title: A region of the Sir1 protein dedicated to recognition of a silencer and required for interaction with the Orc1 protein in saccharomyces cerevisiae.
abstract: Silencing of the cryptic mating-type loci HMR and HML requires the recognition of DNA sequence elements called silencers by the Sir1p, one of four proteins dedicated to the assembly of silenced chromatin in Saccharomyces cerevisiae. The Sir1p is thought to recognize silencers indirectly through interactions with proteins that bind the silencer DNA directly, such as the origin recognition complex (ORC). Eight recessive alleles of SIR1 were discovered that encode mutant Sir1 proteins specifically defective in their ability to recognize the HMR-E silencer. The eight missense mutations all map within a 17-amino-acid segment of Sir1p, and this segment was also required for Sir1p's interaction with Orc1p. The mutant Sir1 proteins could function in silencing if tethered to a silencer directly through a heterologous DNA-binding domain. Thus the amino acids identified are required for Sir1 protein's recognition of the HMR-E silencer and interaction with Orc1p, but not for its ability to function in silencing per se. The approach used to find these mutations may be applicable to defining interaction surfaces on proteins involved in other processes that require the assembly of macromolecular complexes.
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Gardner
authors.forename: J
authors.initials: J
authors.lastname: Rine
authors.forename: C A
authors.initials: CA
authors.lastname: Fox
mesh_terms: D000483:Alleles; D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D005808:Genes, Recessive; D005809:Genes, Regulator; D020125:Mutation, Missense; D051738:Origin Recognition Complex; D010957:Plasmids; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; C497214:ORC1 protein, S cerevisiae; D051738:Origin Recognition Complex; D011993:Recombinant Fusion Proteins; C084121:SIR1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators; D014157:Transcription Factors