title: A RAP1-interacting protein involved in transcriptional silencing and telomere length regulation.
abstract: The yeast RAP1 protein is a sequence-specific DNA-binding protein that functions as both a repressor and an activator of transcription. RAP1 is also involved in the regulation of telomere structure, where its binding sites are found within the terminal poly(C1-3A) sequences. Previous studies have indicated that the regulatory function of RAP1 is determined by the context of its binding site and, presumably, its interactions with other factors. Using the two-hybrid system, a genetic screen for the identification of protein-protein interactions, we have isolated a gene encoding a RAP1-interacting factor (RIF1). Strains carrying gene disruptions of RIF1 grow normally but are defective in transcriptional silencing and telomere length regulation, two phenotypes strikingly similar to those of silencing-defective rap1s mutants. Furthermore, hybrid proteins containing rap1s missense mutations are defective in an interaction with RIF1 in the two-hybrid system. Taken together, these data support the idea that the rap1s phenotypes are attributable to a failure to recruit RIF1 to silencers and telomeres and suggest that RIF1 is a cofactor or mediator for RAP1 in the establishment of a repressed chromatin state at these loci. By use of the two-hybrid system, we have isolated a mutation in RIF1 that partially restores the interaction with rap1s mutant proteins.
authors.affiliation: Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
authors.forename: C F
authors.initials: CF
authors.lastname: Hardy
authors.forename: L
authors.initials: L
authors.lastname: Sussel
authors.forename: D
authors.initials: D
authors.lastname: Shore
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D016615:Telomere / Q000378:metabolism*; D034501:Telomere-Binding Proteins; D014158:Transcription, Genetic / Q000235:genetics*; D020668:rap GTP-Binding Proteins
chemical_list: D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D034501:Telomere-Binding Proteins; C074461:RIF1 protein, S cerevisiae; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins