The Bach2S521A mutant induces poorer survival of CML cells than the wild type. BV173 cells were transduced with retroviruses encoding BACH2/IRES-GFP (WT), BACH2S521A/IRES-GFP (S521A), or IRES-GFP (control). GFP-positive cells were examined by FACS every 2 days. Results are presented as the average percentage of GFP-positive cells normalized as 100% on day 0 ± standard deviations from 3 independent experiments. *Comparison between the 3 types of cells shows a significant difference by the Mann-Whitney U test (P < .05).