title: Sudden telomere lengthening triggers a Rad53-dependent checkpoint in Saccharomyces cerevisiae.
abstract: Telomeres are specialized functional complexes that ensure chromosome stability by protecting chromosome ends from fusions and degradation and avoiding chromosomal termini from being sensed as DNA breaks. Budding yeast Tel1 is required both for telomere metabolism and for a Rad53-dependent checkpoint responding to unprocessed double-strand breaks. We show that overexpression of a GAL1-TEL1 fusion causes transient telomere lengthening and activation of a Rad53-dependent G2/M checkpoint in cells whose telomeres are short due to the lack of either Tel1 or Yku70. Sudden telomere elongation and checkpoint-mediated cell cycle arrest are also triggered in wild-type cells by overproducing a protein fusion between the telomeric binding protein Cdc13 and the telomerase-associated protein Est1. Checkpoint activation by GAL1-TEL1 requires ongoing telomere elongation. In fact, it is turned off concomitantly with telomeres reaching a new stable length and is partially suppressed by deletion of the telomerase EST2 gene. Moreover, both telomere length rebalancing and checkpoint inactivation under galactose-induced conditions are accelerated by high levels of either the Sae2 protein, involved in double-strand breaks processing, or the negative telomere length regulator Rif2. These data suggest that sudden telomere lengthening elicits a checkpoint response that inhibits the G2/M transition.
authors.affiliation: Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, 20126 Milan, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Viscardi
authors.forename: Enrico
authors.initials: E
authors.lastname: Baroni
authors.forename: Michele
authors.initials: M
authors.lastname: Romano
authors.forename: Giovanna
authors.initials: G
authors.lastname: Lucchini
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Longhese
mesh_terms: D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins; D064447:Checkpoint Kinase 2; D004249:DNA Damage / Q000502:physiology; D004720:Endonucleases; D005656:Fungal Proteins / Q000378:metabolism*; D018816:Genes, cdc; D047908:Intracellular Signaling Peptides and Proteins; D009154:Mutation / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D019098:Telomerase / Q000378:metabolism; D016615:Telomere / Q000201:enzymology / Q000235:genetics*; D034501:Telomere-Binding Proteins / Q000378:metabolism
chemical_list: C452219:Cdc13 protein, S cerevisiae; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011993:Recombinant Fusion Proteins; C107849:SAE2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D034501:Telomere-Binding Proteins; D064447:Checkpoint Kinase 2; D017346:Protein Serine-Threonine Kinases; C513623:TEL1 protein, S cerevisiae; C067022:RAD53 protein, S cerevisiae; C099024:EST1 protein, S cerevisiae; D019098:Telomerase; D004720:Endonucleases