p53 accumulates but is functionally impaired when DNA synthesis is blocked.
p53 is required for the induction of a G(1) and/or G(2) irreversible arrest after gamma irradiation (IR), whereas blocked DNA replication causes a p53-independent S-phase arrest. We have examined the response to p53 when DNA synthesis is blocked by hydroxyurea (HU) or aphidicolin or when DNA is damaged by gamma IR. Similarly to gamma IR, blocked DNA synthesis induces high levels of phosphorylated nuclear p53. Surprisingly, several (but not all) p53 transcriptional targets that are rapidly induced by gamma IR are weakly or not induced when DNA replication is blocked. Moreover, the p53 response to gamma IR is inhibited by pretreatment of cells with HU or aphidicolin, suggesting that blocked DNA replication prevents p53 from being fully active as a transcription factor. HU-induced stabilization of p53 neither requires functional ATM (ataxia telangiectasia mutated), nor interferes with the gamma IR-dependent activation of the ATM kinase. Thus, stalled replication forks activate kinases that modify and stabilize p53, yet act downstream of ATM to impair p53 transcriptional activity. The ramifications of this novel regulation of p53 are discussed.
Gottifredi
V
V
Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
Shieh
S
S
Taya
Y
Y
Prives
C
C
D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000502:physiology* / Q000528:radiation effects; D018797:Cell Cycle Proteins; D015179:Colorectal Neoplasms; D004261:DNA Replication / Q000502:physiology* / Q000528:radiation effects; D004268:DNA-Binding Proteins; D016193:G1 Phase; D016195:G2 Phase; D005720:Gamma Rays; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases