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.Activation domains of transcription factors transmit signals to the transcriptional machinery of a cell to ensure proper gene expression. When tethered to a DNA binding domain, either covalently or via protein-protein interaction, they ensure that signals are transmitted to appropriate genes to activate their transcription. Although the specificity of gene expression is determined primarily by the DNA binding domain of transcription factors, activation domains can contribute to this specificity (1-4).Activation domains function by contacting other proteins that are components of the transcriptional machinery (5). The proteins contacted by activation domains include various subunits of TFIID, including TATA-binding protein itself and TATA-binding protein-associated factors, and other general transcription factors such as TFIIB, TFIIH, and members of adaptor or mediator complexes. By contacting these proteins, they recruit RNA polymerase II to the promoter and facilitate initiation and elongation of transcription (5-11).ADR1 encodes a post-translationally regulated transcription factor in the yeast Saccharomyces cerevisiae that activates the expression of the glucose-repressed ADH2 gene as well as genes involved in glycerol metabolism and peroxisome biogenesis (12-23). As with many eukaryotic transcription factors, Adr1p contains multiple domains. The ADR1 DNA binding domain (ABD) 1 is encompassed by amino acids ϳ70 -165 (16). A nuclear targeting signal is found in the first 21 amino acids of the protein (24). Four transcr...
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