ChIPs for acetyl-H3K9 (ab4441), acetyl-H3K27 (ab4729) (both from Abcam) RCOR1 (07-455 from Merck Millipore), SPI1 (2258 from Cell Signaling) and MLL4 (kindly provided by Dr Kai Ge; Wang et al., 2016) were performed using 50-100 million cells and the protocol of Lee et al. (2006). ChIP DNA samples were prepared for sequencing using the Microplex Library Preparation Kit (Diagenode) and 1ng ChIP DNA. Libraries were size selected with AMPure beads (Beckman Coulter) for 200-800 base pair size range and quantified by Q-PCR using a KAPA Library Quantification Kit. ChIPseq data were generated using the NextSeq platform from Illumina with 2x75bp Mid Output.