Figure 3.

p53 targets ΔNp63 (p40 or ΔNp63α) into a protein degradation pathway. (A) Down-regulation of the exogenous p40 protein is mediated by p53^WT expression. SaOs2 cells were coinfected with Ad-p40 (MOI = 1) and either Ad-p53^WT or Ad-p53¹⁷⁵ (MOI = 0–2) for 14 h, and p40 expression was examined at the RNA (5 μg) and protein (20 μg) level (from total cell lysates). Decreasing amounts of p40 were seen with p53^WT (lanes 2 and 3), but not mutant p53¹⁷⁵ (lanes 5 and 6). (B) p53 coexpression mediates degradation of endogenous ΔNp63α protein. 022 cells were infected with Ad-p53^WT (MOI = 1) or Ad-p53¹⁷⁵ (MOI = 1). ΔNp63α protein levels were determined at 0, 4, 8, and 24 h after infection with antibody to ΔNp63. Decreasing amounts of p40 were seen with p53^WT at 8 and 24 h but not with the p53¹⁷⁵.