Journal Article

Linear mitochondrial DNA is rapidly degraded by components of the replication machinery

Rebelo-Guiomar, Pedro, Blei, Daniel, Kudin, Alexei P., Minczuk, Michal, Zsurka, Gábor, Peeva, Viktoriya, Altmüller, Janine, Szukszto, Maciej J., Gammage, Payam A., Kunz, Wolfram S., Corsi, Sarah, Trombly, Genevieve, Becker, Christian

2018

Overview

Emerging gene therapy approaches that aim to eliminate pathogenic mutations of mitochondrial DNA (mtDNA) rely on efficient degradation of linearized mtDNA, but the enzymatic machinery performing this task is presently unknown. Here, we show that, in cellular models of restriction endonuclease-induced mtDNA double-strand breaks, linear mtDNA is eliminated within hours by exonucleolytic activities. Inactivation of the mitochondrial 5′-3′exonuclease MGME1, elimination of the 3′-5′exonuclease activity of the mitochondrial DNA polymerase POLG by introducing the p.D274A mutation, or knockdown of the mitochondrial DNA helicase TWNK leads to severe impediment of mtDNA degradation. We do not observe similar effects when inactivating other known mitochondrial nucleases (EXOG, APEX2, ENDOG, FEN1, DNA2, MRE11, or RBBP8). Our data suggest that rapid degradation of linearized mtDNA is performed by the same machinery that is responsible for mtDNA replication, thus proposing novel roles for the participating enzymes POLG, TWNK, and MGME1. Damaged linearized mtDNA needs to be removed from the cell for mitochondrial genome stability. Here the authors shed light into the identity of the machinery responsible for rapidly degrading linearized DNA, implicating the role of mtDNA replication factors.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Portfolio
• Subject: 13 / 13/106 / 49 / 49/23 / 631/337/1644 / 631/80/642/333 / Base Sequence / CRISPR-Cas Systems / Deactivation / Degradation / Deoxyribonucleases, Type II Site-Specific - genetics / Deoxyribonucleases, Type II Site-Specific - metabolism / Deoxyribonucleic acid / DNA / DNA Breaks, Double-Stranded / DNA Cleavage / DNA helicase / DNA Helicases - genetics / DNA Helicases - metabolism / DNA polymerase / DNA Polymerase gamma - genetics / DNA Polymerase gamma - metabolism / DNA Replication / DNA, Mitochondrial - genetics / DNA, Mitochondrial - metabolism / DNA-directed DNA polymerase / Electron Transport Complex IV - genetics / Electron Transport Complex IV - metabolism / Endonuclease / Exodeoxyribonucleases - genetics / Exodeoxyribonucleases - metabolism / Exonuclease / FEN1 protein / Gene Editing - methods / Gene therapy / Genetic Therapy / HEK293 Cells / Humanities and Social Sciences / Humans / Inactivation / Linearization / Mitochondria - genetics / Mitochondria - metabolism / Mitochondria - pathology / Mitochondrial DNA / MRE11 protein / multidisciplinary / Mutation / Nuclease / Recombinant Fusion Proteins - genetics / Recombinant Fusion Proteins - metabolism / Replication / Science / Science (multidisciplinary)