title: Pathological ribonuclease H1 causes R-loop depletion and aberrant DNA segregation in mitochondria.
abstract: The genetic information in mammalian mitochondrial DNA is densely packed; there are no introns and only one sizeable noncoding, or control, region containing key cis-elements for its replication and expression. Many molecules of mitochondrial DNA bear a third strand of DNA, known as "7S DNA," which forms a displacement (D-) loop in the control region. Here we show that many other molecules contain RNA as a third strand. The RNA of these R-loops maps to the control region of the mitochondrial DNA and is complementary to 7S DNA. Ribonuclease H1 is essential for mitochondrial DNA replication; it degrades RNA hybridized to DNA, so the R-loop is a potential substrate. In cells with a pathological variant of ribonuclease H1 associated with mitochondrial disease, R-loops are of low abundance, and there is mitochondrial DNA aggregation. These findings implicate ribonuclease H1 and RNA in the physical segregation of mitochondrial DNA, perturbation of which represents a previously unidentified disease mechanism.
authors.affiliation: Medical Research Council, Mill Hill Laboratory, London NW7 1AA, United Kingdom;
authors.forename: Gokhan
authors.initials: G
authors.lastname: Akman
authors.affiliation: Medical Research Council, Mill Hill Laboratory, London NW7 1AA, United Kingdom;
authors.forename: Radha
authors.initials: R
authors.lastname: Desai
authors.affiliation: Medical Research Council Mitochondrial Biology Unit, Cambridge CB1 9SY, United Kingdom;
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Bailey
authors.affiliation: Medical Research Council Mitochondrial Biology Unit, Cambridge CB1 9SY, United Kingdom;
authors.forename: Takehiro
authors.initials: T
authors.lastname: Yasukawa
authors.affiliation: Medical Research Council, Mill Hill Laboratory, London NW7 1AA, United Kingdom;
authors.forename: Ilaria
authors.initials: I
authors.lastname: Dalla Rosa
authors.affiliation: Medical Research Council, Mill Hill Laboratory, London NW7 1AA, United Kingdom;
authors.forename: Romina
authors.initials: R
authors.lastname: Durigon
authors.affiliation: Medical Research Council Mitochondrial Biology Unit, Cambridge CB1 9SY, United Kingdom; Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892;
authors.forename: J Bradley
authors.initials: JB
authors.lastname: Holmes
authors.affiliation: Medical Research Council, Mill Hill Laboratory, London NW7 1AA, United Kingdom;
authors.forename: Chloe F
authors.initials: CF
authors.lastname: Moss
authors.affiliation: Medical Research Council, Mill Hill Laboratory, London NW7 1AA, United Kingdom;
authors.forename: Mara
authors.initials: M
authors.lastname: Mennuni
authors.affiliation: Medical Research Council Centre for Neuromuscular Diseases, University College London Institute of Neurology and National Hospital for Neurology and Neurosurgery, London WC1N 3BG, United Kingdom;
authors.forename: Henry
authors.initials: H
authors.lastname: Houlden
authors.affiliation: Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Robert J
authors.identifier: 0000-0002-8714-2786
authors.initials: RJ
authors.lastname: Crouch
authors.affiliation: Medical Research Council Centre for Neuromuscular Diseases, University College London Institute of Neurology and National Hospital for Neurology and Neurosurgery, London WC1N 3BG, United Kingdom;
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hanna
authors.affiliation: Medical Research Council Centre for Neuromuscular Diseases, University College London Institute of Neurology and National Hospital for Neurology and Neurosurgery, London WC1N 3BG, United Kingdom; Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 8AF, United Kingdom.
authors.forename: Robert D S
authors.initials: RD
authors.lastname: Pitceathly
authors.affiliation: Medical Research Council, Mill Hill Laboratory, London NW7 1AA, United Kingdom; ian.holt@headoffice.mrc.ac.uk Antonella.Spinazzola@crick.ac.uk.
authors.forename: Antonella
authors.initials: A
authors.lastname: Spinazzola
authors.affiliation: Medical Research Council, Mill Hill Laboratory, London NW7 1AA, United Kingdom; ian.holt@headoffice.mrc.ac.uk Antonella.Spinazzola@crick.ac.uk.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Holt
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004261:DNA Replication; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism; D028361:Mitochondrial Diseases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009690:Nucleic Acid Conformation; D016914:Ribonuclease H / Q000235:genetics* / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D016914:Ribonuclease H; C078856:ribonuclease HI
keywords: DNA segregation; R-loop; RNase H1; mitochondrial DNA; mitochondrial disease