title: Elevated transcription of the p53 gene in early S-phase leads to a rapid DNA-damage response during S-phase of the cell cycle.
abstract: p53 induces the transcription of genes that negatively regulate progression of the cell cycle in response to DNA damage or other cellular stressors, and thus participates in maintaining genome stability. Under stress conditions, p53 must be activated to prohibit the replication of cells containing damaged DNA. However, in normal, non-stressed cells, p53 activity must be inhibited. Previous studies have demonstrated that p53 transcription is activated before or during early S-phase in cells progressing from G(0)/G(1) into S-phase. Since this is not what would be predicted from a gene involved in growth arrest and apoptosis, in this study, we provide evidence that this induction occurs to provide sufficient p53 mRNA to ensure a rapid response to DNA damage before exiting S-phase. When comparing exponentially growing Swiss3T3 cells to those synchronized to enter S-phase simultaneously and treated with the DNA damaging agent camptothecin, we found that with cells in S-phase, p53 protein levels increased earlier, Bax and p21 transcription was activated earlier and to a greater extent and apoptosis occurred earlier and to a greater extent. These findings are consistent with p53 transcription being induced in S-phase to provide for a rapid DNA-damage response during S-phase of the cell cycle.
authors.affiliation: Department of Biological Sciences, University of South Carolina, Columbia, USA.
authors.forename: Paula
authors.initials: P
authors.lastname: Takahashi
authors.forename: Amanda
authors.initials: A
authors.lastname: Polson
authors.forename: David
authors.initials: D
authors.lastname: Reisman
mesh_terms: D000818:Animals; D017209:Apoptosis; D002166:Camptothecin / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D004249:DNA Damage; D015972:Gene Expression Regulation, Neoplastic; D016158:Genes, p53; D051379:Mice; D012333:RNA, Messenger / Q000378:metabolism; D016196:S Phase; D041701:Swiss 3T3 Cells; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C494827:Bax protein, mouse; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C505409:Casp3 protein, mouse; C505524:Casp7 protein, mouse; D053148:Caspase 3; D053179:Caspase 7; D002166:Camptothecin