Histone H3 acetylation at the γ- and β-globin promoters in purified fetal and adult erythroid cells determined by ChIP assay. (A) Relative promoter H3 acetylation in nucleated fetal erythroid cells. (B) Relative promoter H3 acetylation in nucleated adult erythroid cells. Results are expressed as fold enrichment using anti-AcH3 antibody compared with nonspecific IgG. Error bars indicate plus or minus 1 standard deviation. β-Globin LCR HS2 and HS3 core regions serve as positive controls. The necdin gene promoter, which is not expressed in erythroid cells, serves a negative control.