BRD4 and osteosarcoma: We transfected human osteosarcoma U2OS cells with full-length, GFP-tagged BRD4 individually mutated to alanine or phenylalanine at these four BD1 locations as well as with BRD4 BD2 mutated at Asn-433 (which corresponds to Asn-140 in BD1) and with a double Asn-140/Asn-433 mutant.