Multiple regulatory elements control expression of the gene encoding the Saccharomyces cerevisiae cytochrome P450, lanosterol 14 alpha-demethylase (ERG11).

The major cytochrome P450 in the yeast Saccharomyces cerevisiae, lanosterol 14 alpha-demethylase (ERG11), catalyzes an essential reaction in the biosynthesis of ergosterol, the predominant sterol of yeast. Protein levels of this cytochrome P450 are known to be affected by carbon source, oxygen, and heme, as well as the growth state of the culture. We have determined that ERG11 message levels increase during growth on glucose, in the presence of heme, and during oxygen limiting growth conditions and, unexpectedly, during anaerobic growth. To determine the cis-acting regions responsible for regulation of expression of the ERG11 promoter under optimal conditions of fermentative growth, deletion analysis was performed using the Escherichia coli lacZ as a reporter gene. Two upstream activating sequences, UAS1 and UAS2, and an upstream repressor element, URS1, plus a second possible or cryptic repressor element, URS2, were identified in the ERG11 promoter. The HAP1 protein product apparently participates in activation from UAS1 but not from UAS2. Sequences resembling ERG11 UAS2 were identified in seven additional oxygen-regulated genes. Repression of ERG11 expression was dependent upon the ROX1 repressor and additional repressor(s) designated as Old (overexpression of lanosterol demethylase). These data indicate that ERG11 is a member of the hypoxic gene family which includes ANB1, COX5b, CYC7, and HEM13. Furthermore, NADPH-cytochrome P450 reductase (CPR1), another component in this P450 system, appears to be coordinately regulated with ERG11.