DP thymocytes from control and Rad21-/- mice were FACS-sorted, fixed and subsequently lysed and sonicated to extract soluble chromatin. H3K27Ac was immunoprecipitated using polyclonal antibodies. Smc1a was immunoprecipitated from WT samples only. Library was constructed using NEBNext ChIP-Seq Library Prep Kit (NEB, catalog number E6200S), according to the manufacturer's instructions