RNase L promotes the formation of unique ribonucleoprotein granules distinct from stress granules

Stress granules (SGs) are ribonucleoprotein (RNP) assemblies that form in eukaryotic cells as a result of limited translation in response to stress. SGs form during viral infection and are thought to promote the antiviral response because many viruses encode inhibitors of SG assembly. However, the antiviral endoribonuclease RNase L also alters SG formation, whereby only small punctate SG-like bodies that we term RNase L–dependent bodies (RLBs) form during RNase L activation. How RLBs relate to SGs and their mode of biogenesis is unknown. Herein, using immunofluorescence, live-cell imaging, and MS-based analyses, we demonstrate that RLBs represent a unique RNP granule with a protein and RNA composition distinct from that of SGs in response to dsRNA lipofection in human cells. We found that RLBs are also generated independently of SGs and the canonical dsRNA-induced SG biogenesis pathway, because RLBs did not require protein kinase R, phosphorylation of eukaryotic translation initiation factor 2 subunit 1 (eIF2α), the SG assembly G3BP paralogs, or release of mRNAs from ribosomes via translation elongation. Unlike the transient interactions between SGs and P-bodies, RLBs and P-bodies extensively and stably interacted. However, despite both RLBs and P-bodies exhibiting liquid-like properties, they remained distinct condensates. Taken together, these observations reveal that RNase L promotes the formation of a unique RNP complex that may have roles during the RNase L–mediated antiviral response.

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RNase L amplifies Interferon signaling by inducing PKR-mediated antiviral stress granules

10.1101/2020.02.07.939645 ◽

2020 ◽

Cited By ~ 1

Author(s):

Praveen Manivannan ◽

Mohammad Adnan Siddiqui ◽

Krishnamurthy Malathi

Keyword(s):

Pattern Recognition ◽

Virus Infection ◽

Viral Infections ◽

Stress Granules ◽

Antiviral Response ◽

Pattern Recognition Receptors ◽

Stress Granule ◽

Rna Cleavage ◽

Rnase L ◽

Rna Ligands

ABSTRACTVirus infection leads to activation of the interferon-induced endoribonuclease, RNase L, which results in degradation of viral and cellular RNAs. Both cellular and viral RNA cleavage products of RNase L bind pattern recognition receptors (PRR) like Retinoic acid-inducible I (Rig-I) and or melanoma differentiation-associated protein 5 (MDA5) to further amplify interferon (IFN) production and antiviral response. Although much is known about the mechanics of ligand binding and PRR activation, how the cells coordinate RNA sensing to signaling response and interferon production remains unclear. We show that RNA cleavage products of RNase L activity induce formation of antiviral stress granule (avSG) by regulating activation of double-stranded RNA (dsRNA)-dependent protein kinase R (PKR), and recruit antiviral proteins Rig-I, PKR, OAS and RNase L to avSG. Biochemical analysis of purified avSG showed interaction of key stress granule protein, G3BP1, with only PKR and Rig-I and not with OAS or RNase L. AvSG assembly during RNase L activation is required for IRF3-mediated IFN production and not IFN signaling or proinflammatory cytokine induction. Consequently, cells lacking avSG formation or RNase L signaling produced less IFN and showed higher susceptibility during Sendai virus infection demonstrating the importance of avSG in RNase L-mediated host defense. During viral infection, we propose a role for RNase L-cleaved RNAs in inducing avSG containing antiviral proteins to provide a platform for efficient interaction of RNA ligands with pattern recognition receptors to enhance IFN production to effectively mount antiviral response.IMPORTANCEDouble-stranded RNAs produced during viral infections serve as pathogen associated molecular patterns (PAMPs) and bind pattern recognition receptors to stimulate IFN production. RNase L is an IFN-regulated endoribonuclease that is activated in virus-infected cells and cleaves single-stranded viral and cellular RNAs. The RNase L-cleaved dsRNAs signal to Rig-like helicases to amplify IFN production. This study identifies a novel role of antiviral stress granules induced by RNase L as an antiviral signaling hub to coordinate the RNA ligands with cognate receptors to mount effective host response during viral infections.

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Association of Zinc Finger Antiviral Protein Binding to Viral Genomic RNA with Attenuation of Replication of Echovirus 7

mSphere ◽

10.1128/msphere.01138-20 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

Niluka Goonawardane ◽

Dung Nguyen ◽

Peter Simmonds

Keyword(s):

Zinc Finger ◽

Specific Binding ◽

Stress Granules ◽

Rna Degradation ◽

Rnase L ◽

Oligoadenylate Synthetase ◽

Antiviral Protein ◽

Rna Sequences ◽

Cpg Dinucleotides ◽

Cellular Compartments

ABSTRACT Previous studies have implicated both zinc finger antiviral protein (ZAP) and oligoadenylate synthetase 3 (OAS3)/RNase L in the attenuation of RNA viruses with elevated CpG and UpA dinucleotides. Mechanisms and interrelationships between these two pathways were investigated using an echovirus 7 (E7) replicon with compositionally modified sequences inserted into the 3′ untranslated region. ZAP and OAS3 immunoprecipitation (IP) assays provided complementary data on dinucleotide composition effects on binding. Elevated frequencies of alternative pyrimidine/purine (CpA and UpG) and reversed (GpC and ApU) dinucleotides showed no attenuating effect on replication or specific binding to ZAP by IP. However, the bases 3′ and 5′ of CpG motifs influenced replication and ZAP binding; UCGU enhanced CpG-mediated attenuation and ZAP binding, while A residues shielded CpGs from ZAP recognition. Attenuating effects of elevated frequencies of UpA on replication occurred independently of CpG dinucleotides and bound noncompetitively with CpG-enriched RNA, consistent with a separate recognition site from CpG. Remarkably, immunoprecipitation with OAS3 antibody reproduced the specific binding to CpG- and UpA-enriched RNA sequences. However, OAS3 and ZAP were coimmunoprecipitated in both ZAP and OAS3 IP and colocalized with E7 and stress granules (SGs) by confocal microscopy analysis of infected cells. ZAP’s association with larger cellular complexes may mediate the recruitment of OAS3/RNase L, KHNYN, and other RNA degradation pathways. IMPORTANCE We recently discovered that the OAS3/RNase L antiviral pathway is essential for restriction of CpG- and UpA-enriched viruses, in addition to the requirement for zinc finger antiviral protein (ZAP). The current study provides evidence for the specific dinucleotide and wider recognition contexts associated with virus recognition and attenuation. It further documents the association of ZAP and OAS3 and association with stress granules and a wider protein interactome that may mediate antiviral effects in different cellular compartments. The study provides a striking reconceptualization of the pathways associated with this aspect of antiviral defense.

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RNase L Amplifies Interferon Signaling by Inducing Protein Kinase R-Mediated Antiviral Stress Granules

Journal of Virology ◽

10.1128/jvi.00205-20 ◽

2020 ◽

Vol 94 (13) ◽

Cited By ~ 3

Author(s):

Praveen Manivannan ◽

Mohammad Adnan Siddiqui ◽

Krishnamurthy Malathi

Keyword(s):

Pattern Recognition ◽

Protein Kinase ◽

Virus Infection ◽

Viral Infections ◽

Stress Granules ◽

Pattern Recognition Receptors ◽

Rna Cleavage ◽

Rnase L ◽

Protein Kinase R ◽

Rna Ligands

ABSTRACT Virus infection leads to activation of the interferon (IFN)-induced endoribonuclease RNase L, which results in degradation of viral and cellular RNAs. Both cellular and viral RNA cleavage products of RNase L bind pattern recognition receptors (PRRs), like retinoic acid-inducible I (Rig-I) and melanoma differentiation-associated protein 5 (MDA5), to further amplify IFN production and antiviral response. Although much is known about the mechanics of ligand binding and PRR activation, how cells coordinate RNA sensing with signaling response and interferon production remains unclear. We show that RNA cleavage products of RNase L activity induce the formation of antiviral stress granules (avSGs) by regulating activation of double-stranded RNA (dsRNA)-dependent protein kinase R (PKR) and recruit the antiviral proteins Rig-I, PKR, OAS, and RNase L to avSGs. Biochemical analysis of purified avSGs showed interaction of a key stress granule protein, G3BP1, with only PKR and Rig-I and not with OAS or RNase L. AvSG assembly during RNase L activation is required for IRF3-mediated IFN production, but not IFN signaling or proinflammatory cytokine induction. Consequently, cells lacking avSG formation or RNase L signaling produced less IFN and showed higher susceptibility during Sendai virus infection, demonstrating the importance of avSGs in RNase L-mediated host defense. We propose a role during viral infection for RNase L-cleaved RNAs in inducing avSGs containing antiviral proteins to provide a platform for efficient interaction of RNA ligands with pattern recognition receptors to enhance IFN production to mount an effective antiviral response. IMPORTANCE Double-stranded RNAs produced during viral infections serve as pathogen-associated molecular patterns (PAMPs) and bind pattern recognition receptors to stimulate IFN production. RNase L is an IFN-regulated endoribonuclease that is activated in virus-infected cells and cleaves single-stranded viral and cellular RNAs. The RNase L-cleaved dsRNAs signal to Rig-like helicases to amplify IFN production. This study identifies a novel role of antiviral stress granules induced by RNase L as an antiviral signaling hub to coordinate the RNA ligands with cognate receptors to mount an effective host response during viral infections.

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RNA is required for the maintenance of multiple cytoplasmic and nuclear membrane-less organelles.

10.1101/2021.08.16.456519 ◽

2021 ◽

Author(s):

Carolyn J Decker ◽

James M Burke ◽

Patrick K Mulvaney ◽

Roy Parker

Keyword(s):

Stress Granules ◽

Rna Degradation ◽

Cajal Bodies ◽

Rnase L ◽

Nuclear Speckles ◽

Processing Bodies ◽

Rna Molecules ◽

Super Enhancer ◽

Rnp Granules ◽

The Impact

Numerous membrane-less organelles composed of a combination of RNA and proteins, referred to as RNP granules, are observed in the nucleus and cytoplasm of eukaryotic cells, including stress granules, processing bodies, Cajal bodies, and nuclear speckles. An unresolved issue is how frequently RNA molecules are required for the maintenance of RNP granules in either the nucleus or cytosol. To address this issue, we degraded intracellular RNA in either the cytosol or the nucleus by the activation of RNase L and examined the impact of RNA loss on several RNP granules. Strikingly, we find the majority of RNP granules, including stress granules, processing bodies, Cajal bodies, nuclear speckles and the nucleolus are altered by the degradation of their RNA components. In contrast, super-enhancer complexes and TIS granules were largely unaffected by widespread intracellular RNA degradation. This highlights a critical and widespread role of RNA in the organization of many, but not all, RNP granules.

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