Comparison of pol II recruitment at the human β-globin locus between fetal and adult erythroblasts. (A) Comparison of pol II recruitment in the LCR between fetal and adult erythroblasts. Each data point represents enrichment relative to the external mouse Aire gene of cross-linked chromatin from approximately 100 dpc fetal liver (▒) or adult erythroblasts (■), immunoprecipitated using antibodies against Pol II. The y-axis values measure relative enrichments. Notice that the HS cores of the LCR in fetal erythroblasts bind pol II 2 to 3 times more than in adult erythroblasts, whereas the intervening regions between the HS sites bind similar amounts of pol II at the fetal and adult stages. (B) Comparison of pol II recruitment in fetal and adult erythroblasts at the promoters and exons of the ε-, γ-, and β-globin genes.