The chromatin was then fragmented to a size range of ~200 to 600 bp using a Branson 250 digital sonifier (sonication conditions were separately optimized for each sample). Solubilized chromatin was then diluted and incubated with 1-2 ug antibody overnight at 4°C. Immune complexes were captured with ~ 0.02 ml protein A-sepharose, washed and eluted. Enriched chromatin was then subjected to crosslink reversal and proteinase K digestion at 65°C, phenol-chloroform-isoamyl alcohol extraction and ethanol precipitation. Isolated ChIP DNA was resuspended in RNAase treated water and quantified using the Qubit assay (Invitrogen). ChIP assays were performed using the following antibodies: H3K4me1 (Abcam ab8895, lot 38311/659352, H3K4me3 (Milipore 07-473, lot DAM1623866), H3K27ac (Active Motif 39133, lot 31610003), H3K36me3 (Abcam ab9050, lot 499302, H3K27me3 (Millipore 07-449, lot DAM1514011), H3K79me2 (Cell Signaling 9757, lot 1).