p53-Dependent transcription determined by luciferase activity of a reporter plasmid (WWP/Luc) regulated by the physiologic p21 promoter.

(A) Activation of the p21 promoter (WWP/Luc) was evident in Z+ cells but not Z− cells transfected with p53W expression plasmid (500 ng) and WWP/Luc reporter plasmid (200 ng) (*P < .05). (B) A significant increase in p21 transcription (*P < .05) was evident in Z+ cells transfected with WWP/Luc (200 ng) and exposed to ultraviolet irradiation without cotransfection of p53. With cotransfection of expression plasmid for p53W (200 ng) and WWP/Luc (200 ng) into Z+ cells, increased transcription of the p21 promoter was evident both in the absence (UV−) and the presence (UV+) of UV irradiation (P < .05 for either UV− [**] or UV+ [***] relative to Z+ cells not transfected with p53 [*]). Synergy between p21 promoter activation by p53W transfection in Z+ cells with ultraviolet irradiation (UV+) versus control cells (UV−) was noted (P < .05 for Z+ cells transfected with WWP/Luc and p53 (UV+ [***]) versus (UV−[**]). Increased transcription of WWP/Luc with transfection of 500 ng of p53 expression plasmid (A, Z+/p53W) relative to 200 ng of p53 expression plasmid (B, Z+/p53W/UV−) was also evident in these experiments.