The regulatory domain of the RIG-I family ATPase LGP2 senses double-stranded RNA

Pippig, Diana A.; Hellmuth, Johannes C.; Cui, Sheng; Kirchhofer, Axel; Lammens, Katja; Lammens, Alfred; Schmidt, Andreas; Rothenfußer, Simon; Hopfner, Karl‐Peter

doi:10.1093/nar/gkp059

Cited by 135 publications

(157 citation statements)

References 48 publications

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“…Interestingly, each member of the RIG-I subfamily of DExD/H helicases senses viral RNA differently. For example, RIG-I senses 5′ triphosphate ds/ssRNA, MDA5 senses cytoplasmic dsRNA (33), and LGP2 senses dsRNA independent of 5′ triphosphates (34). In parallel, we found that two members of the RHA subfamily of DExD/H helicases sense microbial DNA differently: DHX36 senses CpG-A using the DEAH domain, whereas DHX9 senses CpG-B using the DUF domain.…”

Section: Discussionmentioning

confidence: 73%

Aspartate-glutamate-alanine-histidine box motif (DEAH)/RNA helicase A helicases sense microbial DNA in human plasmacytoid dendritic cells

Kim

Pazhoor

Bao

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

290

302

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Toll-like receptor 9 (TLR9) senses microbial DNA and triggers type I IFN responses in plasmacytoid dendritic cells (pDCs). Previous studies suggest the presence of myeloid differentiation primary response gene 88 (MyD88)-dependent DNA sensors other than TLR9 in pDCs. Using MS, we investigated C-phosphate-G (CpG)-binding proteins from human pDCs, pDC-cell lines, and interferon regulatory factor 7 (IRF7)-expressing B-cell lines. CpG-A selectively bound the aspartate-glutamate-any amino acid-aspartate/histidine (DExD/H)-box helicase 36 (DHX36), whereas CpG-B selectively bound DExD/H-box helicase 9 (DHX9). Although the aspartateglutamate-alanine-histidine box motif (DEAH) domain of DHX36 was essential for CpG-A binding, the domain of unknown function 1605 (DUF1605 domain) of DHX9 was required for CpG-B binding. DHX36 is associated with IFN-α production and IRF7 nuclear translocation in response to CpG-A, but DHX9 is important for TNF-α and IL-6 production and NF-κB activation in response to CpG-B. Knocking down DHX9 or DHX36 significantly reduced the cytokine responses of pDCs to a DNA virus but had no effect on the cytokine responses to an RNA virus. We further showed that both DHX9 and DHX36 are localized within the cytosol and are directly bound to the Toll-interleukin receptor domain of MyD88 via their helicase-associated domain 2 and DUF domains. This study demonstrates that DHX9/DHX36 represent the MyD88-dependent DNA sensors in the cytosol of pDCs and suggests a much broader role for DHX helicases in viral sensing.cytosolic sensor | innate immunity

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Section: Discussionmentioning

confidence: 73%

Aspartate-glutamate-alanine-histidine box motif (DEAH)/RNA helicase A helicases sense microbial DNA in human plasmacytoid dendritic cells

Kim

Pazhoor

Bao

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

290

302

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“…Both MDA5 and LGP2 contain CTD, but the N-terminal CARDs are found only in MDA5. MDA5 senses viruses that are not detected by RIG-I via a distinct strategy, whereas LGP2 seems to function as a regulator of RIG-I and MDA5 activities through a currently unknown mechanism (29,30,(31)(32)(33)(34).In this study, we show that drh-1 and drh-3 of C. elegans are essential for antiviral RNAi but exhibit distinct antiviral activities. Using a transgenic approach developed to assay for the Significance Retinoic acid inducible gene I-like RNA helicases (RLHs) act as virus sensors in mammalian antiviral immunity.…”

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confidence: 62%

mentioning

confidence: 99%

Homologous RIG-I–like helicase proteins direct RNAi-mediated antiviral immunity in C. elegans by distinct mechanisms

Guo

Zhang

Wang

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

128

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RNAi-mediated antiviral immunity in Caenorhabditis elegans requires Dicer-related helicase 1 (DRH-1), which encodes the helicase and C-terminal domains homologous to the mammalian retinoic acid inducible gene I (RIG-I)-like helicase (RLH) family of cytosolic immune receptors. Here we show that the antiviral function of DRH-1 requires the RIG-I homologous domains as well as its wormspecific N-terminal domain. We also demonstrate that the helicase and C-terminal domains encoded by either worm DRH-2 or human RIG-I can functionally replace the corresponding domains of DRH-1 to mediate antiviral RNAi in C. elegans. Notably, substitutions in a three-residue motif of the C-terminal regulatory domain of RIG-I that physically interacts with viral double-stranded RNA abolish the antiviral activity of C-terminal regulatory domains of both RIG-I and DRH-1 in C. elegans. Genetic analysis revealed an essential role for both DRH-1 and DRH-3 in C. elegans antiviral RNAi targeting a natural viral pathogen. However, Northern blot and small RNA deep sequencing analyses indicate that DRH-1 acts to enhance production of viral primary siRNAs, whereas DRH-3 regulates antiviral RNAi by participating in the biogenesis of secondary siRNAs after Dicer-dependent production of primary siRNAs. We propose that DRH-1 facilitates the acquisition of viral double-stranded RNA by the worm dicing complex for the subsequent processing into primary siRNAs. The strong parallel for the antiviral function of RLHs in worms and mammals suggests that detection of viral doublestranded RNA may activate completely unrelated effector mechanisms or, alternatively, that the mammalian RLHs have a conserved activity to stimulate production of viral siRNAs for antiviral immunity by an RNAi effector mechanism.I nnate immunity refers to ancient host defense systems that act immediately after pathogen attack and are under the control of germline-encoded immune receptors. Pathogen sensing by several classes of immune receptors such as retinoic acid inducible gene I (RIG-I)-like cytosolic sensors in mammals leads to the transcriptional activation of effector genes in the nucleus (1). In contrast, detection of viral double-stranded RNA (dsRNA) by Dicer endonucleases is associated with the production of small interfering RNAs (siRNAs), which subsequently direct sequencespecific antiviral immunity through RNA interference (RNAi) (2-5). Antiviral RNAi is a major antiviral defense mechanism in fungi, plants, insects, and nematodes, so that suppression of the defense by a virus-encoded suppressor of RNAi is essential to establish infection (6-8). Although the RNAi machinery is highly conserved in mammals, conclusive evidence for a natural antiviral role of RNAi in mammals is not available (9).The nematode Caenorhabditis elegans has recently emerged as a small-animal model for innate immunity studies (10, 11). Genetic studies indicate that antiviral RNAi in C. elegans requires the genes essential for RNAi induced by exogenous dsRNA (12-17). These include Dicer-1 and dsRNA-bind...

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“…Importantly, the inhibitory effect was unique to LGP2, as inclusion of FLAG‐tagged MDA5 or FLAG‐tagged RIG‐I had little effect on dicing efficiency (Figs 4C and EV3C). In contrast to full‐length LGP2, purified LGP2 CTD only modestly decreased in vitro dicing of dsRNA despite its ability to associate with Dicer and to bind dsRNA with high affinity (Li et al , 2009; Pippig et al , 2009; Figs 4D and EV3D). Furthermore, there was little difference between the LGP2 CTD and a CTD K634E mutant, which completely lacks RNA binding.…”

Section: Resultsmentioning

confidence: 99%

The RIG‐I‐like receptor LGP2 inhibits Dicer‐dependent processing of long double‐stranded RNA and blocks RNA interference in mammalian cells

et al. 2018

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In vertebrates, the presence of viral RNA in the cytosol is sensed by members of the RIG‐I‐like receptor (RLR) family, which signal to induce production of type I interferons (IFN). These key antiviral cytokines act in a paracrine and autocrine manner to induce hundreds of interferon‐stimulated genes (ISGs), whose protein products restrict viral entry, replication and budding. ISGs include the RLRs themselves: RIG‐I, MDA5 and, the least‐studied family member, LGP2. In contrast, the IFN system is absent in plants and invertebrates, which defend themselves from viral intruders using RNA interference (RNAi). In RNAi, the endoribonuclease Dicer cleaves virus‐derived double‐stranded RNA (dsRNA) into small interfering RNAs (siRNAs) that target complementary viral RNA for cleavage. Interestingly, the RNAi machinery is conserved in mammals, and we have recently demonstrated that it is able to participate in mammalian antiviral defence in conditions in which the IFN system is suppressed. In contrast, when the IFN system is active, one or more ISGs act to mask or suppress antiviral RNAi. Here, we demonstrate that LGP2 constitutes one of the ISGs that can inhibit antiviral RNAi in mammals. We show that LGP2 associates with Dicer and inhibits cleavage of dsRNA into siRNAs both in vitro and in cells. Further, we show that in differentiated cells lacking components of the IFN response, ectopic expression of LGP2 interferes with RNAi‐dependent suppression of gene expression. Conversely, genetic loss of LGP2 uncovers dsRNA‐mediated RNAi albeit less strongly than complete loss of the IFN system. Thus, the inefficiency of RNAi as a mechanism of antiviral defence in mammalian somatic cells can be in part attributed to Dicer inhibition by LGP2 induced by type I IFNs. LGP2‐mediated antagonism of dsRNA‐mediated RNAi may help ensure that viral dsRNA substrates are preserved in order to serve as targets of antiviral ISG proteins.

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The regulatory domain of the RIG-I family ATPase LGP2 senses double-stranded RNA

Cited by 135 publications

References 48 publications

Aspartate-glutamate-alanine-histidine box motif (DEAH)/RNA helicase A helicases sense microbial DNA in human plasmacytoid dendritic cells

Aspartate-glutamate-alanine-histidine box motif (DEAH)/RNA helicase A helicases sense microbial DNA in human plasmacytoid dendritic cells

Homologous RIG-I–like helicase proteins direct RNAi-mediated antiviral immunity in C. elegans by distinct mechanisms

The RIG‐I‐like receptor LGP2 inhibits Dicer‐dependent processing of long double‐stranded RNA and blocks RNA interference in mammalian cells

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