Cells were crossed-linked with formaldehylde solution. Then nuclear extracts were isolated, and sonicated. Chromatin bound to Pol II were isolated using RNA polymerase II, clone CTD4H8, mouse monoclonal antibody. ChIP-Seq libraries were prepared using the NEBNext Ultra II DNA Library Prep Kit for Illumina (New England Biolabs, E7645). Fragments between 200 and 500 base pairs were selected using a Pippin Prep 1.5% agarose cassette (Sage Science, Beverly MA US), pooled and 75 single-end base pair reads were sequenced using the Illumina NEXTseq 500. NEBNext Ultra II DNA Library Prep Kit for Illumina (New England Biolabs, E7645)