Lysates were clarified from sonicated nuclei and histone-DNA complexes were isolated with antibody. 10 ng of the DNA sample was used for Illumina/Solexa sequencing in the following steps: 1) DNA samples were blunt-ended with T4 DNA polymerase and Klenow polymerase; 2) a dA base was added to the 3' end of each strand by Klenow (exo minus) polymerase; 3) Illumina's genomic adapters were ligated to the DNA fragments; 4) PCR amplification was performed to enrich ligated fragments; 5) Enriched product of ~300-400bp was cut out from gel and purified with QIAquick Gel Extraction Kit. The completed libraries were quantified by Agilent 2100 Bioanalyzer. The libraries were denatured with 0.1 M NaOH to generate single-stranded DNA molecules, captured on Illumina flow cell, amplified in situ. The libraries were then sequenced on the Genome Analyzer IIx following the SBS Sequencing 36 Cycle Kit v5 protocol.