Purified PP2A promotes p53/Bcl2 interaction in vitro. (A) Purified p53 was incubated with full-length WT Bcl2 in the absence or presence of increasing concentrations of purified, active PP2A or OA, and coimmunoprecipitation was carried out using an agarose-conjugated p53 antibody. The p53-associated Bcl2 (bound Bcl2) and p53 were analyzed by Western blot using a Bcl2 or p53 antibody, respectively. (B) H7 WT Bcl2 cells were treated with cisplatin in the absence or presence of C2-ceramide or OA followed by lysis in 1% CHAPS-containing buffer. Coimmunoprecipitation was performed using an agarose-conjugated Bcl2 antibody. p53, Bcl2, and Bax were then analyzed by Western blotting using a p53, Bcl2, or Bax antibody as indicated.