title: DNA-dependent protein kinase and checkpoint kinase 2 synergistically activate a latent population of p53 upon DNA damage.
abstract: The role of the checkpoint kinase 2 (Chk2) as an upstream activator of p53 following DNA damage has been controversial. We have recently shown that Chk2 and the DNA-dependent protein kinase (DNA-PK) are both involved in DNA damage-induced apoptosis but not G(1) arrest in mouse embryo fibroblasts. Here we demonstrate that Chk2 is required to activate p53 in vitro as measured by its ability to bind its consensus DNA target sequence following DNA damage and is in fact the previously unidentified factor working synergistically with DNA-PK to activate p53. The gene mutated in ataxia telangiectasia is not involved in this p53 activation. Using wortmannin, serine 15 mutants of p53, DNA-PK null cells and Chk2 null cells, we demonstrate that DNA-PK and Chk2 act independently and sequentially on p53. Furthermore, the p53 target of these two kinases represents a latent (preexisting) population of p53. Taken together, the results from these studies are consistent with a model in which DNA damage causes an immediate and sequential modification of latent p53 by DNA-PK and Chk2, which under appropriate conditions can lead to apoptosis.
authors.affiliation: Cancer Biology Research Group and Department of Microbiology and Infectious Diseases, University of Calgary Health Sciences Centre Calgary, Alberta T2N 4N1, Canada. patrick.lee@dal.ca
authors.forename: Melissa T
authors.initials: MT
authors.lastname: Jack
authors.forename: Richard A
authors.initials: RA
authors.lastname: Woo
authors.forename: Noboru
authors.initials: N
authors.lastname: Motoyama
authors.forename: Hitoyuki
authors.initials: H
authors.lastname: Takai
authors.forename: Patrick W K
authors.initials: PW
authors.lastname: Lee
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D064007:Ataxia Telangiectasia Mutated Proteins; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002474:Cell-Free System; D064447:Checkpoint Kinase 2; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D016193:G1 Phase; D051379:Mice; D008954:Models, Biological; D009154:Mutation; D009687:Nuclear Proteins; D011485:Protein Binding; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D004247:DNA; D064447:Checkpoint Kinase 2; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; C578633:Chek2 protein, mouse; D051747:DNA-Activated Protein Kinase; C497264:Prkdc protein, mouse; D017346:Protein Serine-Threonine Kinases; D000077191:Wortmannin