Coimmunoprecipitation of proapoptotic proteins with Bcl-2. CLL cells were incubated for 18 hours in the presence of 100 μM ZVAD with no further addition (NA) or with 15μM PAS, 60μM chlorambucil (CHL), or 20μM nutlin 3 (NUT). (A) Lysates were immunoprecipitated with anti–Bcl-2 antibody or an isotype control antibody (IC) and analyzed by Western blotting. The blots were probed with p53, Bim, Noxa, Bcl-2, and Hsp60 antibodies. Lysate from CHL-treated cells was run in the right-hand lane to provide migration markers for the proteins analyzed. (B) Unprecipitated lysates were also analyzed directly by Western blotting using anti-Hsp60 and anti–Bcl-2 antibodies.