ZBP-89 occupancy of the globin loci in primary human erythroid precursor cells. Representative ChIP-chip signals for ZBP-89, GATA-1, RNA Pol II, AcH3, 3meH3K4, and 3meH3K27 within the human β-globin (A) and α-globin (B) loci in hCD34⁺ cells harvested on day 5 of the erythroid differentiation culture period. The locations of key cis-regulatory elements and genes are indicated at the bottom of each panel. The data for GATA-1, Pol II, 3meH3K4, and 3meH3K27 were obtained from Xu et al.²⁴  (C-D) Quantitative ChIP validation of key ZBP-89 enrichment peaks from the ENCODE array ChIP-chip studies within the β-globin (C) and α-globin (D) loci from cells on day 6 of differentiation. The positions of the primers used for each site (numbered) are indicated by horizontal lines at the top of the schematic drawing. Note that the primers used for the HBG promoters (#4) detect both HBG1 and HBG2. Likewise, the primers for the HBA promoters (#10) detect both HBA1 and HBA2 promoters. It was not possible to design primers centered at the peak of the ZBP-89 enrichment site between HBG1 and HBD (A) because of high GC content of this region. Primer pair #5 is offset from the center of the peak. Fold enrichments are shown relative to an exonic region of the β-actin gene. Data represent the mean of ≥ 3 independent experiments ± SEM.