STAT5 binds directly to the −344-bp palindromic site within the HIF2α promoter. (A) UT7 cells were cytokine deprived overnight, after which time cells were either left unstimulated (unstim) or stimulated with erythropoietin (Epo; 10 ng/mL) for 15 minutes. Cell lysates were prepared and used for Western blotting. (B) Same experiment as in panel A, but mRNA was isolated from erythropoietin-stimulated cells at several time points, after which the expression of HIF2α and CISH was verified by real-time Q-PCR. (C) ChIP using antibodies against STAT5 or preimmune serum as a negative control. PCRs were performed using primer sets as indicated. Region 1 does not contain STAT5-binding sites, region 2 and 3 do contain STAT5-binding sites within the HIF2α promoter, and region 4 contains the tandem STAT5-binding site within the CISH promoter.