Whole cell extracts were sonicated to solubilize the chromatin. 1x10^8 cells were sonicated at 21 watts in 20 second pulses for 3 min of sonication time. The chromatin extracts containing DNA fragments with an average size of 500 bp were prepared for sequencing according to a modified version of the Solexa Genomic DNA protocol. Fragmented DNA was end repaired and subjected to 18 cycles of LM-PCR using oligos provided by Illumina. Amplified fragments between 150 and 300bp (representing shear fragments between 50 and 200nt in length and ~100bp of primer sequence) were isolated by agarose gel electrophoresis and purified. All protocols for Illumina/Solexa sequence preparation, sequencing and quality control are provided by Illumina (http://www.illumina.com/pages.ilmn?ID=203).