After the appropriate treatment, cells were washed with cold PBS, crosslinked for 5min (RING1B: 10min) with 1% Formaldehyde at room temperature and subsequently quenched with 0.1M Glycin (final concentration) for 5min before harvesting. Then, nuclei were isolated and sonicated using the Covaris Chromatin Shearing Kit. ChIP-Immunoprecipation of chromatin was done using antibodies according to the manufacturers recommendation with EdU-labelled Drosophila S2 chromatin serving as Spike-In control and, where the epitope of the antibody does not recognize the Drosophila homolog (i.e. H2A.Z) , H2AV antibodies to immunoprecipitate Spike-In chromatin as well. Purified fragments were biotinylated, libraries prepared, EdU-biotinylated fragments pulled down using Streptavidin and sequenced