Activation of p21WAF1/Cip1 expression by a temperature-sensitive mutant of human p53 does not lead to apoptosis.

The cyclin-dependent kinase inhibitor p21WAF1/Cip1 (p21) inhibits cellular proliferation and has been implicated in p53-dependent apoptosis. In this study, we examined the regulation of p21 in the K562 erythroleukemia cell line using a human temperature-sensitive mutant of p53, 143Ala. We showed that 143Ala at the permissive temperature (32 degrees C) activated the expression of p21. Stable cell lines expressing 143Ala or other p53 mutants were established. We then examined whether elevation of p21 promotes apoptosis and sensitized cells to radiation-induced apoptosis. Our results showed that p21 elevation did not promote or sensitize K562 cells to apoptosis.