Cells were harvested and washed with PBS prior to a 2-step crosslinking procedure. Proteins were crosslinked by incubating cells for 45min at RT in PBS supplemented with 0.83 mg/ml Di(N-succinimidyl) glutarate (DSG, Sigma). Cells were then washed 4 times with PBS, prior to formaldehyde crosslinking of proteins and DNA for 10min at RT using 1% formaldehyde (Pierce) in IMDM with 10% FCS. Formaldehyde was quenched by adding 1/10th volume 2M glycine and crosslinked cells were washed twice in ice-cold PBS. Single crosslinked samples were treated with 1% formaldehyde crosslinking only. Nuclei were prepared essentially as described in Lefevre et al 2003. Antibody incubated with chromatin 2-4hrs at 4 degrees. Kapa Hyper-prep kit