DNase I digestion profiles of the HBS1L-MYB intergenic region in HMIP block 2. DNase I sensitivity was analyzed by real-time PCR using 68 primer pairs spanning the 24-kb HMIP-2 region. Control primers targeting the β-globin LCR HS2 and HS3 (βHS2 and βHS3) and the NEFM gene were also included in experiments. Relative sensitivity to DNase I for each target was calculated from delta C_T values between treated and untreated samples and normalized to NEFM. DNase I sensitivity was plotted as a function of primer position. Error bars represent differences between 2 biologic repeats. (A) DNase I sensitivity in HMIP-2 compared between hemin-induced and uninduced K562 cells. Three DNase I hypersensitive sites (HMHS1, HMHS2, and HMHS3; gray bars) were identified in hemin-induced K562 cells. (B) DNase I sensitivity in HMIP-2 compared between hemin-induced K562 cells and Jurkat cells. The 3 hypersensitive sites in hemin-induced K562 cells showed no or less sensitivity to DNase I in Jurkat cells. Hypersensitivity was instead observed in Jurkat cells at the site of the HBS1L-1a exon, which showed no hypersensitivity in K562 cells (induced and uninduced). The βHS3 control was not included for DNase I sensitivity analyses in Jurkat cells.