library_construction_protocol: Cells were either single (FA) or double (DSG+FA) crosslinked. Chromatin was sonicated with lysis buffer to obatin fragments of 200-500bp. Sheared chromatin was incubated with antibody and Protein A beads overnight at 4C. ChIP samples were washed and input samples were cleaned up with Speedbeads before library prep. Libraries of ChIP and input samples were prepared with the NEBNext Ultra II Library Prep Kit for Illumina and cleaned with Speedbeads. Indexing adapters were from NEXTflex DNA Barcodes. Libraries were PCR amplified with Solexa 1GA and 1GB primers and size selected with a final Speedbeads cleanup. Library size was estimated with agarose gel, concentrations measured with Qubit HS DNA assay kit.