Nuclear pellets were washed and resuspended in 1× micrococcal nuclease reaction buffer [10 mM Tris–Cl (pH 7.9), 5 mM CaCl2, 0.5 mM DTT] and the chromatin was digested with micrococcal nuclease (New England Biolabs). The digestion was stopped with EDTA. Histone-DNA complexes were isolated with antibody. DNA fragments were ligated to a pair of adaptors for sequencing on an Illumina Hiseq-2000. The ligation products were size-fractionated to obtain 200–300-bp fragments on a 2% agarose gel and PCR-amplified for 18 cycles. Each library was diluted to 8 pM for 76 cycles of single-read sequencing on the Illumina Hiseq-2000 following the manufacturer's recommended protocol.