Figure 2.

Mdm2 is not required to shuttle p53 to mitochondria. (A) Equal amounts of crude lysates (crude) and purified mitochondria (mito) (4 μg) from ML1 cells treated as indicated were immunoblotted. Note that treatment of cells with proteasome inhibitors like ALLN causes extensive accumulation of mono- and polyubiquitylated p53 (not shown), explaining why ALLN alone mediates mitochondrial p53 translocation (see the text). (B) Mitochondria do not contain p53/Mdm2 complexes despite significantly induced translocated p53. Total cell lysates and purified mitochondria (400 μg each) from untreated or treated RKO cells were immunoprecipitated to detect p53–Mdm2 complexes. Similar results were seen with ML1 cells (data not shown).