scholarly journals LGP2 binds to PACT to regulate RIG-I– and MDA5-mediated antiviral responses

2019 ◽  
Vol 12 (601) ◽  
pp. eaar3993 ◽  
Author(s):  
Raul Y. Sanchez David ◽  
Chantal Combredet ◽  
Valérie Najburg ◽  
Gael A. Millot ◽  
Guillaume Beauclair ◽  
...  
Keyword(s):  
Rna Silencing ◽  
Rna Binding ◽  
Inflammatory Responses ◽  
Innate Immune ◽  
Type I ◽  
Double Stranded Rna ◽  
Rna Molecules ◽  
Protein Protein Interaction ◽  
Antiviral Responses ◽  
Inducible Gene

The retinoic acid–inducible gene I (RIG-I)–like receptors (RLRs) RIG-I, MDA5, and LGP2 stimulate inflammatory and antiviral responses by sensing nonself RNA molecules produced during viral replication. Here, we investigated how LGP2 regulates the RIG-I– and MDA5-dependent induction of type I interferon (IFN) signaling and showed that LGP2 interacted with different components of the RNA-silencing machinery. We identified a direct protein-protein interaction between LGP2 and the IFN-inducible, double-stranded RNA binding protein PACT. The LGP2-PACT interaction was mediated by the regulatory C-terminal domain of LGP2 and was necessary for inhibiting RIG-I–dependent responses and for amplifying MDA5-dependent responses. We described a point mutation within LGP2 that disrupted the LGP2-PACT interaction and led to the loss of LGP2-mediated regulation of RIG-I and MDA5 signaling. These results suggest a model in which the LGP2-PACT interaction regulates the inflammatory responses mediated by RIG-I and MDA5 and enables the cellular RNA-silencing machinery to coordinate with the innate immune response.

scholarly journals Virus Sensor RIG-I Represses RNA Interference by Interacting with TRBP through LGP2 in Mammalian Cells

Genes ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 511 ◽  
Author(s):  
Tomoko Takahashi ◽  
Yuko Nakano ◽  
Koji Onomoto ◽  
Mitsutoshi Yoneyama ◽  
Kumiko Ui-Tei
Keyword(s):  
Rna Interference ◽  
Rna Silencing ◽  
Mammalian Cells ◽  
Rna Binding ◽  
Type I ◽  
Hairpin Rna ◽  
Tar Rna ◽  
Sensor Proteins ◽  
The Relationship ◽  
Inducible Gene

Exogenous double-stranded RNAs (dsRNAs) similar to viral RNAs induce antiviral RNA silencing or RNA interference (RNAi) in plants or invertebrates, whereas interferon (IFN) response is induced through activation of virus sensor proteins including Toll like receptor 3 (TLR3) or retinoic acid-inducible gene I (RIG-I) like receptors (RLRs) in mammalian cells. Both RNA silencing and IFN response are triggered by dsRNAs. However, the relationship between these two pathways has remained unclear. Laboratory of genetics and physiology 2 (LGP2) is one of the RLRs, but its function has remained unclear. Recently, we reported that LGP2 regulates endogenous microRNA-mediated RNA silencing by interacting with an RNA silencing enhancer, TAR-RNA binding protein (TRBP). Here, we investigated the contribution of other RLRs, RIG-I and melanoma-differentiation-associated gene 5 (MDA5), in the regulation of RNA silencing. We found that RIG-I, but not MDA5, also represses short hairpin RNA (shRNA)-induced RNAi by type-I IFN. Our finding suggests that RIG-I, but not MDA5, interacts with TRBP indirectly through LGP2 to function as an RNAi modulator in mammalian cells.

scholarly journals RNA Recognition and Immunity—Innate Immune Sensing and Its Posttranscriptional Regulation Mechanisms

Cells ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1701
Author(s):  
Takuya Uehata ◽  
Osamu Takeuchi
Keyword(s):  
Nuclear Export ◽  
Posttranscriptional Regulation ◽  
Rna Binding ◽  
Inflammatory Responses ◽  
Rna Binding Proteins ◽  
Mammalian Species ◽  
Regulation Of Gene Expression ◽  
Innate Immune ◽  
Type I ◽  
Immune Sensing

RNA acts as an immunostimulatory molecule in the innate immune system to activate nucleic acid sensors. It functions as an intermediate, conveying genetic information to control inflammatory responses. A key mechanism for RNA sensing is discriminating self from non-self nucleic acids to initiate antiviral responses reliably, including the expression of type I interferon (IFN) and IFN-stimulated genes. Another important aspect of the RNA-mediated inflammatory response is posttranscriptional regulation of gene expression, where RNA-binding proteins (RBPs) have essential roles in various RNA metabolisms, including splicing, nuclear export, modification, and translation and mRNA degradation. Recent evidence suggests that the control of mRNA stability is closely involved in signal transduction and orchestrates immune responses. In this study, we review the current understanding of how RNA is sensed by host RNA sensing machinery and discuss self/non-self-discrimination in innate immunity focusing on mammalian species. Finally, we discuss how posttranscriptional regulation by RBPs shape immune reactions.

scholarly journals Unified mechanisms for self-RNA recognition by RIG-I Singleton-Merten syndrome variants

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Charlotte Lässig ◽  
Katja Lammens ◽  
Jacob Lucián Gorenflos López ◽  
Sebastian Michalski ◽  
Olga Fettscher ◽  
...  
Keyword(s):  
Immune Response ◽  
Retinoic Acid ◽  
Rna Binding ◽  
Atp Hydrolysis ◽  
Innate Immune ◽  
Rna Recognition ◽  
Double Stranded Rna ◽  
Lower Affinity ◽  
Structural Conformation ◽  
Inducible Gene

The innate immune sensor retinoic acid-inducible gene I (RIG-I) detects cytosolic viral RNA and requires a conformational change caused by both ATP and RNA binding to induce an active signaling state and to trigger an immune response. Previously, we showed that ATP hydrolysis removes RIG-I from lower-affinity self-RNAs (<xref ref-type="bibr" rid="bib19">Lässig et al., 2015</xref>), revealing how ATP turnover helps RIG-I distinguish viral from self-RNA and explaining why a mutation in a motif that slows down ATP hydrolysis causes the autoimmune disease Singleton-Merten syndrome (SMS). Here we show that a different, mechanistically unexplained SMS variant, C268F, which is localized in the ATP-binding P-loop, can signal independently of ATP but is still dependent on RNA. The structure of RIG-I C268F in complex with double-stranded RNA reveals that C268F helps induce a structural conformation in RIG-I that is similar to that induced by ATP. Our results uncover an unexpected mechanism to explain how a mutation in a P-loop ATPase can induce a gain-of-function ATP state in the absence of ATP.

scholarly journals Impaired Antiviral Responses to Extracellular Double-Stranded RNA and Cytosolic DNA, but Not to Interferon-α Stimulation, in TRIM56-Deficient Cells

Viruses ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 89
Author(s):  
Dang Wang ◽  
Ruixue Wang ◽  
Kui Li
Keyword(s):  
Antiviral Treatment ◽  
Interferon Α ◽  
Type I ◽  
Null Cell ◽  
Double Stranded Rna ◽  
Antiviral Responses ◽  
Bioactivity Assay ◽  
Physiologic Function ◽  
Vesicular Stomatitis ◽  
The Impact

The physiologic function of tripartite motif protein 56 (TRIM56), a ubiquitously expressed E3 ligase classified within the large TRIM protein family, remains elusive. Gene knockdown studies have suggested TRIM56 as a positive regulator of the type I interferon (IFN-I) antiviral response elicited via the Toll-like receptor 3 (TLR3) and cyclic GMP–AMP synthase (cGAS)–stimulator of interferon genes (STING) pathways, which detect and respond to danger signals—extracellular double-stranded (ds) RNA and cytosolic dsDNA, respectively. However, to what extent these pathways depend on TRIM56 in human cells is unclear. In addition, it is debatable whether TRIM56 plays a part in controlling the expression of IFN-stimulated genes (ISGs) resulting from IFN-I based antiviral treatment. In this study, we created HeLa-derived TRIM56 null cell lines by gene editing and used these cell models to comprehensively examine the impact of endogenous TRIM56 on innate antiviral responses. Our results showed that TRIM56 knockout severely undermined the upregulation of ISGs by extracellular dsRNA and that loss of TRIM56 weakened the response to cytosolic dsDNA. ISG induction and ISGylation following IFN-α stimulation, however, were not compromised by TRIM56 deletion. Using a vesicular stomatitis virus-based antiviral bioactivity assay, we demonstrated that IFN-α could efficiently establish an antiviral state in TRIM56 null cells, providing direct evidence that TRIM56 is not required for the general antiviral action of IFN-I. Altogether, these data ascertain the contributions of TRIM56 to TLR3- and cGAS–STING-dependent antiviral pathways in HeLa cells and add to our understanding of the roles this protein plays in innate immunity.

scholarly journals CryoEM structures of MDA5-dsRNA filaments at different stages of ATP hydrolysis

2018 ◽  
Author(s):  
Qin Yu ◽  
Kun Qu ◽  
Yorgo Modis
Keyword(s):  
Rna Binding ◽  
Atp Hydrolysis ◽  
Type I ◽  
List Type ◽  
Base Pairs ◽  
Nucleotide Analogs ◽  
Double Stranded Rna ◽  
Transition State Analogs ◽  
Helical Twist ◽  
Dsrna Binding

SummaryDouble-stranded RNA (dsRNA) is a potent proinflammatory signature of viral infection. Long cytosolic dsRNA is recognized by MDA5. The cooperative assembly of MDA5 into helical filaments on dsRNA nucleates the assembly of a multiprotein type-I-interferon signaling platform. Here, we determined cryoEM structures of MDA5-dsRNA filaments with different helical twists and bound nucleotide analogs, at resolutions sufficient to build and refine atomic models. The structures identify the filament forming interfaces, which encode the dsRNA binding cooperativity and length specificity of MDA5. The predominantly hydrophobic interface contacts confer flexibility, reflected in the variable helical twist within filaments. Mutation of filament-forming residues can result in loss or gain of signaling activity. Each MDA5 molecule spans 14 or 15 RNA base pairs, depending on the twist. Variations in twist also correlate with variations in the occupancy and type of nucleotide in the active site, providing insights on how ATP hydrolysis contributes to MDA5-dsRNA recognition.eTOCStructures of MDA5 bound to double-stranded RNA reveal a flexible, predominantly hydrophobic filament forming interface. The filaments have variable helical twist. Structures determined with ATP and transition state analogs show how the ATPase cycle is coupled to changes in helical twist, the mode of RNA binding and the length of the RNA footprint of MDA5.HighlightsCryoEM structures of MDA5-dsRNA filaments determined for three catalytic statesFilament forming interfaces are flexible and predominantly hydrophobicMutation of filament-forming residues can cause loss or gain of IFN-β signalingATPase cycle is coupled to changes in filament twist and size of the RNA footprint

scholarly journals Type I interferon potentiates metabolic dysfunction, inflammation, and accelerated aging in mtDNA mutator mice

2020 ◽  
Author(s):  
Yuanjiu Lei ◽  
Camila Guerra Martinez ◽  
Sylvia Torres-Odio ◽  
Samantha L. Bell ◽  
Christine E. Birdwell ◽  
...  
Keyword(s):  
Mitochondrial Dysfunction ◽  
Inflammatory Responses ◽  
Type I Interferon ◽  
Aerobic Glycolysis ◽  
Accelerated Aging ◽  
Innate Immune ◽  
Related Factor ◽  
Type I ◽  
Metabolic Dysfunction ◽  
Polymerase Gamma

AbstractMitochondrial dysfunction is a key driver of inflammatory responses in human disease. However, it remains unclear whether alterations in mitochondria-innate immune crosstalk contribute to the pathobiology of mitochondrial disorders and aging. Using the polymerase gamma (POLG) mutator model of mitochondrial DNA (mtDNA) instability, we report that aberrant activation of the type I interferon (IFN-I) innate immune axis potentiates immunometabolic dysfunction, reduces healthspan, and accelerates aging in mutator mice. Mechanistically, elevated IFN-I signaling suppresses activation of nuclear factor erythroid 2-related factor 2 (Nrf2), which increases oxidative stress, enhances pro-inflammatory cytokine responses, and accelerates metabolic dysfunction. Ablation of IFN-I signaling attenuates hyper-inflammatory phenotypes by restoring Nrf2 activity and reducing aerobic glycolysis, which combine to lessen cardiovascular and myeloid dysfunction in aged mutator mice. These findings further advance our knowledge of how mitochondrial dysfunction shapes innate immune responses and provide a framework for understanding mitochondria-driven immunopathology in POLG-related diseases and aging.

scholarly journals HIV blocks Type I IFN signaling through disruption of STAT1 phosphorylation

2018 ◽  
Vol 24 (8) ◽  
pp. 490-500 ◽  
Author(s):  
Nam V Nguyen ◽  
James T Tran ◽  
David Jesse Sanchez
Keyword(s):  
Gene Expression ◽  
Adaptor Protein ◽  
Innate Immune ◽  
Type I ◽  
Type I Ifn ◽  
Antiviral State ◽  
Receptor Signaling Pathway ◽  
Multiple Signaling ◽  
Inducible Gene ◽  
Stat Pathway

This study investigates the modulation of Type I IFN induction of an antiviral state by HIV. IFNs, including IFN-α, are key innate immune cytokines that activate the JAK/STAT pathway leading to the expression of IFN-stimulated genes. IFN-stimulated gene expression establishes the antiviral state, limiting viral infection in IFN-α-stimulated microenvironments. Our previous studies have shown that HIV proteins disrupt the induction of IFN-α by degradation of IFN-β promoter stimulator-1, an adaptor protein for the up-regulation and release of IFN-α into the local microenvironment via the retinoic acid-inducible gene 1-like receptor signaling pathway. However, IFN-α is still released from other sources such as plasmacytoid dendritic cells via TLR-dependent recognition of HIV. Here we report that the activation of the JAK/STAT pathway by IFN-α stimulation is disrupted by HIV proteins Vpu and Nef, which both reduce IFN-α induction of STAT1 phosphorylation. Thus, HIV would still be able to avoid antiviral protection induced by IFN-α in the local microenvironment. These findings show that HIV blocks multiple signaling points that would lead to the up-regulation of IFN-stimulated genes, allowing more effective replication in IFN-α-rich environments.

Viroid-induced DNA methylation in plants

2013 ◽  
Vol 4 (6) ◽  
pp. 557-565 ◽  
Author(s):  
Athanasios Dalakouras ◽  
Elena Dadami ◽  
Michael Wassenegger
Keyword(s):  
Dna Methylation ◽  
Small Rnas ◽  
Rna Silencing ◽  
De Novo ◽  
Rna Degradation ◽  
Double Stranded Rna ◽  
Methyl Group ◽  
Rna Molecules ◽  
Cumulative Data

AbstractIn eukaryotes, DNA methylation refers to the addition of a methyl group to the fifth atom in the six-atom ring of cytosine residues. At least in plants, DNA regions that become de novo methylated can be defined by homologous RNA molecules in a process termed RNA-directed DNA methylation (RdDM). RdDM was first discovered in viroid-infected plants. Viroids are pathogenic circular, non-coding, single-stranded RNA molecules. Members of the Pospiviroidae family replicate in the nucleus through double-stranded RNA intermediates, attracting the host RNA silencing machinery. The recruitment of this machinery results in the production of viroid-derived small RNAs (vd-sRNAs) that mediate RNA degradation and DNA methylation of cognate sequences. Here, we provide an overview of the cumulative data on the field of viroid-induced RdDM and discuss three possible scenarios concerning the mechanistic details of its establishment.

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