BRD4 and embryonal carcinoma: FLIP assays using P19 embryonic carcinoma cells transfected with GFP-tagged BRD4 show that GFP-BRD4 fluorescence is lost more slowly in the presence of trichostatin A (TSA), which is a histone deacetylase inhibitor, suggesting the affinity of BRD4 for chromatin is increased by histone acetylation [19].