The Experts below are selected from a list of 81 Experts worldwide ranked by ideXlab platform
Chirlmin Joo - One of the best experts on this subject based on the ideXlab platform.
-
Viral suppressors of RNAi employ a rapid screening mode to discriminate viral RNA from cellular small RNA.
Nucleic acids research, 2018Co-Authors: Mohamed Fareh, Jasper Van Lopik, Iason Katechis, Alfred W. Bronkhorst, Anna C. Haagsma, Ronald P. Van Rij, Chirlmin JooAbstract:RNA interference (RNAi) is an indispensable mechanism for antiviral defense in insects, including mosquitoes that transmit human diseases. To escape this antiviral defense system, Viruses encode suppressors of RNAi that prevent elimination of viral RNAs, and thus ensure efficient Virus accumulation. Although the first animal Viral Suppressor of RNAi (VSR) was identified more than a decade ago, the molecular basis of RNAi suppression by these viral proteins remains unclear. Here, we developed a single-molecule fluorescence assay to investigate how VSRs inhibit the recognition of viral RNAs by Dcr-2, a key endoribonuclease enzyme in the RNAi pathway. Using VSRs from three insect RNA Viruses (CuleX Y Virus, Drosophila X Virus and Drosophila C Virus), we reveal bimodal physical interactions between RNA molecules and VSRs. During initial interactions, these VSRs rapidly discriminate short RNA substrates from long dsRNA. VSRs engage nearly irreversible binding with long dsRNAs, thereby shielding it from recognition by Dcr-2. We propose that the length-dependent switch from rapid screening to irreversible binding reflects the main mechanism by which VSRs distinguish viral dsRNA from cellular RNA species such as microRNAs.
Sara I. Pérez-prieto - One of the best experts on this subject based on the ideXlab platform.
-
Infectious pancreatic necrosis Virus: biology, pathogenesis, and diagnostic methods.
Advances in Virus Research, 2003Co-Authors: Sylvia Rodríguez Saint-jean, Juan J Borrego, Sara I. Pérez-prietoAbstract:Publisher Summary Infectious pancreatic necrosis Virus (IPNV) is the etiological agent of an acute contagious systemic disease of several species of freshwater and marine fish, molluscs, and crustacean. IPNV is the widespread of the piscine Viruses. IPNV belongs to the genus AquabirnaVirus within the family Birnaviridae. The family contains three genera: genus AquabirnaVirus (type species, IPNV and yellowtail ascites Virus) of fish, genus AvibirnaVirus (type species, infectiousbursal disease Virus, IBDV) of birds, and genus EntomobirnaVirus (type species, Drosophila X Virus, DXV) of insects. Several diagnostic methods for IPNV have been reported, including the fluorescent antibody technique, the immunostaphylococcus- protein A test (ISPA), the coagglutination test, the enzyme-linked immunosorbent assay (ELISA), immunoblots and Western blots, and immunoperoXidase phosphatase cell staining (IP). More recently, molecular probes for the detection of nucleic acids using the polymerase chain reaction have been developed and applied for the diagnosis of fish Viruses. Techniques involving detection and characterization of the viral genome or polypeptides are also considered these include DNA-based techniques, mainly nucleic acid hybridization, and the polymerase chain reaction.
Peter Dobos - One of the best experts on this subject based on the ideXlab platform.
-
BirnaVirus VP1 proteins form a distinct subgroup of RNA-dependent RNA polymerases lacking a GDD motif.
Virology, 2002Co-Authors: Philip S. Shwed, Peter Dobos, Lynne A. Cameron, Vikram N. Vakharia, Roy DuncanAbstract:Abstract We have cloned and characterized the Drosophila X Virus (DXV) genome segment B and its encoded VP1, the putative RNA-dependent RNA polymerase (RdRp) present in the virion. The 2991-bp open reading frame encodes the largest birnaVirus VP1 at 977 aa, with a calculated M r of 112.8 kDa. As with the VP1 proteins of the type species of the other two genera in the family Birnaviridae, namely, infectious pancreatic necrosis Virus (genus AquabirnaVirus) and infectious bursal disease Virus (genus AvibirnaVirus), the DXV (genus EntomobirnaVirus) VP1 protein contains a consensus GTP-binding site and appears to possess self-guanylylation activity. All of the birnaVirus VP1 proteins contain conserved RdRp motifs that reside in the catalytic “palm” domain of all classes of polymerases. However, the birnaVirus RdRps lack the highly conserved Gly-Asp-Asp (GDD) sequence, a component of the proposed catalytic site of this enzyme family that eXists in the conserved motif VI of the palm domain of other RdRps. All three birnaVirus RdRps do contain downstream DD motifs that could function as part of the catalytic triad. These motifs are, however, located in spatially distinct regions of the various birnaVirus VP1 proteins. These results suggest that the VP1 proteins of birnaViruses form a defined subgroup of polymerases that either are lacking the conserved RdRp motif VI or have repositioned this motif to different structural regions.
-
SEQUENCE ANALYSIS OF THE BICISTRONIC Drosophila X Virus GENOME SEGMENT A AND ITS ENCODED POLYPEPTIDES
Virology, 1996Co-Authors: Hye Kyung Chung, Scott Kordyban, Lynne Cameron, Peter DobosAbstract:Abstract Drosophila X Virus represents the entomobirnaVirus genus of the Family Birnaviridae. Segment A of this bisegmented dsRNA containing Virus was cloned and sequenced. The 3360-bp-long nucleotide sequence revealed the presence of two open reading frames (ORFs). A large ORF of 3096 nucleotides, which is flanked by a 107-bp 5′ and a 157-bp 3′-untranslated region, and a 711-nucleotide-long small ORF located within the carboXy half of the large ORF but in a different reading frame. The large ORF encodes a 114-kDa polyprotein which is cotranslationally processed by the Virus-coded protease VP4 to generate preVP2, VP3, and VP4 (VP1 is encoded by genome segment B). N-terminal amino acid sequencing of VP3 and VP4 established the order NH 2 -preVP2-VP4-VP3-COOH within the polyprotein. The small ORF straddles the VP4/VP3 junction and is capable of encoding a basic, arginine-rich 27-kDa polypeptide which so far has not been detected in infected cells. The amino acid sequences specified by the two ORFs were compared to those of infectious pancreatic necrosis Virus (IPNV) and infectious bursal disease Virus (IBDV) that represent the two other genera (aquabirnaVirus and avibirnaVirus) of the Birnaviridae family. Significant sequence homology among the three Viruses was found to be restricted to the amino and carboXy regions of preVP2 and to a small 21-residue-long domain near the carboXy terminal region of VP3. Significant sequence homology is eXhibited by the small ORFs of the three Viruses.
Vikram N. Vakharia - One of the best experts on this subject based on the ideXlab platform.
-
RNAi is an antiviral immune response against a dsRNA Virus in Drosophila melanogaster.
Cellular microbiology, 2006Co-Authors: Robert A. Zambon, Vikram N. VakhariaAbstract:Summary Drosophila melanogaster has a robust and efficient innate immune system, which reacts to infections ranging from bacteria to fungi and, as discovered recently, Viruses as well. The known Drosophila immune responses rely on humoral and cellular activities, similar to those found in the innate immune system of other animals. Recently, RNAi or ‘RNA silencing’ has arisen as a possible means by which Drosophila can react to a specific pathogens, transposons and retroviral elements, in a fashion similar to that of a traditional mammalian adaptive immune system instead of in a more generalized and genome encoded innate immune-based response. RNAi is a highly conserved regulation and defence mechanism, which suppresses gene eXpression via targeted RNA degradation directed by either eXogenous dsRNA (cleaved into siRNAs) or endogenous miRNAs. In plants, RNAi has been found to act as an antiviral immune response system. Here we show that RNAi is an antiviral response used by Drosophila to combat infection by Drosophila X Virus, a birnaVirus, as well. Additionally, we identify multiple core RNAi pathway genes, including piwi, vasa intronic gene ( vig ), aubergine ( aub ), armitage ( armi ), Rm62 , r2d2 and Argonaute2 ( AGO2 ) as having vital roles in this response in whole organisms. Our findings establish Drosophila as an ideal model for the study of antiviral RNAi responses in animals.
-
The Toll pathway is important for an antiviral response in Drosophila
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Robert A. Zambon, Madhumitha Nandakumar, Vikram N. VakhariaAbstract:The innate immune response of Drosophila melanogaster is governed by a compleX set of signaling pathways that trigger antimicrobial peptide (AMP) production, phagocytosis, melanization, and encapsulation. Although immune responses against both bacteria and fungi have been demonstrated in Drosophila, identification of an antiviral response has yet to be found. To investigate what responses Drosophila mounts against a viral infection, we have developed an in vivo Drosophila X Virus (DXV)-based screening system that identifies altered sensitivity to viral infection by using DXV's anoXia-induced death pathology. Using this system to screen flies with mutations in genes with known or suggested immune activity, we identified the Toll pathway as a vital part of the Drosophila antiviral response. Inactivation of this pathway instigated a rapid onset of anoXia induced death in infected flies and increases in viral titers compared to those in WT flies. Although constitutive activation of the pathway resulted in similar rapid onset of anoXia sensitivity, it also resulted in decreased viral titer. Additionally, AMP genes were induced in response to viral infection similar to levels observed during Escherichia coli infection. However, enhanced eXpression of single AMPs did not alter resistance to viral infection or viral titer levels, suggesting that the main antiviral response is cellular rather than humoral. Our results show that the Toll pathway is required for efficient inhibition of DXV replication in Drosophila. Additionally, our results demonstrate the validity of using a genetic approach to identify genes and pathways used in viral innate immune responses in Drosophila.
-
BirnaVirus VP1 proteins form a distinct subgroup of RNA-dependent RNA polymerases lacking a GDD motif.
Virology, 2002Co-Authors: Philip S. Shwed, Peter Dobos, Lynne A. Cameron, Vikram N. Vakharia, Roy DuncanAbstract:Abstract We have cloned and characterized the Drosophila X Virus (DXV) genome segment B and its encoded VP1, the putative RNA-dependent RNA polymerase (RdRp) present in the virion. The 2991-bp open reading frame encodes the largest birnaVirus VP1 at 977 aa, with a calculated M r of 112.8 kDa. As with the VP1 proteins of the type species of the other two genera in the family Birnaviridae, namely, infectious pancreatic necrosis Virus (genus AquabirnaVirus) and infectious bursal disease Virus (genus AvibirnaVirus), the DXV (genus EntomobirnaVirus) VP1 protein contains a consensus GTP-binding site and appears to possess self-guanylylation activity. All of the birnaVirus VP1 proteins contain conserved RdRp motifs that reside in the catalytic “palm” domain of all classes of polymerases. However, the birnaVirus RdRps lack the highly conserved Gly-Asp-Asp (GDD) sequence, a component of the proposed catalytic site of this enzyme family that eXists in the conserved motif VI of the palm domain of other RdRps. All three birnaVirus RdRps do contain downstream DD motifs that could function as part of the catalytic triad. These motifs are, however, located in spatially distinct regions of the various birnaVirus VP1 proteins. These results suggest that the VP1 proteins of birnaViruses form a defined subgroup of polymerases that either are lacking the conserved RdRp motif VI or have repositioned this motif to different structural regions.
Mohamed Fareh - One of the best experts on this subject based on the ideXlab platform.
-
Viral suppressors of RNAi employ a rapid screening mode to discriminate viral RNA from cellular small RNA.
Nucleic acids research, 2018Co-Authors: Mohamed Fareh, Jasper Van Lopik, Iason Katechis, Alfred W. Bronkhorst, Anna C. Haagsma, Ronald P. Van Rij, Chirlmin JooAbstract:RNA interference (RNAi) is an indispensable mechanism for antiviral defense in insects, including mosquitoes that transmit human diseases. To escape this antiviral defense system, Viruses encode suppressors of RNAi that prevent elimination of viral RNAs, and thus ensure efficient Virus accumulation. Although the first animal Viral Suppressor of RNAi (VSR) was identified more than a decade ago, the molecular basis of RNAi suppression by these viral proteins remains unclear. Here, we developed a single-molecule fluorescence assay to investigate how VSRs inhibit the recognition of viral RNAs by Dcr-2, a key endoribonuclease enzyme in the RNAi pathway. Using VSRs from three insect RNA Viruses (CuleX Y Virus, Drosophila X Virus and Drosophila C Virus), we reveal bimodal physical interactions between RNA molecules and VSRs. During initial interactions, these VSRs rapidly discriminate short RNA substrates from long dsRNA. VSRs engage nearly irreversible binding with long dsRNAs, thereby shielding it from recognition by Dcr-2. We propose that the length-dependent switch from rapid screening to irreversible binding reflects the main mechanism by which VSRs distinguish viral dsRNA from cellular RNA species such as microRNAs.
