Figure 6.

Mdm2 is functional and contributes to p53 down-regulation in the absence of MdmX. (A) mdmX^+/+;p53^KI/− and mdmX^−/−;p53^KI/− MEFs were treated with either 4-OHT or 4-OHT plus 10 μM Nutlin-3a for the indicated times. Immunoblotting was used to estimate levels of p53, Mdm2, and p21^cip1 at each time point. (B) Mice of the indicated genotypes were treated with either vehicle (V) or tamoxifen (T) for 1 d. The levels of p53 in the livers of these mice are presented (immunoblot; each lane is a separate mouse), together with a quantification of the p53 levels in tamoxifen-treated mice (from the blot shown). The relative induction of p53 target genes cdkn1a and mdm2 (by TaqMan; gus is the control gene) in these mice is also shown. Error bars show the SEM from triplicates.