TRANSCRIPTION OF THE AAC1 GENE ENCODING AN ISOFORM OF MITOCHONDRIAL ADP ATP CARRIER IN SACCHAROMYCES-CEREVISIAE IS REGULATED BY OXYGEN IN AHEME-INDEPENDENT MANNER/

The mitochondrial ADP/ATP carrier in Saccharomyces cerevisiae is encod ed by three independent genes, AAC1, AAC2, and AAC3. In this work, we analysed the 5' upstream region of AAC1 by sequencing and by mapping t he transcription initiation site of the gene. By monitoring the level of AAC1 mRNA and the beta-galactosidase activity of AAC1-lacZ fusion c onstructs, we showed that expression of AAC1 is subjected to regulatio n by oxygen. In contrast to the other two AAC genes, the effect of oxy gen on AAC1 is not mediated by heme and heme-dependent transcription f actors. The AAC1 expression was reduced eightfold in anaerobically gro wn cells compared to expression in cells grown aerobically, but it was not affected by the nature of carbon source used for growth. The data presented show that AAC1 expression, while constitutive under all aer obic conditions tested, is repressed during anaerobiosis in a heme-ind ependent manner.