Quoted from GSE42147: "Native chromatin was prepared by lysing CD4+ cells in low salt buffer and digesting with Micrococcal nuclease. Lysates were then sonicated to assist in recovery of oligonucleosomes and adjusted to RIPA immunoprecipitation buffer conditions. Extracts were then incubated overnight with specific antisera prior to immunoprecipitation with protein A & G beads, and recovery of bound DNA using silica column purification." Sodium butyrate added, and library prep as in Gosselin ChIP-Seq. CD4+ cells were re-isolated from the culture using the Miltenyi MACS system.