Fig. 3. Induction of endogenous p53 and p21 proteins by p73 ectopic overexpression in SH-SY5Y and IGR-N-91 cells. (A) p53 and p21 proteins were detected by western blot analysis of total protein extracts; the blots were incubated with monoclonal anti-p53 antibody (upper panels) for p53 expression and with monoclonal anti-p21 antibody (middle panels) for p21 expression. Upregulation of p21 protein was observed only with Ad-TAp73 but not with Ad-Np73. (B) Northern blot showed no induction of p53 mRNA expression. Total RNA (10 µg) was prepared 48 hours after infection and submitted to northern blotting with p53 cDNA probe. Ethidium bromide staining of 28S and 18S rRNAs is used to allow comparison of RNA loaded.