Fli-1 and GABPα bind to the proximal promoters of megakaryocyte-specific genes in vivo. Panels A and B show ChIP assays using fetal liver–derived mature megakaryocytes and examining the proximal promoter regions containing known functional Ets binding sites.¹³  (A) ChIP with Fli-1 antibody and isotype-matched control antibody. (B) ChIP with GABPα antibody and isotype-matched control antibody. The control represents a region 3 kb upstream of the murine αIIb transcription start site known not to be of functional importance or containing an Ets binding site.¹²  The mean ± one SD of 3 experiments, each in triplicate, is shown. (C) Signal ratio of GABPα to Fli-1 at the various megakaryocyte-specific promoters is shown.