title: Telomere cap components influence the rate of senescence in telomerase-deficient yeast cells.
abstract: Cells lacking telomerase undergo senescence, a progressive reduction in cell division that involves a cell cycle delay and culminates in "crisis," a period when most cells become inviable. In telomerase-deficient Saccharomyces cerevisiae cells lacking components of the nonsense-mediated mRNA decay (NMD) pathway (Upf1,Upf2, or Upf3 proteins), senescence is delayed, with crisis occurring approximately 10 to 25 population doublings later than in Upf+ cells. Delayed senescence is seen in upfDelta cells lacking the telomerase holoenzyme components Est2p and TLC1 RNA, as well as in cells lacking the telomerase regulators Est1p and Est3p. The delay of senescence in upfDelta cells is not due to an increased rate of survivor formation. Rather, it is caused by alterations in the telomere cap, composed of Cdc13p, Stn1p, and Ten1p. In upfDelta mutants, STN1 and TEN1 levels are increased. Increasing the levels of Stn1p and Ten1p in Upf+ cells is sufficient to delay senescence. In addition, cdc13-2 mutants exhibit delayed senescence rates similar to those of upfDelta cells. Thus, changes in the telomere cap structure are sufficient to affect the rate of senescence in the absence of telomerase. Furthermore, the NMD pathway affects the rate of senescence in telomerase-deficient cells by altering the stoichiometry of telomere cap components.
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota, 6-170 MCB Building, 420 Washington Avenue SE, Minneapolis, MN 55455, USA.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Enomoto
authors.forename: Lynn
authors.initials: L
authors.lastname: Glowczewski
authors.forename: Jodi
authors.initials: J
authors.lastname: Lew-Smith
authors.forename: Judith G
authors.initials: JG
authors.lastname: Berman
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D001483:Base Sequence; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division; D018389:Codon, Nonsense / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins; D005800:Genes, Fungal; D008954:Models, Biological; D009154:Mutation; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D051721:Rad52 DNA Repair and Recombination Protein; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D019098:Telomerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D034501:Telomere-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C452219:Cdc13 protein, S cerevisiae; D018797:Cell Cycle Proteins; D018389:Codon, Nonsense; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C099938:MEC3 protein, S cerevisiae; C092470:NMD2 protein, S cerevisiae; D011506:Proteins; C497197:RAD52 protein, S cerevisiae; D012331:RNA, Fungal; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D051721:Rad52 DNA Repair and Recombination Protein; D029701:Saccharomyces cerevisiae Proteins; C428109:Stn1 protein, S cerevisiae; D034501:Telomere-Binding Proteins; D015534:Trans-Activators; C096360:UPF3 protein, S cerevisiae; C099024:EST1 protein, S cerevisiae; C491580:EST3 protein, S cerevisiae; D019098:Telomerase; C074151:NAM7 protein, S cerevisiae; D020365:RNA Helicases