C/EBPα 30-kDa and BRM2 mutant proteins cannot induce granulocytic development of K562 cells with C/EBPα 42-kDa and mutant proteins. Shown are pictures of K562 cells stably transfected with the 42-kDa (A), 30-kDa (B), Δ126-200 (C), and BRM2 (D) C/EBPα-ER fusion proteins 3 days after induction of nuclear localization of the fusion protein with β-estradiol. NBT activity can be detected by the small blue dots observed after counterstaining the cells with safranin. As indicated in Table 1, less than 1% of BRM2 stably transfected cells stained positive; a single positively staining cells is shown in this field. Original magnification, × 1000.