C/EBP consensus binding sites in the PU.1 distal enhancer and interaction of endogenous C/EBPs with the enhancer. (A) Positions of the 5 potential C/EBP-binding sites, C1 to C5, and the PU.1 site¹⁹  in the distal enhancer. (B) Sequences of the C1 to C5 and NE C/EBP sites, with flanking sequences in lower case. (C) HF1 myeloid cells or 32Dcl3 myeloid cells cultured in G-CSF for one day (32D-G1) were subjected to the ChIP assay using C/EBPα or C/EBPβ antiserum or rabbit Ig followed by PCR for a 154–base pair PU.1 −14-kb distal enhancer fragment (PU.1 DE), a 138-bp β-actin promoter fragment, or a 329-bp fragment located at −20 kb in the PU.1 gene. Bands were visualized after agarose gel electrophoresis by ethidium bromide staining. I indicates input DNA.