Regulation of the ADE2 gene from Saccharomyces cerevisiae

Regulation of ADE2 gene expression was investigated in the yeast S. cerevisiae using translational fusions between this gene and the lacZ gene from E. coli. Expression was repressed in the presence of adenine and slightly increased under amino-acid starvation conditions. The promoters of the ADE2 gene, and of other genes involved in adenine biosynthesis, contain the hexanucleotide sequence TGACTC. A search for the hexanucleotide TGACTC in yeast promoter sequences revealed that many genes not related to amino-acid biosynthesis contain such sequences. We show here that these elements play a crucial role in ADE2 regulation since mutations in two such elements drastically reduced gene expression. Maximal expression required the transcriptional activators Bas1, Bas2 and Gcn4, whereas Yap1 had only minor effects.