BRD4_CDT is the short highly conserved C-terminal domain of certain bromodomain proteins, notably Brd4. The Brd4 CTD interacts with the cyclin T1 and Cdk9 subunits of positive transcription elongation factor b (pTEFb) complex. Brd4 displaces negative regulators, the HEXIM1 and 7SKsnRNA complex, from pTEFb, thereby transforming it into an active form that can phosphorylate RNA pol II [1,2].

1: The bromodomain protein Brd4 is a positive regulatory component of P-TEFb and stimulates RNA polymerase II-dependent transcription. Jang MK, Mochizuki K, Zhou M, Jeong HS, Brady JN, Ozato K; Mol Cell. 2005;19:523-534. PMID:16109376

2: The Brd4 extraterminal domain confers transcription activation independent of pTEFb by recruiting multiple proteins, including NSD3. Rahman S, Sowa ME, Ottinger M, Smith JA, Shi Y, Harper JW, Howley PM; Mol Cell Biol. 2011;31:2641-2652. PMID:21555454