Figure 4.

p53 mutants that bind to ΔNp63α mediate its degradation. (A) p53¹⁴³ or p53²⁷³ mediates degradation of ΔNp63α in transfected cells. 022 cells were transfected with either pCEP4-p53¹⁴³ (1 μg, 5 μg) or pCEP4-p53²⁷³ (1 μg, 5 μg). Total lysates were resolved by SDS/PAGE and probed with antibodies to p53, ΔNp63, or β-actin. (B) The half-life of p40 in the presence of overexpressed p53^WT or p53¹⁷⁵. Cells infected with adenoviruses for 18 h were labeled with 200 μCi/ml [³⁵S]methionine for 1 h. Labeled cells were then maintained in nonradioactive medium for 0 min, 60 min, 90 min, 120 min, 3 h, or 6 h before collecting (data for 3 and 6 h not shown). Total lysates were precipitated with antibody to ΔNp63 and resolved by SDS/PAGE followed by autoradiography. The immunoprecipitates were normalized by trichloroacetic acid-precipitable radioactive material, and equal amounts of total radioactive lysates (dpm/mg of total protein) were used for experiments. p53^WT overexpression decreases the p40 half-life (by ≈80%).