cells were cross-linked in 1.0% formaldehyde. Cells were then lysed by lysis buffer. Chromatin was sonicated by bioruptor to an average size of 300~500 bp. ~ 20 million cells was used for one ChIP-nexus DNA-protein-complexes were isolated with specific antibodies. Sequencing libraries were prepared following Illumina's instructions: DNA was end repaired using NEBNext End repair module. A single 3'-A overhang was added to the blunted ends using NEBNext dA-Tailing module. Adapters with single 3'-T overhangs were ligated to the adenylated fragments, and after a size-selection step using AmPure beads (200-250 bp) the adapter modified DNA was PCR-amplified. Following cluster generation on the flowcell surface, the sequencing libraries were sequenced following Illumina's protocol.