γ-Globin gene induction by ZL in K562 cells. K562 cells were treated with ZL at 20 to 100 μM concentration or hydroxyurea (HU) 50 to 100 μM concentrations for comparison. γ-Globin mRNA levels were quantitated by RNase protection assay (RPA) with human γ (Huγ) and internal control gylcearaldehyde-3-phosphate dehydrogenase (GAPD) probes to yield protected fragments of 170 bp and 316 bp, respectively. (A) A representative RPA gel showing the mRNA bands for ZL-treated cells on the left and HU-treated cells in the middle. (B) Quantitative values for Huγ and GAPD mRNA production by phosphorimager analysis. The untreated K562 samples (0 μM) were normalized to one (▪). The total increase in γ mRNA was calculated as a ratio of GAPD to control for variations in sample loading for ZL- (□) or HU-treated (▧) K562 cells. Sodium butyrate (NB, ) and hemin (HE, ) were used as positive control for γ gene induction. *2 = NB at a 2 mM concentration. Error bars indicate SEM (n = 4 for each concentration/groups reported); each study done in triplicate.