ChIP-chip analysis of transcription factors and PolII across 220 kb of chromosome 16p13.3. Binding profile of GATA1 in primary erythroblasts from a homozygote “humanized” mouse (HM Ery) and of SCL, NF-E2 p45, NF-E2 p18, and PolII in day 8 human erythroblasts (Day 8 Ery) are shown. A schematic representation of the α globin locus is shown at the top annotated as in Figure 1. Note that the binding profile of GATA1 is derived from “humanized” mouse because antibodies recognizing human GATA1 do not perform well in ChIP assay.