Cells were crosslinked with 1% formaldehyde for 10 minutes at room temperature. Crosslinking was stopped with 125mM Glycine and cells were washed and scraped in cold PBS. IP was done as described in Reddy et al 2009 using Santa Cruz ERα (HC-20) or Millipore ERα (06-935) TruSeq library construction as described in Reddy et al 2009