Cells were harvested and nuclei isolated. Nuclei were digested with 120-140U MNase in the presence of 3mM CaCl2 for 20min at 25°C. Reactions were stopped and the MNase digested chromatin was centrifuged at 12,000g for 5min. The resulting supernatant was added to 15µl streptavidin magnetic beads and incubated for 1h at 4°C. Beads were washed and DNA eluted and purified according to standard protocols. Sequencing libraries were prepared as described in Bowman et al. (Bowman et al., 2013).