In vivo binding of known transcription factors upstream of GATA1 in mouse and human erythroid cells. Binding of the transcription factors GATA1, SCL, E2A, LMO2, and Ldb1 at different points along the mGata1 locus (A) and the hGATA1 locus (B). GATA1 loci are drawn above each panel, as in Figures 4-5. Transcription factor binding was determined by ChiP using Taqman real-time PCR analysis in a mouse erythroid cell line (MEL) and primary human erythroid cells. The black bars show the relative degree of binding (y-axis) at different points along the GATA1 loci (x-axis) from duplicate real-time PCR reactions. The analysis was performed on 3 independent ChiP preparations, and data from 1 representative experiment are shown.