POS5 Gene of Saccharomyces cerevisiae Encodes a Mitochondrial NADH Kinase Required for Stability of Mitochondrial DNA
AUTOR(ES)
Strand, Micheline K.
FONTE
American Society for Microbiology
RESUMO
In a search for nuclear genes that affect mutagenesis of mitochondrial DNA in Saccharomyces cerevisiae, an ATP-NAD (NADH) kinase, encoded by POS5, that functions exclusively in mitochondria was identified. The POS5 gene product was overproduced in Escherichia coli and purified without a mitochondrial targeting sequence. A direct biochemical assay demonstrated that the POS5 gene product utilizes ATP to phosphorylate both NADH and NAD+, with a twofold preference for NADH. Disruption of POS5 increased minus-one frameshift mutations in mitochondrial DNA 50-fold, as measured by the arg8m reversion assay, with no increase in nuclear mutations. Also, a dramatic increase in petite colony formation and slow growth on glycerol or limited glucose were observed. POS5 was previously described as a gene required for resistance to hydrogen peroxide. Consistent with a role in the mitochondrial response to oxidative stress, a pos5 deletion exhibited a 28-fold increase in oxidative damage to mitochondrial proteins and hypersensitivity to exogenous copper. Furthermore, disruption of POS5 induced mitochondrial biogenesis as a response to mitochondrial dysfunction. Thus, the POS5 NADH kinase is required for mitochondrial DNA stability with a critical role in detoxification of reactive oxygen species. These results predict a role for NADH kinase in human mitochondrial diseases.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=178377Documentos Relacionados
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