Figure 2.

The patterns of core histone acetylation across the human α-globin cluster with the probes used set out below annotated as in Fig. 1 and described in detail in Table 1, which is published as supporting information on the PNAS web site, www.pnas.org. The scale is in kilobases. Acetylation of histone H4 at Lys-16 (white boxes and dashed line) and Lys-5 (black circles and black line) in (a) human EBV-transformed B lymphocytes, (b) fibroblasts, (c) K562, and (d) primary human erythroid progenitors. Levels of acetylation at control loci were established independently for each experiment and include the α-tubulin genes (T), a probe to heterochromatin repeat sequences (het 266) (H), human rDNA (R), a probe directed to a heterochromatic Y chromosome repeat (D), which is also present on the X chromosome, and a probe to the human γ-globin gene (G). The putative boundaries of acetylation are indicated by vertical black lines. Gray lines indicate the position of the erythroid-specific HSs.