Figure 5. p53 in p65 null and reconstituted cells is a non-functional mutant.. (A-B) 0.5 μg of PG13-Luc p53 luciferase reporter (A) or Noxa promoter luciferase reporter (B) were co-transfected into SaOS-2 cells along with increasing amounts of the wild type or P275R mutant p53 vectors. 48 hr after transfection luciferase activity was compared. Results are expressed as fold induction above mock (empty pcDNA3 vector) control. (C) p53 P275R or wild type expression was demonstrated by immunoblotting in extracts derived from SaOS-2 p53 tet-on cells transfected as described for A-B. As a control, p53 was induced by doxocycline treatment. Endogenous p21 induction was assessed by immunoblotting from the same extracts. A non-specific band detected with the p21 antibody was used as loading control.