title: Senescence induced by altered telomere state, not telomere loss.
abstract: Primary human cells in culture invariably stop dividing and enter a state of growth arrest called replicative senescence. This transition is induced by programmed telomere shortening, but the underlying mechanisms are unclear. Here, we report that overexpression of TRF2, a telomeric DNA binding protein, increased the rate of telomere shortening in primary cells without accelerating senescence. TRF2 reduced the senescence setpoint, defined as telomere length at senescence, from 7 to 4 kilobases. TRF2 protected critically short telomeres from fusion and repressed chromosome-end fusions in presenescent cultures, which explains the ability of TRF2 to delay senescence. Thus, replicative senescence is induced by a change in the protected status of shortened telomeres rather than by a complete loss of telomeric DNA.
authors.affiliation: Laboratory for Cell Biology and Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
authors.forename: Jan
authors.initials: J
authors.lastname: Karlseder
authors.forename: Agata
authors.initials: A
authors.lastname: Smogorzewska
authors.forename: Titia
authors.initials: T
authors.lastname: de Lange
mesh_terms: D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000378:metabolism; D002455:Cell Division; D002460:Cell Line; D002478:Cells, Cultured; D016922:Cellular Senescence; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000378:metabolism; D050725:Papillomavirus E7 Proteins; D012097:Repressor Proteins; D016160:Retinoblastoma Protein / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D016615:Telomere / Q000378:metabolism / Q000502:physiology*; D035341:Telomeric Repeat Binding Protein 2; D014170:Transformation, Genetic; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D000952:Antigens, Polyomavirus Transforming; D004268:DNA-Binding Proteins; C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012097:Repressor Proteins; D016160:Retinoblastoma Protein; D035341:Telomeric Repeat Binding Protein 2; D016159:Tumor Suppressor Protein p53; C059731:oncogene protein E7, Human papillomavirus type 16; D004247:DNA