The two bromodomains in BRD4, termed BD1 and BD2, consist of 4 alpha-helices linked by 2 loops.[7] The ET domain structure is made up of 3 alpha-helices and a loop.[8] The C-terminal domain of BRD4 has been implicated in promoting gene transcription through interaction with the transcription elongation factor P-TEFb and RNA polymerase II.[9][10][11]