V6.5 mES cells were fixed with 1% formaldehyde for 10 minutes at room temperature, quenched with 2.5M glycine, washed with 1x PBS (3x) harvested by scraping, pelleting, and resuspended in modified RIPA lysis buffer (150mM NaCl, 50mM Tris, 0.5% Sodium deoxycholate, 0.2% SDS, 1% NP-40) supplemented with RNase inhibitors (Ambion, AM2694) and protease inhibitors. For UV crosslinking experiments, cells were irradiated with 254nm UV light. Cells were kept on ice and crosslinked in 1x PBS using 400,000 μjoules/cm2.
