title: Helicase Hmi1 stimulates the synthesis of concatemeric mitochondrial DNA molecules in yeast Saccharomyces cerevisiae.
abstract: Hmi1p is a helicase in the yeast Saccharomyces cerevisiae required for maintenance of the wild-type mitochondrial genome. Disruption of the HMI1 ORF generates rho(-) and rho(0) cells. Here we demonstrate that, in rho(-) yeast strains, Hmi1p stimulates the synthesis of long concatemeric mitochondrial DNA molecules associated with a reduction in the number of nucleoids used for mitochondrial DNA packaging. Surprisingly, the ATPase negative mutants of Hmi1p can also stimulate the synthesis of long concatemeric rho(-) mitochondrial DNA molecules and support the maintenance of the wild-type mitochondrial genome, albeit with reduced efficiency. We show that, in the mutant hmi1-5 background, the wild-type mitochondrial DNA is fragmented; and we propose that, in hmi1Delta yeast cells, the loss of the wild-type mitochondrial genome is caused by this fragmentation of the mitochondrial DNA.
authors.affiliation: Department of General and Microbial Biochemistry, University of Tartu, Vanemuise 46, Tartu 51014, Estonia.
authors.forename: Tiina
authors.initials: T
authors.lastname: Sedman
authors.forename: Priit
authors.initials: P
authors.lastname: Jõers
authors.forename: Silja
authors.initials: S
authors.lastname: Kuusk
authors.forename: Juhan
authors.initials: J
authors.lastname: Sedman
mesh_terms: D000595:Amino Acid Sequence; D053938:DNA Fragmentation; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004271:DNA, Fungal / Q000235:genetics* / Q000302:isolation & purification; D004272:DNA, Mitochondrial / Q000235:genetics* / Q000302:isolation & purification; D015180:Electrophoresis, Gel, Two-Dimensional; D016681:Genome, Fungal; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010957:Plasmids / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004271:DNA, Fungal; D004272:DNA, Mitochondrial; D024101:Mitochondrial Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D004265:DNA Helicases; C120692:HMI1 protein, S cerevisiae