title: Subtelomeric repeat amplification is associated with growth at elevated temperature in yku70 mutants of Saccharomyces cerevisiae.
abstract: Inactivation of the Saccharomyces cerevisiae gene YKU70 (HDF1), which encodes one subunit of the Ku heterodimer, confers a DNA double-strand break repair defect, shortening of and structural alterations in the telomeres, and a severe growth defect at 37 degrees. To elucidate the basis of the temperature sensitivity, we analyzed subclones derived from rare yku70 mutant cells that formed a colony when plated at elevated temperature. In all these temperature-resistant subclones, but not in cell populations shifted to 37 degrees, we observed substantial amplification and redistribution of subtelomeric Y' element DNA. Amplification of Y' elements and adjacent telomeric sequences has been described as an alternative pathway for chromosome end stabilization that is used by postsenescence survivors of mutants deficient for the telomerase pathway. Our data suggest that the combination of Ku deficiency and elevated temperature induces a potentially lethal alteration of telomere structure or function. Both in yku70 mutants and in wild type, incubation at 37 degrees results in a slight reduction of the mean length of terminal restriction fragments, but not in a significant loss of telomeric (C(1-3)A/TG(1-3))(n) sequences. We propose that the absence of Ku, which is known to bind to telomeres, affects the telomeric chromatin so that its chromosome end-defining function is lost at 37 degrees.
authors.affiliation: GSF-Forschungszentrum, Institut für Strahlenbiologie, 85758 Oberschleissheim, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Fellerhoff
authors.forename: F
authors.initials: F
authors.lastname: Eckardt-Schupp
authors.forename: A A
authors.initials: AA
authors.lastname: Friedl
mesh_terms: D015825:Chromosomes, Fungal; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D005784:Gene Amplification; D047908:Intracellular Signaling Peptides and Proteins; D016296:Mutagenesis; D017346:Protein Serine-Threonine Kinases; D051721:Rad52 DNA Repair and Recombination Protein; D012091:Repetitive Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D013172:Spores, Fungal; D016615:Telomere; D013696:Temperature
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; C497197:RAD52 protein, S cerevisiae; D051721:Rad52 DNA Repair and Recombination Protein; D029701:Saccharomyces cerevisiae Proteins; C520769:YKU70 protein, S cerevisiae; C081647:high affinity DNA-binding factor, S cerevisiae; D017346:Protein Serine-Threonine Kinases; C513623:TEL1 protein, S cerevisiae