Oxygen-dependent upstream activation sites of Saccharomyces cerevisiae cytochrome c genes are related forms of the same sequence.
In Saccharomyces cerevisiae, the two genes, CYC1 and CYC7, that encode the isoforms of cytochrome c are expressed at different levels. Oxygen regulation is mediated by the expression of the CYP1 gene, and the CYP1 protein interacts with both CYC1 upstream activation sequence 1 (UAS1) and CYC7 UASo. In this study, the homology between the CYP1-binding sites of both genes was investigated. The most noticeable difference between the CYC1 and CYC7 UASs is the presence of GC base pairs at the same positions in a repeated sequence in CYC7 compared with CG base pairs in CYC1. Directed mutagenesis changing these GC residues to CG residues in CYC7 led to CYC1-like expression of CYC7 both in a CYP1 wild-type strain and in a strain carrying the semidominant mutation CYP1-16 which reverses the oxygen-dependent expression of the two genes. Our results strongly support the hypothesis that the CYP1-binding sites in CYC1 and CYC7 are related forms of the same sequence and that the CYP1-16 protein has altered specificity for the variant forms of the consensus sequences in both genes.
Cerdan
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ME
Department of Biological Sciences, State University of New York, Albany 12222.
Zitomer
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D001483:Base Sequence; D003001:Cloning, Molecular; D003574:Cytochrome c Group / Q000235:genetics*; D009154:Mutation; D010100:Oxygen / Q000494:pharmacology; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
D003574:Cytochrome c Group; D010100:Oxygen