Raji cells were crosslinked at room temperature by adding 1/10th volume of crosslinking solution (11% formaldehyde, 100 mM NaCl, 1 mM EDTA pH 8.0, 0.5 mM EGTA pH 8.0, 50 mM Hepes pH 7.8) to the cell culture medium for 10 min. The reaction was stopped by the addition of 250 mM glycine for 5 min. Afterwards the cells were washed twice with PBS. 5 x 107 cells were lysed in 2,5 ml LB1 (50 mM Hepes, pH 7.5, 140 mM NaCl, 1 mM EDTA, pH 8.0, 10% Glycerol, 1% NP-40, 0.5% Triton X-100, 1 x phosphatase inhibitors, 1 x EDTA‐free protease inhibitors (Roche)) for 20 min at 4°C on a shaker. The cells were spun down (5 min, 4°C, 1350 g) and washed with LB2 (200 mM NaCl, 1 mM EDTA pH 8.0, 0.5 mM EGTA pH 8.0, 10 mM Tris pH 8.0, 1 x phosphatase inhibitors, 1 x EDTA‐free protease inhibitors) for 20 min at 4°C. The samples were spun down again and suspended in 1.5 ml LB3 (1 mM EDTA pH 8.0, 0.5 mM EGTA pH 8.0, 10 mM Tris pH 8.0, 100 mM NaCl, 0.1 % Na-Deoxycholate, 0.5% N-lauroylsarcosine, 1 x phosphatase inhibitors, 1 x EDTA‐free protease inhibitors). The samples were sonicated with a Misonix 4000 (Misonix Inc.) sonicator for 14 cycles (30 sec on, 30 sec off, amplitude 40). Triton X-100 was added to a final concentration of 1% and the chromatin was collected by centrifugation (20 000 g, 20 min, 4°C). An aliquot of 50 µl was taken as input control. The input was mixed with an equal volume of 2 x elution buffer (100 mM Tris pH 8.0, 20 mM EDTA pH 8.0, 2 % SDS) and incubated at 65°C for 13-15 h. The sample was diluted with same volume of TE (10 mM Tris pH 8.0, 1 mM EDTA pH 8.0) and digested by RNase A (0.2 µg/ml, 2 h, 37°C) and Proteinase K (0.2 µg/ml, 2 h, 55°C). DNA was purified by two phenol:chloroform:isoamylalcohol (25:24:1, pH 8.0) extractions steps and a subsequent PCR column purification (Qiagen). DNA fragmentation was controlled on a 2% agarose gel.