title: Irc3 is a mitochondrial DNA branch migration enzyme.
abstract: Integrity of mitochondrial DNA (mtDNA) is essential for cellular energy metabolism. In the budding yeast Saccharomyces cerevisiae, a large number of nuclear genes influence the stability of mitochondrial genome; however, most corresponding gene products act indirectly and the actual molecular mechanisms of mtDNA inheritance remain poorly characterized. Recently, we found that a Superfamily II helicase Irc3 is required for the maintenance of mitochondrial genome integrity. Here we show that Irc3 is a mitochondrial DNA branch migration enzyme. Irc3 modulates mtDNA metabolic intermediates by preferential binding and unwinding Holliday junctions and replication fork structures. Furthermore, we demonstrate that the loss of Irc3 can be complemented with mitochondrially targeted RecG of Escherichia coli. We suggest that Irc3 could support the stability of mtDNA by stimulating fork regression and branch migration or by inhibiting the formation of irregular branched molecules.
authors.affiliation: Institute of Molecular and Cell Biology, University of Tartu, Riia 23b, Tartu 51010, Estonia.
authors.forename: Ilja
authors.initials: I
authors.lastname: Gaidutšik
authors.affiliation: Institute of Molecular and Cell Biology, University of Tartu, Riia 23b, Tartu 51010, Estonia.
authors.forename: Tiina
authors.initials: T
authors.lastname: Sedman
authors.affiliation: Institute of Molecular and Cell Biology, University of Tartu, Riia 23b, Tartu 51010, Estonia.
authors.forename: Sirelin
authors.initials: S
authors.lastname: Sillamaa
authors.affiliation: Institute of Molecular and Cell Biology, University of Tartu, Riia 23b, Tartu 51010, Estonia.
authors.forename: Juhan
authors.initials: J
authors.lastname: Sedman
mesh_terms: D053903:DNA Breaks, Double-Stranded; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D045566:DNA, Cruciform / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D008928:Mitochondria / Q000737:chemistry / Q000235:genetics; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion
chemical_list: D045566:DNA, Cruciform; D004272:DNA, Mitochondrial; D029701:Saccharomyces cerevisiae Proteins; D004265:DNA Helicases; C000594746:Irc3 protein, S cerevisiae; D005947:Glucose