UV or ionizing radiation) is necessary for p53 activation of the p21(Cip1/WAF1) promoter.     ///    "In contrast, the R273H/P309S-mutated p53 protein in SW480 constitutively activates p21(Cip1/WAF1) in the absence of stress through an unknown mechanism. "    ///    "Analysis of p21(Cip1/WAF1) expression and in vivo footprinting by ligation-mediated PCR (LMPCR) showed that, in wild-type LoVo cells, an exposure to cellular stress (e.g. "