51
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Holt IJ. The mitochondrial R-loop. Nucleic Acids Res 2019; 47:5480-5489. [PMID: 31045202 PMCID: PMC6582354 DOI: 10.1093/nar/gkz277] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 03/11/2019] [Accepted: 04/29/2019] [Indexed: 12/18/2022] Open
Abstract
The DNA in mitochondria contributes essential components of the organelle’s energy producing machinery that is essential for life. In 1971, many mitochondrial DNA molecules were found to have a third strand of DNA that maps to a region containing critical regulatory elements for transcription and replication. Forty-five years later, a third strand of RNA in the same region has been reported. This mitochondrial R-loop is present on thousands of copies of mitochondrial DNA per cell making it potentially the most abundant R-loop in nature. Here, I assess the discovery of the mitochondrial R-loop, discuss why it remained unrecognized for almost half a century and propose for it central roles in the replication, organization and expression of mitochondrial DNA, which if compromised can lead to disease states.
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Affiliation(s)
- Ian J Holt
- Biodonostia Health Research Institute, 20014 San Sebastián, Spain & IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain.,Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, Royal Free Campus, London, NW3 2PF, UK.,CIBERNED (Center for Networked Biomedical Research on Neurodegenerative Diseases, Ministry of Economy and Competitiveness, Institute Carlos III), Madrid, Spain
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52
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R Loops: From Physiological to Pathological Roles. Cell 2019; 179:604-618. [PMID: 31607512 DOI: 10.1016/j.cell.2019.08.055] [Citation(s) in RCA: 353] [Impact Index Per Article: 70.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 08/19/2019] [Accepted: 08/28/2019] [Indexed: 12/13/2022]
Abstract
DNA-RNA hybrids play a physiological role in cellular processes, but often, they represent non-scheduled co-transcriptional structures with a negative impact on transcription, replication and DNA repair. Accumulating evidence suggests that they constitute a source of replication stress, DNA breaks and genome instability. Reciprocally, DNA breaks facilitate DNA-RNA hybrid formation by releasing the double helix torsional conformation. Cells avoid DNA-RNA accumulation by either preventing or removing hybrids directly or by DNA repair-coupled mechanisms. Given the R-loop impact on chromatin and genome organization and its potential relation with genetic diseases, we review R-loop homeostasis as well as their physiological and pathological roles.
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53
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Hensen F, Potter A, van Esveld SL, Tarrés-Solé A, Chakraborty A, Solà M, Spelbrink JN. Mitochondrial RNA granules are critically dependent on mtDNA replication factors Twinkle and mtSSB. Nucleic Acids Res 2019; 47:3680-3698. [PMID: 30715486 PMCID: PMC6468249 DOI: 10.1093/nar/gkz047] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 01/16/2019] [Accepted: 01/24/2019] [Indexed: 01/13/2023] Open
Abstract
Newly synthesized mitochondrial RNA is concentrated in structures juxtaposed to nucleoids, called RNA granules, that have been implicated in mitochondrial RNA processing and ribosome biogenesis. Here we show that two classical mtDNA replication factors, the mtDNA helicase Twinkle and single-stranded DNA-binding protein mtSSB, contribute to RNA metabolism in mitochondria and to RNA granule biology. Twinkle colocalizes with both mitochondrial RNA granules and nucleoids, and it can serve as bait to greatly enrich established RNA granule proteins, such as G-rich sequence factor 1, GRSF1. Likewise, mtSSB also is not restricted to the nucleoids, and repression of either mtSSB or Twinkle alters mtRNA metabolism. Short-term Twinkle depletion greatly diminishes RNA granules but does not inhibit RNA synthesis or processing. Either mtSSB or GRSF1 depletion results in RNA processing defects, accumulation of mtRNA breakdown products as well as increased levels of dsRNA and RNA:DNA hybrids. In particular, the processing and degradation defects become more pronounced with both proteins depleted. These findings suggest that Twinkle is essential for RNA organization in granules, and that mtSSB is involved in the recently proposed GRSF1-mtRNA degradosome pathway, a route suggested to be particularly aimed at degradation of G-quadruplex prone long non-coding mtRNAs.
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Affiliation(s)
- Fenna Hensen
- Radboud Center for Mitochondrial Medicine, Department of Paediatrics, Radboudumc, Nijmegen, The Netherlands
| | - Alisa Potter
- Radboud Center for Mitochondrial Medicine, Department of Paediatrics, Radboudumc, Nijmegen, The Netherlands
| | - Selma L van Esveld
- Radboud Center for Mitochondrial Medicine & Center for Molecular and Biomolecular Informatics, Radboud Institute for Molecular Life Sciences, Radboudumc, Nijmegen, The Netherlands
| | - Aleix Tarrés-Solé
- Structural MitoLab, Department of Structural Biology, "Maria de Maeztu" Unit of Excellence, Molecular Biology Institute Barcelona (IBMB-CSIC), Barcelona 08028, Spain
| | - Arka Chakraborty
- Structural MitoLab, Department of Structural Biology, "Maria de Maeztu" Unit of Excellence, Molecular Biology Institute Barcelona (IBMB-CSIC), Barcelona 08028, Spain
| | - Maria Solà
- Structural MitoLab, Department of Structural Biology, "Maria de Maeztu" Unit of Excellence, Molecular Biology Institute Barcelona (IBMB-CSIC), Barcelona 08028, Spain
| | - Johannes N Spelbrink
- Radboud Center for Mitochondrial Medicine, Department of Paediatrics, Radboudumc, Nijmegen, The Netherlands
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54
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Barroso S, Herrera‐Moyano E, Muñoz S, García‐Rubio M, Gómez‐González B, Aguilera A. The DNA damage response acts as a safeguard against harmful DNA-RNA hybrids of different origins. EMBO Rep 2019; 20:e47250. [PMID: 31338941 PMCID: PMC6726908 DOI: 10.15252/embr.201847250] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 06/28/2019] [Accepted: 07/01/2019] [Indexed: 12/14/2022] Open
Abstract
Despite playing physiological roles in specific situations, DNA-RNA hybrids threat genome integrity. To investigate how cells do counteract spontaneous DNA-RNA hybrids, here we screen an siRNA library covering 240 human DNA damage response (DDR) genes and select siRNAs causing DNA-RNA hybrid accumulation and a significant increase in hybrid-dependent DNA breakage. We identify post-replicative repair and DNA damage checkpoint factors, including those of the ATM/CHK2 and ATR/CHK1 pathways. Thus, spontaneous DNA-RNA hybrids are likely a major source of replication stress, but they can also accumulate and menace genome integrity as a consequence of unrepaired DSBs and post-replicative ssDNA gaps in normal cells. We show that DNA-RNA hybrid accumulation correlates with increased DNA damage and chromatin compaction marks. Our results suggest that different mechanisms can lead to DNA-RNA hybrids with distinct consequences for replication and DNA dynamics at each cell cycle stage and support the conclusion that DNA-RNA hybrids are a common source of spontaneous DNA damage that remains unsolved under a deficient DDR.
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Affiliation(s)
- Sonia Barroso
- Centro Andaluz de Biología Molecular y Medicina Regenerativa‐CABIMERUniversidad de Sevilla‐CSIC‐Universidad Pablo de OlavideSevilleSpain
| | - Emilia Herrera‐Moyano
- Centro Andaluz de Biología Molecular y Medicina Regenerativa‐CABIMERUniversidad de Sevilla‐CSIC‐Universidad Pablo de OlavideSevilleSpain
| | - Sergio Muñoz
- Centro Andaluz de Biología Molecular y Medicina Regenerativa‐CABIMERUniversidad de Sevilla‐CSIC‐Universidad Pablo de OlavideSevilleSpain
| | - María García‐Rubio
- Centro Andaluz de Biología Molecular y Medicina Regenerativa‐CABIMERUniversidad de Sevilla‐CSIC‐Universidad Pablo de OlavideSevilleSpain
| | - Belén Gómez‐González
- Centro Andaluz de Biología Molecular y Medicina Regenerativa‐CABIMERUniversidad de Sevilla‐CSIC‐Universidad Pablo de OlavideSevilleSpain
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa‐CABIMERUniversidad de Sevilla‐CSIC‐Universidad Pablo de OlavideSevilleSpain
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55
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Mersaoui SY, Yu Z, Coulombe Y, Karam M, Busatto FF, Masson J, Richard S. Arginine methylation of the DDX5 helicase RGG/RG motif by PRMT5 regulates resolution of RNA:DNA hybrids. EMBO J 2019; 38:e100986. [PMID: 31267554 PMCID: PMC6669924 DOI: 10.15252/embj.2018100986] [Citation(s) in RCA: 101] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 05/15/2019] [Accepted: 05/28/2019] [Indexed: 01/09/2023] Open
Abstract
Aberrant transcription-associated RNA:DNA hybrid (R-loop) formation often causes catastrophic conflicts during replication, resulting in DNA double-strand breaks and genomic instability. Preventing such conflicts requires hybrid dissolution by helicases and/or RNase H. Little is known about how such helicases are regulated. Herein, we identify DDX5, an RGG/RG motif-containing DEAD-box family RNA helicase, as crucial player in R-loop resolution. In vitro, recombinant DDX5 resolves R-loops in an ATP-dependent manner, leading to R-loop degradation by the XRN2 exoribonuclease. DDX5-deficient cells accumulate R-loops at loci with propensity to form such structures based on RNA:DNA immunoprecipitation (DRIP)-qPCR, causing spontaneous DNA double-strand breaks and hypersensitivity to replication stress. DDX5 associates with XRN2 and resolves R-loops at transcriptional termination regions downstream of poly(A) sites, to facilitate RNA polymerase II release associated with transcriptional termination. Protein arginine methyltransferase 5 (PRMT5) binds and methylates DDX5 at its RGG/RG motif. This motif is required for DDX5 interaction with XRN2 and repression of cellular R-loops, but not essential for DDX5 helicase enzymatic activity. PRMT5-deficient cells accumulate R-loops, resulting in increased formation of γH2AX foci. Our findings exemplify a mechanism by which an RNA helicase is modulated by arginine methylation to resolve R-loops, and its potential role in regulating transcription.
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Affiliation(s)
- Sofiane Y Mersaoui
- Departments of Oncology and MedicineSegal Cancer CenterLady Davis Institute for Medical ResearchMcGill UniversityMontréalQCCanada
| | - Zhenbao Yu
- Departments of Oncology and MedicineSegal Cancer CenterLady Davis Institute for Medical ResearchMcGill UniversityMontréalQCCanada
| | - Yan Coulombe
- Genome Stability LaboratoryOncology DivisionCHU de Québec‐Université LavalQuébecQCCanada
- Department of Molecular Biology, Medical Biochemistry and PathologyLaval University Cancer Research CenterQuébecQCCanada
| | - Martin Karam
- Departments of Oncology and MedicineSegal Cancer CenterLady Davis Institute for Medical ResearchMcGill UniversityMontréalQCCanada
| | - Franciele F Busatto
- Genome Stability LaboratoryOncology DivisionCHU de Québec‐Université LavalQuébecQCCanada
- Department of Molecular Biology, Medical Biochemistry and PathologyLaval University Cancer Research CenterQuébecQCCanada
| | - Jean‐Yves Masson
- Genome Stability LaboratoryOncology DivisionCHU de Québec‐Université LavalQuébecQCCanada
- Department of Molecular Biology, Medical Biochemistry and PathologyLaval University Cancer Research CenterQuébecQCCanada
| | - Stéphane Richard
- Departments of Oncology and MedicineSegal Cancer CenterLady Davis Institute for Medical ResearchMcGill UniversityMontréalQCCanada
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Holt IJ. The Jekyll and Hyde character of RNase H1 and its multiple roles in mitochondrial DNA metabolism. DNA Repair (Amst) 2019; 84:102630. [PMID: 31178343 DOI: 10.1016/j.dnarep.2019.06.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 06/03/2019] [Accepted: 06/03/2019] [Indexed: 02/06/2023]
Abstract
The activity and specificity of ribonuclease H1, RNase H1, has been known for over half a century; like all enzymes in its class, it degrades RNA only when it is hybridized to DNA. However, the essential role of RNase H1 in mitochondrial DNA maintenance was not recognized until 2003, and empirical evidence that it is required to process RNA primers of mitochondrial DNA had to wait until 2015. In the same year, mutations in the RNASEH1 gene were linked to human mitochondrial diseases. The most recent studies suggest that in addition to primer-processing, RNase H1 determines the fate of R-loops, although not primarily those that might present an obstacle to DNA replication, but ones that contribute to the organization of mitochondrial DNA and the unusual mechanism of replication in mitochondria that utilizes transcripts for the strand-asynchronous mechanism of mitochondrial DNA replication. A full understanding of the role of RNase H1 in mtDNA metabolism will depend on further study, including careful consideration of its ability to stabilize, as well as to degrade RNA/DNA hybrids, and its regulation by oxidation or other mechanisms. Nevertheless, RNase H1 is already staking a strong claim to be the most versatile factor involved in propagating the DNA in the mitochondria.
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Affiliation(s)
- Ian J Holt
- Biodonostia Health Research Institute, 20014 San Sebastián, Spain; IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain; Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, Royal Free Campus, London, NW3 2PF, UK; CIBERNED (Center for Networked Biomedical Research on Neurodegenerative Diseases, Ministry of Economy and Competitiveness, Institute Carlos III), Madrid, Spain.
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57
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Jeandard D, Smirnova A, Tarassov I, Barrey E, Smirnov A, Entelis N. Import of Non-Coding RNAs into Human Mitochondria: A Critical Review and Emerging Approaches. Cells 2019; 8:E286. [PMID: 30917553 PMCID: PMC6468882 DOI: 10.3390/cells8030286] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 03/19/2019] [Accepted: 03/23/2019] [Indexed: 01/26/2023] Open
Abstract
Mitochondria harbor their own genetic system, yet critically depend on the import of a number of nuclear-encoded macromolecules to ensure their expression. In all eukaryotes, selected non-coding RNAs produced from the nuclear genome are partially redirected into the mitochondria, where they participate in gene expression. Therefore, the mitochondrial RNome represents an intricate mixture of the intrinsic transcriptome and the extrinsic RNA importome. In this review, we summarize and critically analyze data on the nuclear-encoded transcripts detected in human mitochondria and outline the proposed molecular mechanisms of their mitochondrial import. Special attention is given to the various experimental approaches used to study the mitochondrial RNome, including some recently developed genome-wide and in situ techniques.
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Affiliation(s)
- Damien Jeandard
- UMR 7156 GMGM Strasbourg University/CNRS, 67000 Strasbourg, France.
| | - Anna Smirnova
- UMR 7156 GMGM Strasbourg University/CNRS, 67000 Strasbourg, France.
| | - Ivan Tarassov
- UMR 7156 GMGM Strasbourg University/CNRS, 67000 Strasbourg, France.
| | - Eric Barrey
- GABI-UMR1313, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
| | | | - Nina Entelis
- UMR 7156 GMGM Strasbourg University/CNRS, 67000 Strasbourg, France.
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