| Structural highlights
Disease
[BRD4_HUMAN] Note=A chromosomal aberration involving BRD4 is found in a rare, aggressive, and lethal carcinoma arising in midline organs of young people. Translocation t(15;19)(q14;p13) with NUT which produces a BRD4-NUT fusion protein.[1] [2]
Function
[BRD4_HUMAN] Plays a role in a process governing chromosomal dynamics during mitosis (By similarity). [TF65_HUMAN] NF-kappa-B is a pleiotropic transcription factor present in almost all cell types and is the endpoint of a series of signal transduction events that are initiated by a vast array of stimuli related to many biological processes such as inflammation, immunity, differentiation, cell growth, tumorigenesis and apoptosis. NF-kappa-B is a homo- or heterodimeric complex formed by the Rel-like domain-containing proteins RELA/p65, RELB, NFKB1/p105, NFKB1/p50, REL and NFKB2/p52 and the heterodimeric p65-p50 complex appears to be most abundant one. The dimers bind at kappa-B sites in the DNA of their target genes and the individual dimers have distinct preferences for different kappa-B sites that they can bind with distinguishable affinity and specificity. Different dimer combinations act as transcriptional activators or repressors, respectively. NF-kappa-B is controlled by various mechanisms of post-translational modification and subcellular compartmentalization as well as by interactions with other cofactors or corepressors. NF-kappa-B complexes are held in the cytoplasm in an inactive state complexed with members of the NF-kappa-B inhibitor (I-kappa-B) family. In a conventional activation pathway, I-kappa-B is phosphorylated by I-kappa-B kinases (IKKs) in response to different activators, subsequently degraded thus liberating the active NF-kappa-B complex which translocates to the nucleus. NF-kappa-B heterodimeric p65-p50 and p65-c-Rel complexes are transcriptional activators. The NF-kappa-B p65-p65 complex appears to be involved in invasin-mediated activation of IL-8 expression. The inhibitory effect of I-kappa-B upon NF-kappa-B the cytoplasm is exerted primarily through the interaction with p65. p65 shows a weak DNA-binding site which could contribute directly to DNA binding in the NF-kappa-B complex. Associates with chromatin at the NF-kappa-B promoter region via association with DDX1.[3] [4] [5] [6] [7] [8]
Publication Abstract from PubMed
Acetylation of the RelA subunit of NF-kappaB at lysine-310 regulates the transcriptional activation of NF-kappaB target genes and contributes to maintaining constitutively active NF-kappaB in tumors. Bromodomain-containing factor Brd4 has been shown to bind to acetylated lysine-310 (AcLys310) and to regulate the transcriptional activity of NF-kappaB, but the role of this binding in maintaining constitutively active NF-kappaB in tumors remains elusive. In this study, we demonstrate the structural basis for the binding of bromodomains (BDs) of bromodomain-containing protein 4 (Brd4) to AcLys310 and identify the BD inhibitor JQ1 as an effective small molecule to block this interaction. JQ1 suppresses TNF-alpha-mediated NF-kappaB activation and NF-kappaB-dependent target gene expression. In addition, JQ1 inhibits the proliferation and transformation potential of A549 lung cancer cells and suppresses the tumorigenicity of A549 cells in severe combined immunodeficiency mice. Furthermore, we demonstrate that depletion of Brd4 or treatment of cells with JQ1 induces the ubiquitination and degradation of the constitutively active nuclear form of RelA. Our results identify a novel function of Brd4 in maintaining the persistently active form of NF-kappaB found in tumors, and they suggest that interference with the interaction between acetylated RelA and Brd4 could be a potential therapeutic approach for the treatment of NF-kappaB-driven cancer.Oncogene advance online publication, 20 May 2013; doi:10.1038/onc.2013.179.
Brd4 maintains constitutively active NF-kappaB in cancer cells by binding to acetylated RelA.,Zou Z, Huang B, Wu X, Zhang H, Qi J, Bradner J, Nair S, Chen LF Oncogene. 2013 May 20. doi: 10.1038/onc.2013.179. PMID:23686307[9]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ French CA, Miyoshi I, Kubonishi I, Grier HE, Perez-Atayde AR, Fletcher JA. BRD4-NUT fusion oncogene: a novel mechanism in aggressive carcinoma. Cancer Res. 2003 Jan 15;63(2):304-7. PMID:12543779
- ↑ French CA, Miyoshi I, Aster JC, Kubonishi I, Kroll TG, Dal Cin P, Vargas SO, Perez-Atayde AR, Fletcher JA. BRD4 bromodomain gene rearrangement in aggressive carcinoma with translocation t(15;19). Am J Pathol. 2001 Dec;159(6):1987-92. PMID:11733348 doi:10.1016/S0002-9440(10)63049-0
- ↑ Schulte R, Grassl GA, Preger S, Fessele S, Jacobi CA, Schaller M, Nelson PJ, Autenrieth IB. Yersinia enterocolitica invasin protein triggers IL-8 production in epithelial cells via activation of Rel p65-p65 homodimers. FASEB J. 2000 Aug;14(11):1471-84. PMID:10928981
- ↑ Asamitsu K, Tetsuka T, Kanazawa S, Okamoto T. RING finger protein AO7 supports NF-kappaB-mediated transcription by interacting with the transactivation domain of the p65 subunit. J Biol Chem. 2003 Jul 18;278(29):26879-87. Epub 2003 May 13. PMID:12748188 doi:10.1074/jbc.M211831200
- ↑ Liu Y, Smith PW, Jones DR. Breast cancer metastasis suppressor 1 functions as a corepressor by enhancing histone deacetylase 1-mediated deacetylation of RelA/p65 and promoting apoptosis. Mol Cell Biol. 2006 Dec;26(23):8683-96. Epub 2006 Sep 25. PMID:17000776 doi:10.1128/MCB.00940-06
- ↑ Sun S, Tang Y, Lou X, Zhu L, Yang K, Zhang B, Shi H, Wang C. UXT is a novel and essential cofactor in the NF-kappaB transcriptional enhanceosome. J Cell Biol. 2007 Jul 16;178(2):231-44. Epub 2007 Jul 9. PMID:17620405 doi:jcb.200611081
- ↑ Ishaq M, Ma L, Wu X, Mu Y, Pan J, Hu J, Hu T, Fu Q, Guo D. The DEAD-box RNA helicase DDX1 interacts with RelA and enhances nuclear factor kappaB-mediated transcription. J Cell Biochem. 2009 Feb 1;106(2):296-305. doi: 10.1002/jcb.22004. PMID:19058135 doi:10.1002/jcb.22004
- ↑ Sharif-Askari E, Vassen L, Kosan C, Khandanpour C, Gaudreau MC, Heyd F, Okayama T, Jin J, Rojas ME, Grimes HL, Zeng H, Moroy T. Zinc finger protein Gfi1 controls the endotoxin-mediated Toll-like receptor inflammatory response by antagonizing NF-kappaB p65. Mol Cell Biol. 2010 Aug;30(16):3929-42. doi: 10.1128/MCB.00087-10. Epub 2010 Jun , 14. PMID:20547752 doi:10.1128/MCB.00087-10
- ↑ Zou Z, Huang B, Wu X, Zhang H, Qi J, Bradner J, Nair S, Chen LF. Brd4 maintains constitutively active NF-kappaB in cancer cells by binding to acetylated RelA. Oncogene. 2013 May 20. doi: 10.1038/onc.2013.179. PMID:23686307 doi:http://dx.doi.org/10.1038/onc.2013.179
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