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

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

Journal: Nature communications 2018;9(1):1727

PMID: 29712893

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Abstract

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.

Address: Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105, Bonn, Germany.; Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.; MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, UK.; Graduate Program in Areas of Basic and Applied Biology (GABBA), University of Porto, Porto, 4200-135, Portugal.; Cologne Center for Genomics, Center for Molecular Medicine Cologne (CMMC), University of Cologne, Weyertal 115b, Cologne, D-50931, Germany.; Institute of Human Genetics, University of Cologne, Kerpener Str. 34, Cologne, D-50931, Germany.; MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, UK. [email protected].; Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105, Bonn, Germany. [email protected].; Department of Epileptology and Life & Brain Center, University of Bonn, Sigmund-Freud-Str. 25, Bonn, D-53105, Germany. [email protected].; Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105, Bonn, Germany. [email protected].; Department of Epileptology and Life & Brain Center, University of Bonn, Sigmund-Freud-Str. 25, Bonn, D-53105, Germany. [email protected].

DOI: 10.1038/s41467-018-04131-w