The E3 Ubiquitin Ligase Ro52 Negatively Regulates IFN- Production Post-Pathogen Recognition by Polyubiquitin-Mediated Degradation of IRF3

Molecular and Cellular Therapeutics, Research Institute, Royal College of Surgeons in Ireland, Dublin, Ireland.
The Journal of Immunology (Impact Factor: 4.92). 08/2008; 181(3):1780-6. DOI: 10.4049/jimmunol.181.3.1780
Source: PubMed

ABSTRACT Induction of type I IFNs is a fundamental cellular response to both viral and bacterial infection. The role of the transcription factor IRF3 is well established in driving this process. However, equally as important are cellular mechanisms for turning off type I IFN production to limit this response. In this respect, IRF3 has previously been shown to be targeted for ubiquitin-mediated degradation postviral detection to turn off the IFN-beta response. In this study, we provide evidence that the E3 ligase Ro52 (TRIM21) targets IRF3 for degradation post-pathogen recognition receptor activation. We demonstrate that Ro52 interacts with IRF3 via its C-terminal SPRY domain, resulting in the polyubiquitination and proteasomal degradation of the transcription factor. Ro52-mediated IRF3 degradation significantly inhibits IFN-beta promoter activity, an effect that is reversed in the presence of the proteasomal inhibitor MG132. Specific targeting of Ro52 using short hairpin RNA rescues IRF3 degradation following polyI:C-stimulation of HEK293T cells, with a subsequent increase in IFN-beta production. Additionally, shRNA targeting of murine Ro52 enhances the production of the IRF3-dependent chemokine RANTES following Sendai virus infection of murine fibroblasts. Collectively, this demonstrates a novel role for Ro52 in turning off and thus limiting IRF3-dependent type I IFN production by targeting the transcription factor for polyubiquitination and subsequent proteasomal degradation.

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Available from: Caroline A Jefferies, Sep 26, 2015
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    • "One subset of Trim proteins that include Trim5, Trim14, Trim15, and Trim44 has been shown to positively regulate the antiviral response by ubiquitinating multiple targets in the pathway (Ottosson et al., 2006; Reymond et al., 2001; Uchil et al., 2013; Yang et al., 2013). On the other hand, Trim21, Trim27, Trim30 and Trim38 were recently shown to function as negative regulators of the antiviral response by mediating proteasomal degradation of various signaling factors (Higgs et al., 2008; Shi et al., 2008; Zhao et al., 2012; Zurek et al., 2012). Interestingly, some Trims like Trim21 are functionally flexible and can regulate the innate immune pathway in a positive or negative manner. "
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    ABSTRACT: In this study, using an immunoprecipitation coupled with mass spectrometry approach, we have identified the E3 ubiquitin ligase Trim21 as an interacting partner of IFI35 and Nmi. We found that this interaction leads to K63-linked ubiquitination on K22 residue of Nmi, but not IFI35. Using domain deletion analysis, we found that the interaction is mediated via the coiled-coil domain of Nmi and the carboxyl-terminal SPRY domain of Trim21. Furthermore, we show that depletion of Trim21 leads to significantly reduced interaction of Nmi with IFI35, which results in the abrogation of the negative regulatory function of the Nmi-IFI35 complex on innate antiviral signaling. Thus, Trim21 appears to be a critical regulator of the functions of the Nmi-IFI35 complex. Overall, the results presented here uncover a new mechanism of regulation of the Nmi-IFI35 complex by Trim21, which may have implications for various autoimmune diseases associated uncontrolled antiviral signaling. Copyright © 2015 Elsevier Inc. All rights reserved.
    Virology 09/2015; 485:383-392. DOI:10.1016/j.virol.2015.08.013 · 3.32 Impact Factor
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    • "The effect of TRIM21 on IRF stability relies on its E3 ubiquitin ligase activity: by adding poly-ubiquitin chains on specific lysine residue(s) on the IRFs, TRIM21, like other E3 ubiquitin ligases, creates a signal that targets the activated transcription factor for proteasomal- or lysosomal-mediated degradation, thus achieving termination of signaling [16], [21], [30]. Having shown that all the isoforms interact with TRIM21 uniformly, we next assessed the ability of TRIM21 to ubiquitinate the single IRF5 isoforms. "
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    ABSTRACT: IRF5 is a member of the Interferon Regulatory Factor (IRF) family of transcription factors activated downstream of the Toll-Like receptors (TLRs). Polymorphisms in IRF5 have been shown to be associated with the autoimmune disease Systemic Lupus Erythematosus (SLE) and other autoimmune conditions, suggesting a central role for IRF5 in the regulation of the immune response. Four different IRF5 isoforms originate due to alternative splicing and to the presence or absence of a 30 nucleotide insertion in IRF5 exon 6. Since the polymorphic region disturbs a PEST domain, a region associated with protein degradation, we hypothesized that the isoforms bearing the insertion might have increased stability, thus explaining the association of individual IRF5 isoforms with SLE. As the E3 ubiquitin ligase TRIpartite Motif 21 (TRIM21) has been shown to regulate the stability and hence activity of members of the IRF family, we investigated whether IRF5 is subjected to regulation by TRIM21 and whether dysregulation of this mechanism could explain the association of IRF5 with SLE. Our results show that IRF5 is degraded following TLR7 activation and that TRIM21 is involved in this process. Comparison of the individual IRF5 variants demonstrates that isoforms generated by alternative splicing are resistant to TRIM21-mediated degradation following TLR7 stimulation, thus providing a functional link between isoforms expression and stability/activity which contributes to explain the association of IRF5 with SLE.
    PLoS ONE 08/2014; 9(8):e103609. DOI:10.1371/journal.pone.0103609 · 3.23 Impact Factor
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    • "TRIM21 was first described as a target for autoantibody production in SLE and Sjögren's syndrome (SS) [20]–[22] and was amongst the first of the TRIM proteins shown to negatively regulate IFN production [7], [23]. As a negative regulator, TRIM21 targets the IRF family members IRF3 and IRF7 for degradation [7], [8]. However, a positive role for TRIM21 in driving pro-inflammatory cytokine production has also been demonstrated, underlining the complex role this protein plays in innate immune responses [24]–[26]. "
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    ABSTRACT: In recent years members of the tripartite motif-containing (TRIM) family of E3 ubiquitin ligases have been shown to both positively and negatively regulate viral defence and as such are emerging as compelling targets for modulating the anti-viral immune response. In this study we identify TRIM68, a close homologue of TRIM21, as a novel regulator of Toll-like receptor (TLR)- and RIG-I-like receptor (RLR)-driven type I IFN production. Proteomic analysis of TRIM68-containing complexes identified TRK-fused gene (TFG) as a potential TRIM68 target. Overexpression of TRIM68 and TFG confirmed their ability to associate, with TLR3 stimulation appearing to enhance the interaction. TFG is a known activator of NF-κB via its ability to interact with inhibitor of NF-κB kinase subunit gamma (IKK-γ) and TRAF family member-associated NF-κB activator (TANK). Our data identifies a novel role for TFG as a positive regulator of type I IFN production and suggests that TRIM68 targets TFG for lysosomal degradation, thus turning off TFG-mediated IFN-β production. Knockdown of TRIM68 in primary human monocytes resulted in enhanced levels of type I IFN and TFG following poly(I:C) treatment. Thus TRIM68 targets TFG, a novel regulator of IFN production, and in doing so turns off and limits type I IFN production in response to anti-viral detection systems.
    PLoS ONE 07/2014; 9(7):e101503. DOI:10.1371/journal.pone.0101503 · 3.23 Impact Factor
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