Activated AKT phosphorylates and enhances GATA-1 transactivation activity in erythroid cells. (A) G1E-R2H cells were retrovirally transduced with an empty vector (MIG) or MIG-AKT^* and cultured in the presence or absence of Epo for 16 hours before adding β-estradiol (10^-7 M). Nuclear extracts were prepared 7 hours later and subjected to Western blot analysis using the indicated antibodies. Total RNA was prepared from an aliquot of cells from panel A and subjected to real-time PCR for analysis of genes whose expression is up-regulated (B) or repressed (C) by nuclear GATA-1. Representative graphs from 3 independent experiments are shown.