RNA polymerase II occupancy and histone modifications across the human β-globin locus. ChIPs were performed on culture day 9 using antibodies specific to (A) RNA polymerase II, (B) trimethylated histone H3 lysine 4 (H3K4me3), (C) dimethylated histone H3 lysine 4 (H3K4me2), (D) acetylated histone 3 lysine 9 (H3K9ac), and (E) dimethylated histone H3 lysine 9 (H3K9me2). Plotted values are relative enrichments (y-axis) measured for sites in the β-globin locus (x-axis) in low-HbF (■, black solid line) and high-HbF (○, black broken line). Antibody against IgG was used as a nonspecific control (gray line). Three to 6 separate donor-matched experiments were analyzed for each antibody under each condition; SE is indicated. Note that the scales on the y-axis differ between the panels.