Figure 6.

Phosphorylation of serine 46 on p53 is necessary for UVB-induced apoptosis. Independent clones of n-tert keratinocytes transduced with retroviruses expressing the native p53 gene (p53 WT), a p53 gene containing an inactivating mutation resulting from a substitution of an alanine for the serine at amino acid 46 (p53 S46A), a p53 gene containing an activating mutation resulting from a substitution of an aspartic acid for the serine at amino acid 46 (p53 S46D), or containing only the vector sequences (BABE) were irradiated with the indicated dose of UVB. Six hours after irradiation, the keratinocytes were harvested and assayed for caspase-3–specific activity. Error bars indicate the SEM; the asterisks indicate significant differences between irradiated BABE clones and p53 clones keratinocyte specific activities (p < 0.01, t test). The graph represents data compiled from at least three independent clones of each cell type.