SCF-induced γ-globin reactivation is mediated by activation of Erk1/2 through down-regulation of COUP-TFII. CD34⁺ cells were cultured with or without SCF (50 ng/mL) in the presence or absence of the indicated inhibitors from day 6 to day 14. On day 14, whole cell lysates (30 μg) were analyzed by immunoblot for phosphorylation of PP2A, COUP-TFII, γ-hemoglobin, and β-actin (A), total RNA was analyzed by quantitative real-time PCR to determine the expression of γ-globin mRNA level (B), the expression of β-globin mRNA level (C), the ratios of γ/(γ + β) globin percentages (D). Results are shown as mean ± SD from 3 independent donors that were analyzed in separate experiments. *P < .05 versus SCF-stimulated cells.