Individual Interferon Regulatory Factor-3 Thiol Residues Are Not Critical for Its Activation Following Virus Infection

ABSTRACT Severe acute respiratory syndrome (SARS) is caused by a novel coronavirus termed SARS-CoV. We and others have previously shown that the replication of SARS-CoV can be suppressed by exogenously added interferon (IFN), a cytokine which is normally synthesized by cells as a reaction to virus infection. Here, we demonstrate that SARS-CoV escapes IFN-mediated growth inhibition by preventing the induction of IFN-β. In SARS-CoV-infected cells, no endogenous IFN-β transcripts and no IFN-β promoter activity were detected. Nevertheless, the transcription factor interferon regulatory factor 3 (IRF-3), which is essential for IFN-β promoter activity, was transported from the cytoplasm to the nucleus early after infection with SARS-CoV. However, at a later time point in infection, IRF-3 was again localized in the cytoplasm. By contrast, IRF-3 remained in the nucleus of cells infected with the IFN-inducing control virus Bunyamwera delNSs. Other signs of IRF-3 activation such as hyperphosphorylation, homodimer formation, and recruitment of the coactivator CREB-binding protein (CBP) were found late after infection with the control virus but not with SARS-CoV. Our data suggest that nuclear transport of IRF-3 is an immediate-early reaction to virus infection and may precede its hyperphosphorylation, homodimer formation, and binding to CBP. In order to escape activation of the IFN system, SARS-CoV appears to block a step after the early nuclear transport of IRF-3.

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Transcriptional Profiling of Interferon Regulatory Factor 3 Target Genes: Direct Involvement in the Regulation of Interferon-Stimulated Genes

Journal of Virology ◽

10.1128/jvi.76.11.5532-5539.2002 ◽

2002 ◽

Vol 76 (11) ◽

pp. 5532-5539 ◽

Cited By ~ 361

Author(s):

Nathalie Grandvaux ◽

Marc J. Servant ◽

Benjamin tenOever ◽

Ganes C. Sen ◽

Siddarth Balachandran ◽

...

Keyword(s):

Virus Infection ◽

Target Genes ◽

Expression Profiles ◽

Expression System ◽

Active Form ◽

Interferon Regulatory Factor ◽

Inducible Expression ◽

Immediate Early ◽

Regulatory Factor ◽

Interferon Regulatory Factor 3

ABSTRACT Ubiquitously expressed interferon regulatory factor 3 (IRF-3) is directly activated after virus infection and functions as a key activator of the immediate-early alpha/beta interferon (IFN) genes, as well as the RANTES chemokine gene. In the present study, a tetracycline-inducible expression system expressing a constitutively active form of IRF-3 (IRF-3 5D) was combined with DNA microarray analysis to identify target genes regulated by IRF-3. Changes in mRNA expression profiles of 8,556 genes were monitored after Tet-inducible expression of IRF-3 5D. Among the genes upregulated by IRF-3 were transcripts for several known IFN-stimulated genes (ISGs). Subsequent analysis revealed that IRF-3 directly induced the expression of ISG56 in an IFN-independent manner through the IFN-stimulated responsive elements (ISREs) of the ISG56 promoter. These results demonstrate that, in addition to its role in the formation of a functional immediate-early IFN-β enhanceosome, IRF-3 is able to discriminate among ISRE-containing genes involved in the establishment of the antiviral state as a direct response to virus infection.

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Structural and Functional Analysis of Interferon Regulatory Factor 3: Localization of the Transactivation and Autoinhibitory Domains

Molecular and Cellular Biology ◽

10.1128/mcb.19.4.2465 ◽

1999 ◽

Vol 19 (4) ◽

pp. 2465-2474 ◽

Cited By ~ 243

Author(s):

Rongtuan Lin ◽

Yael Mamane ◽

John Hiscott

Keyword(s):

Amino Acids ◽

Dna Binding ◽

Virus Infection ◽

Nuclear Translocation ◽

Sendai Virus ◽

Interferon Regulatory Factor ◽

Phosphorylation Sites ◽

Transactivation Domain ◽

Regulatory Factor ◽

Interferon Regulatory Factor 3

ABSTRACT The interferon regulatory factor 3 (IRF-3) gene encodes a 55-kDa protein which is expressed constitutively in all tissues. In unstimulated cells, IRF-3 is present in an inactive cytoplasmic form; following Sendai virus infection, IRF-3 is posttranslationally modified by protein phosphorylation at multiple serine and threonine residues located in the carboxy terminus. Virus-induced phosphorylation of IRF-3 leads to cytoplasmic to nuclear translocation of phosphorylated IRF-3, association with the transcriptional coactivator CBP/p300, and stimulation of DNA binding and transcriptional activities of virus-inducible genes. Using yeast and mammalian one-hybrid analysis, we now demonstrate that an extended, atypical transactivation domain is located in the C terminus of IRF-3 between amino acids (aa) 134 and 394. We also show that the C-terminal domain of IRF-3 located between aa 380 and 427 participates in the autoinhibition of IRF-3 activity via an intramolecular association with the N-terminal region between aa 98 and 240. After Sendai virus infection, an intermolecular association between IRF-3 proteins is detected, demonstrating a virus-dependent formation of IRF-3 homodimers; this interaction is also observed in the absence of virus infection with a constitutively activated form of IRF-3. Substitution of the C-terminal Ser-Thr phosphorylation sites with the phosphomimetic Asp in the region ISNSHPLSLTSDQ between amino acids 395 and 407 [IRF-3(5D)], but not the adjacent S385 and S386 residues, generates a constitutively activated DNA binding form of IRF-3. In contrast, substitution of S385 and S386 with either Ala or Asp inhibits both DNA binding and transactivation activities of the IRF-3(5D) protein. These studies thus define the transactivation domain of IRF-3, two domains that participate in the autoinhibition of IRF-3 activity, and the regulatory phosphorylation sites controlling IRF-3 dimer formation, DNA binding activity, and association with the CBP/p300 coactivator.

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Analysis of Genes Induced by Sendai Virus Infection of Mutant Cell Lines Reveals Essential Roles of Interferon Regulatory Factor 3, NF-κB, and Interferon but Not Toll-Like Receptor 3

Journal of Virology ◽

10.1128/jvi.79.7.3920-3929.2005 ◽

2005 ◽

Vol 79 (7) ◽

pp. 3920-3929 ◽

Cited By ~ 84

Author(s):

Christopher P. Elco ◽

Jeanna M. Guenther ◽

Bryan R. G. Williams ◽

Ganes C. Sen

Keyword(s):

Virus Infection ◽

Cell Lines ◽

Sendai Virus ◽

Mutant Cell ◽

Gene Induction ◽

Interferon Regulatory Factor ◽

Toll Like Receptor ◽

Regulatory Factor ◽

Interferon Regulatory Factor 3 ◽

Infected Cells

ABSTRACT Sendai virus (SeV) infection causes the transcriptional induction of many cellular genes that are also induced by interferon (IFN) or double-stranded RNA (dsRNA). We took advantage of various mutant cell lines to investigate the putative roles of the components of the IFN and dsRNA signaling pathways in the induction of those genes by SeV. Profiling the patterns of gene expression in SeV-infected cells demonstrated that Toll-like receptor 3, although essential for gene induction by dsRNA, was dispensable for gene induction by SeV. In contrast, Jak1, which mediates IFN signaling, was required for the induction of a small subset of genes by SeV. NF-κB and interferon regulatory factor 3 (IRF-3), the two major transcription factors activated by virus infection, were essential for the induction of two sets of genes by SeV. As expected, some of the IRF-3-dependent genes, such as ISG56, were more strongly induced by SeV in IRF-3-overexpressing cells. Surprisingly, in those cells, a number of NF-κB-dependent genes, such as the A20 gene, were induced poorly. Using a series of cell lines expressing increasing levels of IRF-3, we demonstrated that the degree of induction of A20 mRNA, upon SeV infection, was inversely proportional to the cellular level of IRF-3, whereas that of ISG56 mRNA was directly proportional. Thus, IRF-3 can suppress the expression of NF-κB-dependent genes in SeV-infected cells.

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Interferon regulatory factor 3 from sea perch (Lateolabrax japonicus) exerts antiviral function against nervous necrosis virus infection

Developmental & Comparative Immunology ◽

10.1016/j.dci.2018.07.014 ◽

2018 ◽

Vol 88 ◽

pp. 200-205 ◽

Cited By ~ 7

Author(s):

Wanwan Zhang ◽

Zelin Li ◽

Peng Jia ◽

Wei Liu ◽

Meisheng Yi ◽

...

Keyword(s):

Virus Infection ◽

Interferon Regulatory Factor ◽

Nervous Necrosis Virus ◽

Regulatory Factor ◽

Necrosis Virus ◽

Lateolabrax Japonicus ◽

Interferon Regulatory Factor 3 ◽

Antiviral Function ◽

Sea Perch

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Transcriptional and Non-Transcriptional Activation, Posttranslational Modifications, and Antiviral Functions of Interferon Regulatory Factor 3 and Viral Antagonism by the SARS-Coronavirus

Viruses ◽

10.3390/v13040575 ◽

2021 ◽

Vol 13 (4) ◽

pp. 575

Author(s):

Anna Glanz ◽

Sukanya Chakravarty ◽

Merina Varghese ◽

Anita Kottapalli ◽

Shumin Fan ◽

...

Keyword(s):

Virus Infection ◽

Posttranslational Modifications ◽

Transcriptional Activation ◽

Viral Infections ◽

Interferon Regulatory Factor ◽

Innate Immune ◽

Type I ◽

Regulatory Factor ◽

Interferon Regulatory Factor 3 ◽

Wide Range

The immune system defends against invading pathogens through the rapid activation of innate immune signaling pathways. Interferon regulatory factor 3 (IRF3) is a key transcription factor activated in response to virus infection and is largely responsible for establishing an antiviral state in the infected host. Studies in Irf3−/−mice have demonstrated the absence of IRF3 imparts a high degree of susceptibility to a wide range of viral infections. Virus infection causes the activation of IRF3 to transcribe type-I interferon (e.g., IFNβ), which is responsible for inducing the interferon-stimulated genes (ISGs), which act at specific stages to limit virus replication. In addition to its transcriptional function, IRF3 is also activated to trigger apoptosis of virus-infected cells, as a mechanism to restrict virus spread within the host, in a pathway called RIG-I-like receptor-induced IRF3 mediated pathway of apoptosis (RIPA). These dual functions of IRF3 work in concert to mediate protective immunity against virus infection. These two pathways are activated differentially by the posttranslational modifications (PTMs) of IRF3. Moreover, PTMs regulate not only IRF3 activation and function, but also protein stability. Consequently, many viruses utilize viral proteins or hijack cellular enzymes to inhibit IRF3 functions. This review will describe the PTMs that regulate IRF3′s RIPA and transcriptional activities and use coronavirus as a model virus capable of antagonizing IRF3-mediated innate immune responses. A thorough understanding of the cellular control of IRF3 and the mechanisms that viruses use to subvert this system is critical for developing novel therapies for virus-induced pathologies.

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