title: p19(Arf) is required for the cellular response to chronic DNA damage.
abstract: The p53 tumor suppressor is a stress sensor, driving cell cycle arrest or apoptosis in response to DNA damage or oncogenic signals. p53 activation by oncogenic signals relies on the p19(Arf) tumor suppressor, while p53 activation downstream of acute DNA damage is reported to be p19(Arf)-independent. Accordingly, p19(Arf)-deficient mouse embryo fibroblasts (MEFs) arrest in response to acute DNA damage. However, p19(Arf) is required for replicative senescence, a condition associated with an activated DNA damage response, as p19(Arf)-/- MEFs do not senesce after serial passage. A possible explanation for these seemingly disparate roles for p19(Arf) is that acute and chronic DNA damage responses are mechanistically distinct. Replicative senescence may result from chronic, low-dose DNA damage responses in which p19(Arf) has a specific role. We therefore examined the role of p19(Arf) in cellular responses to chronic, low-dose DNA-damaging agent treatment by maintaining MEFs in low oxygen and administering 0.5 G y γ-irradiation daily or 150 μM hydroxyurea, a replication stress inducer. In contrast to their response to acute DNA damage, p19(Arf)-/- MEFs exposed to chronic DNA damage do not senesce, revealing a selective role for p19(Arf) in senescence upon low-level, chronic DNA damage. We show further that p53 pathway activation in p19(Arf)-/- MEFs exposed to chronic DNA damage is attenuated relative to wild-type MEFs, suggesting a role for p19(Arf) in fine-tuning p53 activity. However, combined Nutlin3a and chronic DNA-damaging agent treatment is insufficient to promote senescence in p19(Arf)-/- MEFs, suggesting that the role of p19(Arf) in the chronic DNA damage response may be partially p53-independent. These data suggest the importance of p19(Arf) for the cellular response to the low-level DNA damage incurred in culture or upon oncogene expression, providing new insight into how p19(Arf) serves as a tumor suppressor. Moreover, our study helps reconcile reports suggesting crucial roles for both p19(Arf) and DNA damage-signaling pathways in tumor suppression.
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: K T
authors.initials: KT
authors.lastname: Bieging-Rolett
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: T M
authors.initials: TM
authors.lastname: Johnson
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Brady
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: V G
authors.initials: VG
authors.lastname: Beaudry
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: N
authors.initials: N
authors.lastname: Pathak
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Han
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA.|Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: L D
authors.initials: LD
authors.lastname: Attardi
mesh_terms: D000818:Animals; D059447:Cell Cycle Checkpoints; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000502:physiology*; D004249:DNA Damage; D005720:Gamma Rays; D016147:Genes, Tumor Suppressor; D051379:Mice; D016159:Tumor Suppressor Protein p53 / Q000502:physiology
chemical_list: C417743:Cdkn2a protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D016159:Tumor Suppressor Protein p53