The Cd19 enhancer is reorganized and accessible before PAX5 expression. (A) DNaseI hypersensitivity assays were performed in bone marrow–derived macrophages (BM-Mø), wild-type (Pax5^+/+), and Pax5^−/− pro-B cells and Pax5-ER cells induced with OHT for 0, 2, 6, and 24 hours. DNaseI-treated DNA was analyzed by Southern blot as described in Figure 1. (B) RNAP II recruitment, the levels of monomethylated histone H3 lysine 9 (H3K9), monomethylated, and trimethylated histone H3 lysine 4 (H3K4) were measured by ChIP assays in Pax5-ER cells induced with OHT. The enrichment was measured at the promoter, enhancer, and a downstream region at +10 kb. The values were normalized against the enrichment at a control region on chromosome 11 (Gapdh pseudogene). Data represent the mean value of 3 (RNAP II) or 2 (histone modification) independent experiments performed in triplicate.