Apoptosis-associated Bax cleavage following drug treatment or IL-3 withdrawal and Bax cDNAs constructs. (A) HL-60 cells were treated with various doses of camptothecin, a DNA topoisomerase I inhibitor, for 20 hours. (B) H-7 cells were deprived of IL-3 for the indicated times. (Upper panels) Proteins were extracted and subjected to SDS-PAGE and Western blotting with anti-Bax antibody. (Lower panels) DNA fragmentations were determined as described in “Materials and methods” to confirm that cells underwent apoptosis. (C) K-562, U-937, and A-549 cells were treated with 20 μM cisplatin for 36 hours. (D) K-562, U-937, and A-549 cells were treated with 50 μM etoposide for 36 hours. Cell viabilities were measured by trypan blue exclusion method. Proteins were extracted and subjected to SDS-PAGE and Western blotting with anti-Bax antibody. Error bars indicate means ± SD (n = 3). (E) WT Bax cDNA was cloned from H-7 cells with a T7 tag at the N-terminal. Asp33Ala, Glu6Ala, and N-terminal-deleted p18 (Δ1-33) Bax cDNA mutants were constructed as described.