IL-3 enhances intracellular ROS levels and promotes G1/S cell cycle progression that can be retarded by phosphomimetic Bcl2. (A) and (B) H7 cells expressing WT, S70A, S70E, AAA or EEE mutant Bcl2 were washed 3 times with RPMI1640 and incubated in IL-3–free medium with 10% fetal bovine serum (FBS) for 24 hours. Recombinant IL-3 was added to each cell culture for various times as indicated. The cells were harvested at each time point. Intracellular ROS (A) or cell cycle status (B) was assessed as described in “Materials and methods.” The data represent the mean ± SD of 3 determinations.