Bortezomib-induced polyubiquitination and Bax–ubiquitin conjugation. Fresh CLL cells were treated with bortezomib for 16 hours. (A) Polyubiquitination. CLL cells from 3 different patients were lysed with the lysis buffer. A total of 50 μg proteins was loaded into each lane. The antiubiquitin antibody was used at 1:500 dilution. Multiple ladders in the blot show an accumulation of polyubiquitinated proteins. (B) CLL cells were lysed with Chaps containing lysis buffer. A total of 500 μg protein was used for immunoprecipitation (IP) with Bax 6A7 antibody overnight at 4°C, and Bax–ubiquitin conjugation was probed with the antiubiquitin antibody at 1:500 dilution. The numbers on the left side of the blot are molecular weights of standard proteins. WB indicates Western blotting.