EKLF, Fli1, and GATA1 expression during MEP differentiation and repression of Fli1 by EKLF. Cell populations were sorted as detailed in Table S1 and monitored for EKLF, Fli1, and GATA1 expression by quantitative RT-PCR. Each sample was monitored in triplicate; values were normalized to the expression level in MEPs which was set to 100. (A) Relative levels are directly compared between EKLF and Fli1 (top) or EKLF and GATA1 (bottom). (B) Summary of the common and divergent expression patterns during bipotential differentiation from the MEP. Abbreviations are as in Table S1. (C) K562 cells were cotransfected with the pFli1 + i-Luc reporter plasmid and the indicated amounts (in μg) of Fli1 and EKLF expression plasmids. The graph displays the effects of increasing quantities of transfected EKLF plasmid on the reporter luciferase activity after normalization for transfection efficiency. Levels are expressed relative to that seen with reporter alone (given a value of 1). In the panel below, nuclear cell extracts from the transfected cells were tested for the presence of Fli1 or EKLF protein by Western blotting. Error bars represent SD.