title: Transcriptional repression in Saccharomyces cerevisiae by a SIN3-LexA fusion protein.
abstract: The yeast SIN3 gene (also known as SDI1, UME4, RPD1, and GAM2) has been identified as a transcriptional regulator. Previous work has led to the suggestion that SIN3 regulates transcription via interactions with DNA-binding proteins. Although the SIN3 protein is located in the nucleus, it does not bind directly to DNA in vitro. We have expressed a LexA-SIN3 fusion protein in Saccharomyces cerevisiae and show that this fusion protein represses transcription from heterologous promoters that contain lexA operators. The predicted amino acid sequence of the SIN3 protein contains four copies of a paired amphipathic helix (PAH) motif, similar to motifs found in HLH (helix-loop-helix) and TPR (tetratricopeptide repeat) proteins, and these motifs are proposed to be involved in protein-protein interactions. We have conducted a deletion analysis of the SIN3 gene and show that the PAH motifs are required for SIN3 activity. Additionally, the C-terminal region of the SIN3 protein is sufficient for repression activity in a LexA-SIN3 fusion, and deletion of a PAH motif in this region inactivates this repression activity. A model is presented in which SIN3 recognizes specific DNA-binding proteins in vivo in order to repress transcription.
authors.affiliation: Department of Cellular, Viral, and Molecular Biology, University of Utah Medical Center, Salt Lake City 84132.
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.forename: D J
authors.initials: DJ
authors.lastname: Stillman
mesh_terms: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins / Q000235:genetics*; D018797:Cell Cycle Proteins; D004252:DNA Mutational Analysis; D015252:Deoxyribonucleases, Type II Site-Specific / Q000096:biosynthesis / Q000235:genetics; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D006023:Glycoproteins; D006655:Histone Deacetylases; D047908:Intracellular Signaling Peptides and Proteins; D011401:Promoter Regions, Genetic / Q000235:genetics; D011487:Protein Conformation; D011494:Protein Kinases / Q000096:biosynthesis / Q000235:genetics; D017346:Protein Serine-Threonine Kinases; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D012097:Repressor Proteins / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D012697:Serine Endopeptidases; D013172:Spores, Fungal / Q000502:physiology; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000187:drug effects; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics; D000099160:LexA Repressor Protein
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D018797:Cell Cycle Proteins; D015252:Deoxyribonucleases, Type II Site-Specific; D005656:Fungal Proteins; D006023:Glycoproteins; D006655:Histone Deacetylases; D047908:Intracellular Signaling Peptides and Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D012697:Serine Endopeptidases; D014157:Transcription Factors; D001616:beta-Galactosidase; D000099160:LexA Repressor Protein; C071731:SIN3 protein, S cerevisiae; C489277:STE6 protein, S cerevisiae; C064979:IME2 protein, S cerevisiae; C037725:SCEI protein, S cerevisiae