ChIP was performed as previously described (Ci et al., Blood, 2009). Briefly, 108 cells were fixed with 1% formaldehyde, lysed, and sonicated (Branson Sonicator; Branson) leading to a DNA average size of 200 bp. Five µg of antibodies were added to the precleared sample and incubated overnight at 4°C. The complexes were purified using protein-A beads (Roche) followed by elution from the beads and decrosslinking. DNA was purified using PCR purification columns (QIAGEN). ChIP-seq and RNA-seq libraries were prepared using the Illumina ChIP-Seq and TruSeq RNA sample kits, respectively, according to the manufacturer. Libraries were validated using the Agilent Technologies 2100 Bioanalyzer and Quant-iT™ dsDNA HS Assay (Life Technologies)