Questioning the role of checkpoint kinase 2 in the p53 DNA damage response.
Cdc25C and p53 have been reported to be physiological targets of checkpoint kinase 2 (Chk2). Surprisingly, although Chk2 purified from DNA damage sustaining cells has dramatically increased ability to phosphorylate Cdc25C when compared with untreated cells, its ability to phosphorylate p53 is weak before treatment, and there is no increase in its activity toward p53 after DNA damage by gamma irradiation or the radiomimetic agent neocarzinostatin. Furthermore, introduction of Chk2 short interfering RNA into three different human tumor cell lines leads to marked reduction of Chk2 protein, but p53 is still stabilized and active after DNA damage. The results with Chk1 short interfering RNA indicate as well that Chk1 does not play a role in human p53 stabilization after DNA damage. Thus, Chk1 and Chk2 are unlikely to be regulators of p53 in at least some human tumor cells. We discuss our results in the context of previous findings demonstrating a requirement for Chk2 in p53 stabilization and activity.
Ahn
Jinwoo
J
Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
Urist
Marshall
M
Prives
Carol
C
D018797:Cell Cycle Proteins / Q000378:metabolism; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D003110:Colonic Neoplasms; D004249:DNA Damage / Q000502:physiology*; D005720:Gamma Rays; D006801:Humans; D019384:Nucleic Acid Synthesis Inhibitors; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D009353:Zinostatin; D020687:cdc25 Phosphatases / Q000378:metabolism
D018797:Cell Cycle Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D016159:Tumor Suppressor Protein p53; D009353:Zinostatin; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C000605867:CHEK1 protein, human; C578634:CHEK2 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases