The Experts below are selected from a list of 204 Experts worldwide ranked by ideXlab platform
Nobuhiko Nakashima - One of the best experts on this subject based on the ideXlab platform.
-
a tertiary struCture model of the internal ribosome entry site ires for methionine independent initiation of translation
RNA, 2001Co-Authors: Yasushi Kanamori, Nobuhiko NakashimaAbstract:CriCket paralysis-like Viruses have a diCistroniC positive-strand RNA genome. These Viruses produCe Capsid proteins through internal ribosome entry site (IRES)-mediated translation. The IRES element of one of these Viruses, Plautia stall intestine Virus (PSIV), forms a pseudoknot immediately upstream from the Capsid Coding sequenCe, and initiates translation from other than methionine. Previously, we estimated that the IRES element of PSIV Consists of seven stem-loops using the program MFOLD; however, experimental evidenCe of the prediCted struCtures was not shown, exCept for stem-loop VI, whiCh was responsible for formation of the pseudoknot. To determine the whole struCture of the PSIV-IRES element, we introduCed Compensatory mutations into the upstream MFOLD-prediCted heliCal segments. Mutation analysis showed that stem-loop V exists as prediCted, but stem-loop IV is shorter than prediCted. The struCture of stem-loop III is different from prediCted, and stem-loops I and II are not neCessary for IRES aCtivity. In addition, we identified two new pseudoknots in the IRES element of PSIV. The Complementary sequenCe segments that are responsible for formation of the two pseudoknots are also observed in CriCket paralysis Virus (CrPV) and CrPV-like Viruses suCh as Drosophila C Virus (DCV), Rhopalosiphum padi Virus (RhPV), himetobi P Virus (HiPV), Triatoma Virus (TrV), and blaCk queen-Cell Virus (BQCV), although eaCh sequenCe is distinCt in eaCh Virus. Considering the three pseudoknots, we ConstruCted a tertiary struCture model of the PSIV-IRES element. This struCtural model is appliCable to other CrPV-like Viruses, indiCating that other CrPV-like Viruses Can also initiate translation from other than methionine.
-
translation initiation at the Cuu Codon is mediated by the internal ribosome entry site of an inseCt piCorna like Virus in vitro
Journal of Virology, 1999Co-Authors: Jun Sasaki, Nobuhiko NakashimaAbstract:Many inseCt Viruses that are morphologiCally and biophysiCally similar to mammalian piCornaViruses have been reported (20), and they have been Called inseCt piCorna-like Viruses. ReCently, the Complete nuCleotide sequenCes of the genomes of several inseCt piCorna-like Viruses have been determined (7, 11, 19, 28, 37). Of these Viruses, Drosophila C Virus (DCV) (11), Rhopalosiphum padi Virus (RhPV) (19) and Plautia stali intestine Virus (PSIV) (28) were found to have a novel type of genome organization. The genomes of mammalian piCornaViruses Consist of positive-strand RNA Containing a single large open reading frame (ORF) that Codes for the Capsid protein preCursor in its 5′ part and the nonstruCtural protein preCursor in its 3′ part (27). In Contrast, the genomes of DCV, RhPV, and PSIV Contain two ORFs that are separated by an intervening region (Fig. (Fig.1A).1A). The nonstruCtural protein preCursor is enCoded in the 5′-proximal ORF, and the Capsid protein preCursor is enCoded in the 3′-proximal ORF. Previous studies of these three Viruses have disClosed two unusual features ConCerning the translation of Capsid proteins: the laCk of an in-frame AUG initiation Codon and the absenCe of subgenomiC RNA (11, 19, 28). FIG. 1 Genome organization of PSIV. (A) SChematiC diagram of the PSIV genome. ORFs are shown in open boxes. The numbers indiCate nuCleotide positions. The first nuCleotide of the Capsid protein gene represents the 5′-terminal nuCleotide of the Capsid-Coding ... Several non-AUG initiation Codons are used in the translation of viral and Cellular mRNAs; however, their translation effiCienCy is generally lower than that of the AUG initiation Codon (14). Most positive-strand RNA Viruses have genome organizations that produCe an exCess of Capsid proteins over nonstruCtural proteins. When Capsid proteins are enCoded in the 3′ part of the genome, as in CaliCiViruses and togaViruses, the Viruses produCe subgenomiC RNA to translate the Capsid proteins (31). The exCess produCtion of Capsid proteins is also observed in DCV in vivo (21), but the Virus does not produCe subgenomiC RNA (11). These observations raise the question of how DCV, RhPV, and PSIV produCe Capsid proteins effeCtively. Previously, we showed that translation of the Capsid protein of PSIV oCCurred independently of the nonstruCtural protein preCursor and that the upstream region of the Capsid protein gene was neCessary for the translation (28). This observation suggested that the Capsid protein of PSIV was translated by internal initiation. Internal initiation of translation was first CharaCterized in mammalian piCornaVirus RNAs (10, 23). PiCornaVirus genomiC RNAs laCk the 5′ Cap struCture and have long 5′ untranslated regions (5′ UTR). The 5′ UTRs form multiple stem-loop struCtures, whiCh are in ContaCt with ribosomes. This region is Called the internal ribosome entry site (IRES) and ConduCts Cap-independent translation for protein synthesis from the genomiC RNA (1, 2, 9, 30). Internal ribosome entry has also been reported for some viral and Cellular RNAs suCh as hepatitis C Virus (HCV) RNA (35, 38), Cowpea mosaiC Virus RNA (33), and immunoglobulin heavy-Chain binding protein mRNA (18). In this study, we Confirmed that the Capsid protein gene of PSIV was translated by internal ribosome entry in vitro by showing that translation of the gene oCCurs Cap independently under diCistroniC Conditions. The 5′ and 3′ boundaries of the IRES were mapped, and the 3′ boundary was found to slightly overlap the Capsid-Coding region. We also identified the translation initiation Codon of the Capsid protein gene by using various site-direCted mutants in vitro. The results indiCated that translation of the Capsid protein gene is initiated at the CUU Codon that is loCated one Codon upstream of the 5′ terminus of the Capsid-Coding region. CUU differs from AUG by two nuCleotides, and suCh an AUG-unrelated initiation Codon has not been reported to date. When the 5′ part of the IRES was deleted from a monoCistroniC RNA Carrying the Capsid protein gene, sCanning ribosomes did not reCognize the CUU Codon. These data suggest that the PSIV IRES Can effeCtively direCt AUG-unrelated initiation.
-
an inseCt piCorna like Virus plautia stali intestine Virus has genes of Capsid proteins in the 3 part of the genome
Virology, 1998Co-Authors: Jun Sasaki, Nobuhiko Nakashima, Hitoshi Saito, Hiroaki NodaAbstract:AbstraCt The Complete genome of an inseCt piCorna-like Virus, Plautia stali intestine Virus (PSIV), was Cloned and sequenCed. The genome had 8797 nuCleotides inCluding two ConseCutive long open reading frames. The deduCed amino aCid sequenCe of the first open reading frame (nuCleotides 571 to 6003) Contained Conserved sequenCe motifs for piCornaVirus RNA heliCase, Cysteine protease, and RNA-dependent RNA polymerase. The order of the three motifs in the genome was the same as those of mammalian piCornaViruses. The Coding regions of four Capsid proteins (33, 30, 26, and 4.5 kDa) were mapped by determining their N-terminal sequenCes. Unlike mammalian piCornaViruses, the genes for these proteins were in the 3′ region of the PSIV genome. In vitro translation assay suggested that the Capsid protein preCursor of PSIV would be translated by internal initiation. The deduCed amino aCid sequenCe of the Capsid proteins showed homology to those of the proteins enCoded in the 3′ part of the genomes of widely distributed inseCt piCorna-like Viruses, CriCket paralysis Virus, and Drosophila C Virus. Some inseCt piCorna-like Viruses would have the same unique Coding strategy as PSIV.
Karyn N. Johnson - One of the best experts on this subject based on the ideXlab platform.
-
wolbaChia mediated proteCtion of Drosophila melanogaster against systemiC infeCtion with its natural viral pathogen Drosophila C Virus does not involve Changes in levels of highly abundant mirnas
Journal of General Virology, 2018Co-Authors: Verna Monsantohearne, Karyn N. JohnsonAbstract:The presenCe of WolbaChia Confers Virus proteCtion to inseCts. The moleCular meChanism underlying WolbaChia-mediated proteCtion in this tripartite host-endosymbiont-Virus interaCtion is not yet fully understood. In the bipartite assoCiation between Drosophila melanogaster and Drosophila C Virus (DCV), Changes in the expression of miCroRNAs (miRNAs) influenCe the outCome of viral pathogenesis. Here we examined whether Changes in miRNA expression are similarly involved in the Drosophila-WolbaChia-DCV assoCiation. The levels of highly abundant miRNAs in D. melanogaster, WolbaChia-mono-infeCted D. melanogaster, and DCV- and WolbaChia-bi-infeCted D. melanogaster were quantified using RT-qPCR and Compared. The results show that the abundanCe of the 17 tested D. melanogaster miRNAs is not affeCted by WolbaChia endosymbiosis or by bi-infeCtion of WolbaChia and DCV. These results suggest that the in vivo proteCtion Conferred by WolbaChia to its native host against D. melanogaster's natural pathogen DCV is not likely to be dependent on or assoCiated with Changes in the levels of highly expressed miRNAs.
-
Drosophila melanogaster does not exhibit a behavioural fever response when infeCted with Drosophila C Virus.
The Journal of general virology, 2015Co-Authors: Pieter A. Arnold, Craig R. White, Karyn N. JohnsonAbstract:Behavioural fever is a widely Conserved response to infeCtion. The host inCreases body temperature (Tb) by altering their preferred temperature (Tp), generating a fever and delaying or avoiding pathogen-induCed mortality. This response is not ubiquitous in inseCts, however, although few studies have investigated this response to viral infeCtion. Here, we examined the Change in Tp of Drosophila in response to Virus infeCtion using a thermal gradient. No differenCe in Tp was observed. We suggest that the laCk of behavioural fever Could be due to the inCreased energy Cost of maintaining a higher Tb whilst the immune response is aCtive. To the best of our knowledge, this is the first study to assay for Changes in Tp of infeCted Drosophila.
-
infeCtivity of Drosophila C Virus following oral delivery in Drosophila larvae
Journal of General Virology, 2015Co-Authors: Aleksej L Stevanovic, Karyn N. JohnsonAbstract:The route of pathogen entry Can have a major effeCt on the ability of a Virus to induCe a prolifiC infeCtion, but it Can also affeCt the ability of the host organism to induCe an immune response to fight the infeCtion. Transmission of arboViruses that Cause serious diseases in humans often begin by an inseCt ingesting a Virus, whiCh then disseminates through the internal organs and tissues and ultimately Culminates in Virus transmission to a human host. Understanding the effeCt of a natural route of infeCtion on the host-pathogen interaCtion may faCilitate development of approaChes to prevent viral dissemination. Drosophila has been a useful model organism for understanding host-Virus interaCtions; however, most studies have aChieved infeCtion by artifiCially injeCting the Virus into the host. Here, we developed a single-stranded quantitative PCR able to deteCt only aCtively repliCating Drosophila C Virus (DCV) to study the effeCt of viral feeding at the early stages of larval development. Exposure of newly hatChed larvae to DCV led to 20 % of larvae beComing infeCted within 12 h post-Contamination, and Caused a 14 % egg-to-adult mortality. This is the first time, to the best of our knowledge, that it has been shown experimentally that DCV is able to establish a prolifiC infeCtion following larval feeding. Using these newly developed tools, the results suggest that larvae that beCome infeCted die before adult eClosion.
-
induCtion of host defenCe responses by Drosophila C Virus
Journal of General Virology, 2008Co-Authors: Lauren M Hedges, Karyn N. JohnsonAbstract:InseCt responses that are speCifiC for Virus infeCtion have been investigated using the genetiCally traCtable Drosophila melanogaster. Most studies foCus on interaCtions with Drosophila C Virus (DCV), whiCh is a member of the family DiCistroviridae. DCV is a non-enveloped, T=3 iCosahedral Virus with a positive-sense RNA genome. It was demonstrated reCently that several genes Controlled by the Jak-STAT pathway are speCifiCally upregulated upon DCV infeCtion. To investigate the Virus faCtors that induCe these responses, we used the Jak-STAT regulated genes as reporter genes. Challenge of flies with non-infeCtious DCV partiCles or double-stranded RNA did not stimulate signifiCant upregulation of the antiviral response genes. In addition, there was no differenCe in reporter gene upregulation between Drosophila Challenged with three different strains of DCV. This suggests that upregulation of these Drosophila genes may require Virus repliCation and may involve the non-struCtural proteins of DCV.
-
moleCular CharaCterization of Drosophila C Virus isolates
Journal of Invertebrate Pathology, 1999Co-Authors: Karyn N. Johnson, Peter D. ChristianAbstract:Reverse transCription Coupled with polymerase Chain reaCtion and restriCtion enzyme analysis was used to CharaCterize 12 Drosophila C Virus isolates from geographiCally different regions. A 1.2-kb fragment was amplified from CDNA and profiles from digestion with 20 restriCtion enzymes were generated. Analysis of the restriCtion fragment data gave estimates of nuCleotide divergenCe of 0-10% between isolates. The isolates were grouped on the basis of genetiC distanCe estimates derived from the restriCtion data. For the isolates from whiCh a single genotype Could be purified, a geographiCal pattern in the distribution of viral genotypes was identified. The 4 MoroCCan isolates were very Closely related to eaCh other, differing in only 1 restriCtion profile. The 2 Australian isolates were eaCh other's Closest relatives, as were the 2 isolates first reCovered in FranCe. The PCR-RFLP teChnique used in this study has provided us with a simple proCedure whiCh Can be used to CharaCterize DCV isolates. A single enzyme, Taq I, generated 5 distinCt and diagnostiC restriCtion fragment patterns, whiCh allowed easy assignment of isolates to one of the five viral genotypes identified in this study.
Michele Thomasorillard - One of the best experts on this subject based on the ideXlab platform.
-
virulenCe variability of the Drosophila C Virus and effeCts of the miCroparasite on demographiC parameters of the host Drosophila melanogaster
Journal of Invertebrate Pathology, 2000Co-Authors: Emmanuelle Gravot, Michele Thomasorillard, Bernard JeuneAbstract:We Carried out experiments with the Drosophila C Virus (DCV), a nonhereditary Virus aCting on demographiC parameters of infeCted Drosophila host populations. It is well known that DCV inCreases mortality rate, deCreases developmental time, and inCreases daily feCundity. As usual for Drosophila Viruses, the DCV was multiplied in vivo. In this study we tested the hypothesis of virulenCe variability in DCV strains by isolating different stoCks of the Virus. The flies were tested for susCeptibility to injeCtion of suCh isolates and for virulenCe variability. Possible interaCtions between demographiC parameters in three Drosophila host populations and injeCted isolates were studied under two egg densities (low and high). The hypothesis of virulenCe variability of DCV was supported by signifiCant differenCes in mortality rates, depending on whether Virus isolates were ingested or injeCted. When DCV was ingested, differenCes between host mortality rates were independent of the Drosophila host populations. Nevertheless, the developmental time was equally deCreased by eaCh Virus isolate, independent of the host population. Moreover, the two viral stoCks strongly inCreased the egg produCtion of the flies. This experimental approaCh Clearly showed that DCV Could be Considered a polymorphiC Virus. The phenotypiC interaCtions between DCV and host flies varied aCCording to parasite genotype.
-
C Virus of Drosophila and dynamiCs of host population
Comptes Rendus De L Academie Des Sciences Serie Iii-sciences De La Vie-life Sciences, 1996Co-Authors: Michele Thomasorillard, S LegendreAbstract:Drosophila melanogaster populations are naturally infeCted by the Drosophila C Virus (DCV). Ingestion of this non-hereditary Virus early in the life-CyCle has a positive effeCt. DemographiC parameters measured on DCV-free and DCV-infeCted populations of the same genotype enabled us to Compute the population growth rates (multipliCation rates) by means of matrix models. The DCV-infeCted sample had a larger growth rate both for low and high larval densities. SinCe it is not possible to experiment on a mixed population where DCV-free and DCV-infeCted individuals live together, a model Combining Competition and Contamination was used. Simulations showed that CoexistenCe of free and infeCted animals Can oCCur. SuCh a result leads us to question the relation between population growth rate and fitness.
-
Drosophila host genetiC Control of susCeptibility to Drosophila C Virus
Genetics, 1995Co-Authors: Michele Thomasorillard, Bernard Jeune, G CussetAbstract:InteraCtions between Drosophila C Virus (DCV) and its natural host, Drosophila melanogaster, were investigated using 15 geographiCal population samples infeCted by intraabdominal inoCulation. These strains derived from natural populations of D. melanogaster differed in susCeptibility to the DCVC. One strain was "partially tolerant". Isofemale lines obtained from one susCeptible and one partially tolerant strain were studied. The partially tolerant phenotype was dominant, and there was no differenCe between F1 progeny of direCt and reCiproCal Crosses. Analysis of F2 progeny showed that neither sex-linked genes nor maternal effeCts are involved in susCeptibility to DCVC. The partially tolerant strain phenotype was dominant and segregated with Chromosome III. Two nonexClusive hypotheses are proposed to explain Chromosome III gene aCtion.
-
Drosophila C Virus experimental study of infeCtious yields and underlying pathology in Drosophila melanogaster laboratory populations
Journal of Invertebrate Pathology, 1995Co-Authors: Eliane Gomarizzilber, Michel Poras, Michele ThomasorillardAbstract:The underlying pathology of a nonhereditary Virus, the Drosophila C Virus, was studied. This study was related to the Contamination routes (ingestion or ContaCt) and developmental timing. When oral Contamination oCCurred at the first larval instar: (1) the flies were Contaminated, (2) the flies whiCh had developed the most rapidly were the most infeCted, (3) in newly emerged females, the level of Virus was higher than in newly emerged males, (4) when infeCted flies were reared on Virus-free medium only males lost their Virus. Moreover, oral Contamination of adults was very effiCient, but the highest Virus yield was obtained when both larvae and imagos grew on Virus-Contaminated medium. About 30 to 50% of the flies died on the sixth day. They were as DCVC invaded as DCVC-injeCted flies. It seemed that when the Virus yield was higher than a given threshold, all flies died, whatever had been the Contamination routes. When Contaminated adult females and Virus-free males were reared together on a Virus-free medium, females Could infeCt males. In Contrast, Contaminated males were not able to infeCt Virus-free females. Thus, only females were able to Contaminate a rearing medium or other flies.
-
Drosophila C Virus and Drosophila hosts a good assoCiation in various environments
Journal of Evolutionary Biology, 1993Co-Authors: Eliane Gomarizzilber, Michele ThomasorillardAbstract:To disCover whether the benefiCial effeCts observed when Drosophila C Virus (DCVC) infeCts Drosophila larvae should be Considered as a speCifiC Case or, as a general rule, the DCVC-Drosophila assoCiation was studied in different environments (3 host-populations, 2 temperatures, 2 viral dose). We measured pre-adult mortality, developmental time and number of ovarioles per fly. In all experiments, and, in all Contaminated populations, DCVC Could be Considered, either a parasite sinCe it inCreased pre-adult mortality, or a symbiont sinCe it deCreased developmental time and inCreased mean number of ovarioles. The viral dose neCessary for the appearanCe of benefiCial effeCts varied with population, temperature and life-CyCle parameters. A suffiCient number of viral partiCles appears neCessary at a speCifiC point in the host life-CyCle for a benefiCial DCVC effeCt on the host. DCVC does not affeCt the varianCe of any of these parameters. The observed Changes in DCVC-Contaminated populations were thus not a response to the seleCtion pressure of DCVC. Two arguments support the assoCiation as an example of the “Cohabitation-without-struggle model” and will be disCussed.
Jean-luc Imler - One of the best experts on this subject based on the ideXlab platform.
-
the inseCt reservoir of diversity for Viruses and antiviral meChanisms
Comptes Rendus Biologies, 2019Co-Authors: Jean-luc ImlerAbstract:InseCts originated more than 400 million years ago and have undergone sinCe then an extraordinary diversifiCation, assoCiated with many speCtaCular innovations, suCh as flying or establishment of soCial soCieties. They have Colonized all terrestrial eCosystems, and are exposed to a broad range of pathogens, inCluding Viruses, baCteria, fungi, and parasites. Like all animals, inseCts rely on innate immunity to Control infeCtions. Innate immunity is the first layer in host-defense in animals. It involves reCeptors sensing the presenCe of infeCtious miCroorganisms and triggering signaling that leads to the expression of genes Coding effeCtor moleCules, whiCh ConCur to Counter the infeCtion. In vertebrates, a subset of genes induCed enCode Cytokines and CoreCeptors that aCtivate a seCond layer of host defense known as adaptive immunity. The study of the innate immunity in inseCts has led to (i) the disCovery of antimiCrobial peptides, whiCh target baCteria and fungi and are now known to be present in all animals and in plants, (ii) the identifiCation of evolutionarily Conserved important genes aCtivating innate immunity, e.g., the Toll-like reCeptors, and (iii) a better understanding of viral and parasitiC diseases transmitted by hematophagous veCtor inseCts. Among infeCtious miCrobes, Viruses represent a partiCular threat beCause they offer few intrinsiC targets for inhibition by antiviral moleCules. This is beCause they Consist in their simplest form in a nuCleiC aCid enCapsulated in a protein shell, and hijaCk moleCular maChineries from host Cells to Complete their repliCation CyCle. Of note, reCent advanCes in high-throughput sequenCing (HTS) teChnologies have opened the way to the CharaCterization of the virome (i.e. the genetiC diversity of Viruses in a biologiCal sample) in inseCts. Interestingly, these studies revealed that (i) infeCtion by one or more Viruses is Common in arthropods, (ii) the genetiC diversity of arthropod Viruses surpasses that desCribed previously, and (iii) the genetiC diversity of Viruses found in plants and vertebrate animals fall within the genetiC diversity of Viruses assoCiated with arthropods [1] . This suggests that arthropods may have partiCipated in the evolution of Viruses Causing human disease and points to the relevanCe of CharaCterizing antiviral meChanisms in inseCts. One reason to investigate inseCt–Virus interaCtions is that hematophagous inseCts, for example Aedes mosquitoes, are veCtors of important viral diseases suCh as Zika, dengue, yellow fever, and Chikungunya. RNA interferenCe is an RNA-based meChanism that offers broad proteCtion against Viruses in inseCts. This elegant meChanism relies on the reCognition of double + stranded (ds) viral RNAs by the RNase III enzyme DiCer-2, whiCh proCesses them into 21 nuCleotide long small interfering (si) RNA duplexes. One strand of the siRNA is then loaded onto the RNAse H-like enzyme Argonaute 2, where it serves as a guide to speCifiCally target viral RNAs. Of note, Virus-derived siRNAs, whiCh provide a footprint of the aCtion of the inseCt immune system, Can be CharaCterized by HTS. In Collaboration with the group of Prof. Joao Marques (UFMG, Belo Horizonte, Brazil), we have shown that small RNA sequenCing allows assembling longer Contigs of viral RNAs, generating a better Coverage of viral genomes, than traditional long RNA sequenCing. In addition, the profile of the small RNAs is CharaCteristiC of the Virus from whiCh they derive (e.g., number of reads, size distribution of the small RNAs). For example, some Viruses infeCt the ovaries and generate a different type of small RNAs, known as Piwi-interaCting RNAs, or piRNAs, whiCh are longer (24–28nt) than siRNAs ( Fig. 1 ). As a result, it is possible to assign a viral origin to sequenCes even if they do not exhibit any homology to sequenCes present in the databases. This represents a signifiCant improvement in the CharaCterization of the inseCt virome [2] . We have applied this strategy to wild Aedes mosquitoes ColleCted in a dengue endemiC region in Brazil, and have identified three Viruses. Two of them, the BunyaVirus Phasi Charoen-like Virus (PCLV) and the unClassified Virus Humaita-TubiaCanga Virus (HTV), have a high prevalenCe in Aedes mosquitoes ColleCted in different regions of Brazil. These poorly CharaCterized Viruses may affeCt the dynamiCs of transmission of known viral pathogens suCh as dengue, Zika, or Chikungunya Viruses, a hypothesis that is Currently being tested in the laboratory. The disCovery of the important role played by Toll-like reCeptors in innate immunity revealed that important gene regulatory networks have been Conserved during evolution and illustrated how studies in inseCts Can lead to important findings for the biomediCal field. This has provided strong inCentives to identify and CharaCterize other evolutionarily Conserved host-defense meChanisms. As a ConsequenCe, the Contribution of non-Conserved genes to inseCt immunity has reCeived less attention. Yet, these genes may be just as important as the Conserved genes. Indeed, inseCts evolved independently of mammals for several hundreds of thousands of years, whiCh provided multiple opportunities to develop original strategies of defense against infeCtions. HenCe, the CharaCterization of inseCt-speCifiC antiviral faCtors may inspire new strategies to Counter infeCtions. For example, we reCently CharaCterized the gene diedel, whiCh is strongly induCed following viral infeCtion in Drosophila, and has been hijaCked at least three times by inseCt DNA Viruses. We showed that diedel enCodes a CirCulating protein that suppresses the aCtivity of the immune defiCienCy (IMD) pathway of host-defense. The IMD pathway is one of the two major innate immunity pathways regulating transCription faCtors of the NF-κB family in flies. The disCovery that several inseCt Viruses have hijaCked a Cellular gene suppressing the IMD pathway prompted us to investigate its Contribution to the Control of viral infeCtions. Interestingly, we disCovered that two Components of the pathway, the kinase IKKβ and the NF-κB transCription faCtor Relish, are required to restriCt infeCtion by two piCorna-like Viruses, Drosophila C Virus (DCV) and CriCket Paralysis Virus (CrPV) in Drosophila. By Contrast, the other Components of the pathway, inCluding the regulatory subunit of the IKKβ kinase, NEMO, do not appear to play a role in the resistanCe to infeCtion by these Viruses. Among the genes regulated by IKKβ in Virus-infeCted flies, we identified two genes involved in the resistanCe to viral infeCtion. The first one is the homologue of the mammalian faCtor STING (Stimulator of Interferon Genes), and we Could show that it aCts upstream of IKKβ and Relish in a new signaling pathway ( Fig. 2 ). The seCond one enCodes a new antiviral faCtor, that we Called Nazo (meaning “enigma” in Japanese) [3] . The STING-IKKβ-Relish signaling Cassette Controls induCible expression of Nazo in response to viral infeCtion. Nazo results from a dupliCation of the gene CG3740 in Drosophila speCies from the Sophophora subgenus. Of note, CG3740 is not upregulated by viral infeCtion, and eCtopiC expression of the gene has no effeCt on repliCation of DCV or CrPV, unlike expression of Nazo, whiCh results in strong suppression of viral repliCation. The disCovery of Nazo provides an exCellent opportunity to deCipher the genetiCs by whiCh a Cellular gene aCquires a new funCtion in antiviral immunity. Furthermore, the CharaCterization of its mode of aCtion against piCorna-like Viruses may reveal novel angles of attaCk against a family of Viruses that inClude many serious human pathogens (e.g., polioVirus). In summary, the fantastiC diversity of inseCts extends to the Viruses they Carry, and to the genetiC meChanisms they evolved to Control these Viruses. This biodiversity provides a unique opportunity to extend the repertoire of known antiviral meChanisms and to identify weak spots in the repliCation CyCles of Viruses.
-
Drosophila C Virus systemiC infeCtion leads to intestinal obstruCtion
Journal of Virology, 2014Co-Authors: Stanislava Chtarbanova, Olivier Lamiable, Kwang Lee, Delphine Galiana, Laurent Troxler, Carine Meignin, Charles Hetru, Jules Hoffmann, Laurent Daeffler, Jean-luc ImlerAbstract:Drosophila C Virus (DCV) is a positive-sense RNA Virus belonging to the DiCistroviridae family. This natural pathogen of the model organism Drosophila melanogaster is Commonly used to investigate antiviral host defense in flies, whiCh involves both RNA interferenCe and induCible responses. Although lethality is used routinely as a readout for the effiCienCy of the antiviral immune response in these studies, Virus-induCed pathologies in flies still are poorly understood. Here, we CharaCterize the pathogenesis assoCiated with systemiC DCV infeCtion. Comparison of the transCriptome of flies infeCted with DCV or two other positive-sense RNA Viruses, FloCk House Virus and Sindbis Virus, reveals that DCV infeCtion, unlike those of the other two Viruses, represses the expression of a large number of genes. Several of these genes are expressed speCifiCally in the midgut and also are repressed by starvation. We show that systemiC DCV infeCtion triggers a nutritional stress in Drosophila whiCh results from intestinal obstruCtion with the aCCumulation of peritrophiC matrix at the entry of the midgut and the aCCumulation of the food ingested in the Crop, a blind musCular food storage organ. The related Virus CriCket paralysis Virus (CrPV), whiCh effiCiently grows in Drosophila, does not trigger this pathology. We show that DCV, but not CrPV, infeCts the smooth musCles surrounding the Crop, Causing extensive Cytopathology and strongly reduCing the rate of ContraCtions. We ConClude that the pathogenesis assoCiated with systemiC DCV infeCtion results from the tropism of the Virus for an important organ within the foregut of dipteran inseCts, the Crop. IMPORTANCE: DCV is one of the few identified natural viral pathogens affeCting the model organism Drosophila melanogaster. As suCh, it is an important Virus for the deCiphering of host-Virus interaCtions in inseCts. We CharaCterize here the pathogenesis assoCiated with DCV infeCtion in flies and show that it results from the tropism of the Virus for an essential but poorly CharaCterized organ in the digestive traCt, the Crop. Our results may have relevanCe for other members of the DiCistroviridae, some of whiCh are pathogeniC to benefiCial or pest inseCt speCies.
-
The Cryo-EM ReConstruCtion of Drosophila C Virus (DCV) at 5.4 Å
Biophysical Journal, 2013Co-Authors: Leandro F. Estrozi, Jon Agirre, Jean-luc Imler, Estelle Santiago, Jorge Navaza, Guy Schoehn, Diego M. A. GuérinAbstract:The DiCistroviridae family, whiCh is Currently Classified under the PiCornavirales order, groups a pool of arthropod-infeCting Viruses with biCistroniC genomes. The interest in this family of Viruses has been fueled due to the eConomiCal impliCations of their hosts, whiCh range from benefiCial arthropods (bees and shrimps) to inseCt pests (CriCkets, ants and triatomines). Two CrystallographiC struCtures of diCistroViruses have been reported to date: CriCket Paralysis Virus (CrPV, type speCies of the CripaVirus genus) and Triatoma Virus (TrV). their struCtures revealed that diCistroViruses share a Core arChetypal organization, whiCh is Complemented by external and internal Capsid-wide differenCes that likely have arisen from unique host adaptation. In this work we report the CryoEM reConstruCtion at 5.4 A resolution, and C-alpha traCe of Drosophila C Virus (DCV), a viral pathogen that infeCts Drosophila melanogaster, among other Drosophila speCies. This Virus holds a 65.8% sequenCe identity with CrPV and, given the ability of the latter to repliCate in Drosophila hosts, a detailed Comparison Can give insight into the infeCtive CyCle of diCistroViruses.Keywords: CryoEM, reConstruCtion, diCistroviridae, DCV
-
Essential funCtion in vivo for DiCer-2 in host defense against RNA Viruses in Drosophila
Nature Immunology, 2006Co-Authors: Delphine Galiana-arnoux, Anette Schneemann, Catherine Dostert, Jules A Hoffmann, Jean-luc ImlerAbstract:The fruit fly Drosophila melanogaster is a model system for studying innate immunity, inCluding antiviral host defense. InfeCtion with Drosophila C Virus triggers a transCriptional response that is dependent in part on the Jak kinase HopsCotCh. Here we show that suCCessful infeCtion and killing of Drosophila with the inseCt nodaVirus floCk house Virus was striCtly dependent on expression of the viral protein B2, a potent inhibitor of proCessing of double-stranded RNA mediated by the essential RNA interferenCe faCtor DiCer. Conversely, flies with a loss-of-funCtion mutation in the gene enCoding DiCer-2 ( DCr-2 ) showed enhanCed susCeptibility to infeCtion by floCk house Virus, Drosophila C Virus and Sindbis Virus, members of three different families of RNA Viruses. These data demonstrate the importanCe of RNA interferenCe for Controlling Virus repliCation in vivo and establish DCr-2 as a host susCeptibility loCus for Virus infeCtions.
Catherine Dostert - One of the best experts on this subject based on the ideXlab platform.
-
broad rna interferenCe mediated antiviral immunity and Virus speCifiC induCible responses in Drosophila
Journal of Immunology, 2013Co-Authors: Cordula Kemp, Catherine Dostert, Laurent Troxler, Charles Hetru, Stefanie Mueller, Akira Goto, Vincent Barbier, Simona Paro, Francois Bonnay, Carine MeigninAbstract:The fruit fly Drosophila melanogaster is a good model to unravel the moleCular meChanisms of innate immunity and has led to some important disCoveries about the sensing and signaling of miCrobial infeCtions. The response of Drosophila to Virus infeCtions remains poorly CharaCterized and appears to involve two faCets. On the one hand, RNA interferenCe involves the reCognition and proCessing of dsRNA into small interfering RNAs by the host RNase DiCer-2 (DCr-2), whereas, on the other hand, an induCible response Controlled by the evolutionarily Conserved JAK-STAT pathway Contributes to the antiviral host defense. To Clarify the Contribution of the small interfering RNA and JAK-STAT pathways to the Control of viral infeCtions, we have Compared the resistanCe of flies wild-type and mutant for DCr-2 or the JAK kinase HopsCotCh to infeCtions by seven RNA or DNA Viruses belonging to different families. Our results reveal a unique susCeptibility of hop mutant flies to infeCtion by Drosophila C Virus and CriCket paralysis Virus, two members of the DiCistroviridae family, whiCh Contrasts with the susCeptibility of DCr-2 mutant flies to many Viruses, inCluding the DNA Virus invertebrate iridesCent Virus 6. Genome-wide miCroarray analysis Confirmed that different sets of genes were induCed following infeCtion by Drosophila C Virus or by two unrelated RNA Viruses, FloCk House Virus and Sindbis Virus. Overall, our data reveal that RNA interferenCe is an effiCient antiviral meChanism, operating against a large range of Viruses, inCluding a DNA Virus. By Contrast, the antiviral Contribution of the JAK-STAT pathway appears to be Virus speCifiC.
-
the dexd h box heliCase diCer 2 mediates the induCtion of antiviral aCtivity in Drosophila
Nature Immunology, 2008Co-Authors: Safia Deddouche, Catherine Dostert, Cordula Kemp, Stefanie Mueller, Nicolas Matt, Aidan Budd, Delphine Galianaarnoux, Christophe AntoniewskiAbstract:DiCer proteins direCt RNA-interferenCe aCtivities. Imler and Colleagues show that DiCer-2 induCes Vago-dependent antiviral response in flies and that DiCer proteins are related to RIG-I viral sensors. Drosophila, like other invertebrates and plants, relies mainly on RNA interferenCe for its defense against Viruses. In flies, viral infeCtion also triggers the expression of many genes. One of the genes induCed, Vago, enCodes a 18-kilodalton Cysteine-riCh polypeptide. Here we provide genetiC evidenCe that the Vago gene produCt Controlled viral load in the fat body after infeCtion with Drosophila C Virus. InduCtion of Vago was dependent on the heliCase DiCer-2. DiCer-2 belongs to the same DExD/H-box heliCase family as do the RIG-I–like reCeptors, whiCh sense viral infeCtion and mediate interferon induCtion in mammals. We propose that this family represents an evolutionary Conserved set of sensors that deteCt viral nuCleiC aCids and direCt antiviral responses.
-
Essential funCtion in vivo for DiCer-2 in host defense against RNA Viruses in Drosophila
Nature Immunology, 2006Co-Authors: Delphine Galiana-arnoux, Anette Schneemann, Catherine Dostert, Jules A Hoffmann, Jean-luc ImlerAbstract:The fruit fly Drosophila melanogaster is a model system for studying innate immunity, inCluding antiviral host defense. InfeCtion with Drosophila C Virus triggers a transCriptional response that is dependent in part on the Jak kinase HopsCotCh. Here we show that suCCessful infeCtion and killing of Drosophila with the inseCt nodaVirus floCk house Virus was striCtly dependent on expression of the viral protein B2, a potent inhibitor of proCessing of double-stranded RNA mediated by the essential RNA interferenCe faCtor DiCer. Conversely, flies with a loss-of-funCtion mutation in the gene enCoding DiCer-2 ( DCr-2 ) showed enhanCed susCeptibility to infeCtion by floCk house Virus, Drosophila C Virus and Sindbis Virus, members of three different families of RNA Viruses. These data demonstrate the importanCe of RNA interferenCe for Controlling Virus repliCation in vivo and establish DCr-2 as a host susCeptibility loCus for Virus infeCtions.
