Characterization of a p53-related activation domain in Adr1p that is sufficient for ADR1-dependent gene expression.

The yeast transcriptional activator Adr1p controls expression of the glucose-repressible alcohol dehydrogenase gene (ADH2), genes involved in glycerol metabolism, and genes required for peroxisome biogenesis and function. Previous data suggested that promoter-specific activation domains might contribute to expression of the different types of ADR1-dependent genes. By using gene fusions encoding the Gal4p DNA binding domain and portions of Adr1p, we identified a single, strong acidic activation domain spanning amino acids 420-462 of Adr1p. Both acidic and hydrophobic amino acids within this activation domain were important for its function. The critical hydrophobic residues are in a motif previously identified in p53 and related acidic activators. A mini-Adr1 protein consisting of the DNA binding domain of Adr1p fused to this 42-residue activation domain carried out all of the known functions of wild-type ADR1. It conferred stringent glucose repression on the ADH2 locus and on UAS1-containing reporter genes. The putative inhibitory region of Adr1p encompassing the protein kinase A phosphorylation site at Ser-230 is thus not essential for glucose repression mediated by ADR1. Mini-ADR1 allowed efficient derepression of gene expression. In addition it complemented an ADR1-null allele for growth on glycerol and oleate media, indicating efficient activation of genes required for glycerol metabolism and peroxisome biogenesis. Thus, a single activation domain can activate all ADR1-dependent promoters.