title: Sister telomeres rendered dysfunctional by persistent cohesion are fused by NHEJ.
abstract: Telomeres protect chromosome ends from being viewed as double-strand breaks and from eliciting a DNA damage response. Deprotection of chromosome ends occurs when telomeres become critically short because of replicative attrition or inhibition of TRF2. In this study, we report a novel form of deprotection that occurs exclusively after DNA replication in S/G2 phase of the cell cycle. In cells deficient in the telomeric poly(adenosine diphosphate ribose) polymerase tankyrase 1, sister telomere resolution is blocked. Unexpectedly, cohered sister telomeres become deprotected and are inappropriately fused. In contrast to telomeres rendered dysfunctional by TRF2, which engage in chromatid fusions predominantly between chromatids from different chromosomes (Bailey, S.M., M.N. Cornforth, A. Kurimasa, D.J. Chen, and E.H. Goodwin. 2001. Science. 293:2462-2465; Smogorzewska, A., J. Karlseder, H. Holtgreve-Grez, A. Jauch, and T. de Lange. 2002. Curr. Biol. 12:1635-1644), telomeres rendered dysfunctional by tankyrase 1 engage in chromatid fusions almost exclusively between sister chromatids. We show that cohered sister telomeres are fused by DNA ligase IV-mediated nonhomologous end joining. These results demonstrate that the timely removal of sister telomere cohesion is essential for the formation of a protective structure at chromosome ends after DNA replication in S/G2 phase of the cell cycle.
authors.affiliation: Molecular Pathogenesis Program, The Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Hsiao
authors.forename: Susan
authors.initials: S
authors.lastname: Smith
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D004249:DNA Damage; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism; D004261:DNA Replication; D006801:Humans; D038501:Tankyrases / Q000378:metabolism; D016615:Telomere / Q000378:metabolism*
chemical_list: D000072481:DNA Ligase ATP; D011088:DNA Ligases; D038501:Tankyrases; C000607893:LIG4 protein, human; C418109:TNKS protein, human