Sterol metabolism and ERG2 gene regulation in the yeast Saccharomyces cerevisiae

Abstract

Certain exogenously‐supplied sterols, like ergost‐8‐enol, are efficiently converted into ergosterol in yeast. We have taken advantage of this property to study the regulation of the Δ8‐Δ7‐sterol isomerase‐encoding ERG2 gene in an ergosterol auxotrophic mutant devoid of squalene‐synthase activity. Ergosterol starvation leads to an 8–16‐fold increase in ERG2 gene expression. Such an increase was also observed in wild‐type cells either grown anaerobically or treated with SR31747A a sterol isomerase inhibitor. Exogenously‐supplied zymosterol is entirely transformed into ergosterol, which represses ERG2 transcription. By contrast, exogenously‐supplied ergosterol has little or no effect on ERG2 transcription.