title: Role of negative regulation in promoter specificity of the homologous transcriptional activators Ace2p and Swi5p.
abstract: The Ace2p and Swi5p zinc finger proteins have nearly identical DNA-binding domains, yet in vivo they activate transcription of different genes, CTS1 and HO. We now demonstrate that Ace2p and Swi5p recognize sites in the CTS1 and HO promoters with the same affinities, raising the question of how promoter specificity is achieved by these proteins with similar DNA-binding domains. It has been previously shown that Swi5p binds to the HO promoter cooperatively with the Pho2p (Base2p/Grf10p) homeodomain protein, and we now show that Ace2p does not interact with Pho2p. Analysis of CTS1 promoter fragments inserted into a heterologous promoter identify a sequence 90 bp away from the Ace2p binding sites which is required to prevent activation by Swi5p through these binding sites. These results suggest that a regulatory protein bound to the CTS1 promoter is needed to prevent Swi5p from activating CT1S expression. A genetic screen was conducted to identify suppressor mutations which allow CTS1 expression in the absence of the Ace2p activator. The nce3 mutation suppresses the ace2 defect in CTS1 expression only if the strain contains a functional SWI5 gene, suggesting that NCE3 normally functions to prevent Swi5p from activating CTS1. The role of negative regulators such as NCE3, as well as the previously described SIN5 gene, in determining the promoter specificity of homologous activators is discussed.
authors.affiliation: Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, 84132, USA.
authors.forename: P R
authors.initials: PR
authors.lastname: Dohrmann
authors.forename: W P
authors.initials: WP
authors.lastname: Voth
authors.forename: D J
authors.initials: DJ
authors.lastname: Stillman
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D017385:Sequence Homology; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D016335:Zinc Fingers
chemical_list: C066778:ACE2 protein, S cerevisiae; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C080218:SWI5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors