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ILF3 contributes to the establishment of the antiviral type I interferon program.

ABSTRACT: Upon detection of viral infections, cells activate the expression of type I interferons (IFNs) and pro-inflammatory cytokines to control viral dissemination. As part of their antiviral response, cells also trigger the translational shutoff response which prevents translation of viral mRNAs and cellular mRNAs in a non-selective manner. Intriguingly, mRNAs encoding for antiviral factors bypass this translational shutoff, suggesting the presence of additional regulatory mechanisms enabling expression of the self-defence genes. Here, we identified the dsRNA binding protein ILF3 as an essential host factor required for efficient translation of the central antiviral cytokine, IFNB1, and a subset of interferon-stimulated genes. By combining polysome profiling and next-generation sequencing, ILF3 was also found to be necessary to establish the dsRNA-induced transcriptional and translational programs. We propose a central role for the host factor ILF3 in enhancing expression of the antiviral defence mRNAs in cellular conditions where cap-dependent translation is compromised.

SUBMITTER: Watson SF

PROVIDER: S-EPMC7145544 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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ILF3 contributes to the establishment of the antiviral type I interferon program.

Watson Samir F SF Bellora Nicolas N Macias Sara S

Nucleic acids research 20200101 1

Upon detection of viral infections, cells activate the expression of type I interferons (IFNs) and pro-inflammatory cytokines to control viral dissemination. As part of their antiviral response, cells also trigger the translational shutoff response which prevents translation of viral mRNAs and cellular mRNAs in a non-selective manner. Intriguingly, mRNAs encoding for antiviral factors bypass this translational shutoff, suggesting the presence of additional regulatory mechanisms enabling expressi ...[more]

PMID: 31701124

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Project description:Several members of the tripartite motif (TRIM) family of E3 ubiquitin ligases regulate immune pathways, including the antiviral type I interferon (IFN-I) system. Previously, we demonstrated that TRIM6 is involved in IFN-I induction and signaling. In the absence of TRIM6, optimal IFN-I signaling is reduced, allowing increased replication of interferon-sensitive viruses. Despite having evolved numerous mechanisms to restrict the vertebrate host's IFN-I response, West Nile virus (WNV) replication is sensitive to pretreatment with IFN-I. However, the regulators and products of the IFN-I pathway that are important in regulating WNV replication are incompletely defined. Consistent with WNV's sensitivity to IFN-I, we found that in TRIM6 knockout (TRIM6-KO) A549 cells, WNV replication is significantly increased and IFN-I induction and signaling are impaired compared to wild-type (wt) cells. IFN-β pretreatment was more effective in protecting against subsequent WNV infection in wt cells than TRIM6-KO, indicating that TRIM6 contributes to the establishment of an IFN-induced antiviral response against WNV. Using next-generation sequencing, we identified VAMP8 as a potential factor involved in this TRIM6-mediated antiviral response. VAMP8 knockdown resulted in reduced JAK1 and STAT1 phosphorylation and impaired induction of several interferon-stimulated genes (ISGs) following WNV infection or IFN-β treatment. Furthermore, VAMP8-mediated STAT1 phosphorylation required the presence of TRIM6. Therefore, the VAMP8 protein is a novel regulator of IFN-I signaling, and its expression and function are dependent on TRIM6 activity. Overall, these results provide evidence that TRIM6 contributes to the antiviral response against WNV and identify VAMP8 as a novel regulator of the IFN-I system.IMPORTANCE WNV is a mosquito-borne flavivirus that poses a threat to human health across large discontinuous areas throughout the world. Infection with WNV results in febrile illness, which can progress to severe neurological disease. Currently, there are no approved treatment options to control WNV infection. Understanding the cellular immune responses that regulate viral replication is important in diversifying the resources available to control WNV. Here, we show that the elimination of TRIM6 in human cells results in an increase in WNV replication and alters the expression and function of other components of the IFN-I pathway through VAMP8. Dissecting the interactions between WNV and host defenses both informs basic molecular virology and promotes the development of host- and virus-targeted antiviral strategies.

Project description:Purpose: Several members of the tripartite motif (TRIM) family of E3 ubiquitin ligases regulate immune pathways including the antiviral type I interferon (IFN-I) system. Therefore, we aimed to investigate the mechanism of IFN-I regulation upon West Nile virus infection using TRIM6 knockout (TRIM6-KO) human airway epithelial cells (A549). Methods: RNAs were extracted from wild-type (WT) and TRIM6KO A549 cells infected with WNV or mock-treated. RNA quality was assessed by visualization of 18S and 28S RNA bands using an Agilent BioAnalyzer 2100 (Agilent Technologies, CA); the electropherograms were used to calculate the 28S/18S ratio and the RNA Integrity Number. Poly-A+ RNA was enriched from total RNA (1 μg) using oligo dT-attached magnetic beads. First and second strand synthesis, adapter ligation, and amplification of the library were performed using the Illumina TruSeq RNA Sample Preparation kit as recommended by the manufacturer (Illumina, Inc). Library quality was evaluated using an Agilent DNA-1000 chip on an Agilent 2100 Bioanalyzer. Quantification of library DNA templates was performed using qPCR and a known-size reference standard. Cluster formation of the library DNA templates was performed using the TruSeq PE Cluster Kit v3 (Illumina) and the Illumina cBot workstation using conditions recommended by the manufacturer. Paired end 50 base sequencing by synthesis was performed using TruSeq SBS kit v3 (Illumina) on an Illumina HiSeq 1500 using protocols defined by the manufacturer. The alignment of NGS sequence reads was performed using the Spliced Transcript Alignment to a Reference (STAR) program, version 2.5.1b, using default parameters. We used the human hg38 assembly as a reference with the UCSC gene annotation file. The –quantMode GeneCounts option of STAR provided read counts per gene, which were input into the DESeq2 (version 1.12.1) differential expression analysis program to determine expression levels and differentially expressed genes. Processed data are presented as reads per kilobase transcript per million (RPKM). Results: Using next generation sequencing, we identified VAMP8 as a factor involved in this TRIM6-mediated antiviral response. In support, VAMP8 knockdown resulted in reduced Jak1 and STAT1 phosphorylation and impaired induction of several ISGs following WNV infection or IFNβ treatment. Conclusions: Our results provide evidence that TRIM6 contributes to the antiviral response against WNV and identified VAMP8 as a novel regulator of the IFN-I system

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ILF3 contributes to the establishment of the antiviral type I interferon program.

Publications

ILF3 contributes to the establishment of the antiviral type I interferon program.

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