Figure 4.
p53, ARF, and Mdm2 expression and genotypic analysis of ARF and p53 in Eμ–myc lymphomas. (A) Levels of p53 (top), p19ARF (middle), and Mdm2 (bottom) in extracts of tumors from Eμ–myc transgenic mice were assessed by immunoblotting with antibodies specific for each protein. Extracts from ARF−/− and p53−/− MEFs (right two lanes) were used as controls. The asterisk in the left margin defines the position of a background band detected with Mdm2 C-18 antibody. Arrows indicate the locations of p53, p19ARF, and p92, p90, and p85 Mdm2 isoforms. (B) Southern blot analysis for genomic AflII and BamHI restriction fragments containing ARF exon1β (top) and p53 exons 2–10 (bottom), respectively. Tail DNAs extracted from ARF+/+, ARF+/−, and ARF−/− animals were used as controls (top, three right lanes) and indicate the positions of AflII restriction fragments containing (7.8 kb) or lacking (6.0 kb) ARF exon1β.