For ChIP-seq, cells were harvested and crosslinked in suspension with 1% formaldehyde for 10 minute at room temperature. Crosslinked cells were lysed, sonicated and chromatin was collected for IP. 2-5 ug of antibody was used for each IP. IPed chromatin was captured by Protein A beads. After washing, bound complexes were eluted and crosslinking was reversed. DNA was extracted using phenol-chloroform and purified by ethanol precipitation.