title: DNA-end capping by the budding yeast transcription factor and subtelomeric binding protein Tbf1.
abstract: Telomere repeats in budding yeast are maintained at a constant average length and protected ('capped'), in part, by mechanisms involving the TG(1-3) repeat-binding protein Rap1. However, metazoan telomere repeats (T(2)AG(3)) can be maintained in yeast through a Rap1-independent mechanism. Here, we examine the dynamics of capping and telomere formation at an induced DNA double-strand break flanked by varying lengths of T(2)AG(3) repeats. We show that a 60-bp T(2)AG(3) repeat array induces a transient G2/M checkpoint arrest, but is rapidly elongated by telomerase to generate a stable T(2)AG(3)/TG(1-3) hybrid telomere. In contrast, a 230-bp T(2)AG(3) array induces neither G2/M arrest nor telomerase elongation. This capped state requires the T(2)AG(3)-binding protein Tbf1, but is independent of two Tbf1-interacting factors, Vid22 and Ygr071c. Arrays of binding sites for three other subtelomeric or Myb/SANT domain-containing proteins fail to display a similar end-protection effect, indicating that Tbf1 capping is an evolved function. Unexpectedly, we observed strong telomerase association with non-telomeric ends, whose elongation is blocked by a Mec1-dependent mechanism, apparently acting at the level of Cdc13 binding.
authors.affiliation: Department of Molecular Biology, NCCR Program Frontiers in Genetics, University of Geneva, Geneva, Switzerland.
authors.forename: Virginie
authors.initials: V
authors.lastname: Ribaud
authors.forename: Cyril
authors.initials: C
authors.lastname: Ribeyre
authors.forename: Pascal
authors.initials: P
authors.lastname: Damay
authors.forename: David
authors.initials: D
authors.lastname: Shore
mesh_terms: D001665:Binding Sites; D004271:DNA, Fungal / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018900:Dinucleotide Repeats; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D000089804:Shelterin Complex; D016615:Telomere / Q000378:metabolism*; D034501:Telomere-Binding Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C452219:Cdc13 protein, S cerevisiae; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; C440829:RAP1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000089804:Shelterin Complex; C079376:TBF1 protein, S cerevisiae; D034501:Telomere-Binding Proteins; D014157:Transcription Factors