Fig. 7.

Augmentation of BMP signaling leads to p53-mediated apoptosis by preventing MDM2-mediated p53 degradation. (A) Expression levels of p53, Bax, caspase 3, p21, Gadd45a, Mdm2, Pten, Atm and Atr were measured by RT-PCR. Total RNA was isolated from the nasal tissue of newborn controls, type 1 and type 2 mutants (n=4-6 per group). Expression levels of these mRNAs were normalized to Gapdh mRNA. *P<0.01, **P<0.005 (Student's t-test). (B) p-p53-Ser15, total p53 and MDM2 levels were examined by western blotting. GAPDH was used as a loading control. Protein lysate was isolated from nasal tissues of controls (CT), type 1 (Ty1) and type 2 (Ty2) mutants. The levels of p-p53-Ser15 (left), total p53 (center) and MDM2 (right) were normalized to GAPDH and compared between control (CT), type 1 and type 2 mutants (n=4 per group). *P<0.05 (Student's t-test). (C) MDM2-p53 and pSMAD1/5/9-p53 complex formation levels were examined by immunoprecipitation (IP) and immunoblotting (IB). Immunoprecipitation was performed using p53 antibody. MDM2 and pSMAD1/5/9 levels were examined using cell lysates after immunoprecipitation. Input indicates levels of MDM2 or pSMAD1/5/9 in 10% protein lysates before immunoprecipitation. MDM2 (left graph) and pSMAD1/5/9 (right graph) interaction levels were quantified and compared between control, type 1 and type 2 mutants (n=3 per group). *P<0.05, **P<0.005 (Student's t-test). All data are represented as mean±s.d.