Cells were crosslinked with 1% PFA 10 minutes on ice and lysed. Cross-linked DNA was incubated with H3 antibody. H3-bound chromatin was used to attach NEXTflexTM adapters. Chromatin with ligated adapters was incubated with H3K27Ac antibody. H3K27Ac+ chromatin was decrosslinked and amplified with primers recognizing adapters.