Figure 6. Apoptosis of oncogenically transformed cells after Ubf gene inactivation is p53 independent.

A. Ubf^fl/fl/Er-cre^+/+/p53^−/− and Ubf^wt/wt/Er-cre^+/+/p53^−/− MEFs and C. Ubf^fl/fl/Er-cre^+/+/Sv-T/p53^−/− and Ubf^wt/wt/Er-cre^+/+/Sv-T/p53^−/− iMEFs were subjected to a TUNEL reaction and B. and D. assayed for activation (proteolytic cleavage) of Caspase 3 immediately before and at several time points after treatment with 4-HT. P53-null iMEFs (Ubf^fl/fl/Er-cre^+/+/Sv-T/p53^−/−) displayed the same TUNEL positive cell death, but Caspase 3 cleavage was not detected in these cells. In B) and D) “Ctrl” refers to an extract from iMEFs cells treated with 1 μM Staurosporin. Recombination of the Ubf gene and UBF protein levels were assayed in parallel and closely followed those shown in Figure S2B and S2C.