ChIP-Seq analysis of EKLF occupancy in primary erythroid progenitor cells and erythroblasts. (A) Day E13.5 fetal liver cells from HA-tagged EKLF mice were FACS sorted into populations of erythroid progenitor cells (TER119⁻) and erythroblasts (CD71⁺ TER119⁺). The cells were cross-linked and the chromatin processed for immune precipitation with an anti-HA antibody followed by massively parallel sequencing (ChIP-Seq). Peaks of EKLF occupancy were determined using the program MACS. (B) EKLF peaks were identified that are specific to progenitor cells (4472), erythroblasts (6490), and common to both populations (8753). (C) EKLF occupancy in the mouse Ank1 locus. Top panel: Organization of the Ank1 locus on the UCSC browser. The 3 alternative promoters (Ank1A, Ank1B, and the erythroid-specific Ank1E) are indicated along with the direction of transcription (arrows). The Control, Pro, and Ery tracks represent the sequence reads derived from libraries of input chromatin or HA-enriched chromatin from progenitor cells or erythroblasts, respectively. The bars in the MACS Pro and MACS Ery tracks represent the EKLF peaks (at the p06 level of significance) identified by MACS in the progenitor cell and erythroblast data, respectively. *An unannotated repetitive sequence that is mapped to this location in both the control and HA-enriched chromatin. Several of these sites were chosen for validation by PCR-based ChIP analysis. White bars represent the mean (± SD) fold enrichment in HA-enriched chromatin from unfractionated day E13.5 fetal liver cells compared with input chromatin (black bars). Sites 9, 11, 12, and 14 were selected as negative controls and show no significant enrichment. Peaks 10 and 13 are seen in progenitor cells or erythroblasts, respectively. Both show significant enrichment (P < .0001).