Transcriptional response to mitochondrial NADH kinase deficiency in Saccharomyces cerevisiae

Yeast cells lacking the mitochondrial NADH kinase encoded by POS5 display increased sensitivity to hydrogen peroxide, a slow-growth phenotype, reduced mitochondrial function and increased levels of mitochondrial protein oxidation and mtDNA mutations. Here we examined gene expression in pos5 Δ cells, comparing these data to those from cells containing deletions of superoxide dismutase-encoding genes SOD1 or SOD2 . Surprisingly, stress–response genes were down-regulated in pos5 Δ, sod1 Δ and sod2 Δ cells, implying that cells infer stress levels from mitochondrial activity rather than sensing reactive oxygen species directly. Additionally, pos5 Δ, but not sod1 or sod2 , cells displayed an anaerobic expression profile, indicating a defect in oxygen sensing that is specific to pos5 , and is not a general stress–response. Finally, the pos5 Δ expression profile is quite similar to the hap1 Δ expression profile previously reported, which may indicate a shared mechanism.