Fig. 4.

Bim and p19Arf expression in Eμ-Myc tumors. (A) Western blot analysis of Bim protein in individual tumors from Eμ-Myc-transgenic mice of the indicated Bim genotype. BimEL and BimL are the two most abundant Bim isoforms. Heat shock protein 70 protein served as loading control. (B) Western blot analysis of p19Arf in the same tumors. Heat shock protein 70 and a 60-kDa protein detected by nonspecific staining with the anti-p19 antibody served as loading control, and p53-null mouse embryo fibroblasts (MEF) provided a positive control for p19Arf expression. p19Arf was detected with rabbit antibody. The diagram depicts Myc regulation of the p19Arf/Mdm2/p53 axis (modified from ref. 22).