FIG. 5.

Conditional activation of GATA-1 in G1E-ER4 cells results in repression of c-Kit and its downstream substrates. (A) Time-dependent decline in the mRNA levels of c-Kit, Vav1, Rac1, and Akt in the presence of GATA-1 activation. The y axes of the graphs indicate the absolute signal value from microarrays. Hours after β-estradiol treatment are indicated. Similar results were found in three independent experiments. (B) Cell surface expression of c-Kit in the absence (−) and presence (+) of GATA-1. G1E-ER4 cells were cultured for 48 h in the presence of β-estradiol and subjected to flow cytometric analysis using an anti-c-Kit antibody. Open histograms indicate isotype control staining, and closed histograms indicate c-Kit staining. (C and D) Western blot analysis on lysates derived from G1E-ER4 cells cultured in the absence or in the presence of GATA-1 activation for 48 h. Similar results were observed in three independent experiments.