Live cells were isolated by Histopaque gradient centrifugation. Cross-linking was done by addition of 1% paraformaldehyde at room temperature for 10 min, followed by sonication and immunoprecipitation with 10 μg of anti-IRF4 (clone sc-6059) and a corresponding goat polyclonal-IgG control (clone sc-2028) (Santa Cruz Technologies). The DNA fragments were blunt-end ligated to the Illumina adaptors, amplified, and sequenced with an Illumina HiSeq 2000.