ChIP was performed using the ChIP Assay Kit (Millipore, #17-295) according to the manufacturer's instructions, with the following modifications. After cell lysis, extracts were subjected to sonication with a 60 Sonic Dismembrator (Fisher Scientific) at 4°C for 20 cycles, cycling ON for 20 seconds and OFF for 1 minute at power setting 5, leading to an average DNA size of 200 bp. Samples were pre-cleared using 200 μL of Protein A Agarose/Salmon Sperm DNA for 4 hrs at 4°C with rotation. Antibody immunoprecipitations were performed overnight at 4°C. To collect histone complexes of interest, 100 μL Protein A Agarose/Salmon Sperm DNA was added for 4 hrs at 4°C with rotation. Each wash step (“Low Salt Immune Complex Wash Buffer,” “High Salt Immune Complex Wash Buffer,” “LiCl Immune Complex Wash Buffer,” and “TE Buffer”) was performed twice. After reverse-crosslinking overnight, samples were treated with RNase A, and subsequently treated with Proteinase K. Immunoprecipitated chromatin was extracted using QIAquick PCR Purification Kit (Qiagen). 10 ng of input and ChIP material were used to prepare libraries. Libraries were prepared using the ChIP-seq DNA Sample Kit (Illumina).