For each transcription factor, ~3x107 cells were cross-linked with 1% formaldehyde for 10 min at room temperature, and stopped by adding glycine to a final concentration of 0.2M. Chromatin was extracted and sonicated to ~500bp (Vibra cell, SONICS). The total volume of immunoprecipitation was 1.5 ml and the amount of antibody used was 15 µg. The input DNA was precleared with protein G Dynabeads (LifeTechnologies) for 2 hr at 4°C and then incubated with antibodies conjugated protein G beads overnight at 4°C. The beads were washed 6 times with wash buffer at room temperature. Amplified DNA was used with NEBNext ChIP-Seq library prep reagent set (NEB)