For ChIP-seq, samples were prepared according to Myers lab ChIP-seq protocol: cells were cross-linked with 1% formaldehyde at room temperature for 10 min, cells were extracted with Farnham and RIPA buffers, and chromatin was fragmented by sonication. For ChIP-Seq, libraries were prepared according to the Illumina ChIP-seq library preparation protocol: ChIP DNA was blunt ended, ligated to Solexa adaptors, amplified using adaptor primers and size-selected on agarose gel.