MCF7 human breast cancer cells were grown as previously described (Neve et al. 2006). Unless otherwise stated, during all experiments oestrogen was added at a final concentration of 100 nM for 45 minutes (ChIP) or 24 hours (cell cycle analysis). HepG2 cells were grown in DMEM supplemented with 10% FBS. ChIP experiments were performed with well-characterized antibodies against CTCF (Millipore, 07-729), STAG1 (abcam, ab4457), RAD21 (abcam, ab992), ERa (santa cruz, sc-543), CEBPa (santa cruz, sc-9314) and MED12 (abcam, ab70842). ChIP-seq experiments were performed as recently described (Schmidt et al. 2009)