Nuclei were lysed and chromatin was resuspended in sonication buffer The chromatin was sonicated to average 220 bp and incubated with antibody overnight at 4'C. Antibody-bound chromatin was incubated with Protein G Dynabeads (Invitrogen, 10004D) for 4 hours at 4'C and eluted in Tris buffer (10mM Tris pH 8.0, 10mM EDTA, 1% SDS). Crosslinks were reversed by incubation overnight at 65'C followed by treatment with 0.2 mg/mL proteinase K (Life Technologies, AM2548) and 0.2 mg/mL RNAse A (Qiagen). DNA was purified using Qiagen Minelute Columns (Qiagen, 28006). Libraries were prepared by DNA tagmentation (Nextera) followed by PCR amplification.