scholarly journals USP18 – a multifunctional component in the interferon response

2018 ◽  
Vol 38 (6) ◽  
Author(s):  
Anja Basters ◽  
Klaus-Peter Knobeloch ◽  
Günter Fritz

Ubiquitin-specific proteases (USPs) represent the largest family of deubiquitinating enzymes (DUB). These proteases cleave the isopeptide bond between ubiquitin and a lysine residue of a ubiquitin-modified protein. USP18 is a special member of the USP family as it only deconjugates the ubiquitin-like protein ISG15 (interferon-stimulated gene (ISG) 15) from target proteins but is not active towards ubiquitin. Independent of its protease activity, USP18 functions as a major negative regulator of the type I interferon response showing that USP18 is – at least – a bifunctional protein. In this review, we summarise our current knowledge of protease-dependent and -independent functions of USP18 and discuss the structural basis of its dual activity.

2021 ◽  
Author(s):  
Hongyun Wang ◽  
Lu Zhang ◽  
Cong Zeng ◽  
Jiangpeng Feng ◽  
Yu Zhou ◽  
...  

5-Methylcytosine (m5C) is a widespread post-transcriptional RNA modification and is reported to be involved in manifold cellular responses and biological processes through regulating RNA metabolism. However, its regulatory role in antiviral innate immunity has not yet been elucidated. Here, we report that NSUN2, a typical m5C methyltransferase, can negatively regulate type I interferon responses during viral infection. NSUN2 specifically mediates m5C methylation of IRF3 mRNA and accelerates its degradation, resulting in low levels of IRF3 and downstream IFN-β production. Knockout or knockdown of NSUN2 could enhance type I interferon responses and downstream ISG expression after viral infection in vitro. And in vivo, the antiviral innate responses is more dramatically enhanced in Nsun2+/− mice than in Nsun2+/+ mice. Four highly m5C methylated cytosines in IRF3 mRNA were identified, and their mutation could enhance the cellular IRF3 mRNA levels. Moreover, infection with Sendai virus (SeV), vesicular stomatitis virus (VSV), herpes simplex virus 1 (HSV-1), Zika virus (ZIKV), or especially SARS-CoV-2 resulted in a reduction in endogenous levels of NSUN2. Together, our findings reveal that NSUN2 serves as a negative regulator of interferon response by accelerating the fast turnover of IRF3 mRNA, while endogenous NSUN2 levels decrease after viral infection to boost antiviral responses for the effective elimination of viruses. Our results suggest a paradigm of innate antiviral immune responses ingeniously involving NSUN2-mediated m5C modification.


2019 ◽  
Author(s):  
Caitlyn T. Hoffpauir ◽  
Samantha L. Bell ◽  
Kelsi O. West ◽  
Tao Jing ◽  
Sylvia Torres-Odio ◽  
...  

ABSTRACTTripartite motif-containing proteins (TRIMs) play a variety of recently described roles in innate immunity. While many TRIMs regulate type I interferon (IFN) expression following cytosolic nucleic acid sensing of viruses, their contribution to innate immune signaling and gene expression during bacterial infection remains largely unknown. Because Mycobacterium tuberculosis is a potent activator of cGAS-dependent cytosolic DNA sensing, we set out to investigate a role for TRIM proteins in regulating macrophage responses to M. tuberculosis. Here we demonstrate that TRIM14, a non-canonical TRIM that lacks an E3 ligase RING domain, is a critical negative regulator of the type I IFN response in macrophages. We show that TRIM14 physically interacts with both cGAS and TBK1 and that macrophages lacking TRIM14 dramatically hyperinduce interferon stimulated gene (ISG) expression following cytosolic nucleic acid transfection, IFN-β treatment, and M. tuberculosis infection. Consistent with a defect in resolution of the type I IFN response, Trim14 knockout (KO) macrophages have more phospho-Ser754 STAT3 relative to phospho-727 and fail to upregulate the STAT3 target Socs3 (Suppressor of Cytokine Signaling 3), which is required to turn off IFNAR signaling. These data support a model whereby TRIM14 acts as a scaffold between TBK1 and STAT3 to promote phosphorylation of STAT3 at Ser727 and enhance negative regulation of ISG expression. Remarkably, Trim14 KO macrophages hyperinduce antimicrobials like Inos2 and are significantly better than control cells at limiting M. tuberculosis replication. Collectively, these data reveal a previously unappreciated role for TRIM14 in resolving type I IFN responses and controlling M. tuberculosis infection.


Author(s):  
Lai Wei ◽  
Siqi Ming ◽  
Bin Zou ◽  
Yongjian Wu ◽  
Zhongsi Hong ◽  
...  

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Elena N. Judd ◽  
Alison R. Gilchrist ◽  
Nicholas R. Meyerson ◽  
Sara L. Sawyer

Abstract Background The Type I interferon response is an important first-line defense against viruses. In turn, viruses antagonize (i.e., degrade, mis-localize, etc.) many proteins in interferon pathways. Thus, hosts and viruses are locked in an evolutionary arms race for dominance of the Type I interferon pathway. As a result, many genes in interferon pathways have experienced positive natural selection in favor of new allelic forms that can better recognize viruses or escape viral antagonists. Here, we performed a holistic analysis of selective pressures acting on genes in the Type I interferon family. We initially hypothesized that the genes responsible for inducing the production of interferon would be antagonized more heavily by viruses than genes that are turned on as a result of interferon. Our logic was that viruses would have greater effect if they worked upstream of the production of interferon molecules because, once interferon is produced, hundreds of interferon-stimulated proteins would activate and the virus would need to counteract them one-by-one. Results We curated multiple sequence alignments of primate orthologs for 131 genes active in interferon production and signaling (herein, “induction” genes), 100 interferon-stimulated genes, and 100 randomly chosen genes. We analyzed each multiple sequence alignment for the signatures of recurrent positive selection. Counter to our hypothesis, we found the interferon-stimulated genes, and not interferon induction genes, are evolving significantly more rapidly than a random set of genes. Interferon induction genes evolve in a way that is indistinguishable from a matched set of random genes (22% and 18% of genes bear signatures of positive selection, respectively). In contrast, interferon-stimulated genes evolve differently, with 33% of genes evolving under positive selection and containing a significantly higher fraction of codons that have experienced selection for recurrent replacement of the encoded amino acid. Conclusion Viruses may antagonize individual products of the interferon response more often than trying to neutralize the system altogether.


Author(s):  
Letizia Santinelli ◽  
Gabriella De Girolamo ◽  
Cristian Borrazzo ◽  
Paolo Vassalini ◽  
Claudia Pinacchio ◽  
...  

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