GATA-1 overexpression impairs erythroid differentiation. (A) Primary erythroblasts were transduced 3 times with an empty lentivirus construct (■) or one encoding GATA-1 (▵). Then, differentiation was induced as in Figure 1A. The percentage of differentiated cells was evaluated by benzidine assay at the indicated times. (Bottom) The percentages of basophilic and polychromatic cells was quantified at day 2 as in Figure 2A. (B) K562 cells were transiently transfected with empty plasmid () or with Myc-GATA-1 (). After 24 hours, differentiation was induced with hemin (40μM). The percentage of differentiated cells was evaluated by benzidine assay at the indicated times. GATA-1 expression was monitored by Western blotting. HSC70 and actin are the loading controls. Data are expressed as the mean ± SE (n = 3; *P < .05).