The Bromodomain Protein Brd4 Is a Positive Regulatory Component of P-TEFb and Stimulates RNA Polymerase II-Dependent Transcription

Jang, Moon Kyoo; Mochizuki, Kazuki; Zhou, Meisheng; Jeong, Ho‐Sang; Brady, John; Ozato, Keiko

doi:10.1016/j.molcel.2005.06.027

Cited by 1,131 publications

(1,190 citation statements)

References 38 publications

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“…S6A, bars 1-3). Importantly, these effects were counteracted by coexpressing siRNA against Brd4, an integral component of transcriptionally active P-TEFb (13,14), suggesting that the enhanced EDA inclusion levels were P-TEFb-dependent (Fig. 3C and Fig.…”

Section: Disintegration Of 7sk Snrnp Promotes Alternative Splicing VImentioning

confidence: 99%

“…Therein, 7SK is a molecular scaffold, which binds HEXIM1, HEXIM2, and LARP7 directly, enabling the sequestration and repression of P-TEFb. Another major fraction of P-TEFb constitutes the Brd4/P-TEFb complex, which represents the transcriptionally active P-TEFb and could be recruited to target genes because of the binding of Brd4 to acetylated histones or the mediator (13,14). The dynamic partitioning of P-TEFb between the complexes constitutes a functional equilibrium that can be perturbed.…”

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confidence: 99%

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7SK snRNP/P-TEFb couples transcription elongation with alternative splicing and is essential for vertebrate development

Barborič

Lenasi

Chen

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

151

176

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Eukaryotic gene expression is commonly controlled at the level of RNA polymerase II (RNAPII) pausing subsequent to transcription initiation. Transcription elongation is stimulated by the positive transcription elongation factor b (P-TEFb) kinase, which is suppressed within the 7SK small nuclear ribonucleoprotein (7SK snRNP). However, the biogenesis and functional significance of 7SK snRNP remain poorly understood. Here, we report that LARP7, BCDIN3, and the noncoding 7SK small nuclear RNA (7SK) are vital for the formation and stability of a cell stress-resistant core 7SK snRNP. Our functional studies demonstrate that 7SK snRNP is not only critical for controlling transcription elongation, but also for regulating alternative splicing of pre-mRNAs. Using a transient expression splicing assay, we find that 7SK snRNP disintegration promotes inclusion of an alternative exon via the increased occupancy of P-TEFb, Ser2-phosphorylated (Ser2-P) RNAPII, and the splicing factor SF2/ASF at the minigene. Importantly, knockdown of larp7 or bcdin3 orthologues in zebrafish embryos destabilizes 7SK and causes severe developmental defects and aberrant splicing of analyzed transcripts. These findings reveal a key role for P-TEFb in coupling transcription elongation with alternative splicing, and suggest that maintaining core 7SK snRNP is essential for vertebrate development.C hallenging the once predominantly held view that RNA polymerase II (RNAPII) recruitment to promoters is the rate-limiting event in regulating eukaryotic transcription, several recent studies indicate that RNAPII pauses subsequently to transcription initiation at a large number of genes in Drosophila and in several cell lineages in humans (1). A paradigm for this type of control is the regulation of HIV-1 transcription, which is paused because of concerted actions of the negative transcription elongation factors (N-TEFs) (1, 2). The block is reversed by the positive transcription elongation factor b (P-TEFb), consisting of a heterodimer between the cyclin-dependent kinase 9 (Cdk9) and one of the four C-type cyclins (CycT1/T2a(b)/K) (2), which phosphorylates Ser2 within the multiple heptapeptide repeats YSPTSPS of the carboxy-terminal domain (CTD) of the Rpb1 subunit of RNAPII, as well as components of N-TEFs. Of note, P-TEFb is critical for expressing early embryonic genes in C. elegans (3), and experiments in yeast and Drosophila demonstrate that it is also vital for proper 3Ј end pre-mRNA processing (4, 5). Thus, regulating transcription elongation is a key checkpoint for modulating eukaryotic gene expression.P-TEFb exists in 2 mutually exclusive complexes that differ in their kinase activity (2). A transcriptionally inactive complex [referred to herein as 7SK small nuclear ribonucleoprotein (7SK snRNP)] contains P-TEFb, hexamethylene bisacetamide-induced protein (HEXIM) 1 (HEXIM1) and/or HEXIM2, the noncoding 7SK small nuclear RNA (7SK) and the La-related protein 7 (LARP7) (6-12). Therein, 7SK is a molecular scaffold, which binds HEXIM1, HEXIM2, and LARP7 d...

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Section: Disintegration Of 7sk Snrnp Promotes Alternative Splicing VImentioning

confidence: 99%

mentioning

confidence: 99%

7SK snRNP/P-TEFb couples transcription elongation with alternative splicing and is essential for vertebrate development

Barborič

Lenasi

Chen

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

151

176

View full text Add to dashboard Cite

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“…Binding of CCNT1, NFkB1, DDX6 and HEXIM1 was validated by co-immunoprecipitation experiments Characterization of the oncogenic AF4-MLL complex A Benedikt et al (Figure 2c, panels I-IV). For the validation of NPM1 and BRD4, full-length NPM1 and a 80 kDa fragment of BRD4Fknown to still confer binding to P-TEFb 24 Fwere both fused to GFP. This was necessary because wild-type BRD4 migrates in the SDS-PAGE at a similar position as AF4.…”

Section: Composition Of the Af4 And Af4-mll Protein Complexmentioning

confidence: 99%

“…14 Bound BRD4 stimulates the P-TEFb kinase function, facilitates binding of the AF4 complex to chromatin and prevents binding of HEXIM1. 24,33 Of interest, BRD4 binds to the acetylated NFkB1/RELA (K310) and functions as specific co-activator of NFkB1/RELA to regulate transcription of a subset of NFkB1-responsive inflammatory genes 34, and has been described as binding partner of NPM1. NFkB1/NPM1 heterodimers …”

Section: Characterization Of the Oncogenic Af4-mll Complex A Benediktmentioning

confidence: 99%

The leukemogenic AF4–MLL fusion protein causes P-TEFb kinase activation and altered epigenetic signatures

et al. 2010

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Expression of the AF4-MLL fusion protein in murine hematopoietic progenitor/stem cells results in the development of proB acute lymphoblastic leukemia. In this study, we affinity purified the AF4-MLL and AF4 protein complexes to elucidate their function. We observed that the AF4 complex consists of 11 binding partners and exhibits positive transcription elongation factor b (P-TEFb)-mediated activation of promoter-arrested RNA polymerase (pol) II in conjunction with several chromatin-modifying activities. In contrast, the AF4-MLL complex consists of at least 16 constituents including P-TEFb kinase, H3K4 me3 and H3K79 me3 histone methyltransferases (HMT), a protein arginine N-methyltransferase and a histone acetyltransferase. These findings suggest that the AF4-MLL protein disturbs the fine-tuned activation cycle of promoter-arrested RNA Pol II and causes altered histone methylation signatures. Thus, we propose that these two processes are key to trigger cellular reprogramming that leads to the onset of acute leukemia.

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“…This methodology not only allowed us to identify Rrp1b as a dual ECM and metastasis efficiency modifier, but also to demonstrate that the cell growth regulator Bromodomain 4 (Brd4) [15][16][17], which also binds Sipa1, has similar properties with regards to metastasis and ECM gene expression (Bromodomain 4 activation predicts breast cancer survival; N.Crawford, J.Alsarraj, L.Lukes, R.Walker, H.Yang, M.Lee, K. Ozato, K.Hunter; PNAS, in press). Furthermore, we demonstrated that differential activity of BRD4 in primary breast cancers accurately predicts outcome in five different tumor gene expression datasets.…”

Section: Introductionmentioning

confidence: 99%

The Diasporin Pathway: a tumor progression-related transcriptional network that predicts breast cancer survival

Crawford

Walker

Lukes

et al. 2008

Clin Exp Metastasis

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Microarray expression signature analyses have suggested that extracellular matrix (ECM) gene dysregulation is predictive of metastasis in both mouse mammary tumorigenesis and human breast cancer. We have previously demonstrated that such ECM dysregulation is influenced by hereditary germline-encoded variation. To identify novel metastasis efficiency modifiers, we performed expression QTL (eQTL) mapping in recombinant inbred mice by characterizing genetic loci modulating metastasis-predictive ECM gene expression. Three reproducible eQTLs were observed on chromosomes 7, 17 and 18. Candidate genes were identified by correlation analyses and known associations with metastasis. Seven candidates were identified (Ndn, Pi16, Luc7l, Rrp1b, Brd4, Centd3 and Csf1r). Stable transfection of the highly metastatic Mvt-1 mouse mammary tumor cell line with expression vectors encoding each candidate modulated metastasis-predictive ECM gene expression. Implantation of these cells into mice demonstrated that candidate gene ectopic expression impacts tumor progression. Gene expression analyses facilitated the construction of a transcriptional network that we have termed the 'Diasporin Pathway'. This pathway contains the seven candidates, as well as metastasis-predictive ECM genes and metastasis suppressors. Brd4 and Rrp1b appear to form a central node within this network, which likely is a consequence of their physical interaction with the metastasis efficiency modifier Sipa1. Furthermore, we demonstrate that the microarray gene expression signatures induced by activation of ECM eQTL genes in the Mvt-1 cell line can be used to accurately predict survival in a human breast cancer cohort. These data imply that the Diasporin Pathway may be an important nexus in tumor progression in both mice and humans.

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The Bromodomain Protein Brd4 Is a Positive Regulatory Component of P-TEFb and Stimulates RNA Polymerase II-Dependent Transcription

Cited by 1,131 publications

References 38 publications

7SK snRNP/P-TEFb couples transcription elongation with alternative splicing and is essential for vertebrate development

7SK snRNP/P-TEFb couples transcription elongation with alternative splicing and is essential for vertebrate development

The leukemogenic AF4–MLL fusion protein causes P-TEFb kinase activation and altered epigenetic signatures

The Diasporin Pathway: a tumor progression-related transcriptional network that predicts breast cancer survival

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