title: Mutation of yeast Ku genes disrupts the subnuclear organization of telomeres.
abstract: The mammalian Ku70 and Ku86 proteins form a heterodimer that binds to the ends of double-stranded DNA in vitro and is required for repair of radiation-induced strand breaks and V(D)J recombination [1,2]. Deletion of the Saccharomyces cerevisiae genes HDF1 and HDF2--encoding yKu70p and yKu80p, respectively--enhances radiation sensitivity in a rad52 background [3,4]. In addition to repair defects, the length of the TG-rich repeat on yeast telomere ends shortens dramatically [5,6]. We have shown previously that in yeast interphase nuclei, telomeres are clustered in a limited number of foci near the nuclear periphery [7], but the elements that mediate this localization remained unknown. We report here that deletion of the genes encoding yKu70p or its partner yKu80p altered the positioning of telomeric DNA in the yeast nucleus. These are the first mutants shown to affect the subnuclear localization of telomeres. Strains deficient for either yKu70p or yKu80p lost telomeric silencing, although they maintained repression at the silent mating-type loci. In addition, the telomere-associated silencing factors Sir3p and Sir4p and the TG-repeat-binding protein Rap1p lost their punctate pattern of staining and became dispersed throughout the nucleoplasm. Our results implicate the yeast Ku proteins directly in aspects of telomere organization, which in turn affects the repression of telomere-proximal genes.
authors.affiliation: Swiss Institute for Experimental Cancer Research, Chemin des Boveresses, Epalinges/Lausanne, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Laroche
authors.forename: S G
authors.initials: SG
authors.lastname: Martin
authors.forename: M
authors.initials: M
authors.lastname: Gotta
authors.forename: H C
authors.initials: HC
authors.lastname: Gorham
authors.forename: F E
authors.initials: FE
authors.lastname: Pryde
authors.forename: E J
authors.initials: EJ
authors.lastname: Louis
authors.forename: S M
authors.initials: SM
authors.lastname: Gasser
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear; D002467:Cell Nucleus / Q000378:metabolism; D004265:DNA Helicases; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D000072200:Ku Autoantigen; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D000089804:Shelterin Complex; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D016615:Telomere / Q000235:genetics / Q000378:metabolism; D034501:Telomere-Binding Proteins; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009687:Nuclear Proteins; C440829:RAP1 protein, S cerevisiae; C084122:SIR3 protein, S cerevisiae; C061573:SIR4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000089804:Shelterin Complex; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D034501:Telomere-Binding Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C520769:YKU70 protein, S cerevisiae; C520770:YKU80 protein, S cerevisiae; C081647:high affinity DNA-binding factor, S cerevisiae; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen