title: RAP1 and telomere structure regulate telomere position effects in Saccharomyces cerevisiae.
abstract: To investigate the role of the yeast telomere-, silencing-, and UAS-binding protein RAP1 in telomere position effects, we have characterized two sets of mutant cells: (1) a set of rap1 alleles (termed the rap1t alleles) that produce truncated RAP1 proteins missing the carboxy-terminal 144-165 amino acids; and (2) null mutants of the RIF1 gene, encoding a protein capable of interaction with the carboxyl terminus of RAP1. The data presented here indicate that loss of the carboxyl terminus of RAP1 abolishes position effects at yeast telomeres and diminishes silencing at the HML locus. Elimination of position effects in these cells is associated with increased accessibility to the Escherichia coli dam methylase in vivo. Thus, the carboxy-terminal domain of RAP1 is required for telomere position effects. In contrast, rif1 deletion alleles increase the frequency of repressed cells. Using the rap1t alleles to generate wild-type cells differing only in telomere tract lengths, we also show that telomere position effects are highly sensitive to changes in the size (or structure) of the telomeric tract. Longer poly(G1-3T) tracts can increase the frequency of transcriptional repression at the telomere, suggesting that telomeric poly(G1-3T) tracts play an active role in the formation or stability of subtelomeric transcriptional states.
authors.affiliation: Molecular Biology Program, Sloan-Kettering Institute, New York, New York.
authors.forename: G
authors.initials: G
authors.lastname: Kyrion
authors.forename: K
authors.initials: K
authors.lastname: Liu
authors.forename: C
authors.initials: C
authors.lastname: Liu
authors.forename: A J
authors.initials: AJ
authors.lastname: Lustig
mesh_terms: D002843:Chromatin / Q000737:chemistry; D015825:Chromosomes, Fungal; D004271:DNA, Fungal / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D004926:Escherichia coli / Q000201:enzymology; D029968:Escherichia coli Proteins; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000502:physiology; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal / Q000235:genetics*; D008780:Methyltransferases / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D013489:Suppression, Genetic; D016615:Telomere / Q000737:chemistry*; D034501:Telomere-Binding Proteins; D014158:Transcription, Genetic; D020668:rap GTP-Binding Proteins
chemical_list: D002843:Chromatin; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D005656:Fungal Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D034501:Telomere-Binding Proteins; C074461:RIF1 protein, S cerevisiae; D008780:Methyltransferases; C058693:Dam methyltransferase; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); C499294:dam protein, E coli; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins