title: Wild-type p53-induced phosphatase 1 (Wip1) forestalls cellular premature senescence at physiological oxygen levels by regulating DNA damage response signaling during DNA replication.
abstract: Wip1 (protein phosphatase Mg(2+)/Mn(2+)-dependent 1D, Ppm1d) is a nuclear serine/threonine protein phosphatase that is induced by p53 following the activation of DNA damage response (DDR) signaling. Ppm1d(-/-) mouse embryonic fibroblasts (MEFs) exhibit premature senescence under conventional culture conditions; however, little is known regarding the role of Wip1 in regulating cellular senescence. In this study, we found that even at a representative physiological concentration of 3% O2, Ppm1d(-/-) MEFs underwent premature cellular senescence that depended on the functional activation of p53. Interestingly, Ppm1d(-/-) MEFs showed increased H2AX phosphorylation levels without increased levels of reactive oxygen species (ROS) or DNA base damage compared with wild-type (Wt) MEFs, suggesting a decreased threshold for DDR activation or sustained DDR activation during recovery. Notably, the increased H2AX phosphorylation levels observed in Ppm1d(-/-) MEFs were primarily associated with S-phase cells and predominantly dependent on the activation of ATM. Moreover, these same phenotypes were observed when Wt and Ppm1d(-/-) MEFs were either transiently or chronically exposed to low levels of agents that induce replication-mediated double-stranded breaks. These findings suggest that Wip1 prevents the induction of cellular senescence at physiological oxygen levels by attenuating DDR signaling in response to endogenous double-stranded breaks that form during DNA replication.
authors.affiliation: Laboratory of Cell Biology; National Cancer Institute; National Institutes of Health; Bethesda, MD USA.
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Sakai
authors.affiliation: Laboratory of Cell Biology; National Cancer Institute; National Institutes of Health; Bethesda, MD USA.
authors.forename: Hidetsugu
authors.initials: H
authors.lastname: Fujigaki
authors.affiliation: Laboratory of Cell Biology; National Cancer Institute; National Institutes of Health; Bethesda, MD USA.
authors.forename: Sharlyn J
authors.initials: SJ
authors.lastname: Mazur
authors.affiliation: Laboratory of Cell Biology; National Cancer Institute; National Institutes of Health; Bethesda, MD USA.
authors.forename: Ettore
authors.initials: E
authors.lastname: Appella
mesh_terms: D019588:Aging, Premature / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D004249:DNA Damage / Q000502:physiology*; D004261:DNA Replication / Q000502:physiology*; D006657:Histones / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010100:Oxygen / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D000071636:Protein Phosphatase 2C; D017382:Reactive Oxygen Species / Q000378:metabolism; D016196:S Phase / Q000502:physiology; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D006657:Histones; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; D010749:Phosphoprotein Phosphatases; C000607468:Ppm1d protein, mouse; D000071636:Protein Phosphatase 2C; D010100:Oxygen
keywords: ATM; DNA damage response; Wip1; camptothecin; cellular senescence; p53