Chromatin shearing from HeLa cells is performed according to Diagenode’s Chromatin Shearing Optimization kit – Low SDS protocol (Cat. No, AA-001-0100). Nuclei are resuspended in buffer iS1 at a final concentration of 1x10e6 per 100 μl. 2 ml nuclei aliquots are sonicated with the Bioruptor® Pico in 15 ml Bioruptor® Tubes (Cat. No. C01020031) with or without sonication beads (sonication beads are part of Cat. No. C01020031) for 10, 20 or 30 cycles (30 sec ON/30 sec OFF).