The PRC2 polycomb complex is recruited to the inactive HBA genes. ChIP experiments were carried out in primary T lymphocytes or primary proerythroblasts using antibodies against H3K27me3 (A), SUZ12 (B), or RNA pol II (C). For (A) and (B), immunoprecipitated and input material were labeled with Cy3 or Cy5, respectively, and applied to a custom tiled microarray covering the terminal region of human chromosome 16. Shown is a 250-kb genomic segment containing the α-globin locus (delineated by gray dashed lines) with the fold enrichments at each probe plotted against chromosomal position. The locus is annotated as described in Figure 1. For panel C, immunoprecipitated material was analyzed by real-time PCR at amplicons 53 (within the middle of the DIST1 gene [see Figure 1]) and an amplicon within the 18S rRNA gene (both representing background enrichment), an amplicon at the promoter of the β-actin gene (ACTB) used as a positive control, and an amplicon spanning exons 1-2 of the adult HBA genes (HBA ex1-2; see Figure 1). Data indicate the percentage of input material precipitated at each amplicon. Shown are the mean values obtained from replicate ChIPs with error bars indicating the range of values.