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Nucleic Acids Res. 2014 Dec 1;42(21):13214-27. doi: 10.1093/nar/gku1148. Epub 2014 Nov 11.

Double-stranded DNA-dependent ATPase Irc3p is directly involved in mitochondrial genome maintenance.

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Institute of Molecular and Cell Biology, University of Tartu, Riia 23b, Tartu 51010, Estonia.
Institute of Molecular and Cell Biology, University of Tartu, Riia 23b, Tartu 51010, Estonia


Nucleic acid-dependent ATPases are involved in nearly all aspects of DNA and RNA metabolism. Previous studies have described a number of mitochondrial helicases. However, double-stranded DNA-dependent ATPases, including translocases or enzymes remodeling DNA-protein complexes, have not been identified in mitochondria of the yeast Saccharomyces cerevisae. Here, we demonstrate that Irc3p is a mitochondrial double-stranded DNA-dependent ATPase of the Superfamily II. In contrast to the other mitochondrial Superfamily II enzymes Mss116p, Suv3p and Mrh4p, which are RNA helicases, Irc3p has a direct role in mitochondrial DNA (mtDNA) maintenance. Specific Irc3p-dependent mtDNA metabolic intermediates can be detected, including high levels of double-stranded DNA breaks that accumulate in irc3Δ mutants. irc3Δ-related topology changes in rho- mtDNA can be reversed by the deletion of mitochondrial RNA polymerase RPO41, suggesting that Irc3p counterbalances adverse effects of transcription on mitochondrial genome stability.

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