Cells were washed 2x with ice cold PBS and crosslinked for 10 minutes at room temperature in 1% formaldehyde PBS (thermos fischer #28906). The cross-linked chromatin was sheared by sonication, providing fragments of 200 - 1400 base pairs in length.Protein-DNA complexes were selectively immunoprecipitated using STAT1,STAT2 and IRF9 antibodies. The immunoprecipitated complexes were washed to remove non-specifically bound chromatin, the protein-DNA cross-link was reversed and proteins were removed by proteinase K digest. Four IPs were pooled for each sample, in order to obtain enough DNA precipitated. The DNA associated with the complex was furthermore purified and used for ChIP-seq. For library generation, the NEBNext Ultra II DNA Library Prep Kit for Illumina from NEB was used according to the manufacturer's protocol. The chromatin quality was analyzed on an Agilent 2100 Bioanalyzer and a size selection of 200-1400bp was carried out.