title: Yeast mitochondrial HMG proteins: DNA-binding properties of the most evolutionarily divergent component of mitochondrial nucleoids.
abstract: Yeast mtDNA is compacted into nucleoprotein structures called mitochondrial nucleoids (mt-nucleoids). The principal mediators of nucleoid formation are mitochondrial high-mobility group (HMG)-box containing (mtHMG) proteins. Although these proteins are some of the fastest evolving components of mt-nucleoids, it is not known whether the divergence of mtHMG proteins on the level of their amino acid sequences is accompanied by diversification of their biochemical properties. In the present study we performed a comparative biochemical analysis of yeast mtHMG proteins from Saccharomyces cerevisiae (ScAbf2p), Yarrowia lipolytica (YlMhb1p) and Candida parapsilosis (CpGcf1p). We found that all three proteins exhibit relatively weak binding to intact dsDNA. In fact, ScAbf2p and YlMhb1p bind quantitatively to this substrate only at very high protein to DNA ratios and CpGcf1p shows only negligible binding to dsDNA. In contrast, the proteins exhibit much higher preference for recombination intermediates such as Holliday junctions (HJ) and replication forks (RF). Therefore, we hypothesize that the roles of the yeast mtHMG proteins in maintenance and compaction of mtDNA in vivo are in large part mediated by their binding to recombination/replication intermediates. We also speculate that the distinct biochemical properties of CpGcf1p may represent one of the prerequisites for frequent evolutionary tinkering with the form of the mitochondrial genome in the CTG-clade of hemiascomycetous yeast species.
authors.affiliation: Departments of Genetics and Biochemistry, Comenius University in Bratislava, Faculty of Natural Sciences, Mlynska dolina, Ilkovicova 6, 842 15 Bratislava, Slovak Republic.
authors.forename: Jana
authors.initials: J
authors.lastname: Bakkaiova
authors.affiliation: Department of Biology, Masaryk University, Kamenice 5/A7, Brno 625 00, Czech Republic International Clinical Research Center, St. Anne's University Hospital in Brno, Brno 60200, Czech Republic.
authors.forename: Victoria
authors.initials: V
authors.lastname: Marini
authors.affiliation: Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, NC 27599, U.S.A.
authors.forename: Smaranda
authors.initials: S
authors.lastname: Willcox
authors.affiliation: Departments of Genetics and Biochemistry, Comenius University in Bratislava, Faculty of Natural Sciences, Mlynska dolina, Ilkovicova 6, 842 15 Bratislava, Slovak Republic.
authors.forename: Jozef
authors.initials: J
authors.lastname: Nosek
authors.affiliation: Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, NC 27599, U.S.A.
authors.forename: Jack D
authors.initials: JD
authors.lastname: Griffith
authors.affiliation: Department of Biology, Masaryk University, Kamenice 5/A7, Brno 625 00, Czech Republic International Clinical Research Center, St. Anne's University Hospital in Brno, Brno 60200, Czech Republic National Center for Biomolecular Research, Masaryk University, Kamenice 5/A7, Brno 625 00, Czech Republic.
authors.forename: Lumir
authors.initials: L
authors.lastname: Krejci
authors.affiliation: Departments of Genetics and Biochemistry, Comenius University in Bratislava, Faculty of Natural Sciences, Mlynska dolina, Ilkovicova 6, 842 15 Bratislava, Slovak Republic tomaska@fns.uniba.sk.
authors.forename: Lubomir
authors.initials: L
authors.lastname: Tomaska
mesh_terms: D002175:Candida / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D006609:High Mobility Group Proteins / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D025062:Yarrowia / Q000235:genetics / Q000378:metabolism*
chemical_list: D006609:High Mobility Group Proteins; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins
keywords: DNA compaction; DNA-binding protein; HMG-box containing protein; Holliday junction; mitochondrial DNA (mtDNA); mitochondrial nucleoid