BirA-ChIP seq experiments were performed as described (PMID: 22412018). Briefly, 1*10^7 cells were fixed with 4% formaldehyde for 10min at RT, and then the cells were divided into six part equally. Cells were lysed at 25°C in 200ul lysis buffer for 5 min.After cell lysis, the chromatin was sonicated by the Bioruptor sonicator. The cell lysate was centrifuged at 17,000g for 15min at 4°C. Supernatants were incubated with 30 μl High Capacity Streptavidin Agarose (Thermo Fisher Scientific) overnight. Beads were washed twice for 5 min with buffer 1 (2% SDS) at 25°C,once with buffer 2,once with buffer 3 and twice with buffer 4. Lastly, adding 60μl Elution buffer to the beads, and then placed in a 70°C water bath overnight with shaking. ChIP DNA libraries were prepared for sequencing using standard Illumina protocols.