Effects of Protein Kinase Inhibitors on the Accumulation Kinetics of p53 Protein in Normal Human Embryo Cells following X-irradiation

DNA-damaging agents induce phosphorylation of the p53 protein, resulting in its accumulation in the nucleus. To clarify the signal transduction pathway(s) involved in p53 protein accumulation in normal human embryo cells following X-irradiation, the effects of three protein kinase inhibitors were examined. Quercetin, an inhibitor of heat-shock response, dose dependently suppressed the p53 accumulation induced by X-rays at more than 100 microM. No suppression, however, was observed with calphostin-C, a specific inhibitor of protein kinase C, in the range of 0.05 to 0.25 microM. Wortmannin was the most potent inhibitor of p53 accumulation. Its suppressive effect appears within a few minutes of pretreatment with a dose of 25 microM, but posttreatment was less effective. Our findings suggest that PKC is not involved in X-ray-induced p53 accumulation in normal human embryo cells and that a wortmannin-sensitive pathway acts as a sensor of DNA damage.