RESUMO
Mitochondria are dynamic organelles that fuse and divide. These changes alter the number and distribution of mitochondrial structures throughout the cell in response to developmental and metabolic cues. We have demonstrated that mitochondrial fission is essential to the maintenance of mitochondrial DNA (mtDNA) under changing metabolic conditions in wild-type Saccharomyces cerevisiae. While increased loss of mtDNA integrity has been demonstrated for dnm1-∆ fission mutants after growth in a non-fermentable carbon source, we demonstrate that growth of yeast in different carbon sources affects the frequency of mtDNA loss, even when the carbon sources are fermentable. In addition, we demonstrate that the impact of fission on mtDNA maintenance during growth in different carbon sources is neither mediated by retrograde signaling nor mitophagy. Instead, we demonstrate that mitochondrial distribution and mtDNA maintenance phenotypes conferred by loss of Dnm1p are suppressed by the loss of Sod2p, the mitochondrial matrix superoxide dismutase.
Assuntos
Genoma Mitocondrial , Instabilidade Genômica , Mitocôndrias/genética , Mitocôndrias/metabolismo , Dinâmica Mitocondrial , Carbono/metabolismo , Respiração Celular/genética , Quebras de DNA de Cadeia Dupla , Reparo do DNA , DNA Mitocondrial , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo , Deleção de Genes , Membranas Mitocondriais/metabolismo , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Mutação , Rafinose/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Deleção de SequênciaRESUMO
Microsatellites, or simple repetitive sequences, are abundant in eukaryotic genomes and in the mitochondrial genome of Saccharomyces cerevisiae. These sequences alter at rates significantly higher than non-repetitive sequences of comparable size. The stability of a mitochondrial microsatellite is nearly 100-fold greater in diploid yeast cells than in isogenic haploid cells. We were able to demonstrate that this effect is likely due to ploidy alone, rather than mating-type-specific gene expression. In addition, we demonstrated that amino acid starvation affects the organization of the mitochondrial DNA and its segregation into the bud. We also tested the effect of amino acid starvation on the copy number and the mutation rate of mitochondrial DNA in both haploid and diploid yeast cells. Yeast cells grown in rich medium have a lower mitochondrial DNA content than cells starved for amino acids and have a correspondingly higher mutation rate for both frameshift mutations and point mutations in mitochondrial DNA. These effects appear to be dependent on the mitochondrial nucleoid-associated protein Ilv5p.
