title: DNA damage-induced apoptosis requires the DNA-dependent protein kinase, and is mediated by the latent population of p53.
abstract: Mouse embryo fibroblasts (MEFs) expressing the adenovirus E1A protein undergo apoptosis upon exposure to ionizing radiation. We show here that immediately following gamma-irradiation, latent p53 formed a complex with the catalytic subunit of the DNA-dependent protein kinase (DNA-PK(CS)). The complex formation was DNase sensitive, suggesting that the proteins came together on the DNA, conceivably at strand breaks. This association was accompanied by phosphorylation of pre-existing, latent p53 at Ser18 (corresponding to Ser15 in human p53), which was not found in DNA-PK(CS)(-/-) cells. Most significantly, DNA damage-induced apoptosis was abolished in both DNA-PK(CS)(-/-) and p53(-/-) cells. In addition, blocking synthesis of inducible p53 by cycloheximide did not abrogate apoptosis, suggesting that the latent population of p53 is sufficient for executing the apoptotic program. Finally, E1A-expressing MEFs from a p53 "knock-in" mouse where Ser18 was mutated to an alanine had an attenuated apoptotic response, indicating that phosphorylation of this site by DNA-PK is a contributing factor for apoptosis.
authors.affiliation: Cancer Biology Research Group and Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Woo
authors.forename: Melissa T
authors.initials: MT
authors.lastname: Jack
authors.forename: Yang
authors.initials: Y
authors.lastname: Xu
authors.forename: Sandeep
authors.initials: S
authors.lastname: Burma
authors.forename: David J
authors.initials: DJ
authors.lastname: Chen
authors.forename: Patrick W K
authors.initials: PW
authors.lastname: Lee
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002458:Cell Fractionation; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004249:DNA Damage; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D005720:Gamma Rays; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009687:Nuclear Proteins; D017354:Point Mutation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011500:Protein Synthesis Inhibitors; D016159:Tumor Suppressor Protein p53; D003513:Cycloheximide; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; C497264:Prkdc protein, mouse; D017346:Protein Serine-Threonine Kinases