserved sequence block 1 (CSB1). The other motif, here denoted coreTAS, is at the D-loop 3'-end. Both these sequences may prevent transcription across the D-loop region, since light and heavy strand transcription is terminated at CSB1 and coreTAS, respectively. Interestingly, the replication of the nascent D-loop strand, occurring in a direction opposite to that of heavy strand transcription, is also terminated at coreTAS, suggesting that coreTAS is involved in termination of both transcription and replication. Finally, we demonstrate that the loading of the helicase TWINKLE at coreTAS is reversible, implying that this site is a crucial component of a switch between D-loop formation and full-length mitochondrial DNA replication.
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Affiliation(s)
- Elisabeth Jemt
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden
| | - Örjan Persson
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden
| | - Yonghong Shi
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden
| | - Majda Mehmedovic
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden
| | - Jay P Uhler
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden
| | - Marcela Dávila López
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden
| | - Christoph Freyer
- Department of Laboratory Medicine, Karolinska Institutet, Retzius väg 8, 171 77 Stockholm, Sweden
| | - Claes M Gustafsson
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden
| | - Tore Samuelsson
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden
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52
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Abstract
In the past century, considerable efforts were made to understand the role of mitochondrial DNA (mtDNA) mutations and of oxidative stress in aging. The classic mitochondrial free radical theory of aging, in which mtDNA mutations cause genotoxic oxidative stress, which in turn creates more mutations, has been a central hypothesis in the field for decades. In the past few years, however, new elements have discredited this original theory. The major sources of mitochondrial DNA mutations seem to be replication errors and failure of the repair mechanisms, and the accumulation of these mutations as observed in aged organisms seems to occur by clonal expansion and not to be caused by a reactive oxygen species-dependent vicious cycle. New hypotheses of how age-associated mitochondrial dysfunction may lead to aging are based on the role of reactive oxygen species as signaling molecules and on their role in mediating stress responses to age-dependent damage. Here, we review the changes that mtDNA undergoes during aging and the past and most recent hypotheses linking these changes to the tissue failure observed in aging.
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Affiliation(s)
- Milena Pinto
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Carlos T Moraes
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA; Department of Cell Biology and Anatomy, Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
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53
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Posse V, Shahzad S, Falkenberg M, Hällberg BM, Gustafsson CM. TEFM is a potent stimulator of mitochondrial transcription elongation in vitro. Nucleic Acids Res 2015; 43:2615-24. [PMID: 25690892 PMCID: PMC4357710 DOI: 10.1093/nar/gkv105] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
A single-subunit RNA polymerase, POLRMT, transcribes the mitochondrial genome in human cells. Recently, a factor termed as the mitochondrial transcription elongation factor, TEFM, was shown to stimulate transcription elongation in vivo, but its effect in vitro was relatively modest. In the current work, we have isolated active TEFM in recombinant form and used a reconstituted in vitro transcription system to characterize its activities. We show that TEFM strongly promotes POLRMT processivity as it dramatically stimulates the formation of longer transcripts. TEFM also abolishes premature transcription termination at conserved sequence block II, an event that has been linked to primer formation during initiation of mtDNA synthesis. We show that POLRMT pauses at a wide range of sites in a given DNA sequence. In the absence of TEFM, this leads to termination; however, the presence of TEFM abolishes this effect and aids POLRMT in continuation of transcription. Further, we show that TEFM substantially increases the POLRMT affinity to an elongation-like DNA:RNA template. In combination with previously published in vivo observations, our data establish TEFM as an essential component of the mitochondrial transcription machinery.
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Affiliation(s)
- Viktor Posse
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, SE-40530 Gothenburg, Sweden
| | - Saba Shahzad
- Department of Cell and Molecular Biology, Karolinska Institutet, SE-17177 Stockholm, Sweden Röntgen-Ångström-Cluster, Karolinska Institutet Outstation, Centre for Structural Systems Biology, DESY-Campus, D-22603 Hamburg, Germany
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, SE-40530 Gothenburg, Sweden
| | - B Martin Hällberg
- Department of Cell and Molecular Biology, Karolinska Institutet, SE-17177 Stockholm, Sweden Röntgen-Ångström-Cluster, Karolinska Institutet Outstation, Centre for Structural Systems Biology, DESY-Campus, D-22603 Hamburg, Germany European Molecular Biology Laboratory, Hamburg Unit, D-22603 Hamburg, Germany
| | - Claes M Gustafsson
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, SE-40530 Gothenburg, Sweden
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54
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Fonseca MM, Harris DJ, Posada D. The inversion of the Control Region in three mitogenomes provides further evidence for an asymmetric model of vertebrate mtDNA replication. PLoS One 2014; 9:e106654. [PMID: 25268704 PMCID: PMC4182315 DOI: 10.1371/journal.pone.0106654] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Accepted: 08/04/2014] [Indexed: 11/29/2022] Open
Abstract
Mitochondrial genomes are known to have a strong strand-specific compositional bias that is more pronounced at fourfold redundant sites of mtDNA protein-coding genes. This observation suggests that strand asymmetries, to a large extent, are caused by mutational asymmetric mechanisms. In vertebrate mitogenomes, replication and not transcription seems to play a major role in shaping compositional bias. Hence, one can better understand how mtDNA is replicated – a debated issue – through a detailed picture of mitochondrial genome evolution. Here, we analyzed the compositional bias (AT and GC skews) in protein-coding genes of almost 2,500 complete vertebrate mitogenomes. We were able to identify three fish mitogenomes with inverted AT/GC skew coupled with an inversion of the Control Region. These findings suggest that the vertebrate mitochondrial replication mechanism is asymmetric and may invert its polarity, with the leading-strand becoming the lagging-strand and vice-versa, without compromising mtDNA maintenance and expression. The inversion of the strand-specific compositional bias through the inversion of the Control Region is in agreement with the strand-displacement model but it is also compatible with the RITOLS model of mtDNA replication.
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Affiliation(s)
- Miguel M. Fonseca
- Department of Biochemistry, Genetics and Immunology, University of Vigo, Vigo, Spain
- CIBIO/InBIO, Research Center in Biodiversity and Genetic Resources, University of Porto, Vairão, Portugal
- * E-mail:
| | - D. James Harris
- CIBIO/InBIO, Research Center in Biodiversity and Genetic Resources, University of Porto, Vairão, Portugal
| | - David Posada
- Department of Biochemistry, Genetics and Immunology, University of Vigo, Vigo, Spain
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55
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Blumberg A, Sri Sailaja B, Kundaje A, Levin L, Dadon S, Shmorak S, Shaulian E, Meshorer E, Mishmar D. Transcription factors bind negatively selected sites within human mtDNA genes. Genome Biol Evol 2014; 6:2634-46. [PMID: 25245407 PMCID: PMC4224337 DOI: 10.1093/gbe/evu210] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Transcription of mitochondrial DNA (mtDNA)-encoded genes is thought to be regulated by a handful of dedicated transcription factors (TFs), suggesting that mtDNA genes are separately regulated from the nucleus. However, several TFs, with known nuclear activities, were found to bind mtDNA and regulate mitochondrial transcription. Additionally, mtDNA transcriptional regulatory elements, which were proved important in vitro, were harbored by a deletion that normally segregated among healthy individuals. Hence, mtDNA transcriptional regulation is more complex than once thought. Here, by analyzing ENCODE chromatin immunoprecipitation sequencing (ChIP-seq) data, we identified strong binding sites of three bona fide nuclear TFs (c-Jun, Jun-D, and CEBPb) within human mtDNA protein-coding genes. We validated the binding of two TFs by ChIP-quantitative polymerase chain reaction (c-Jun and Jun-D) and showed their mitochondrial localization by electron microscopy and subcellular fractionation. As a step toward investigating the functionality of these TF-binding sites (TFBS), we assessed signatures of selection. By analyzing 9,868 human mtDNA sequences encompassing all major global populations, we recorded genetic variants in tips and nodes of mtDNA phylogeny within the TFBS. We next calculated the effects of variants on binding motif prediction scores. Finally, the mtDNA variation pattern in predicted TFBS, occurring within ChIP-seq negative-binding sites, was compared with ChIP-seq positive-TFBS (CPR). Motifs within CPRs of c-Jun, Jun-D, and CEBPb harbored either only tip variants or their nodal variants retained high motif prediction scores. This reflects negative selection within mtDNA CPRs, thus supporting their functionality. Hence, human mtDNA-coding sequences may have dual roles, namely coding for genes yet possibly also possessing regulatory potential.
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Affiliation(s)
- Amit Blumberg
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Badi Sri Sailaja
- Department of Genetics, The Institute of Life Sciences, and The Edmond Lily Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Israel
| | - Anshul Kundaje
- Department of Genetics, Stanford University Department of Computer Science, Stanford University
| | - Liron Levin
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Sara Dadon
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Shimrit Shmorak
- Department of Biochemistry and Molecular Biology, IMRIC, The Hebrew University Medical School, Ein Karem, Jerusalem, Israel
| | - Eitan Shaulian
- Department of Biochemistry and Molecular Biology, IMRIC, The Hebrew University Medical School, Ein Karem, Jerusalem, Israel
| | - Eran Meshorer
- Department of Genetics, The Institute of Life Sciences, and The Edmond Lily Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Israel
| | - Dan Mishmar
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
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56
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Zheng KW, Wu RY, He YD, Xiao S, Zhang JY, Liu JQ, Hao YH, Tan Z. A competitive formation of DNA:RNA hybrid G-quadruplex is responsible to the mitochondrial transcription termination at the DNA replication priming site. Nucleic Acids Res 2014; 42:10832-44. [PMID: 25140009 PMCID: PMC4176368 DOI: 10.1093/nar/gku764] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Human mitochondrial DNA contains a distinctive guanine-rich motif denoted conserved sequence block II (CSB II) that stops RNA transcription, producing prematurely terminated transcripts to prime mitochondrial DNA replication. Recently, we reported a general phenomenon that DNA:RNA hybrid G-quadruplexes (HQs) readily form during transcription when the non-template DNA strand is guanine-rich and such HQs in turn regulate transcription. In this work, we show that transcription of mitochondrial DNA leads to the formation of a stable HQ or alternatively an unstable intramolecular DNA G-quadruplex (DQ) at the CSB II. The HQ is the dominant species and contributes to the majority of the premature transcription termination. Manipulating the stability of the DQ has little effect on the termination even in the absence of HQ; however, abolishing the formation of HQs by preventing the participation of either DNA or RNA abolishes the vast majority of the termination. These results demonstrate that the type of G-quadruplexes (HQ or DQ) is a crucial determinant in directing the transcription termination at the CSB II and suggest a potential functionality of the co-transcriptionally formed HQ in DNA replication initiation. They also suggest that the competition/conversion between an HQ and a DQ may regulate the function of a G-quadruplex-forming sequence.
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Affiliation(s)
- Ke-wei Zheng
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Ren-yi Wu
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Yi-de He
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Shan Xiao
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Jia-yu Zhang
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Jia-quan Liu
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Yu-hua Hao
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Zheng Tan
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
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57
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Nicholls TJ, Zsurka G, Peeva V, Schöler S, Szczesny RJ, Cysewski D, Reyes A, Kornblum C, Sciacco M, Moggio M, Dziembowski A, Kunz WS, Minczuk M. Linear mtDNA fragments and unusual mtDNA rearrangements associated with pathological deficiency of MGME1 exonuclease. Hum Mol Genet 2014; 23:6147-62. [PMID: 24986917 PMCID: PMC4222359 DOI: 10.1093/hmg/ddu336] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
MGME1, also known as Ddk1 or C20orf72, is a mitochondrial exonuclease found to be involved in the processing of mitochondrial DNA (mtDNA) during replication. Here, we present detailed insights on the role of MGME1 in mtDNA maintenance. Upon loss of MGME1, elongated 7S DNA species accumulate owing to incomplete processing of 5′ ends. Moreover, an 11-kb linear mtDNA fragment spanning the entire major arc of the mitochondrial genome is generated. In contrast to control cells, where linear mtDNA molecules are detectable only after nuclease S1 treatment, the 11-kb fragment persists in MGME1-deficient cells. In parallel, we observed characteristic mtDNA duplications in the absence of MGME1. The fact that the breakpoints of these mtDNA rearrangements do not correspond to either classical deletions or the ends of the linear 11-kb fragment points to a role of MGME1 in processing mtDNA ends, possibly enabling their repair by homologous recombination. In agreement with its functional involvement in mtDNA maintenance, we show that MGME1 interacts with the mitochondrial replicase PolgA, suggesting that it is a constituent of the mitochondrial replisome, to which it provides an additional exonuclease activity. Thus, our results support the viewpoint that MGME1-mediated mtDNA processing is essential for faithful mitochondrial genome replication and might be required for intramolecular recombination of mtDNA.
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Affiliation(s)
| | - Gábor Zsurka
- Department of Epileptology, Life and Brain Center and
| | | | | | - Roman J Szczesny
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland and
| | - Dominik Cysewski
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland and
| | - Aurelio Reyes
- Mitochondrial Biology Unit, Medical Research Council, Cambridge, UK
| | - Cornelia Kornblum
- Department of Neurology, University of Bonn Medical Center, Bonn, Germany
| | - Monica Sciacco
- Neuromuscular Unit, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Centro Dino Ferrari, University of Milan, Milan, Italy
| | - Maurizio Moggio
- Neuromuscular Unit, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Centro Dino Ferrari, University of Milan, Milan, Italy
| | - Andrzej Dziembowski
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland and
| | | | - Michal Minczuk
- Mitochondrial Biology Unit, Medical Research Council, Cambridge, UK,
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58
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Knoll N, Jarick I, Volckmar AL, Klingenspor M, Illig T, Grallert H, Gieger C, Wichmann HE, Peters A, Wiegand S, Biebermann H, Fischer-Posovszky P, Wabitsch M, Völzke H, Nauck M, Teumer A, Rosskopf D, Rimmbach C, Schreiber S, Jacobs G, Lieb W, Franke A, Hebebrand J, Hinney A. Mitochondrial DNA variants in obesity. PLoS One 2014; 9:e94882. [PMID: 24788344 PMCID: PMC4008486 DOI: 10.1371/journal.pone.0094882] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 03/19/2014] [Indexed: 12/28/2022] Open
Abstract
Heritability estimates for body mass index (BMI) variation are high. For mothers and their offspring higher BMI correlations have been described than for fathers. Variation(s) in the exclusively maternally inherited mitochondrial DNA (mtDNA) might contribute to this parental effect. Thirty-two to 40 mtDNA single nucleotide polymorphisms (SNPs) were available from genome-wide association study SNP arrays (Affymetrix 6.0). For discovery, we analyzed association in a case-control (CC) sample of 1,158 extremely obese children and adolescents and 435 lean adult controls. For independent confirmation, 7,014 population-based adults were analyzed as CC sample of n = 1,697 obese cases (BMI ≥ 30 kg/m2) and n = 2,373 normal weight and lean controls (BMI<25 kg/m2). SNPs were analyzed as single SNPs and haplogroups determined by HaploGrep. Fisher's two-sided exact test was used for association testing. Moreover, the D-loop was re-sequenced (Sanger) in 192 extremely obese children and adolescents and 192 lean adult controls. Association testing of detected variants was performed using Fisher's two-sided exact test. For discovery, nominal association with obesity was found for the frequent allele G of m.8994G/A (rs28358887, p = 0.002) located in ATP6. Haplogroup W was nominally overrepresented in the controls (p = 0.039). These findings could not be confirmed independently. For two of the 252 identified D-loop variants nominal association was detected (m.16292C/T, p = 0.007, m.16189T/C, p = 0.048). Only eight controls carried the m.16292T allele, five of whom belonged to haplogroup W that was initially enriched among these controls. m.16189T/C might create an uninterrupted poly-C tract located near a regulatory element involved in replication of mtDNA. Though follow-up of some D-loop variants still is conceivable, our hypothesis of a contribution of variation in the exclusively maternally inherited mtDNA to the observed larger correlations for BMI between mothers and their offspring could not be substantiated by the findings of the present study.
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Affiliation(s)
- Nadja Knoll
- Department of Child and Adolescent Psychiatry, University of Duisburg-Essen, Essen, Germany
| | - Ivonne Jarick
- Institute of Medical Biometry and Epidemiology, Philipps-University of Marburg, Marburg, Germany
| | - Anna-Lena Volckmar
- Department of Child and Adolescent Psychiatry, University of Duisburg-Essen, Essen, Germany
| | - Martin Klingenspor
- Molecular Nutritional Medicine, Technical University of Munich, Else Kröner-Fresenius Center, Freising-Weihenstephan, Germany
| | - Thomas Illig
- Research Unit of Molecular Epidemiology, Helmholtz Center Munich – German Research Center for Environmental Health, Neuherberg, Germany
- Hannover Unified Biobank, Hannover Medical School, Hannover, Germany
| | - Harald Grallert
- Research Unit of Molecular Epidemiology, Helmholtz Center Munich – German Research Center for Environmental Health, Neuherberg, Germany
- Institute of Epidemiology II, Helmholtz Center Munich – German Research Center for Environmental Health, Neuherberg, Germany
- German Center for Diabetes Research, Neuherberg, Germany
| | - Christian Gieger
- Institute of Genetic Epidemiology, Helmholtz Center Munich – German Research Center for Environmental Health, Neuherberg, Germany
| | - Heinz-Erich Wichmann
- Institute of Epidemiology I, Helmholtz Center Munich – German Research Center for Environmental Health, Neuherberg, Germany, Neuherberg, Germany
- Institute of Medical Informatics, Biometry, and Epidemiology, Chair of Epidemiology, Ludwig-Maximilians-Universität, Munich, Germany
- Munich University Hospital, Campus Grosshadern, Munich, Germany
| | - Annette Peters
- Institute of Epidemiology II, Helmholtz Center Munich – German Research Center for Environmental Health, Neuherberg, Germany
| | - Susanna Wiegand
- Institute of Experimental Pediatric Endocrinology, Charité Berlin, Germany
| | - Heike Biebermann
- Institute of Experimental Pediatric Endocrinology, Charité Berlin, Germany
| | - Pamela Fischer-Posovszky
- Division of Pediatric Endocrinology and Diabetes, Department of Children and Adolescent Medicine, University of Ulm University Medical Center, Ulm, Germany
| | - Martin Wabitsch
- Division of Pediatric Endocrinology and Diabetes, Department of Children and Adolescent Medicine, University of Ulm University Medical Center, Ulm, Germany
| | - Henry Völzke
- Institute for Community Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Matthias Nauck
- Institute for Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Alexander Teumer
- Institute for Community Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Dieter Rosskopf
- Institute for Pharmacology, University Medicine Greifswald, Greifswald, Greifswald, Germany
| | - Christian Rimmbach
- Institute for Pharmacology, University Medicine Greifswald, Greifswald, Greifswald, Germany
| | - Stefan Schreiber
- Institute of Clinical Molecular Biology, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Gunnar Jacobs
- Institute of Epidemiology and Biobank popgen, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Wolfgang Lieb
- Institute of Epidemiology and Biobank popgen, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Andre Franke
- Institute of Clinical Molecular Biology, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Johannes Hebebrand
- Department of Child and Adolescent Psychiatry, University of Duisburg-Essen, Essen, Germany
| | - Anke Hinney
- Department of Child and Adolescent Psychiatry, University of Duisburg-Essen, Essen, Germany
- * E-mail:
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59
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In D-loop: 40 years of mitochondrial 7S DNA. Exp Gerontol 2014; 56:175-81. [PMID: 24709344 DOI: 10.1016/j.exger.2014.03.027] [Citation(s) in RCA: 172] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 03/27/2014] [Accepted: 03/28/2014] [Indexed: 11/23/2022]
Abstract
Given the tiny size of the mammalian mitochondrial genome, at only 16.5 kb, it is often surprising how little we know about some of its molecular features, and the molecular mechanisms governing its maintenance. One such conundrum is the biogenesis and function of the mitochondrial displacement loop (D-loop). The mitochondrial D-loop is a triple-stranded region found in the major non-coding region (NCR) of many mitochondrial genomes, and is formed by stable incorporation of a third, short DNA strand known as 7S DNA. In this article we review the current affairs regarding the main features of the D-loop structure, the diverse frequency of D-loops in the mtDNAs of various species and tissues, and also the mechanisms of its synthesis and turnover. This is followed by an account of the possible functions of the mitochondrial D-loop that have been proposed over the last four decades. In the last section, we discuss the potential links of the D-loop with mammalian ageing.
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60
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Tommasi S, Favia P, Weigl S, Bianco A, Pilato B, Russo L, Paradiso A, Petruzzella V. Mitochondrial DNA variants and risk of familial breast cancer: an exploratory study. Int J Oncol 2014; 44:1691-8. [PMID: 24603941 DOI: 10.3892/ijo.2014.2324] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 01/14/2014] [Indexed: 11/06/2022] Open
Abstract
To assess if mitochondrial DNA (mtDNA) variants are associated with mutations in BRCA susceptibility genes and to investigate the possible role of mitochondrial alterations as susceptibility markers in familial breast cancer (BC), 22 patients with or without BRCA1/BRCA2 mutations, 14 sporadic BC patients and 20 healthy subjects were analyzed. In the D-loop and in the MTND4 region, variants significantly associated with BRCA1 carriers were identified. Moreover, examination of mitochondrial haplogroups revealed X as the most significantly frequent haplogroup in BRCA1 carriers (P=0.005), and H as significantly linked to BRCA2 carriers (P=0.05). Our data suggest the involvement of the mitochondrial genome in the pathogenetic and molecular mechanism of familial BC disease.
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Affiliation(s)
- Stefania Tommasi
- National Cancer Research Centre, Istituto Tumori 'Giovanni Paolo II', Bari, Italy
| | - Paola Favia
- Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari 'Aldo Moro', Bari, Italy
| | - Stefania Weigl
- National Cancer Research Centre, Istituto Tumori 'Giovanni Paolo II', Bari, Italy
| | - Angelica Bianco
- Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari 'Aldo Moro', Bari, Italy
| | - Brunella Pilato
- National Cancer Research Centre, Istituto Tumori 'Giovanni Paolo II', Bari, Italy
| | - Luciana Russo
- Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari 'Aldo Moro', Bari, Italy
| | - Angelo Paradiso
- National Cancer Research Centre, Istituto Tumori 'Giovanni Paolo II', Bari, Italy
| | - Vittoria Petruzzella
- Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari 'Aldo Moro', Bari, Italy
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61
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Tipirisetti NR, Govatati S, Pullari P, Malempati S, Thupurani MK, Perugu S, Guruvaiah P, K LR, Digumarti RR, Nallanchakravarthula V, Bhanoori M, Satti V. Mitochondrial control region alterations and breast cancer risk: a study in South Indian population. PLoS One 2014; 9:e85363. [PMID: 24497926 PMCID: PMC3907410 DOI: 10.1371/journal.pone.0085363] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 11/26/2013] [Indexed: 01/10/2023] Open
Abstract
Background Mitochondrial displacement loop (D-loop) is the hot spot for mitochondrial DNA (mtDNA) alterations which influence the generation of cellular reactive oxygen species (ROS). Association of D-loop alterations with breast cancer has been reported in few ethnic groups; however none of the reports were documented from Indian subcontinent. Methodology We screened the entire mitochondrial D-loop region (1124 bp) of breast cancer patients (n = 213) and controls (n = 207) of south Indian origin by PCR-sequencing analysis. Haplotype frequencies for significant loci, the standardized disequilibrium coefficient (D′) for pair-wise linkage disequilibrium (LD) were assessed by Haploview Software. Principal Findings We identified 7 novel mutations and 170 reported polymorphisms in the D-loop region of patients and/or controls. Polymorphisms were predominantly located in hypervariable region I (60%) than in II (30%) of D-loop region. The frequencies of 310‘C’ insertion (P = 0.018), T16189C (P = 0.0019) variants and 310‘C’ins/16189C (P = 0.00019) haplotype were significantly higher in cases than in controls. Furthermore, strong LD was observed between nucleotide position 310 and 16189 in controls (D′ = 0.49) as compared to patients (D′ = 0.14). Conclusions Mitochondrial D-loop alterations may constitute inherent risk factors for breast cancer development. The analysis of genetic alterations in the D-loop region might help to identify patients at high risk for bad progression, thereby helping to refine therapeutic decisions in breast cancer.
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Affiliation(s)
| | - Suresh Govatati
- Department of Biochemistry, Osmania University, Hyderabad, India
| | - Priyanka Pullari
- Department of Biotechnology, Periyar University, Salem, Tamilnadu, India
| | - Sravanthi Malempati
- Department of Biochemistry, DrMRAR PG Center, Krishna University, Nuzvid, India
| | | | - Shyam Perugu
- Department of Biochemistry, Osmania University, Hyderabad, India
| | | | - Lakshmi Rao K
- Centre for Cellular and Molecular Biology (CCMB), Hyderabad, India
| | | | | | - Manjula Bhanoori
- Department of Biochemistry, Osmania University, Hyderabad, India
| | - Vishnupriya Satti
- Department of Genetics, Osmania University, Hyderabad, India
- * E-mail:
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Williams SL, Mash DC, Züchner S, Moraes CT. Somatic mtDNA mutation spectra in the aging human putamen. PLoS Genet 2013; 9:e1003990. [PMID: 24339796 PMCID: PMC3854840 DOI: 10.1371/journal.pgen.1003990] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 10/16/2013] [Indexed: 12/21/2022] Open
Abstract
The accumulation of heteroplasmic mitochondrial DNA (mtDNA) deletions and single nucleotide variants (SNVs) is a well-accepted facet of the biology of aging, yet comprehensive mutation spectra have not been described. To address this, we have used next generation sequencing of mtDNA-enriched libraries (Mito-Seq) to investigate mtDNA mutation spectra of putamen from young and aged donors. Frequencies of the “common” deletion and other “major arc” deletions were significantly increased in the aged cohort with the fold increase in the frequency of the common deletion exceeding that of major arc deletions. SNVs also increased with age with the highest rate of accumulation in the non-coding control region which contains elements necessary for translation and replication. Examination of predicted amino acid changes revealed a skew towards pathogenic SNVs in the coding region driven by mutation bias. Levels of the pathogenic m.3243A>G tRNA mutation were also found to increase with age. Novel multimeric tandem duplications that resemble murine control region multimers and yeast ρ− mtDNAs, were identified in both young and aged specimens. Clonal ∼50 bp deletions in the control region were found at high frequencies in aged specimens. Our results reveal the complex manner in which the mitochondrial genome alters with age and provides a foundation for studies of other tissues and disease states. Mitochondria are unique among animal organelles in that they contain their own multi-copy genome (mtDNA). For the past 20 years it has been known that tissues like brain and muscle accumulate somatic mtDNA mutations with age. Because individual mtDNA mutations are present at very low levels, few details are known about the spectrum of mutations associated with aging. Advances in sequencing technology now permit the examination of mtDNA mutations at high resolution. We have examined the spectrum of mtDNA mutations present in putamen, a brain region prone to the accumulation of somatic mtDNA mutations. We were able to quantify the accumulation of clonal and non-clonal deletions in the mtDNA coding region which are known to have a strong association with aging. Partial deletions and novel duplications of the mtDNA control region were also identified, and appear to be more prevalent than previously recognized, but levels showed weaker associations with age than coding region deletions. Single nucleotide variants accumulate fastest in the control region, with a skew towards the accumulation of pathogenic mutations in the coding region. Understanding how the mitochondrial genome alters with age provides a benchmark for studies of somatic mtDNA mutations and dissection of the role they play in normal aging and degenerative diseases.
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Affiliation(s)
- Siôn L. Williams
- Department of Neurology, University of Miami, Miller School of Medicine, Miami, Florida, United States of America
- * E-mail:
| | - Deborah C. Mash
- Department of Neurology, University of Miami, Miller School of Medicine, Miami, Florida, United States of America
- Department of Molecular and Cellular Pharmacology, University of Miami, Miller School of Medicine, Miami, Florida, United States of America
| | - Stephan Züchner
- Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami, Miller School of Medicine, Miami, Florida, United States of America
- John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, Florida, United States of America
| | - Carlos T. Moraes
- Department of Neurology, University of Miami, Miller School of Medicine, Miami, Florida, United States of America
- Department of Cell Biology and Anatomy, University of Miami, Miller School of Medicine, Miami, Florida, United States of America
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DING YU, XIA BOHOU, YU JINFANG, LENG JIANHANG, HUANG JINYU. Mitochondrial DNA mutations and essential hypertension (Review). Int J Mol Med 2013; 32:768-74. [DOI: 10.3892/ijmm.2013.1459] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 07/22/2013] [Indexed: 11/06/2022] Open
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Fischer C, Koblmüller S, Gülly C, Schlötterer C, Sturmbauer C, Thallinger GG. Complete mitochondrial DNA sequences of the threadfin cichlid (Petrochromis trewavasae) and the blunthead cichlid (Tropheus moorii) and patterns of mitochondrial genome evolution in cichlid fishes. PLoS One 2013; 8:e67048. [PMID: 23826193 PMCID: PMC3691221 DOI: 10.1371/journal.pone.0067048] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 05/13/2013] [Indexed: 01/28/2023] Open
Abstract
The cichlid fishes of the East African Great Lakes represent a model especially suited to study adaptive radiation and speciation. With several African cichlid genome projects being in progress, a promising set of closely related genomes is emerging, which is expected to serve as a valuable data base to solve questions on genotype-phenotype relations. The mitochondrial (mt) genomes presented here are the first results of the assembly and annotation process for two closely related but eco-morphologically highly distinct Lake Tanganyika cichlids, Petrochromis trewavasae and Tropheus moorii. The genomic sequences comprise 16,588 bp (P. trewavasae) and 16,590 bp (T. moorii), and exhibit the typical mitochondrial structure, with 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and a non-coding control region. Analyses confirmed that the two species are very closely related with an overall sequence similarity of 96%. We analyzed the newly generated sequences in the phylogenetic context of 21 published labroid fish mitochondrial genomes. Consistent with other vertebrates, the D-loop region was found to evolve faster than protein-coding genes, which in turn are followed by the rRNAs; the tRNAs vary greatly in the rate of sequence evolution, but on average evolve the slowest. Within the group of coding genes, ND6 evolves most rapidly. Codon usage is similar among examined cichlid tribes and labroid families; although a slight shift in usage patterns down the gene tree could be observed. Despite having a clearly different nucleotide composition, ND6 showed a similar codon usage. C-terminal ends of Cox1 exhibit variations, where the varying number of amino acids is related to the structure of the obtained phylogenetic tree. This variation may be of functional relevance for Cox1 synthesis.
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Affiliation(s)
- Christoph Fischer
- Institute for Genomics and Bioinformatics, Graz University of Technology, Graz, Austria
| | | | - Christian Gülly
- Center for Medical Research, Medical University of Graz, Graz, Austria
| | - Christian Schlötterer
- Institute of Population Genetics, University of Veterinary Medicine Vienna, Vienna, Austria
| | | | - Gerhard G. Thallinger
- Institute for Genomics and Bioinformatics, Graz University of Technology, Graz, Austria
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Mitochondrial displacement loop alterations are associated with endometriosis. Fertil Steril 2013; 99:1980-6.e9. [PMID: 23490167 DOI: 10.1016/j.fertnstert.2013.02.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 01/28/2013] [Accepted: 02/13/2013] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To evaluate the association of mitochondrial displacement (D-) loop alterations with endometriosis in south Indian women. DESIGN Case-control study. SETTING Biochemistry and molecular biology laboratories. PATIENT(S) Women with (n = 152) and without (n = 150) endometriosis of south Indian origin. INTERVENTION(S) All women had a transvaginal ultrasound scan at screening followed by a laparoscopy to confirm the diagnosis (revised American Fertility Society stage III = 54; stage IV = 98). MAIN OUTCOME MEASURE(S) Genotyping of entire D-loop (1,124 bp) was carried out on genomic DNA of blood from cases and controls by polymerase chain reaction sequencing analysis. RESULT(S) Twelve novel mutations and 187 reported polymorphisms were identified in the D-loop region of cases and/or controls. The A189G, 310 C insertion, T16189C polymorphisms, and 189G/310TC/16189C haplotype have significantly higher frequency in cases compared with controls. CONCLUSION(S) Mitochondrial D-loop alterations may constitute an inheritable risk factor for endometriosis. The analysis of D-loop alterations may help to identify patients at high risk for disease outcome.
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Abstract
Elucidation of the process of DNA replication in mitochondria is in its infancy. For many years, maintenance of the mitochondrial genome was regarded as greatly simplified compared to the nucleus. Mammalian mitochondria were reported to lack all DNA repair systems, to eschew DNA recombination, and to possess but a single DNA polymerase, polymerase γ. Polγ was said to replicate mitochondrial DNA exclusively via one mechanism, involving only two priming events and a handful of proteins. In this "strand-displacement model," leading strand DNA synthesis begins at a specific site and advances approximately two-thirds of the way around the molecule before DNA synthesis is initiated on the "lagging" strand. Although the displaced strand was long-held to be coated with protein, RNA has more recently been proposed in its place. Furthermore, mitochondrial DNA molecules with all the features of products of conventional bidirectional replication have been documented, suggesting that the process and regulation of replication in mitochondria is complex, as befits a genome that is a core factor in human health and longevity.
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Affiliation(s)
- Ian J Holt
- MRC Mitochondrial Biology Unit, Cambridge, United Kingdom.
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67
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Bernt M, Braband A, Schierwater B, Stadler PF. Genetic aspects of mitochondrial genome evolution. Mol Phylogenet Evol 2012; 69:328-38. [PMID: 23142697 DOI: 10.1016/j.ympev.2012.10.020] [Citation(s) in RCA: 161] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2012] [Revised: 10/20/2012] [Accepted: 10/22/2012] [Indexed: 11/30/2022]
Abstract
Many years of extensive studies of metazoan mitochondrial genomes have established differences in gene arrangements and genetic codes as valuable phylogenetic markers. Understanding the underlying mechanisms of replication, transcription and the role of the control regions which cause e.g. different gene orders is important to assess the phylogenetic signal of such events. This review summarises and discusses, for the Metazoa, the general aspects of mitochondrial transcription and replication with respect to control regions as well as several proposed models of gene rearrangements. As whole genome sequencing projects accumulate, more and more observations about mitochondrial gene transfer to the nucleus are reported. Thus occurrence and phylogenetic aspects concerning nuclear mitochondrial-like sequences (NUMTS) is another aspect of this review.
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Affiliation(s)
- Matthias Bernt
- Parallel Computing and Complex Systems Group, Department of Computer Science, University of Leipzig, Augustusplatz 10, D-04109 Leipzig, Germany.
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Mammalian transcription factor A is a core component of the mitochondrial transcription machinery. Proc Natl Acad Sci U S A 2012; 109:16510-5. [PMID: 23012404 DOI: 10.1073/pnas.1119738109] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transcription factor A (TFAM) functions as a DNA packaging factor in mammalian mitochondria. TFAM also binds sequence-specifically to sites immediately upstream of mitochondrial promoters, but there are conflicting data regarding its role as a core component of the mitochondrial transcription machinery. We here demonstrate that TFAM is required for transcription in mitochondrial extracts as well as in a reconstituted in vitro transcription system. The absolute requirement of TFAM can be relaxed by conditions that allow DNA breathing, i.e., low salt concentrations or negatively supercoiled DNA templates. The situation is thus very similar to that described in nuclear RNA polymerase II-dependent transcription, in which the free energy of supercoiling can circumvent the need for a subset of basal transcription factors at specific promoters. In agreement with these observations, we demonstrate that TFAM has the capacity to induce negative supercoils in DNA, and, using the recently developed nucleobase analog FRET-pair tC(O)-tC(nitro), we find that TFAM distorts significantly the DNA structure. Our findings differ from recent observations reporting that TFAM is not a core component of the mitochondrial transcription machinery. Instead, our findings support a model in which TFAM is absolutely required to recruit the transcription machinery during initiation of transcription.
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69
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Wanrooij PH, Uhler JP, Shi Y, Westerlund F, Falkenberg M, Gustafsson CM. A hybrid G-quadruplex structure formed between RNA and DNA explains the extraordinary stability of the mitochondrial R-loop. Nucleic Acids Res 2012; 40:10334-44. [PMID: 22965135 PMCID: PMC3488243 DOI: 10.1093/nar/gks802] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In human mitochondria the transcription machinery generates the RNA primers needed for initiation of DNA replication. A critical feature of the leading-strand origin of mitochondrial DNA replication is a CG-rich element denoted conserved sequence block II (CSB II). During transcription of CSB II, a G-quadruplex structure forms in the nascent RNA, which stimulates transcription termination and primer formation. Previous studies have shown that the newly synthesized primers form a stable and persistent RNA–DNA hybrid, a R-loop, near the leading-strand origin of DNA replication. We here demonstrate that the unusual behavior of the RNA primer is explained by the formation of a stable G-quadruplex structure, involving the CSB II region in both the nascent RNA and the non-template DNA strand. Based on our data, we suggest that G-quadruplex formation between nascent RNA and the non-template DNA strand may be a regulated event, which decides the fate of RNA primers and ultimately the rate of initiation of DNA synthesis in human mitochondria.
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Affiliation(s)
- Paulina H Wanrooij
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, SE-405 30 Gothenburg, Sweden
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70
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Lyubetsky VA, Zverkov OA, Pirogov SA, Rubanov LI, Seliverstov AV. Modeling RNA polymerase interaction in mitochondria of chordates. Biol Direct 2012; 7:26. [PMID: 22873568 PMCID: PMC3583402 DOI: 10.1186/1745-6150-7-26] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 07/12/2012] [Indexed: 11/29/2022] Open
Abstract
Background In previous work, we introduced a concept, a mathematical model and its computer realization that describe the interaction between bacterial and phage type RNA polymerases, protein factors, DNA and RNA secondary structures during transcription, including transcription initiation and termination. The model accurately reproduces changes of gene transcription level observed in polymerase sigma-subunit knockout and heat shock experiments in plant plastids. The corresponding computer program and a user guide are available at http://lab6.iitp.ru/en/rivals. Here we apply the model to the analysis of transcription and (partially) translation processes in the mitochondria of frog, rat and human. Notably, mitochondria possess only phage-type polymerases. We consider the entire mitochondrial genome so that our model allows RNA polymerases to complete more than one circle on the DNA strand. Results Our model of RNA polymerase interaction during transcription initiation and elongation accurately reproduces experimental data obtained for plastids. Moreover, it also reproduces evidence on bulk RNA concentrations and RNA half-lives in the mitochondria of frog, human with or without the MELAS mutation, and rat with normal (euthyroid) or hyposecretion of thyroid hormone (hypothyroid). The transcription characteristics predicted by the model include: (i) the fraction of polymerases terminating at a protein-dependent terminator in both directions (the terminator polarization), (ii) the binding intensities of the regulatory protein factor (mTERF) with the termination site and, (iii) the transcription initiation intensities (initiation frequencies) of all promoters in all five conditions (frog, healthy human, human with MELAS syndrome, healthy rat, and hypothyroid rat with aberrant mtDNA methylation). Using the model, absolute levels of all gene transcription can be inferred from an arbitrary array of the three transcription characteristics, whereas, for selected genes only relative RNA concentrations have been experimentally determined. Conversely, these characteristics and absolute transcription levels can be obtained using relative RNA concentrations and RNA half-lives known from various experimental studies. In this case, the “inverse problem” is solved with multi-objective optimization. Conclusions In this study, we demonstrate that our model accurately reproduces all relevant experimental data available for plant plastids, as well as the mitochondria of chordates. Using experimental data, the model is applied to estimate binding intensities of phage-type RNA polymerases to their promoters as well as predicting terminator characteristics, including polarization. In addition, one can predict characteristics of phage-type RNA polymerases and the transcription process that are difficult to measure directly, e.g., the association between the promoter’s nucleotide composition and the intensity of polymerase binding. To illustrate the application of our model in functional predictions, we propose a possible mechanism for MELAS syndrome development in human involving a decrease of Phe-tRNA, Val-tRNA and rRNA concentrations in the cell. In addition, we describe how changes in methylation patterns of the mTERF binding site and three promoters in hypothyroid rat correlate with changes in intensities of the mTERF binding and transcription initiations. Finally, we introduce an auxiliary model to describe the interaction between polysomal mRNA and ribonucleases.
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Affiliation(s)
- Vassily A Lyubetsky
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute), 19 Bolshoy Karetny per, Moscow, 127994, Russia.
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71
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Mattijssen S, Pruijn GJM. Viperin, a key player in the antiviral response. Microbes Infect 2011; 14:419-26. [PMID: 22182524 DOI: 10.1016/j.micinf.2011.11.015] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 11/29/2011] [Indexed: 02/02/2023]
Abstract
Viperin is an antiviral protein that is induced by different viruses, type I interferon, poly(I:C) and lipopolysaccharide, which is localized to the endoplasmic reticulum and lipid droplets. Recently, our knowledge on the mechanism by which viperin inhibits viral replication has strongly increased. Interestingly, it also became clear that viperin can be used by viruses to increase their infectivity. Here, our current knowledge on the induction of viperin and its effect on virus replication will be reviewed.
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Affiliation(s)
- Sandy Mattijssen
- Department of Biomolecular Chemistry-271, Nijmegen Center for Molecular Life Sciences and Institute for Molecules and Materials, Radboud University Nijmegen, P.O. Box 9101, NL-6500 HB Nijmegen, The Netherlands
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72
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Elango S, Govindaraj P, Vishwanadha VP, Reddy AG, Tamang R, Muthusami U, Kunnoth S, Koyilil VK, Lakshman M, Shanmugasundharam N, Singh L, Thangaraj K. Analysis of mitochondrial genome revealed a rare 50bp deletion and substitutions in a family with hypertension. Mitochondrion 2011; 11:878-85. [DOI: 10.1016/j.mito.2011.07.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2011] [Revised: 07/02/2011] [Accepted: 07/08/2011] [Indexed: 11/15/2022]
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Ngo HB, Kaiser JT, Chan DC. The mitochondrial transcription and packaging factor Tfam imposes a U-turn on mitochondrial DNA. Nat Struct Mol Biol 2011; 18:1290-6. [PMID: 22037171 PMCID: PMC3210390 DOI: 10.1038/nsmb.2159] [Citation(s) in RCA: 194] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Accepted: 09/13/2011] [Indexed: 11/11/2022]
Abstract
Tfam, a DNA binding protein with tandem HMG (high mobility group)-box domains, plays a central role in expression, maintenance, and organization of the mitochondrial genome. It activates transcription from mitochondrial promoters and organizes the mitochondrial genome into nucleoids. Using X-ray crystallography, we show that human Tfam forces promoter DNA to undergo a U-turn, reversing the direction of the DNA helix. Each HMG-box domain wedges into the DNA minor groove to generate two kinks on one face of the DNA. On the opposite face, a positively charged α-helix serves as a platform to facilitate DNA bending. The structural principles underlying DNA bending converge with those of the unrelated HU family proteins, which play analogous architectural roles in organizing bacterial nucleoids. The functional importance of this extreme DNA bending is promoter-specific and appears related to the orientation of Tfam on the promoters.
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Affiliation(s)
- Huu B Ngo
- Division of Biology, California Institute of Technology, Pasadena, California, USA
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74
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Jemt E, Farge G, Bäckström S, Holmlund T, Gustafsson CM, Falkenberg M. The mitochondrial DNA helicase TWINKLE can assemble on a closed circular template and support initiation of DNA synthesis. Nucleic Acids Res 2011; 39:9238-49. [PMID: 21840902 PMCID: PMC3241658 DOI: 10.1093/nar/gkr653] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mitochondrial DNA replication is performed by a simple machinery, containing the TWINKLE DNA helicase, a single-stranded DNA-binding protein, and the mitochondrial DNA polymerase γ. In addition, mitochondrial RNA polymerase is required for primer formation at the origins of DNA replication. TWINKLE adopts a hexameric ring-shaped structure that must load on the closed circular mtDNA genome. In other systems, a specialized helicase loader often facilitates helicase loading. We here demonstrate that TWINKLE can function without a specialized loader. We also show that the mitochondrial replication machinery can assemble on a closed circular DNA template and efficiently elongate a DNA primer in a manner that closely resembles initiation of mtDNA synthesis in vivo.
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Affiliation(s)
- Elisabeth Jemt
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, SE-405 30 Gothenburg, Sweden
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75
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Cameron SL, Yoshizawa K, Mizukoshi A, Whiting MF, Johnson KP. Mitochondrial genome deletions and minicircles are common in lice (Insecta: Phthiraptera). BMC Genomics 2011; 12:394. [PMID: 21813020 PMCID: PMC3199782 DOI: 10.1186/1471-2164-12-394] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 08/04/2011] [Indexed: 01/16/2023] Open
Abstract
Background The gene composition, gene order and structure of the mitochondrial genome are remarkably stable across bilaterian animals. Lice (Insecta: Phthiraptera) are a major exception to this genomic stability in that the canonical single chromosome with 37 genes found in almost all other bilaterians has been lost in multiple lineages in favour of multiple, minicircular chromosomes with less than 37 genes on each chromosome. Results Minicircular mt genomes are found in six of the ten louse species examined to date and three types of minicircles were identified: heteroplasmic minicircles which coexist with full sized mt genomes (type 1); multigene chromosomes with short, simple control regions, we infer that the genome consists of several such chromosomes (type 2); and multiple, single to three gene chromosomes with large, complex control regions (type 3). Mapping minicircle types onto a phylogenetic tree of lice fails to show a pattern of their occurrence consistent with an evolutionary series of minicircle types. Analysis of the nuclear-encoded, mitochondrially-targetted genes inferred from the body louse, Pediculus, suggests that the loss of mitochondrial single-stranded binding protein (mtSSB) may be responsible for the presence of minicircles in at least species with the most derived type 3 minicircles (Pediculus, Damalinia). Conclusions Minicircular mt genomes are common in lice and appear to have arisen multiple times within the group. Life history adaptive explanations which attribute minicircular mt genomes in lice to the adoption of blood-feeding in the Anoplura are not supported by this expanded data set as minicircles are found in multiple non-blood feeding louse groups but are not found in the blood-feeding genus Heterodoxus. In contrast, a mechanist explanation based on the loss of mtSSB suggests that minicircles may be selectively favoured due to the incapacity of the mt replisome to synthesize long replicative products without mtSSB and thus the loss of this gene lead to the formation of minicircles in lice.
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Affiliation(s)
- Stephen L Cameron
- Discipline of Biogeosciences, Faculty of Science & Technology, Queensland University of Technology, Brisbane, QLD 4001, Australia.
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Association of mtDNA D-loop polymorphisms with risk of gastric cancer in Chinese population. Pathol Oncol Res 2011; 17:735-42. [PMID: 21461645 DOI: 10.1007/s12253-011-9378-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Accepted: 02/02/2011] [Indexed: 02/02/2023]
Abstract
The aim of present study was to evaluate the association of common polymorphisms detected in mitochondrial DNA (mtDNA) D-loop region (mononucleotide repetitive D310, single nucleotide polymorphism (SNP) D16521) with susceptibility to gastric cancer (GC) in northwestern Chinese population. A total of 180 GC patients and 218 healthy controls were investigated by using PCR- denaturing high performance liquid chromatography (DHPLC) assay. Genotype and allele distributions and haplotype construction were analyzed in case-control study. We found D310 and D16521 heteroplasmy were significantly different between GC cases and controls (p < 0.05), and D16521 homoplasmy showed association with histological grade of GC (p < 0.05). Haplotype 7C/T, 8C/C and 9C/C had significant association with GC risk implied from analysis of D310 and D16521. Taken together, these findings suggested that mtDNA D-Loop polymorphisms and haplotypes may contribute to genetic susceptibility to GC in Chinese population.
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Abstract
In all organisms, oxidation threatens the integrity of the genome. DNA-mediated charge transport (CT) may play an important role in the generation and repair of this oxidative damage. In studies involving long-range CT from intercalating Ru and Rh complexes to 5'-GG-3' sites, we have examined the efficiency of CT as a function of distance, temperature, and the electronic coupling of metal oxidants bound to the base stack. Most striking is the shallow distance dependence and the sensitivity of DNA CT to how the metal complexes are stacked in the helix. Experiments with cyclopropylamine-modified bases have revealed that charge occupation occurs at all sites along the bridge. Using Ir complexes, we have seen that the process of DNA-mediated reduction is very similar to that of DNA-mediated oxidation. Studies involving metalloproteins have, furthermore, shown that their redox activity is DNA-dependent and can be DNA-mediated. Long range DNA-mediated CT can facilitate the oxidation of DNA-bound base excision repair proteins to initiate a redox-active search for DNA lesions. DNA CT can also activate the transcription factor SoxR, triggering a cellular response to oxidative stress. Indeed, these studies show that within the cell, redox-active proteins may utilize the same chemistry as that of synthetic metal complexes in vitro, and these proteins may harness DNA-mediated CT to reduce damage to the genome and regulate cellular processes.
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Affiliation(s)
- Jacqueline K. Barton
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Eric D. Olmon
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Pamela A. Sontz
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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78
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Pohjoismäki JLO, Goffart S. Of circles, forks and humanity: Topological organisation and replication of mammalian mitochondrial DNA. Bioessays 2011; 33:290-9. [PMID: 21290399 DOI: 10.1002/bies.201000137] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The organisation of mammalian mitochondrial DNA (mtDNA) is more complex than usually assumed. Despite often being depicted as a simple circle, the topology of mtDNA can vary from supercoiled monomeric circles over catenanes and oligomers to complex multimeric networks. Replication of mtDNA is also not clear cut. Two different mechanisms of replication have been found in cultured cells and in most tissues: a strand-asynchronous mode involving temporary RNA coverage of one strand, and a strand-coupled mode rather resembling conventional nuclear DNA replication. In addition, a recombination-initiated replication mechanism is likely to be associated with the multimeric mtDNA networks found in human heart. Although an insight into the general principles and key factors of mtDNA organisation and maintenance has been gained over the last few years, there are many open questions regarding replication initiation, termination and physiological factors determining mtDNA organisation and replication mode. However, common themes in mtDNA maintenance across eukaryotic kingdoms can provide valuable lessons for future work.
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Affiliation(s)
- Jaakko L O Pohjoismäki
- Department of Cardiac Development and Remodelling, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany.
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79
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Coskun PE, Wyrembak J, Derbereva O, Melkonian G, Doran E, Lott IT, Head E, Cotman CW, Wallace DC. Systemic mitochondrial dysfunction and the etiology of Alzheimer's disease and down syndrome dementia. J Alzheimers Dis 2010; 20 Suppl 2:S293-310. [PMID: 20463402 DOI: 10.3233/jad-2010-100351] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Increasing evidence is implicating mitochondrial dysfunction as a central factor in the etiology of Alzheimer's disease (AD). The most significant risk factor in AD is advanced age and an important neuropathological correlate of AD is the deposition of amyloid-beta peptide (Abeta40 and Abeta42) in the brain. An AD-like dementia is also common in older individuals with Down syndrome (DS), though with a much earlier onset. We have shown that somatic mitochondrial DNA (mtDNA) control region (CR) mutations accumulate with age in post-mitotic tissues including the brain and that the level of mtDNA mutations is markedly elevated in the brains of AD patients. The elevated mtDNA CR mutations in AD brains are associated with a reduction in the mtDNA copy number and in the mtDNA L-strand transcript levels. We now show that mtDNA CR mutations increase with age in control brains; that they are markedly elevated in the brains of AD and DS and dementia (DSAD) patients; and that the increased mtDNA CR mutation rate in DSAD brains is associated with reduced mtDNA copy number and L-strand transcripts. The increased mtDNA CR mutation rate is also seen in peripheral blood DNA and in lymphoblastoid cell DNAs of AD and DSAD patients, and distinctive somatic mtDNA mutations, often at high heteroplasmy levels, are seen in AD and DSAD brain and blood cells DNA. In aging, DS, and DSAD, the mtDNA mutation level is positively correlated with beta-secretase activity and mtDNA copy number is inversely correlated with insoluble Abeta40 and Abeta42 levels. Therefore, mtDNA alterations may be responsible for both age-related dementia and the associated neuropathological changes observed in AD and DSAD.
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Affiliation(s)
- Pinar E Coskun
- Mitochondrial and Molecular Medicine and Genetics, University of California Irvine, Irvine, CA, USA
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80
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Klemba A, Kowalewska M, Kukwa W, Tonska K, Szybinska A, Mossakowska M, Scinska A, Golik P, Koper K, Radziszewski J, Kukwa A, Czarnecka AM, Bartnik E. Mitochondrial genotype in vulvar carcinoma - cuckoo in the nest. J Biomed Sci 2010; 17:73. [PMID: 20825678 PMCID: PMC2944255 DOI: 10.1186/1423-0127-17-73] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Accepted: 09/08/2010] [Indexed: 01/09/2023] Open
Abstract
Vulvar squamous cell carcinoma (VSCC) is a rare female genital neoplasm. Although numerous molecular changes have been reported in VSCC, biomarkers of clinical relevance are still lacking. On the other hand, there is emerging evidence on the use of mtDNA as a diagnostic tool in oncology. In order to investigate mtDNA status in VSCC patients, haplogroup distribution analysis and D-loop sequencing were performed. The results were compared with available data for the general Polish population, cancer free-centenarians as well as patients with endometrial and head and neck cancer. The obtained data were also compared with the current status of mitochondrial databases. Significant differences in haplogroup distribution between VSCC cohort, general Polish population and cancer-free centenarians cohort were found. Moreover, a correlation between the VSCC patients haplogroup and HPV status was observed. Finally, a specific pattern of mtDNA polymorphisms was found in VSCC. Our results suggest that the mitochondrial genetic background may influence the risk of VSCC occurrence as well as susceptibility to HPV infection.
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Affiliation(s)
- Aleksandra Klemba
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, ul, Pawinskiego 5A, 02-106, Warsaw, Poland
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81
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G-quadruplex structures in RNA stimulate mitochondrial transcription termination and primer formation. Proc Natl Acad Sci U S A 2010; 107:16072-7. [PMID: 20798345 DOI: 10.1073/pnas.1006026107] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The human mitochondrial transcription machinery generates the primers required for initiation of leading-strand DNA replication. According to one model, the 3' end of the primer is defined by transcription termination at conserved sequence block II (CSB II) in the mitochondrial DNA control region. We here demonstrate that this site-specific termination event is caused by G-quadruplex structures formed in nascent RNA upon transcription of CSB II. We also demonstrate that a poly-dT stretch downstream of CSB II has a modest stimulatory effect on the termination efficiency. The mechanism is reminiscent of Rho-independent transcription termination in prokaryotes, with the exception that a G-quadruplex structure replaces the hairpin loop formed in bacterial mRNA during transcription of terminator sequences.
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82
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Bi R, Zhang AM, Zhang W, Kong QP, Wu BL, Yang XH, Wang D, Zou Y, Zhang YP, Yao YG. The acquisition of an inheritable 50-bp deletion in the human mtDNA control region does not affect the mtDNA copy number in peripheral blood cells. Hum Mutat 2010; 31:538-43. [PMID: 20151402 DOI: 10.1002/humu.21220] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The mitochondrial DNA (mtDNA) control region is believed to play an important biological role in mtDNA replication. Large deletions in this region are rarely found, but when they do occur they might be expected to interfere with the replication of the molecule, thus leading to a reduction of mtDNA copy number. During a survey for mtDNA sequence variations in 5,559 individuals from the general Chinese population and 2,538 individuals with medical disorders, we identified a 50-bp deletion (m.298_347del50) in the mtDNA control region in a member of a healthy Han Chinese family belonging to haplogroup B4c1b2, as suggested by complete mtDNA genome sequencing. This deletion removes the conserved sequence block II (CSBII; region 299-315) and the replication primer location (region 317-321). However, quantification of the mtDNA copy number in this subject showed a value within a range that was observed in 20 healthy subjects without the deletion. The deletion was detected in the hair samples of the maternal relatives of the subject and exhibited variable heteroplasmy. Our current observation, together with a recent report for a benign 154-bp deletion in the mtDNA control region, suggests that the control of mtDNA replication may be more complex than we had thought.
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Affiliation(s)
- Rui Bi
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Kunming, Yunnan, People's Republic of China
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83
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Core human mitochondrial transcription apparatus is a regulated two-component system in vitro. Proc Natl Acad Sci U S A 2010; 107:12133-8. [PMID: 20562347 DOI: 10.1073/pnas.0910581107] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The core human mitochondrial transcription apparatus is currently regarded as an obligate three-component system comprising the bacteriophage T7-related mitochondrial RNA polymerase, the rRNA methyltransferase-related transcription factor, h-mtTFB2, and the high mobility group box transcription/DNA-packaging factor, h-mtTFA/TFAM. Using a faithful recombinant human mitochondrial transcription system from Escherichia coli, we demonstrate that specific initiation from the mtDNA promoters, LSP and HSP1, only requires mitochondrial RNA polymerase and h-mtTFB2 in vitro. When h-mtTFA is added to these basal components, LSP exhibits a much lower threshold for activation and a larger amplitude response than HSP1. In addition, when LSP and HSP1 are together on the same transcription template, h-mtTFA-independent transcription from HSP1 and h-mtTFA-dependent transcription from both promoters is enhanced and a higher concentration of h-mtTFA is required to stimulate HSP1. Promoter competition experiments revealed that, in addition to LSP competing transcription components away from HSP1, additional cis-acting signals are involved in these aspects of promoter regulation. Based on these results, we speculate that the human mitochondrial transcription system may have evolved to differentially regulate transcription initiation and transcription-primed mtDNA replication in response to the amount of h-mtTFA associated with nucleoids, which could begin to explain the heterogeneity of nucleoid structure and activity in vivo. Furthermore, this study sheds new light on the evolution of mitochondrial transcription components by showing that the human system is a regulated two-component system in vitro, and thus more akin to that of budding yeast than thought previously.
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84
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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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85
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Lodeiro MF, Uchida AU, Arnold JJ, Reynolds SL, Moustafa IM, Cameron CE. Identification of multiple rate-limiting steps during the human mitochondrial transcription cycle in vitro. J Biol Chem 2010; 285:16387-402. [PMID: 20351113 DOI: 10.1074/jbc.m109.092676] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have reconstituted human mitochondrial transcription in vitro on DNA oligonucleotide templates representing the light strand and heavy strand-1 promoters using protein components (RNA polymerase and transcription factors A and B2) isolated from Escherichia coli. We show that 1 eq of each transcription factor and polymerase relative to the promoter is required to assemble a functional initiation complex. The light strand promoter is at least 2-fold more efficient than the heavy strand-1 promoter, but this difference cannot be explained solely by the differences in the interaction of the transcription machinery with the different promoters. In both cases, the rate-limiting step for production of the first phosphodiester bond is open complex formation. Open complex formation requires both transcription factors; however, steps immediately thereafter only require transcription factor B2. The concentration of nucleotide required for production of the first dinucleotide product is substantially higher than that required for subsequent cycles of nucleotide addition. In vitro, promoter-specific differences in post-initiation control of transcription exist, as well as a second rate-limiting step that controls conversion of the transcription initiation complex into a transcription elongation complex. Rate-limiting steps of the biochemical pathways are often those that are targeted for regulation. Like the more complex multisubunit transcription systems, multiple steps may exist for control of transcription in human mitochondria. The tools and mechanistic framework presented here will facilitate not only the discovery of mechanisms regulating human mitochondrial transcription but also interrogation of the structure, function, and mechanism of the complexes that are regulated during human mitochondrial transcription.
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Affiliation(s)
- Maria F Lodeiro
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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86
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Fusté JM, Wanrooij S, Jemt E, Granycome CE, Cluett TJ, Shi Y, Atanassova N, Holt IJ, Gustafsson CM, Falkenberg M. Mitochondrial RNA polymerase is needed for activation of the origin of light-strand DNA replication. Mol Cell 2010; 37:67-78. [PMID: 20129056 DOI: 10.1016/j.molcel.2009.12.021] [Citation(s) in RCA: 148] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 07/21/2009] [Accepted: 10/14/2009] [Indexed: 11/19/2022]
Abstract
Mitochondrial DNA is replicated by a unique enzymatic machinery, which is distinct from the replication apparatus used for copying the nuclear genome. We examine here the mechanisms of origin-specific initiation of lagging-strand DNA synthesis in human mitochondria. We demonstrate that the mitochondrial RNA polymerase (POLRMT) is the primase required for initiation of DNA synthesis from the light-strand origin of DNA replication (OriL). Using only purified POLRMT and DNA replication factors, we can faithfully reconstitute OriL-dependent initiation in vitro. Leading-strand DNA synthesis is initiated from the heavy-strand origin of DNA replication and passes OriL. The single-stranded OriL is exposed and adopts a stem-loop structure. At this stage, POLRMT initiates primer synthesis from a poly-dT stretch in the single-stranded loop region. After about 25 nt, POLRMT is replaced by DNA polymerase gamma, and DNA synthesis commences. Our findings demonstrate that POLRMT can function as an origin-specific primase in mammalian mitochondria.
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Affiliation(s)
- Javier Miralles Fusté
- Division of Metabolic Diseases, Karolinska Institutet, Novum, SE-141 86 Stockholm, Sweden
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87
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Czarnecka AM, Klemba A, Semczuk A, Plak K, Marzec B, Krawczyk T, Kofler B, Golik P, Bartnik E. Common mitochondrial polymorphisms as risk factor for endometrial cancer. Int Arch Med 2009; 2:33. [PMID: 19863780 PMCID: PMC2775024 DOI: 10.1186/1755-7682-2-33] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Accepted: 10/28/2009] [Indexed: 01/15/2023] Open
Abstract
Endometrial carcinoma is the most commonly diagnosed gynaecological cancer in developed countries. Although the molecular genetics of this disease has been in the focus of many research laboratories for the last 20 years, relevant prognostic and diagnostic markers are still missing. At the same time mitochondrial DNA mutations have been reported in many types of cancer during the last two decades. It is therefore very likely that the mitochondrial genotype is one of the cancer susceptibility factors. To investigate the presence of mtDNA somatic mutations and distribution of inherited polymorphisms in endometrial adenocarcinoma patients we analyzed the D-loop sequence of cancer samples and their corresponding normal tissues and moreover performed mitochondrial haplogroup analysis. We detected 2 somatic mutation and increased incidence of mtDNA polymorphisms, in particular 16223C (80% patients, p = 0.005), 16126C (23%, p = 0.025) and 207A (19%, p = 0.027). Subsequent statistical analysis revealed that endometrial carcinoma population haplogroup distribution differs from the Polish population and that haplogroup H (with its defining polymorphism - C7028T) is strongly underrepresented (p = 0.003), therefore might be a cancer-protective factor. Our report supports the notion that mtDNA polymorphisms establish a specific genetic background for endometrial adenocarcinoma development and that mtDNA analysis may result in the development of new molecular tool for cancer detection.
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Affiliation(s)
- Anna M Czarnecka
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106, Warsaw, Poland.,School of Molecular Medicine, Medical University of Warsaw, Zwirki i Wigury 61, 02-091 Warsaw, Poland
| | - Aleksandra Klemba
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106, Warsaw, Poland
| | - Andrzej Semczuk
- II Clinic and Ward of Gynecology, Medical University of Lublin, Lublin, Poland
| | - Katarzyna Plak
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106, Warsaw, Poland
| | - Barbara Marzec
- Department of Human Genetics, Lublin University School of Medicine, Lublin, Poland
| | - Tomasz Krawczyk
- Clinical Pathology Laboratory, Monument Institute of Polish Mothers Health Center, Lodz, Poland
| | - Barbara Kofler
- Department of Pediatrics, University Hospital Salzburg, Paracelsus Medical University, Müllner Hauptstr 48, A-5020 Salzburg, Austria
| | - Pawel Golik
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106, Warsaw, Poland.,Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Ewa Bartnik
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106, Warsaw, Poland.,Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
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88
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Fukuoh A, Ohgaki K, Hatae H, Kuraoka I, Aoki Y, Uchiumi T, Jacobs HT, Kang D. DNA conformation-dependent activities of human mitochondrial RNA polymerase. Genes Cells 2009; 14:1029-42. [PMID: 19624753 DOI: 10.1111/j.1365-2443.2009.01328.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Mitochondrial RNA polymerase (POLRMT) is a core protein for mitochondrial DNA (mtDNA) transcription. In addition, POLRMT is assumed to be involved in replication, although its exact role is not yet clearly elucidated. We have found novel properties of human POLRMT using a reconstituted transcription system. Various lengths of RNA molecules were synthesized from templates even without a defined promoter sequence, when we used supercoiled circular double-stranded DNA as a template. This promoter-independent activity was as strong as the promoter-dependent one. Promoter-independent DNA conformation-dependent transcription required TFB2M. On supercoiled templates, the promoter-independent activity was strongly suppressed by a putatively physiological amount of TFAM, while promoter-dependent transcription was inhibited to a lesser extent. These different inhibition patterns by TFAM may be important for prevention of random RNA synthesis in vivo. Promoter-independent activity was also observed on relaxed circular single-stranded DNA, where its activity no longer required TFB2M. RNA synthesis on single-stranded DNA was weakly suppressed by a putatively physiological amount of TFAM but restored by the addition of mitochondrial single-stranded DNA binding protein. We suggest that these properties of POLRMT could explain the characteristic features of mammalian mtDNA transcription and replication.
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Affiliation(s)
- Atsushi Fukuoh
- Department of Clinical Chemistry and Laboratory Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
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89
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Holt IJ. Mitochondrial DNA replication and repair: all a flap. Trends Biochem Sci 2009; 34:358-65. [DOI: 10.1016/j.tibs.2009.03.007] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 03/04/2009] [Accepted: 03/10/2009] [Indexed: 10/20/2022]
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90
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Kuchta RD, Stengel G. Mechanism and evolution of DNA primases. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1804:1180-9. [PMID: 19540940 DOI: 10.1016/j.bbapap.2009.06.011] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 05/11/2009] [Accepted: 06/02/2009] [Indexed: 01/31/2023]
Abstract
DNA primase synthesizes short RNA primers that replicative polymerases further elongate in order to initiate the synthesis of all new DNA strands. Thus, primase owes its existence to the inability of DNA polymerases to initiate DNA synthesis starting with 2 dNTPs. Here, we discuss the evolutionary relationships between the different families of primases (viral, eubacterial, archael, and eukaryotic) and the catalytic mechanisms of these enzymes. This includes how they choose an initiation site, elongate the growing primer, and then only synthesize primers of defined length via an inherent ability to count. Finally, the low fidelity of primases along with the development of primase inhibitors is described.
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Affiliation(s)
- Robert D Kuchta
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA.
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91
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White MM, Martin HR. Structure and conservation of tandem repeats in the mitochondrial DNA control region of the Least Brook lamprey (Lampetra aepyptera). J Mol Evol 2009; 68:715-23. [PMID: 19449051 DOI: 10.1007/s00239-009-9246-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 04/21/2009] [Accepted: 04/27/2009] [Indexed: 10/20/2022]
Abstract
Tandemly repeated sequences are a common feature of vertebrate mitochondrial DNA control regions. However, questions still remain about their mode of evolution, function, and phylogenetic distribution. We report phylogenetic and geographic patterns of variation of control region repeat sequence and number in a nonparasitic lamprey, Lampetra aepyptera. A survey of populations from throughout the species' range revealed remarkably low repeat sequence polymorphism but some interpopulation variation in repeat number. The high sequence similarity extended to repeats observed in other species in the genus Lampetra and other lamprey genera. The very low levels of variation suggest a high copy turnover. Our data are consistent with the illegitimate elongation model of repeat gain and loss and further suggest that repeat change occurs at internal copies. However, the limited variation across some species of lamprey suggests that functional constraints may further limit variation.
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Affiliation(s)
- Matthew M White
- Department of Biological Sciences, Ohio University, Athens, OH 45701, USA.
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92
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Suissa S, Wang Z, Poole J, Wittkopp S, Feder J, Shutt TE, Wallace DC, Shadel GS, Mishmar D. Ancient mtDNA genetic variants modulate mtDNA transcription and replication. PLoS Genet 2009; 5:e1000474. [PMID: 19424428 PMCID: PMC2673036 DOI: 10.1371/journal.pgen.1000474] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Accepted: 04/07/2009] [Indexed: 11/18/2022] Open
Abstract
Although the functional consequences of mitochondrial DNA (mtDNA) genetic backgrounds (haplotypes, haplogroups) have been demonstrated by both disease association studies and cell culture experiments, it is not clear which of the mutations within the haplogroup carry functional implications and which are "evolutionary silent hitchhikers". We set forth to study the functionality of haplogroup-defining mutations within the mtDNA transcription/replication regulatory region by in vitro transcription, hypothesizing that haplogroup-defining mutations occurring within regulatory motifs of mtDNA could affect these processes. We thus screened >2500 complete human mtDNAs representing all major populations worldwide for natural variation in experimentally established protein binding sites and regulatory regions comprising a total of 241 bp in each mtDNA. Our screen revealed 77/241 sites showing point mutations that could be divided into non-fixed (57/77, 74%) and haplogroup/sub-haplogroup-defining changes (i.e., population fixed changes, 20/77, 26%). The variant defining Caucasian haplogroup J (C295T) increased the binding of TFAM (Electro Mobility Shift Assay) and the capacity of in vitro L-strand transcription, especially of a shorter transcript that maps immediately upstream of conserved sequence block 1 (CSB1), a region associated with RNA priming of mtDNA replication. Consistent with this finding, cybrids (i.e., cells sharing the same nuclear genetic background but differing in their mtDNA backgrounds) harboring haplogroup J mtDNA had a >2 fold increase in mtDNA copy number, as compared to cybrids containing haplogroup H, with no apparent differences in steady state levels of mtDNA-encoded transcripts. Hence, a haplogroup J regulatory region mutation affects mtDNA replication or stability, which may partially account for the phenotypic impact of this haplogroup. Our analysis thus demonstrates, for the first time, the functional impact of particular mtDNA haplogroup-defining control region mutations, paving the path towards assessing the functionality of both fixed and un-fixed genetic variants in the mitochondrial genome.
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Affiliation(s)
- Sarit Suissa
- Department of Life Sciences and National Institute of Biotechnology (NIBN), Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Zhibo Wang
- Department of Pathology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Jason Poole
- The Center for Molecular and Mitochondrial Medicine and Genetics (MAMMAG), University of California Irvine, Irvine, California, United States of America
- Nanogen, Inc., San Diego, California, United States of America
| | - Sharine Wittkopp
- The Center for Molecular and Mitochondrial Medicine and Genetics (MAMMAG), University of California Irvine, Irvine, California, United States of America
| | - Jeanette Feder
- Department of Life Sciences and National Institute of Biotechnology (NIBN), Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Timothy E. Shutt
- Department of Pathology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Douglas C. Wallace
- The Center for Molecular and Mitochondrial Medicine and Genetics (MAMMAG), University of California Irvine, Irvine, California, United States of America
| | - Gerald S. Shadel
- Department of Pathology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Dan Mishmar
- Department of Life Sciences and National Institute of Biotechnology (NIBN), Ben-Gurion University of the Negev, Beer-Sheva, Israel
- * E-mail:
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93
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Merino EJ, Davis ML, Barton JK. Common mitochondrial DNA mutations generated through DNA-mediated charge transport. Biochemistry 2009; 48:660-6. [PMID: 19128037 DOI: 10.1021/bi801570j] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mutation sites that arise in human mitochondrial DNA as a result of oxidation by a rhodium photooxidant have been identified. HeLa cells were incubated with [Rh(phi)(2)bpy]Cl(3) (phi is 9,10-phenanthrenequinone diimine), an intercalating photooxidant, to allow the complex to enter the cell and bind mitochondrial DNA. Photoexcitation of DNA-bound [Rh(phi)(2)bpy](3+) can promote the oxidation of guanine from a distance through DNA-mediated charge transport. After two rounds of photolysis and growth of cells incubated with the rhodium complex, DNA mutations in a portion of the mitochondrial genome were assessed via manual sequencing. The mutational pattern is consistent with dG to dT transversions in the repetitive guanine tracts. Significantly, the mutational pattern found overlaps oxidative damage hot spots seen previously. These mutations are found within conserved sequence block II, a critical regulatory element involved in DNA replication, and these have been identified as sites of low oxidation potential to which oxidative damage is funneled. On the basis of this mutational analysis and its correspondence to sites of long-range oxidative damage, we infer a critical role for DNA charge transport in generating these mutations and, thus, in regulating mitochondrial DNA replication under oxidative stress.
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Affiliation(s)
- Edward J Merino
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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94
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Human mitochondrial RNA polymerase primes lagging-strand DNA synthesis in vitro. Proc Natl Acad Sci U S A 2008; 105:11122-7. [PMID: 18685103 DOI: 10.1073/pnas.0805399105] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The mitochondrial transcription machinery synthesizes the RNA primers required for initiation of leading-strand DNA synthesis in mammalian mitochondria. RNA primers are also required for initiation of lagging-strand DNA synthesis, but the responsible enzyme has so far remained elusive. Here, we present a series of observations that suggests that mitochondrial RNA polymerase (POLRMT) can act as lagging-strand primase in mammalian cells. POLRMT is highly processive on double-stranded DNA, but synthesizes RNA primers with a length of 25 to 75 nt on a single-stranded template. The short RNA primers synthesized by POLRMT are used by the mitochondrial DNA polymerase gamma to initiate DNA synthesis in vitro. Addition of mitochondrial single-stranded DNA binding protein (mtSSB) reduces overall levels of primer synthesis, but stimulates primer-dependent DNA synthesis. Furthermore, when combined, POLRMT, DNA polymerase gamma, the DNA helicase TWINKLE, and mtSSB are capable of simultaneous leading- and lagging-strand DNA synthesis in vitro. Based on our observations, we suggest that POLRMT is the lagging-strand primase in mammalian mitochondria.
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95
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Scarpulla RC. Transcriptional paradigms in mammalian mitochondrial biogenesis and function. Physiol Rev 2008; 88:611-38. [PMID: 18391175 DOI: 10.1152/physrev.00025.2007] [Citation(s) in RCA: 1156] [Impact Index Per Article: 72.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mitochondria contain their own genetic system and undergo a unique mode of cytoplasmic inheritance. Each organelle has multiple copies of a covalently closed circular DNA genome (mtDNA). The entire protein coding capacity of mtDNA is devoted to the synthesis of 13 essential subunits of the inner membrane complexes of the respiratory apparatus. Thus the majority of respiratory proteins and all of the other gene products necessary for the myriad mitochondrial functions are derived from nuclear genes. Transcription of mtDNA requires a small number of nucleus-encoded proteins including a single RNA polymerase (POLRMT), auxiliary factors necessary for promoter recognition (TFB1M, TFB2M) and activation (Tfam), and a termination factor (mTERF). This relatively simple system can account for the bidirectional transcription of mtDNA from divergent promoters and key termination events controlling the rRNA/mRNA ratio. Nucleomitochondrial interactions depend on the interplay between transcription factors (NRF-1, NRF-2, PPARalpha, ERRalpha, Sp1, and others) and members of the PGC-1 family of regulated coactivators (PGC-1alpha, PGC-1beta, and PRC). The transcription factors target genes that specify the respiratory chain, the mitochondrial transcription, translation and replication machinery, and protein import and assembly apparatus among others. These factors are in turn activated directly or indirectly by PGC-1 family coactivators whose differential expression is controlled by an array of environmental signals including temperature, energy deprivation, and availability of nutrients and growth factors. These transcriptional paradigms provide a basic framework for understanding the integration of mitochondrial biogenesis and function with signaling events that dictate cell- and tissue-specific energetic properties.
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Affiliation(s)
- Richard C Scarpulla
- Department of Cell and Molecular Biology, Northwestern Medical School, Chicago, Illinois 60611, USA
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96
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Adán C, Matsushima Y, Hernández-Sierra R, Marco-Ferreres R, Fernández-Moreno MA, González-Vioque E, Calleja M, Aragón JJ, Kaguni LS, Garesse R. Mitochondrial transcription factor B2 is essential for metabolic function in Drosophila melanogaster development. J Biol Chem 2008; 283:12333-42. [PMID: 18308726 DOI: 10.1074/jbc.m801342200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Characterization of the basal transcription machinery of mitochondrial DNA (mtDNA) is critical to understand mitochondrial pathophysiology. In mammalian in vitro systems, mtDNA transcription requires mtRNA polymerase, transcription factor A (TFAM), and either transcription factor B1 (TFB1M) or B2 (TFB2M). We have silenced the expression of TFB2M by RNA interference in Drosophila melanogaster. RNA interference knockdown of TF2BM causes lethality by arrest of larval development. Molecular analysis demonstrates that TF2BM is essential for mtDNA transcription during Drosophila development and is not redundant with TFB1M. The impairment of mtDNA transcription causes a dramatic decrease in oxidative phosphorylation and mitochondrial ATP synthesis in the long-lived larvae, and a metabolic shift to glycolysis, which partially restores ATP levels and elicits a compensatory response at the nuclear level that increases mitochondrial mass. At the cellular level, the mitochondrial dysfunction induced by TFB2M knockdown causes a severe reduction in cell proliferation without affecting cell growth, and increases the level of apoptosis. In contrast, cell differentiation and morphogenesis are largely unaffected. Our data demonstrate the essential role of TFB2M in mtDNA transcription in a multicellular organism, and reveal the complex cellular, biochemical, and molecular responses induced by impairment of oxidative phosphorylation during Drosophila development.
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Affiliation(s)
- Cristina Adán
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, CIBERER ISCIII, Facultad de Medicina, Universidad Autónoma de Madrid, C/Arzobispo Morcillo 4, E-28029 Madrid, Spain
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97
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Hyvärinen AK, Pohjoismäki JLO, Reyes A, Wanrooij S, Yasukawa T, Karhunen PJ, Spelbrink JN, Holt IJ, Jacobs HT. The mitochondrial transcription termination factor mTERF modulates replication pausing in human mitochondrial DNA. Nucleic Acids Res 2007; 35:6458-74. [PMID: 17884915 PMCID: PMC2095818 DOI: 10.1093/nar/gkm676] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The mammalian mitochondrial transcription termination factor mTERF binds with high affinity to a site within the tRNA(Leu(UUR)) gene and regulates the amount of read through transcription from the ribosomal DNA into the remaining genes of the major coding strand of mitochondrial DNA (mtDNA). Electrophoretic mobility shift assays (EMSA) and SELEX, using mitochondrial protein extracts from cells induced to overexpress mTERF, revealed novel, weaker mTERF-binding sites, clustered in several regions of mtDNA, notably in the major non-coding region (NCR). Such binding in vivo was supported by mtDNA immunoprecipitation. Two-dimensional neutral agarose gel electrophoresis (2DNAGE) and 5' end mapping by ligation-mediated PCR (LM-PCR) identified the region of the canonical mTERF-binding site as a replication pause site. The strength of pausing was modulated by the expression level of mTERF. mTERF overexpression also affected replication pausing in other regions of the genome in which mTERF binding was found. These results indicate a role for TERF in mtDNA replication, in addition to its role in transcription. We suggest that mTERF could provide a system for coordinating the passage of replication and transcription complexes, analogous with replication pause-region binding proteins in other systems, whose main role is to safeguard the integrity of the genome whilst facilitating its efficient expression.
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Affiliation(s)
- Anne K. Hyvärinen
- Institute of Medical Technology and Tampere University Hospital, FI-33014, University of Tampere, Finland, MRC-Dunn Human Nutrition Unit, Cambridge, UK, Department of Forensic Medicine and Tampere University Hospital, FI-33014, University of Tampere, Finland and Institute of Biomedical and Life Sciences, University of Glasgow, Scotland, UK
| | - Jaakko L. O. Pohjoismäki
- Institute of Medical Technology and Tampere University Hospital, FI-33014, University of Tampere, Finland, MRC-Dunn Human Nutrition Unit, Cambridge, UK, Department of Forensic Medicine and Tampere University Hospital, FI-33014, University of Tampere, Finland and Institute of Biomedical and Life Sciences, University of Glasgow, Scotland, UK
| | - Aurelio Reyes
- Institute of Medical Technology and Tampere University Hospital, FI-33014, University of Tampere, Finland, MRC-Dunn Human Nutrition Unit, Cambridge, UK, Department of Forensic Medicine and Tampere University Hospital, FI-33014, University of Tampere, Finland and Institute of Biomedical and Life Sciences, University of Glasgow, Scotland, UK
| | - Sjoerd Wanrooij
- Institute of Medical Technology and Tampere University Hospital, FI-33014, University of Tampere, Finland, MRC-Dunn Human Nutrition Unit, Cambridge, UK, Department of Forensic Medicine and Tampere University Hospital, FI-33014, University of Tampere, Finland and Institute of Biomedical and Life Sciences, University of Glasgow, Scotland, UK
| | - Takehiro Yasukawa
- Institute of Medical Technology and Tampere University Hospital, FI-33014, University of Tampere, Finland, MRC-Dunn Human Nutrition Unit, Cambridge, UK, Department of Forensic Medicine and Tampere University Hospital, FI-33014, University of Tampere, Finland and Institute of Biomedical and Life Sciences, University of Glasgow, Scotland, UK
| | - Pekka J. Karhunen
- Institute of Medical Technology and Tampere University Hospital, FI-33014, University of Tampere, Finland, MRC-Dunn Human Nutrition Unit, Cambridge, UK, Department of Forensic Medicine and Tampere University Hospital, FI-33014, University of Tampere, Finland and Institute of Biomedical and Life Sciences, University of Glasgow, Scotland, UK
| | - Johannes N. Spelbrink
- Institute of Medical Technology and Tampere University Hospital, FI-33014, University of Tampere, Finland, MRC-Dunn Human Nutrition Unit, Cambridge, UK, Department of Forensic Medicine and Tampere University Hospital, FI-33014, University of Tampere, Finland and Institute of Biomedical and Life Sciences, University of Glasgow, Scotland, UK
| | - Ian J. Holt
- Institute of Medical Technology and Tampere University Hospital, FI-33014, University of Tampere, Finland, MRC-Dunn Human Nutrition Unit, Cambridge, UK, Department of Forensic Medicine and Tampere University Hospital, FI-33014, University of Tampere, Finland and Institute of Biomedical and Life Sciences, University of Glasgow, Scotland, UK
| | - Howard T. Jacobs
- Institute of Medical Technology and Tampere University Hospital, FI-33014, University of Tampere, Finland, MRC-Dunn Human Nutrition Unit, Cambridge, UK, Department of Forensic Medicine and Tampere University Hospital, FI-33014, University of Tampere, Finland and Institute of Biomedical and Life Sciences, University of Glasgow, Scotland, UK
- *To whom correspondence should be addressed. +358 3 3551 7731+358 3 3551 7710; E-mail:
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98
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Falkenberg M, Larsson NG, Gustafsson CM. DNA replication and transcription in mammalian mitochondria. Annu Rev Biochem 2007; 76:679-99. [PMID: 17408359 DOI: 10.1146/annurev.biochem.76.060305.152028] [Citation(s) in RCA: 479] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The mitochondrion was originally a free-living prokaryotic organism, which explains the presence of a compact mammalian mitochondrial DNA (mtDNA) in contemporary mammalian cells. The genome encodes for key subunits of the electron transport chain and RNA components needed for mitochondrial translation. Nuclear genes encode the enzyme systems responsible for mtDNA replication and transcription. Several of the key components of these systems are related to proteins replicating and transcribing DNA in bacteriophages. This observation has led to the proposition that some genes required for DNA replication and transcription were acquired together from a phage early in the evolution of the eukaryotic cell, already at the time of the mitochondrial endosymbiosis. Recent years have seen a rapid development in our molecular understanding of these machineries, but many aspects still remain unknown.
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Affiliation(s)
- Maria Falkenberg
- Division of Metabolic Diseases, Karolinska Institutet, Novum, SE-141 86 Stockholm.
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99
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Asari M, Tan Y, Watanabe S, Shimizu K, Shiono H. Effect of length variations at nucleotide positions 303-315 in human mitochondrial DNA on transcription termination. Biochem Biophys Res Commun 2007; 361:641-4. [PMID: 17673181 DOI: 10.1016/j.bbrc.2007.07.055] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Accepted: 07/13/2007] [Indexed: 11/18/2022]
Abstract
In addition to stabilizing the RNA-DNA hybrid, conserved sequence block (CSB) II, which is located at nucleotides 299-315 on mitochondrial DNA, relates with the transcription termination for initiation of heavy strand synthesis in human mitochondrial replication. Due to length polymorphisms at nucleotides 303-315, individuals contain homo- or heteroplasmic profiles with length variants from C(5)TC(6) to C(15)TC(6) or from C(9) to C(13). Using in vitro transcription with templates containing these variations, we demonstrated that the production of prematurely terminated (PT) transcripts depends on the 303-315 sequences, and that longer templates result in relatively higher levels of PT transcripts. The 3' ends of PT transcripts were observed within or downstream of CSB II. Termination positions downstream of nucleotide 303 were shifted upstream by longer variations, but not shifted by shorter variations. We found that length variations between 303 and 315 generate quantitative and qualitative differences in PT transcripts.
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Affiliation(s)
- Masaru Asari
- Department of Legal Medicine, Asahikawa Medical College, 2-1 Midorigaokahigashi, Asahikawa 078-8510, Japan.
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100
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Polosa PL, Deceglie S, Falkenberg M, Roberti M, Di Ponzio B, Gadaleta MN, Cantatore P. Cloning of the sea urchin mitochondrial RNA polymerase and reconstitution of the transcription termination system. Nucleic Acids Res 2007; 35:2413-27. [PMID: 17392338 PMCID: PMC1874651 DOI: 10.1093/nar/gkm159] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Termination of transcription is a key process in the regulation of mitochondrial gene expression in animal cells. To investigate transcription termination in sea urchin mitochondria, we cloned the mitochondrial RNA polymerase (mtRNAP) of Paracentrotus lividus and used a recombinant form of the enzyme in a reconstituted transcription system, in the presence of the DNA-binding protein mtDBP. Cloning of mtRNAP was performed by a combination of PCR with degenerate primers and library screening. The enzyme contains 10 phage-like conserved motifs, two pentatricopeptide motifs and a serine-rich stretch. The protein expressed in insect cells supports transcription elongation in a promoter-independent assay. Addition of recombinant mtDBP caused arrest of the transcribing mtRNAP when the enzyme approached the mtDBP-binding site in the direction of transcription of mtDNA l-strand. When the polymerase encountered the protein-binding site in the opposite direction, termination occurred in a protein-independent manner, inside the mtDBP-binding site. Pulse-chase experiments show that mtDBP caused true transcription termination rather than pausing. These data indicate that mtDBP acts as polar termination factor and suggest that transcription termination in sea urchin mitochondria could take place by two alternative modes based on protein-mediated or sequence-dependent mechanisms.
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Affiliation(s)
- Paola Loguercio Polosa
- Dipartimento di Biochimica e Biologia Molecolare “Ernesto Quagliariello”, Università degli Studi di Bari, Istituto di Biomembrane e Bioenergetica, CNR, Via Orabona, 4, 70125 Bari, Italy and Department of Laboratory Medicine, Division of Metabolic Diseases, Karolinska Institutet, Novum, SE-141 86 Stockholm, Sweden
| | - Stefania Deceglie
- Dipartimento di Biochimica e Biologia Molecolare “Ernesto Quagliariello”, Università degli Studi di Bari, Istituto di Biomembrane e Bioenergetica, CNR, Via Orabona, 4, 70125 Bari, Italy and Department of Laboratory Medicine, Division of Metabolic Diseases, Karolinska Institutet, Novum, SE-141 86 Stockholm, Sweden
| | - Maria Falkenberg
- Dipartimento di Biochimica e Biologia Molecolare “Ernesto Quagliariello”, Università degli Studi di Bari, Istituto di Biomembrane e Bioenergetica, CNR, Via Orabona, 4, 70125 Bari, Italy and Department of Laboratory Medicine, Division of Metabolic Diseases, Karolinska Institutet, Novum, SE-141 86 Stockholm, Sweden
| | - Marina Roberti
- Dipartimento di Biochimica e Biologia Molecolare “Ernesto Quagliariello”, Università degli Studi di Bari, Istituto di Biomembrane e Bioenergetica, CNR, Via Orabona, 4, 70125 Bari, Italy and Department of Laboratory Medicine, Division of Metabolic Diseases, Karolinska Institutet, Novum, SE-141 86 Stockholm, Sweden
| | - Barbara Di Ponzio
- Dipartimento di Biochimica e Biologia Molecolare “Ernesto Quagliariello”, Università degli Studi di Bari, Istituto di Biomembrane e Bioenergetica, CNR, Via Orabona, 4, 70125 Bari, Italy and Department of Laboratory Medicine, Division of Metabolic Diseases, Karolinska Institutet, Novum, SE-141 86 Stockholm, Sweden
| | - Maria Nicola Gadaleta
- Dipartimento di Biochimica e Biologia Molecolare “Ernesto Quagliariello”, Università degli Studi di Bari, Istituto di Biomembrane e Bioenergetica, CNR, Via Orabona, 4, 70125 Bari, Italy and Department of Laboratory Medicine, Division of Metabolic Diseases, Karolinska Institutet, Novum, SE-141 86 Stockholm, Sweden
| | - Palmiro Cantatore
- Dipartimento di Biochimica e Biologia Molecolare “Ernesto Quagliariello”, Università degli Studi di Bari, Istituto di Biomembrane e Bioenergetica, CNR, Via Orabona, 4, 70125 Bari, Italy and Department of Laboratory Medicine, Division of Metabolic Diseases, Karolinska Institutet, Novum, SE-141 86 Stockholm, Sweden
- *To whom correspondence should be addressed. +39-080-5443378+39-080-5443403
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