Cytochrome c 1
HAP1, HAP2 transcription factors
Centromere and promoter-binding factor (CPF1)
Springer Online Journal Archives 1860-2000
Summary The nuclear gene for cytochrome c 1 in Saccharomyces cerevisiae (CYT1) was localized on chromosome XV. Its upstream region was identified by functional complementation. Fusion to the lacZ reporter gene on a CEN plasmid allowed study of the effect of carbon sources and of specific deletion mutations on expression of the gene in yeast transformants. Detailed promoter analysis combined with expression studies in recipient strains defective in regulatory genes identified cis-acting sites and transcription factors involved in the regulated expression of the cytochrome c 1 gene. These analyses showed that, in the presence of glucose, transcription of CYT1 is positively controlled by oxygen, presumably through the haem signal, and mediated by the HAP1-encoded transactivator. It is additionally regulated by the HAP2/3/4 complex which mediates gene activation mainly under glucose-free conditions. Basal transcription is, in part, effected by CPF1, a centromere and promoter-binding factor.
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