Complexes were precipitated with Dynabeads Protein A beads (Invitrogen), and immunoprecipitated chromatin was eluted in elution buffer de-crosslinked at 65°C for 8 hr (or O/N), and treated with proteinase K (Roche). DNA was purified by extracting with phenol and chloroform and precipitating in ethanol. Library preparation was carried out using the NEBNext Ultra DNA Library Prep Kit for Illumina (NEB Cat#E73705), according to the manufacturer's instructions.