title: Genetic analysis of Rap1p/Sir3p interactions in telomeric and HML silencing in Saccharomyces cerevisiae.
abstract: We have identified three SIR3 suppressors of the telomeric silencing defects conferred by missense mutations within the Rap1p C-terminal tail domain (aa 800-827). Each SIR3 suppressor was also capable of suppressing a rap1 allele (rap1-21), which deletes the 28 aa C-terminal tail domain, but none of the suppressors restored telometric silencing to a 165 amino acid truncation allele. These data suggest a Rap1p site for Sir3p association between the two truncation points (aa 664-799). In SIR3 suppressor strains lacking the Rap1p C-terminal tail domain, the presence of a second intragenic mutation within the rap1s domain (aa 727-747), enhanced silencing 30-300-fold. These data suggest a competition between Sir3p and factors that interfere with silencing for association in the rap1s domain. Rap1-21 strains containing both wild-type Sir3p and either of the Sir3 suppressor proteins displayed a 400-4000-fold increase in telomeric silencing over rap1-21 strains carrying either Sir3p suppressor in the absence of wild-type Sir3p. We propose that this telomere-specific synergism is mediated in part through stabilization of Rap1p/Sir3p telometric complexes by Sir3p-Sir3p interactions.
authors.affiliation: Cornell University, Graduate School of Medical Sciences, New York, New York 10021, USA.
authors.forename: C
authors.initials: C
authors.lastname: Liu
authors.forename: A J
authors.initials: AJ
authors.lastname: Lustig
mesh_terms: D000483:Alleles; D001665:Binding Sites; D015825:Chromosomes, Fungal; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005800:Genes, Fungal; D005838:Genotype; D000072235:Mating Factor; D010452:Peptide Biosynthesis; D010455:Peptides / Q000235:genetics*; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D013489:Suppression, Genetic; D016615:Telomere; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic; D020668:rap GTP-Binding Proteins
chemical_list: D005656:Fungal Proteins; D010455:Peptides; C084122:SIR3 protein, S cerevisiae; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators; D014157:Transcription Factors; D000072235:Mating Factor; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins