title: The Brd4 extraterminal domain confers transcription activation independent of pTEFb by recruiting multiple proteins, including NSD3.
abstract: Bromodomain protein 4 (Brd4) plays critical roles in development, cancer progression, and virus-host pathogenesis. To gain mechanistic insight into the various biological functions of Brd4, we performed a proteomic analysis to identify and characterize Brd4-associated cellular proteins. We found that the extraterminal (ET) domain, whose function has to date not been determined, interacts with NSD3, JMJD6, CHD4, GLTSCR1, and ATAD5. These ET-domain interactions were also conserved for Brd2 and Brd3, the other human BET proteins tested. We demonstrated that GLTSCR1, NSD3, and JMJD6 impart a pTEFb-independent transcriptional activation function on Brd4. NSD3 as well as JMJD6 is recruited to regulated genes in a Brd4-dependent manner. Moreover, we found that depletion of Brd4 or NSD3 reduces H3K36 methylation, demonstrating that the Brd4/NSD3 complex regulates this specific histone modification. Our results indicate that the Brd4 ET domain through the recruitment of the specific effectors regulates transcriptional activity. In particular, we show that one of these effectors, NSD3, regulates transcription by modifying the chromatin microenvironment at Brd4 target genes. Our study thus identifies the ET domain as a second important transcriptional regulatory domain for Brd4 in addition to the carboxyl-terminal domain (CTD) that interacts with pTEFb.
authors.affiliation: Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Shaila
authors.initials: S
authors.lastname: Rahman
authors.forename: Mathew E
authors.initials: ME
authors.lastname: Sowa
authors.forename: Matthias
authors.initials: M
authors.lastname: Ottinger
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Smith
authors.forename: Yang
authors.initials: Y
authors.lastname: Shi
authors.forename: J Wade
authors.initials: JW
authors.lastname: Harper
authors.forename: Peter M
authors.initials: PM
authors.lastname: Howley
mesh_terms: D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins; D002460:Cell Line; D002868:Chromosomal Proteins, Non-Histone; D011495:Histone-Lysine N-Methyltransferase / Q000378:metabolism*; D006801:Humans; D056484:Jumonji Domain-Containing Histone Demethylases; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D042925:Positive Transcriptional Elongation Factor B / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D000092468:Bromodomain Containing Proteins
chemical_list: D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D011495:Histone-Lysine N-Methyltransferase; D056484:Jumonji Domain-Containing Histone Demethylases; D009687:Nuclear Proteins; D042925:Positive Transcriptional Elongation Factor B; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C560430:BICRA protein, human; C441289:BRD4 protein, human; D000092468:Bromodomain Containing Proteins; C498707:JMJD6 protein, human; C432968:NSD3 protein, human