title: Senescence of human fibroblasts after psoralen photoactivation is mediated by ATR kinase and persistent DNA damage foci at telomeres.
abstract: Cellular senescence is a phenotype that is likely linked with aging. Recent concepts view different forms of senescence as permanently maintained DNA damage responses partially characterized by the presence of senescence-associated DNA damage foci at dysfunctional telomeres. Irradiation of primary human dermal fibroblasts with the photosensitizer 8-methoxypsoralen and ultraviolet A radiation (PUVA) induces senescence. In the present study, we demonstrate that senescence after PUVA depends on DNA interstrand cross-link (ICL) formation that activates ATR kinase. ATR is necessary for the manifestation and maintenance of the senescent phenotype, because depletion of ATR expression before PUVA prevents induction of senescence, and reduction of ATR expression in PUVA-senesced fibroblasts releases cells from growth arrest. We find an ATR-dependent phosphorylation of the histone H2AX (gamma-H2AX). After PUVA, ATR and gamma-H2AX colocalize in multiple nuclear foci. After several days, only few predominantly telomere-localized foci persist and telomeric DNA can be coimmunoprecipitated with ATR from PUVA-senesced fibroblasts. We thus identify ATR as a novel mediator of telomere-dependent senescence in response to ICL induced by photoactivated psoralens.
authors.affiliation: Department of Dermatology, University of Cologne, 50924 Cologne, Germany.
authors.forename: Miriam Grosse
authors.initials: MG
authors.lastname: Hovest
authors.forename: Nicole
authors.initials: N
authors.lastname: Brüggenolte
authors.forename: Kijawasch Shah
authors.initials: KS
authors.lastname: Hosseini
authors.forename: Thomas
authors.initials: T
authors.lastname: Krieg
authors.forename: Gernot
authors.initials: G
authors.lastname: Herrmann
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D016922:Cellular Senescence / Q000235:genetics / Q000502:physiology*; D003432:Cross-Linking Reagents / Q000633:toxicity*; D004247:DNA / Q000187:drug effects / Q000528:radiation effects; D004249:DNA Damage; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects; D006657:Histones / Q000032:analysis / Q000378:metabolism; D006801:Humans; D008730:Methoxsalen / Q000633:toxicity*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D016615:Telomere / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D018797:Cell Cycle Proteins; D003432:Cross-Linking Reagents; C468783:H2AX protein, human; D006657:Histones; D034741:RNA, Small Interfering; D004247:DNA; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D008730:Methoxsalen