Genomic regions that lose the elongation mark HK36me3 do not gain the heterochromatin mark H3K27me3. (A) Genomic distribution of H3K36me3 and H3K27me3 in intermediate (early basophilic erythroblasts) and late (orthochromatic) erythroblasts relative to known genomic features. Early and late erythroblasts for these studies were sorted from CD34⁺ cultures based on cell surface marker expression. The antibody used for these experiments cannot distinguish different isoforms of histone H3. (B-D) Occupancy of H3K36me3 and H3K27me3 in indicated erythroid populations at the glycophorin A (GYPA; B), FLI1 (C), and MYB (D) loci. (E) Gene ontogeny terms associated with regions that lose H3K36me3 during maturation. (F) Gene ontogeny terms associated with regions that gain H3K27me3 during maturation. (G) Heatmap depicting hierarchically clustered and z-score normalized differentially bound regions identified through maturation (basophilic erythroblast to orthochromatic erythroblast) for H3K36me3 and H3K27me3. (H) Occupancy of H3K36me3 and H3K27me3 in indicated erythroid populations at the Ankryin1 locus. Red arrow depicts erythroid ankyrin promoter and black arrow depicts the neural ankyrin promoter.