Novel mode of GATA-1 function: FOG-1–independent repression. Real-time RT-PCR analysis of mRNA levels in (A) G1E cells expressing either wild-type ER–GATA-1(WT) or ER–GATA-1(V205G) and (B) FOG-1^−/− cells expressing wild-type ER–GATA-1. Transcript levels from cells treated with 1 μM β-estradiol for 24 hours were compared with untreated controls. Transcript levels were normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) transcript levels and, for each clone, the mean value for untreated samples was set to 1 (mean ± standard error [SE] from 3 independent experiments). (C) Real-time RT-PCR analysis of mRNA levels during ex vivo human erythropoiesis. CD34⁺ cells isolated from peripheral blood were cultured for up to 14 days. RNA was isolated at days 3, 7, 10, and 14 from 2 independent samples. Transcript levels were normalized to 18S RNA levels and the relative level of transcript from day 3 for each sample was set to 1.