CDK9-Dependent Transcriptional Elongation in the Innate Interferon-Stimulated Gene Response to Respiratory Syncytial Virus Infection in Airway Epithelial Cells

Tian, Bing; Zhao, Yingxin; Kalita, Mridul; Edeh, Chukwudi B.; Paessler, Slobodan; Casola, Antonella; Teng, Michael N.; Garofalo, Roberto P.; Brasier, Allan R.

doi:10.1128/jvi.03399-12

Cited by 55 publications

(86 citation statements)

References 73 publications

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“…Activated CDK9 binds to sequence-specific DNA binding factors, including NF-B/RelA (21,24) and STAT3 (25), responsible for recruiting CDK9 to inducible gene promoters. Specifically, we found that CDK9 targets to inflammatory GRNs in a RelA-dependent manner (19,21,24). In this study, we further extend our study of the CDK9-interacting complex.…”

Section: Importancesupporting

confidence: 56%

“…We previously observed that innate pathway activation dynamically transitions P-TEFb into an activated state by dissociating it from inhibitory 7SK small nuclear RNA (19) and forming a distinct protein interaction network involving over 407 proteins (22). These studies showed that innate activation reprogrammed the CDK9 complex to associate with RNA/DNA helicases, ribosomal/translation elongation subunits, and unfolded protein response proteins.…”

Section: Importancementioning

confidence: 99%

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BRD4 Couples NF-κB/RelA with Airway Inflammation and the IRF-RIG-I Amplification Loop in Respiratory Syncytial Virus Infection

Tian

Yang

Zhao

et al. 2017

J Virol

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138

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The airway mucosa expresses protective interferon (IFN) and inflammatory cytokines in response to respiratory syncytial virus (RSV) infection. In this study, we examine the role of bromodomain containing 4 (BRD4) in mediating this innate immune response in human small airway epithelial cells. We observe that RSV induces BRD4 to complex with NF-B/RelA. BRD4 is functionally required for expression of the NF-Bdependent inflammatory gene regulatory network (GRN), including the IFN response factor 1 (IRF1) and IRF7, which mediate a cross talk pathway for RIG-I upregulation. Mechanistically, BRD4 is required for cyclin-dependent kinase 9 (CDK9) recruitment and phospho-Ser 2 carboxy-terminal domain (CTD) RNA polymerase (Pol) II formation on the promoters of IRF1, IRF7, and RIG-I, producing their enhanced expression by transcriptional elongation. We also find that BRD4 independently regulates CDK9/ phospho-Ser 2 CTD RNA Pol II recruitment to the IRF3-dependent IFN-stimulated genes (ISGs). In vivo, poly(I·C)-induced neutrophilia and mucosal chemokine production are blocked by a small-molecule BRD4 bromodomain inhibitor. Similarly, BRD4 inhibition reduces RSV-induced neutrophilia, mucosal CXC chemokine expression, activation of the IRF7-RIG-I autoamplification loop, mucosal IFN expression, and airway obstruction. RSV infection activates BRD4 acetyltransferase activity on histone H3 Lys (K) 122, demonstrating that RSV infection activates BRD4 in vivo. These data validate BRD4 as a major effector of RSV-induced inflammation and disease. BRD4 is required for coupling NF-B to expression of inflammatory genes and the IRF-RIG-I autoamplification pathway and independently facilitates antiviral ISG expression. BRD4 inhibition may be a strategy to reduce exuberant virus-induced mucosal airway inflammation. IMPORTANCEIn the United States, 2.1 million children annually require medical attention for RSV infections. A first line of defense is the expression of the innate gene network by infected epithelial cells. Expression of the innate response requires the recruitment of transcriptional elongation factors to rapidly induce innate response genes through an unknown mechanism. We discovered that RSV infection induces a complex of bromodomain containing 4 (BRD4) with NF-B and cyclindependent kinase 9 (CDK9). BRD4 is required for stable CDK9 binding, phosphoSer 2 RNA Pol II formation, and histone acetyltransferase activity. Inhibition of BRD4 blocks Toll-like receptor 3 (TLR3)-dependent neutrophilia and RSV-induced inflammation, demonstrating its importance in the mucosal innate response in vivo. Our study shows that BRD4 plays a central role in inflammation and activation of the IRF7-RIG-I amplification loop vital for mucosal interferon expression. BRD4 inhibition may be a strategy for modulating exuberant mucosal airway inflammation.

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Section: Importancesupporting

confidence: 56%

Section: Importancementioning

confidence: 99%

BRD4 Couples NF-κB/RelA with Airway Inflammation and the IRF-RIG-I Amplification Loop in Respiratory Syncytial Virus Infection

Tian

Yang

Zhao

et al. 2017

J Virol

Self Cite

138

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“…These data suggest that Brd4 might have a more generalized regulatory role in the innate immune response, fighting not only the bacterial infection but also the viral infection. In line with this notion, Brd4 has been shown to be involved in the virus-induced expression of IFN-stimulated genes by facilitating CDK9-mediated transcription elongation (38,39). The availability of these CKO mice might allow future research on dissecting the different functions of Brd4 in the immune response elicited by various pathogen challenges.…”

Section: Discussionmentioning

confidence: 73%

Brd4 modulates the innate immune response through Mnk2–eIF4E pathway-dependent translational control of IκBα

Bao

Chen

et al. 2017

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

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Bromodomain-containing factor Brd4 has emerged as an important transcriptional regulator of NF-κB-dependent inflammatory gene expression. However, the in vivo physiological function of Brd4 in the inflammatory response remains poorly defined. We now demonstrate that mice deficient for Brd4 in myeloid-lineage cells are resistant to LPS-induced sepsis but are more susceptible to bacterial infection. Gene-expression microarray analysis of bone marrow-derived macrophages (BMDMs) reveals that deletion of Brd4 decreases the expression of a significant amount of LPS-induced inflammatory genes while reversing the expression of a small subset of LPS-suppressed genes, including MAP kinase-interacting serine/ threonine-protein kinase 2 (Mknk2). Brd4-deficient BMDMs display enhanced Mnk2 expression and the corresponding eukaryotic translation initiation factor 4E (eIF4E) activation after LPS stimulation, leading to an increased translation of IκBα mRNA in polysomes. The enhanced newly synthesized IκBα reduced the binding of NF-κB to the promoters of inflammatory genes, resulting in reduced inflammatory gene expression and cytokine production. By modulating the translation of IκBα via the Mnk2-eIF4E pathway, Brd4 provides an additional layer of control for NF-κB-dependent inflammatory gene expression and inflammatory response.T he inducible transcription factor NF-κB plays a key role in regulating the inflammatory and immune responses in mammals (1, 2). The prototypical NF-κB complex, the heterodimer of p50 and RelA, is sequestered in the cytoplasm by its assembly with its inhibitor IκBα (1, 2). Upon stimulation, IκB kinase complex is activated and phosphorylates IκBα, leading to the degradation of IκBα, the nuclear translocation of NF-κB complex, and the activation of NF-κB target genes (1-3). Importantly, one of NF-κB target genes is its inhibitor, IκBα. The resynthesized IκBα enters the nucleus, where it removes the NF-κB from the DNA and terminates activated NF-κB (1, 2, 4). The resynthesis of IκBα therefore creates a negative feedback regulation of NF-κB signaling, preventing sustained NF-κB activation and prolonged inflammatory response.In addition to the negative feedback regulation from resynthesized IκBα, the NF-κB-mediated inflammatory response is subjected to many layers of regulation, including transcriptional, translational, and posttranslational regulation (5-8). Recent studies demonstrate that selective translational control of gene expression plays an important regulatory role in the inflammatory response (7, 9). The eukaryotic translation initiation factor eIF4E has been shown to be the node of the translational control of immune response via the mTOR signaling pathway or the MAPK-Mnk1-Mnk2-eIF4E pathway (9). Upon LPS stimulation, eIF4E can be activated via its phosphorylation at S209 by Mnk1/2 (10). The phosphorylated eIF4E then activates the translation of mRNA of inflammatory genes, including IRF8 (11, 12). Interestingly, the translation of IκBα is also regulated by the phosphorylation and activation of e...

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“…PCR products were subjected to melting curve analysis to ensure that a single amplification product was produced. Quantification of relative changes in gene expression was done using the threshold cycle (⌬⌬C T ) method (44).…”

Section: Methodsmentioning

confidence: 99%

Ataxia Telangiectasia Mutated Kinase Mediates NF-κB Serine 276 Phosphorylation and Interferon Expression via the IRF7-RIG-I Amplification Loop in Paramyxovirus Infection

Fang

Choudhary

Tian

et al. 2015

J Virol

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Respiratory syncytial virus (RSV) is Respiratory syncytial virus (RSV), a negative-sense, singlestranded RNA (ssRNA) virus of the Paramyxoviridae family, is one of the most important respiratory pathogens of young children worldwide (1). Epidemiological studies have shown that RSV infects almost all children in the United States by the age of 3, producing primarily upper respiratory tract infections and otitis media (2). In a small subset of immunologically naive or predisposed infants, RSV infection produces a more severe, lower respiratory tract infection (LRTI), an event that accounts for over 3 million hospitalizations and about 200,000 deaths (3, 4). Importantly, there are no effective vaccines or treatments available (2).In seasonal epidemics, RSV is spread via large droplets and self-inoculation (3). Once infected, RSV replicates in the nasal mucosa intraepithelial bridges into the lower respiratory tract or by free virus in respiratory secretions binding to epithelial cilia (5, 6). In the lower airway, RSV replicates primarily in epithelial cells, where it generates bronchial inflammation, epithelial necrosis, sloughing, peribronchial mononuclear cell infiltration, and submucosal edema producing obstructive physiology (7-9). The pathogenesis of LRTI involves an interplay between viral inoculum, host factors, and immune response and is not fully understood (10). Children with bronchiolitis present symptoms at times

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CDK9-Dependent Transcriptional Elongation in the Innate Interferon-Stimulated Gene Response to Respiratory Syncytial Virus Infection in Airway Epithelial Cells

Cited by 55 publications

References 73 publications

BRD4 Couples NF-κB/RelA with Airway Inflammation and the IRF-RIG-I Amplification Loop in Respiratory Syncytial Virus Infection

BRD4 Couples NF-κB/RelA with Airway Inflammation and the IRF-RIG-I Amplification Loop in Respiratory Syncytial Virus Infection

Brd4 modulates the innate immune response through Mnk2–eIF4E pathway-dependent translational control of IκBα

Ataxia Telangiectasia Mutated Kinase Mediates NF-κB Serine 276 Phosphorylation and Interferon Expression via the IRF7-RIG-I Amplification Loop in Paramyxovirus Infection

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