ChIP DNA samples were obtained with Native ChIP protocol; briefly, chromatin were fractionated and then subject to Mnase digestion to generate mononucleosomes. Then the mononucleosome fraction was extracted with high salt buffer and H2A.X-containing nucleosomes were isolated and enriched with anti-H2A.X (Xiaolab_Maked) antibodies. Libraries were prepared according to Illumina's standard protocol, with instructions accompanying the TruSeq ChIP DNA Sample Kit