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1.
J Exp Med ; 218(9)2021 09 06.
Article in English | MEDLINE | ID: covidwho-1467276

ABSTRACT

The three classes of interferons (IFNs) share the ability to inhibit viral replication, activating cell transcriptional programs that regulate both innate and adaptive responses to viral and intracellular bacterial challenge. Due to their unique potency in regulating viral replication, and their association with numerous autoimmune diseases, the tightly orchestrated transcriptional regulation of IFNs has long been a subject of intense investigation. The protective role of early robust IFN responses in the context of infection with SARS-CoV-2 has further underscored the relevance of these pathways. In this viewpoint, rather than focusing on the downstream effects of IFN signaling (which have been extensively reviewed elsewhere), we will summarize the historical and current understanding of the stepwise assembly and function of factors that regulate IFNß enhancer activity (the "enhanceosome") and highlight opportunities for deeper understanding of the transcriptional control of the ifnb gene.


Subject(s)
Epigenesis, Genetic , Gene Expression Regulation , Host-Pathogen Interactions/physiology , Interferon-beta/genetics , CCAAT-Enhancer-Binding Proteins/genetics , CCAAT-Enhancer-Binding Proteins/metabolism , DNA Methylation , Enhancer Elements, Genetic , Host-Pathogen Interactions/genetics , Humans , Influenza A Virus, H5N1 Subtype/pathogenicity , Interferon-beta/metabolism , Promoter Regions, Genetic , SARS-CoV-2/pathogenicity , Transcription, Genetic , Ubiquitin-Protein Ligases/genetics , Ubiquitin-Protein Ligases/metabolism
2.
PLoS Pathog ; 17(8): e1009800, 2021 08.
Article in English | MEDLINE | ID: covidwho-1435629

ABSTRACT

Type I Interferons (IFN-Is) are a family of cytokines which play a major role in inhibiting viral infection. Resultantly, many viruses have evolved mechanisms in which to evade the IFN-I response. Here we tested the impact of expression of 27 different SARS-CoV-2 genes in relation to their effect on IFN production and activity using three independent experimental methods. We identified six gene products; NSP6, ORF6, ORF7b, NSP1, NSP5 and NSP15, which strongly (>10-fold) blocked MAVS-induced (but not TRIF-induced) IFNß production. Expression of the first three of these SARS-CoV-2 genes specifically blocked MAVS-induced IFNß-promoter activity, whereas all six genes induced a collapse in IFNß mRNA levels, corresponding with suppressed IFNß protein secretion. Five of these six genes furthermore suppressed MAVS-induced activation of IFNλs, however with no effect on IFNα or IFNγ production. In sharp contrast, SARS-CoV-2 infected cells remained extremely sensitive to anti-viral activity exerted by added IFN-Is. None of the SARS-CoV-2 genes were able to block IFN-I signaling, as demonstrated by robust activation of Interferon Stimulated Genes (ISGs) by added interferon. This, despite the reduced levels of STAT1 and phospho-STAT1, was likely caused by broad translation inhibition mediated by NSP1. Finally, we found that a truncated ORF7b variant that has arisen from a mutant SARS-CoV-2 strain harboring a 382-nucleotide deletion associating with mild disease (Δ382 strain identified in Singapore & Taiwan in 2020) lost its ability to suppress type I and type III IFN production. In summary, our findings support a multi-gene process in which SARS-CoV-2 blocks IFN-production, with ORF7b as a major player, presumably facilitating evasion of host detection during early infection. However, SARS-CoV-2 fails to suppress IFN-I signaling thus providing an opportunity to exploit IFN-Is as potential therapeutic antiviral drugs.


Subject(s)
Interferon-beta/metabolism , SARS-CoV-2/immunology , Viral Proteins/metabolism , Adaptor Proteins, Signal Transducing/metabolism , Adaptor Proteins, Vesicular Transport/metabolism , Animals , Chlorocebus aethiops , Eukaryotic Initiation Factor-2/metabolism , HEK293 Cells , Humans , Interferon-beta/genetics , Interferon-beta/pharmacology , SARS-CoV-2/drug effects , STAT1 Transcription Factor/metabolism , Vero Cells , Viral Proteins/genetics
3.
Signal Transduct Target Ther ; 5(1): 221, 2020 10 06.
Article in English | MEDLINE | ID: covidwho-1387195
4.
Cytokine ; 148: 155697, 2021 12.
Article in English | MEDLINE | ID: covidwho-1385382

ABSTRACT

The prevalence of SARS-CoV-2 is a great threat to global public health. However, the relationship between the viral pathogen SARS-CoV-2 and host innate immunity has not yet been well studied. The genome of SARS-CoV-2 encodes a viral protease called 3C-like protease. This protease is responsible for cleaving viral polyproteins during replication. In this investigation, 293T cells were transfected with SARS-CoV-2 3CL and then infected with Sendai virus (SeV) to induce the RIG-I like receptor (RLR)-based immune pathway. q-PCR, luciferase reporter assays, and western blotting were used for experimental analyses. We found that SARS-CoV-2 3CL significantly downregulated IFN-ß mRNA levels. Upon SeV infection, SARS-CoV-2 3CL inhibited the nuclear translocation of IRF3 and p65 and promoted the degradation of IRF3. This effect of SARS-CoV-2 3CL on type I IFN in the RLR immune pathway opens up novel ideas for future research on SARS-CoV-2.


Subject(s)
Coronavirus 3C Proteases/metabolism , Interferon Regulatory Factor-3/metabolism , Interferon-beta/biosynthesis , Proteolysis , DEAD Box Protein 58/metabolism , Gene Expression Regulation , HEK293 Cells , Humans , Interferon-beta/genetics , NF-kappa B/genetics , Promoter Regions, Genetic/genetics , RNA, Messenger/genetics , RNA, Messenger/metabolism , Receptors, Immunologic/metabolism , Response Elements/genetics , Sendai virus/physiology , Signal Transduction
5.
J Virol ; 95(17): e0074721, 2021 08 10.
Article in English | MEDLINE | ID: covidwho-1356909

ABSTRACT

The coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is bringing an unprecedented health crisis to the world. To date, our understanding of the interaction between SARS-CoV-2 and host innate immunity is still limited. Previous studies reported that SARS-CoV-2 nonstructural protein 12 (NSP12) was able to suppress interferon-ß (IFN-ß) activation in IFN-ß promoter luciferase reporter assays, which provided insights into the pathogenesis of COVID-19. In this study, we demonstrated that IFN-ß promoter-mediated luciferase activity was reduced during coexpression of NSP12. However, we could show NSP12 did not affect IRF3 or NF-κB activation. Moreover, IFN-ß production induced by Sendai virus (SeV) infection or other stimulus was not affected by NSP12 at mRNA or protein level. Additionally, the type I IFN signaling pathway was not affected by NSP12, as demonstrated by the expression of interferon-stimulated genes (ISGs). Further experiments revealed that different experiment systems, including protein tags and plasmid backbones, could affect the readouts of IFN-ß promoter luciferase assays. In conclusion, unlike as previously reported, our study showed SARS-CoV-2 NSP12 protein is not an IFN-ß antagonist. It also rings the alarm on the general usage of luciferase reporter assays in studying SARS-CoV-2. IMPORTANCE Previous studies investigated the interaction between SARS-CoV-2 viral proteins and interferon signaling and proposed that several SARS-CoV-2 viral proteins, including NSP12, could suppress IFN-ß activation. However, most of these results were generated from IFN-ß promoter luciferase reporter assay and have not been validated functionally. In our study, we found that, although NSP12 could suppress IFN-ß promoter luciferase activity, it showed no inhibitory effect on IFN-ß production or its downstream signaling. Further study revealed that contradictory results could be generated from different experiment systems. On one hand, we demonstrated that SARS-CoV-2 NSP12 could not suppress IFN-ß signaling. On the other hand, our study suggests that caution needs to be taken with the interpretation of SARS-CoV-2-related luciferase assays.


Subject(s)
Coronavirus RNA-Dependent RNA Polymerase , Interferon-beta , Promoter Regions, Genetic , SARS-CoV-2 , Coronavirus RNA-Dependent RNA Polymerase/genetics , Coronavirus RNA-Dependent RNA Polymerase/metabolism , HEK293 Cells , Humans , Interferon Regulatory Factor-3/genetics , Interferon Regulatory Factor-3/metabolism , Interferon-beta/antagonists & inhibitors , Interferon-beta/biosynthesis , Interferon-beta/genetics , NF-kappa B/genetics , NF-kappa B/metabolism , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , SARS-CoV-2/genetics , SARS-CoV-2/metabolism
6.
J Virol ; 95(17): e0074721, 2021 08 10.
Article in English | MEDLINE | ID: covidwho-1350002

ABSTRACT

The coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is bringing an unprecedented health crisis to the world. To date, our understanding of the interaction between SARS-CoV-2 and host innate immunity is still limited. Previous studies reported that SARS-CoV-2 nonstructural protein 12 (NSP12) was able to suppress interferon-ß (IFN-ß) activation in IFN-ß promoter luciferase reporter assays, which provided insights into the pathogenesis of COVID-19. In this study, we demonstrated that IFN-ß promoter-mediated luciferase activity was reduced during coexpression of NSP12. However, we could show NSP12 did not affect IRF3 or NF-κB activation. Moreover, IFN-ß production induced by Sendai virus (SeV) infection or other stimulus was not affected by NSP12 at mRNA or protein level. Additionally, the type I IFN signaling pathway was not affected by NSP12, as demonstrated by the expression of interferon-stimulated genes (ISGs). Further experiments revealed that different experiment systems, including protein tags and plasmid backbones, could affect the readouts of IFN-ß promoter luciferase assays. In conclusion, unlike as previously reported, our study showed SARS-CoV-2 NSP12 protein is not an IFN-ß antagonist. It also rings the alarm on the general usage of luciferase reporter assays in studying SARS-CoV-2. IMPORTANCE Previous studies investigated the interaction between SARS-CoV-2 viral proteins and interferon signaling and proposed that several SARS-CoV-2 viral proteins, including NSP12, could suppress IFN-ß activation. However, most of these results were generated from IFN-ß promoter luciferase reporter assay and have not been validated functionally. In our study, we found that, although NSP12 could suppress IFN-ß promoter luciferase activity, it showed no inhibitory effect on IFN-ß production or its downstream signaling. Further study revealed that contradictory results could be generated from different experiment systems. On one hand, we demonstrated that SARS-CoV-2 NSP12 could not suppress IFN-ß signaling. On the other hand, our study suggests that caution needs to be taken with the interpretation of SARS-CoV-2-related luciferase assays.


Subject(s)
Coronavirus RNA-Dependent RNA Polymerase , Interferon-beta , Promoter Regions, Genetic , SARS-CoV-2 , Coronavirus RNA-Dependent RNA Polymerase/genetics , Coronavirus RNA-Dependent RNA Polymerase/metabolism , HEK293 Cells , Humans , Interferon Regulatory Factor-3/genetics , Interferon Regulatory Factor-3/metabolism , Interferon-beta/antagonists & inhibitors , Interferon-beta/biosynthesis , Interferon-beta/genetics , NF-kappa B/genetics , NF-kappa B/metabolism , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , SARS-CoV-2/genetics , SARS-CoV-2/metabolism
7.
Viruses ; 13(8)2021 07 23.
Article in English | MEDLINE | ID: covidwho-1325791

ABSTRACT

A weak production of INF-ß along with an exacerbated release of pro-inflammatory cytokines have been reported during infection by the novel SARS-CoV-2 virus. SARS-CoV-2 encodes several proteins able to counteract the host immune system, which is believed to be one of the most important features contributing to the viral pathogenesis and development of a severe clinical picture. Previous reports have demonstrated that SARS-CoV-2 N protein, along with some non-structural and accessory proteins, efficiently suppresses INF-ß production by interacting with RIG-I, an important pattern recognition receptor (PRR) involved in the recognition of pathogen-derived molecules. In the present study, we better characterized the mechanism by which the SARS-CoV-2 N counteracts INF-ß secretion and affects RIG-I signaling pathways. In detail, when the N protein was ectopically expressed, we noted a marked decrease in TRIM25-mediated RIG-I activation. The capability of the N protein to bind to, and probably mask, TRIM25 could be the consequence of its antagonistic activity. Furthermore, this interaction occurred at the SPRY domain of TRIM25, harboring the RNA-binding activity necessary for TRIM25 self-activation. Here, we describe new findings regarding the interplay between SARS-CoV-2 and the IFN system, filling some gaps for a better understanding of the molecular mechanisms affecting the innate immune response in COVID-19.


Subject(s)
COVID-19/immunology , Coronavirus Nucleocapsid Proteins/immunology , DEAD Box Protein 58/immunology , Receptors, Immunologic/immunology , SARS-CoV-2/immunology , Transcription Factors/immunology , Tripartite Motif Proteins/immunology , Ubiquitin-Protein Ligases/immunology , COVID-19/genetics , COVID-19/virology , Coronavirus Nucleocapsid Proteins/genetics , DEAD Box Protein 58/genetics , Gene Expression Regulation , Host-Pathogen Interactions , Humans , Immunity, Innate , Interferon-beta/genetics , Interferon-beta/immunology , Promoter Regions, Genetic , Receptors, Immunologic/genetics , SARS-CoV-2/genetics , Signal Transduction , Transcription Factors/genetics , Tripartite Motif Proteins/genetics , Ubiquitin-Protein Ligases/genetics
8.
J Immunol ; 206(10): 2420-2429, 2021 05 15.
Article in English | MEDLINE | ID: covidwho-1215526

ABSTRACT

We have recently shown that type 2 transglutaminase (TG2) plays a key role in the host's inflammatory response during bacterial infections. In this study, we investigated whether the enzyme is involved in the regulation of the STING pathway, which is the main signaling activated in the presence of both self- and pathogen DNA in the cytoplasm, leading to type I IFN (IFN I) production. In this study, we demonstrated that TG2 negatively regulates STING signaling by impairing IRF3 phosphorylation in bone marrow-derived macrophages, isolated from wild-type and TG2 knockout mice. In the absence of TG2, we found an increase in the IFN-ß production and in the downstream JAK/STAT pathway activation. Interestingly, proteomic analysis revealed that TG2 interacts with TBK1, affecting its interactome composition. Indeed, TG2 ablation facilitates the TBK1-IRF3 interaction, thus indicating that the enzyme plays a negative regulatory effect on IRF3 recruitment in the STING/TBK1 complex. In keeping with these findings, we observed an increase in the IFNß production in bronchoalveolar lavage fluids from COVID-19-positive dead patients paralleled by a dramatic decrease of the TG2 expression in the lung pneumocytes. Taken together, these results suggest that TG2 plays a negative regulation on the IFN-ß production associated with the innate immunity response to the cytosolic presence of both self- and pathogen DNA.


Subject(s)
COVID-19/immunology , GTP-Binding Proteins/immunology , Immunity, Innate , Interferon Regulatory Factor-3/immunology , Membrane Proteins/immunology , SARS-CoV-2/immunology , Signal Transduction/immunology , Transglutaminases/immunology , Animals , COVID-19/genetics , COVID-19/pathology , GTP-Binding Proteins/genetics , Humans , Interferon Regulatory Factor-3/genetics , Interferon-beta/genetics , Interferon-beta/immunology , Membrane Proteins/genetics , Mice , Mice, Knockout , Signal Transduction/genetics , Transglutaminases/genetics
9.
Cell Mol Immunol ; 18(4): 945-953, 2021 04.
Article in English | MEDLINE | ID: covidwho-1104474

ABSTRACT

SARS-CoV-2 is the pathogenic agent of COVID-19, which has evolved into a global pandemic. Compared with some other respiratory RNA viruses, SARS-CoV-2 is a poor inducer of type I interferon (IFN). Here, we report that SARS-CoV-2 nsp12, the viral RNA-dependent RNA polymerase (RdRp), suppresses host antiviral responses. SARS-CoV-2 nsp12 attenuated Sendai virus (SeV)- or poly(I:C)-induced IFN-ß promoter activation in a dose-dependent manner. It also inhibited IFN promoter activation triggered by RIG-I, MDA5, MAVS, and IRF3 overexpression. Nsp12 did not impair IRF3 phosphorylation but suppressed the nuclear translocation of IRF3. Mutational analyses suggested that this suppression was not dependent on the polymerase activity of nsp12. Given these findings, our study reveals that SARS-CoV-2 RdRp can antagonize host antiviral innate immunity and thus provides insights into viral pathogenesis.


Subject(s)
COVID-19/metabolism , Coronavirus RNA-Dependent RNA Polymerase/metabolism , Interferon Regulatory Factor-3/metabolism , Interferon Type I/metabolism , SARS-CoV-2/metabolism , Adaptor Proteins, Signal Transducing/genetics , Adaptor Proteins, Signal Transducing/metabolism , Cell Nucleus/metabolism , DEAD Box Protein 58/genetics , DEAD Box Protein 58/metabolism , Host-Pathogen Interactions/immunology , Humans , Immunity, Innate , Interferon Regulatory Factor-3/genetics , Interferon Type I/genetics , Interferon-Induced Helicase, IFIH1/genetics , Interferon-Induced Helicase, IFIH1/metabolism , Interferon-beta/genetics , Interferon-beta/metabolism , Mutation , Phosphorylation , Promoter Regions, Genetic , Receptors, Immunologic/genetics , Receptors, Immunologic/metabolism , SARS-CoV-2/enzymology , Sendai virus/metabolism
10.
Pathog Dis ; 79(1)2021 01 09.
Article in English | MEDLINE | ID: covidwho-963763

ABSTRACT

A vast proportion of coronavirus disease 2019 (COVID-19) individuals remain asymptomatic and can shed severe acute respiratory syndrome (SARS-CoV) type 2 virus to transmit the infection, which also explains the exponential increase in the number of COVID-19 cases globally. Furthermore, the rate of recovery from clinical COVID-19 in certain pockets of the globe is surprisingly high. Based on published reports and available literature, here, we speculated a few immunovirological mechanisms as to why a vast majority of individuals remain asymptomatic similar to exotic animal (bats and pangolins) reservoirs that remain refractile to disease development despite carrying a huge load of diverse insidious viral species, and whether such evolutionary advantage would unveil therapeutic strategies against COVID-19 infection in humans. Understanding the unique mechanisms that exotic animal species employ to achieve viral control, as well as inflammatory regulation, appears to hold key clues to the development of therapeutic versatility against COVID-19.


Subject(s)
COVID-19/immunology , Cytokine Release Syndrome/immunology , NLR Family, Pyrin Domain-Containing 3 Protein/immunology , Receptors, KIR/immunology , Receptors, NK Cell Lectin-Like/immunology , Zoonoses/immunology , Animals , Animals, Exotic/virology , Asymptomatic Diseases , COVID-19/genetics , COVID-19/transmission , COVID-19/virology , Chiroptera/virology , Cytokine Release Syndrome/genetics , Cytokine Release Syndrome/prevention & control , Cytokine Release Syndrome/virology , Disease Reservoirs , Eutheria/virology , Gene Expression , Host Specificity , Humans , Immune Tolerance , Immunity, Innate , Interferon-beta/deficiency , Interferon-beta/genetics , Interferon-beta/immunology , Killer Cells, Natural/immunology , Killer Cells, Natural/virology , Monocytes/immunology , Monocytes/virology , NLR Family, Pyrin Domain-Containing 3 Protein/deficiency , NLR Family, Pyrin Domain-Containing 3 Protein/genetics , Receptors, KIR/deficiency , Receptors, KIR/genetics , Receptors, NK Cell Lectin-Like/deficiency , Receptors, NK Cell Lectin-Like/genetics , SARS-CoV-2/pathogenicity , Tumor Necrosis Factor-alpha/deficiency , Tumor Necrosis Factor-alpha/genetics , Tumor Necrosis Factor-alpha/immunology , Zoonoses/genetics , Zoonoses/transmission , Zoonoses/virology
11.
Int J Mol Sci ; 21(23)2020 Nov 25.
Article in English | MEDLINE | ID: covidwho-951247

ABSTRACT

Activation of TLR7 by small imidazoquinoline molecules such as R848 or R837 initiates signaling cascades leading to the activation of transcription factors, such as AP-1, NF-κB, and interferon regulatory factors (IRFs) and afterward to the induction of cytokines and anti-viral Type I IFNs. In general, TLRs mediate these effects by utilizing different intracellular signaling molecules, one of them is Mal. Mal is a protein closely related to the antibacterial response, and its role in the TLR7 pathways remains poorly understood. In this study, we show that Mal determines the expression and secretion of IFNß following activation of TLR7, a receptor that recognizes ssRNA and imidazoquinolines. Moreover, we observed that R848 induces Mal-dependent IFNß production via ERK1/2 activation as well as the transcription factor IRF7 activation. Although activation of TLR7 leads to NF-κB-dependent expression of IRF7, this process is independent of Mal. We also demonstrate that secretion of IFNß regulated by TLR7 and Mal in macrophages and dendritic cells leads to the IP-10 chemokine expression. In conclusion, our data demonstrate that Mal is a critical regulator of the imidazoquinolinones-dependent IFNß production via ERK1/2/IRF7 signaling cascade which brings us closer to understanding the molecular mechanism's regulation of innate immune response.


Subject(s)
Interferon Regulatory Factor-7/genetics , Interferon-beta/genetics , Membrane Glycoproteins/genetics , Myelin and Lymphocyte-Associated Proteolipid Proteins/genetics , Toll-Like Receptor 7/genetics , Animals , Cytokines/genetics , Humans , Immunity, Innate/genetics , Interferon Type I/genetics , MAP Kinase Signaling System/genetics , Mice , Mice, Knockout , NF-kappa B/genetics , Quinolones/toxicity , Transcription Factor AP-1/genetics
12.
Virus Res ; 278: 197843, 2020 03.
Article in English | MEDLINE | ID: covidwho-833528

ABSTRACT

Swine acute diarrhea syndrome coronavirus (SADS-CoV), a newly emerging enteric coronavirus, is considered to be associated with swine acute diarrhea syndrome (SADS) which has caused significantly economic losses to the porcine industry. Interactions between SADS-CoV and the host innate immune response is unclear yet. In this study, we used IPEC-J2 cells as a model to explore potential evasion strategies employed by SADS-CoV. Our results showed that SADS-CoV infection failed to induce IFN-ß production, and inhibited poly (I:C) and Sendai virus (SeV)-triggered IFN-ß expression. SADS-CoV also blocked poly (I:C)-induced phosphorylation and nuclear translocation of IRF-3 and NF-κB. Furthermore, SADS-CoV did not interfere with the activity of IFN-ß promoter stimulated by IRF3, TBK1 and IKKε, but counteracted its activation induced by IPS-1 and RIG-I. Collectively, this study is the first investigation that shows interactions between SADS-CoV and the host innate immunity, which provides information of the molecular mechanisms underlying SASD-CoV infection.


Subject(s)
Alphacoronavirus/physiology , Coronavirus Infections/immunology , DEAD Box Protein 58/antagonists & inhibitors , Interferon-beta/antagonists & inhibitors , Active Transport, Cell Nucleus , Animals , Cell Line , Cell Nucleus/metabolism , Coronavirus Infections/virology , DEAD Box Protein 58/metabolism , Host-Pathogen Interactions/immunology , Immunity, Innate , Interferon Regulatory Factor-3/metabolism , Interferon-beta/genetics , Interferon-beta/metabolism , NF-kappa B/metabolism , Phosphorylation , Promoter Regions, Genetic , Signal Transduction , Swine
13.
Nat Rev Immunol ; 20(10): 585-586, 2020 10.
Article in English | MEDLINE | ID: covidwho-713702
14.
Nat Commun ; 11(1): 3810, 2020 07 30.
Article in English | MEDLINE | ID: covidwho-690732

ABSTRACT

The pandemic of COVID-19 has posed an unprecedented threat to global public health. However, the interplay between the viral pathogen of COVID-19, SARS-CoV-2, and host innate immunity is poorly understood. Here we show that SARS-CoV-2 induces overt but delayed type-I interferon (IFN) responses. By screening 23 viral proteins, we find that SARS-CoV-2 NSP1, NSP3, NSP12, NSP13, NSP14, ORF3, ORF6 and M protein inhibit Sendai virus-induced IFN-ß promoter activation, whereas NSP2 and S protein exert opposite effects. Further analyses suggest that ORF6 inhibits both type I IFN production and downstream signaling, and that the C-terminus region of ORF6 is critical for its antagonistic effect. Finally, we find that IFN-ß treatment effectively blocks SARS-CoV-2 replication. In summary, our study shows that SARS-CoV-2 perturbs host innate immune response via both its structural and nonstructural proteins, and thus provides insights into the pathogenesis of SARS-CoV-2.


Subject(s)
Betacoronavirus/physiology , Coronavirus Infections/virology , Immune Evasion , Interferon Type I/metabolism , Pneumonia, Viral/virology , Signal Transduction , Betacoronavirus/genetics , Betacoronavirus/immunology , Betacoronavirus/metabolism , COVID-19 , Cell Line , Coronavirus Infections/immunology , Humans , Immunity, Innate , Interferon-beta/genetics , Interferon-beta/metabolism , Interferon-beta/pharmacology , Mutation , Open Reading Frames , Pandemics , Pneumonia, Viral/immunology , Promoter Regions, Genetic , SARS-CoV-2 , Signal Transduction/drug effects , Viral Proteins/genetics , Viral Proteins/metabolism , Virus Replication/drug effects
16.
Science ; 369(6508): 1249-1255, 2020 09 04.
Article in English | MEDLINE | ID: covidwho-654484

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the current coronavirus disease 2019 (COVID-19) pandemic. A major virulence factor of SARS-CoVs is the nonstructural protein 1 (Nsp1), which suppresses host gene expression by ribosome association. Here, we show that Nsp1 from SARS-CoV-2 binds to the 40S ribosomal subunit, resulting in shutdown of messenger RNA (mRNA) translation both in vitro and in cells. Structural analysis by cryo-electron microscopy of in vitro-reconstituted Nsp1-40S and various native Nsp1-40S and -80S complexes revealed that the Nsp1 C terminus binds to and obstructs the mRNA entry tunnel. Thereby, Nsp1 effectively blocks retinoic acid-inducible gene I-dependent innate immune responses that would otherwise facilitate clearance of the infection. Thus, the structural characterization of the inhibitory mechanism of Nsp1 may aid structure-based drug design against SARS-CoV-2.


Subject(s)
Betacoronavirus/chemistry , Immune Evasion , Immunity, Innate , Protein Biosynthesis , Viral Nonstructural Proteins/chemistry , Viral Nonstructural Proteins/metabolism , Betacoronavirus/immunology , Betacoronavirus/metabolism , Betacoronavirus/physiology , Binding Sites , COVID-19 , Coronavirus Infections/immunology , Coronavirus Infections/virology , Cryoelectron Microscopy , DEAD Box Protein 58/genetics , DEAD Box Protein 58/metabolism , Humans , Interferon-beta/genetics , Interferon-beta/metabolism , Models, Molecular , Pandemics , Pneumonia, Viral/immunology , Pneumonia, Viral/virology , Protein Binding , Protein Domains , Protein Interaction Domains and Motifs , Protein Structure, Secondary , RNA, Messenger/metabolism , Receptors, Immunologic , Ribosome Subunits, Small, Eukaryotic/chemistry , Ribosome Subunits, Small, Eukaryotic/metabolism , SARS-CoV-2
17.
Virus Res ; 286: 198074, 2020 09.
Article in English | MEDLINE | ID: covidwho-611212

ABSTRACT

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel human coronavirus causing the pandemic of severe pneumonia (Coronavirus Disease 2019, COVID-19). SARS-CoV-2 is highly pathogenic in human, having posed immeasurable public health challenges to the world. Innate immune response is critical for the host defense against viral infection and the dysregulation of the host innate immune responses probably aggravates SARS-CoV-2 infection, contributing to the high morbidity and lethality of COVID-19. It has been reported that some coronavirus proteins play an important role in modulating innate immunity of the host, but few studies have been conducted on SARS-CoV-2. In this study, we screened the viral proteins of SARS-CoV-2 and found that the viral ORF6, ORF8 and nucleocapsid proteins were potential inhibitors of type I interferon signaling pathway, a key component for antiviral response of host innate immune. All the three proteins showed strong inhibition on type I interferon (IFN-ß) and NF-κB-responsive promoter, further examination revealed that these proteins were able to inhibit the interferon-stimulated response element (ISRE) after infection with Sendai virus, while only ORF6 and ORF8 proteins were able to inhibit the ISRE after treatment with interferon beta. These findings would be helpful for the further study of the detailed signaling pathway and unveil the key molecular player that may be targeted.


Subject(s)
Betacoronavirus/genetics , Host-Pathogen Interactions/genetics , Interferon-beta/genetics , NF-kappa B/genetics , Nucleocapsid Proteins/genetics , Viral Proteins/genetics , Betacoronavirus/immunology , Coronavirus Nucleocapsid Proteins , Gene Expression Regulation , Genes, Reporter , HEK293 Cells , Host-Pathogen Interactions/immunology , Humans , Immunity, Innate , Influenza A Virus, H1N1 Subtype/genetics , Influenza A Virus, H1N1 Subtype/immunology , Interferon-beta/immunology , Luciferases/genetics , Luciferases/metabolism , NF-kappa B/immunology , Nucleocapsid Proteins/immunology , Phosphoproteins , Plasmids/chemistry , Plasmids/metabolism , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Response Elements , SARS-CoV-2 , Sendai virus/genetics , Sendai virus/immunology , Signal Transduction , Transfection/methods , Viral Proteins/immunology
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