The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Malcolm F. White - One of the best experts on this subject based on the ideXlab platform.
-
The dynamic interplay of host and Viral Enzymes in type III CRISPR-mediated cyclic nucleotide signalling
eLife, 2020Co-Authors: Januka S Athukoralage, Shirley Graham, Christophe Rouillon, Sabine Grüschow, Clarissa M. Czekster, Malcolm F. WhiteAbstract:Cyclic nucleotide second messengers are increasingly implicated in prokaryotic anti-Viral defence systems. Type III CRISPR systems synthesise cyclic oligoadenylate (cOA) upon detecting foreign RNA, activating ancillary nucleases that can be toxic to cells, necessitating mechanisms to remove cOA in systems that operate via immunity rather than abortive infection. Previously, we demonstrated that the Sulfolobus solfataricus type III-D CRISPR complex generates cyclic tetra-adenylate (cA4), activating the ribonuclease Csx1, and showed that subsequent RNA cleavage and dissociation acts as an 'off-switch' for the cyclase activity. Subsequently, we identified the cellular ring nuclease Crn1, which slowly degrades cA4 to reset the system (Rouillon et al., 2018), and demonstrated that viruses can subvert type III CRISPR immunity by means of a potent anti-CRISPR ring nuclease variant AcrIII-1. Here, we present a comprehensive analysis of the dynamic interplay between these Enzymes, governing cyclic nucleotide levels and infection outcomes in virus-host conflict.
Wade P. Parks - One of the best experts on this subject based on the ideXlab platform.
-
[14] Identification of Viral reverse-transcriptase
Methods in Enzymology, 2004Co-Authors: Edward M. Scolnick, Wade P. ParksAbstract:Publisher Summary This chapter describes methods that were developed based on the use of synthetic templates that allow specifically detecting and identifying C-type Viral reverse transcriptases. Physical separation of cellular and microbial DNA polymerases from Viral reverse transcriptase was found to be possible. Immunologically, cellular and microbial DNA polymerases were found to be distinct from C-type Viral reverse transcriptases. Thus, the combination of synthetic templates, column chromatography, and antisera against the Viral enzyme provided both the sensitivity and specificity required in epidemiologic studies in which the reverse transcriptase was being used as a marker for a virus that might contain such an enzyme. Using antisera to the Viral Enzymes, classifications of C-type viruses of avian, reptilian, and mammalian origin can be easily distinguished with essentially no cross-reactions between them. Among mammalian viruses with such a polymerase, C-type viruses can also be distinguished unambiguously from B-type viruses, visna virus, syncytium-forming viruses, and Mason–Pfizer monkey virus (MP–MV).
Alexander E. Gorbalenya - One of the best experts on this subject based on the ideXlab platform.
-
The VIZIER project: preparedness against pathogenic RNA viruses
Antiviral research, 2007Co-Authors: Bruno Coutard, Alexander E. Gorbalenya, Eric J. Snijder, Andrey M. Leontovich, Anne Poupon, X. De Lamballerie, Rémi N. Charrel, Ernest A. Gould, Stephan Günther, Helene NorderAbstract:Life-threatening RNA viruses emerge regularly, and often in an unpredictable manner. Yet, the very few drugs available against known RNA viruses have sometimes required decades of research for development. Can we generate preparedness for outbreaks of the, as yet, unknown viruses? The VIZIER (Viral Enzymes InvolvEd in Replication) (http://www.vizier-europe.org/) project has been set-up to develop the scientific foundations for countering this challenge to society. VIZIER studies the most conserved Viral Enzymes (that of the replication machinery, or replicases) that constitute attractive targets for drug-design. The aim of VIZIER is to determine as many replicase crystal structures as possible from a carefully selected list of viruses in order to comprehensively cover the diversity of the RNA virus universe, and generate critical knowledge that could be efficiently utilized to jump-start research on any emerging RNA virus. VIZIER is a multidisciplinary project involving (i) bioinformatics to define functional domains, (ii) Viral genomics to increase the number of characterized Viral genomes and prepare defined targets, (iii) proteomics to express, purify, and characterize targets, (iv) structural biology to solve their crystal structures, and (v) pre-lead discovery to propose active scaffolds of antiViral molecules.
-
Unique and conserved features of genome and proteome of SARS-coronavirus, an early split-off from the coronavirus group 2 lineage.
Journal of molecular biology, 2003Co-Authors: Eric J. Snijder, Peter J. Bredenbeek, Jessika C. Dobbe, Volker Thiel, John Ziebuhr, Leo L.m. Poon, Yi Guan, Mikhail Rozanov, Willy J. M. Spaan, Alexander E. GorbalenyaAbstract:The genome organization and expression strategy of the newly identified severe acute respiratory syndrome coronavirus (SARS-CoV) were predicted using recently published genome sequences. Fourteen putative open reading frames were identified, 12 of which were predicted to be expressed from a nested set of eight subgenomic mRNAs. The synthesis of these mRNAs in SARS-CoV-infected cells was confirmed experimentally. The 4382- and 7073 amino acid residue SARS-CoV replicase polyproteins are predicted to be cleaved into 16 subunits by two Viral proteinases (bringing the total number of SARS-CoV proteins to 28). A phylogenetic analysis of the replicase gene, using a distantly related torovirus as an outgroup, demonstrated that, despite a number of unique features, SARS-CoV is most closely related to group 2 coronaviruses. Distant homologs of cellular RNA processing Enzymes were identified in group 2 coronaviruses, with four of them being conserved in SARS-CoV. These newly recognized Viral Enzymes place the mechanism of coronavirus RNA synthesis in a completely new perspective. Furthermore, together with previously described Viral Enzymes, they will be important targets for the design of antiViral strategies aimed at controlling the further spread of SARS-CoV.
Pascal Meylan - One of the best experts on this subject based on the ideXlab platform.
-
resistance to nucleoside analog reverse transcriptase inhibitors mediated by human immunodeficiency virus type 1 p6 protein
Journal of Virology, 2001Co-Authors: Solange Peters, Miguel Munoz, Sabine Yerly, Victor Sanchezmerino, Cecilio Lopezgalindez, Luc Perrin, Brendan A Larder, Dusan Cmarko, Stanislav Fakan, Pascal MeylanAbstract:Resistance of human immunodeficiency virus type 1 (HIV-1) to antiretroViral agents results from target gene mutation within the pol gene, which encodes the Viral protease, reverse transcriptase (RT), and integrase. We speculated that mutations in genes other that the drug target could lead to drug resistance. For this purpose, the p1-p6(gag)-p6(pol) region of HIV-1, placed immediately upstream of pol, was analyzed. This region has the potential to alter Pol through frameshift regulation (p1), through improved packaging of Viral Enzymes (p6(Gag)), or by changes in activation of the Viral protease (p6(Pol)). Duplication of the proline-rich p6(Gag) PTAP motif, necessary for late Viral cycle activities, was identified in plasma virus from 47 of 222 (21.2%) patients treated with nucleoside analog RT inhibitor (NRTI) antiretroViral therapy but was identified very rarely from drug-naive individuals. Molecular clones carrying a 3-amino-acid duplication, APPAPP (transframe duplication SPTSPT in p6(Pol)), displayed a delay in protein maturation; however, they packaged a 34% excess of RT and exhibited a marked competitive growth advantage in the presence of NRTIs. This phenotype is reminiscent of the inoculum effect described in bacteriology, where a larger input, or a greater infectivity of an organism with a wild-type antimicrobial target, leads to escape from drug pressure and a higher MIC in vitro. Though the mechanism by which the PTAP region participates in Viral maturation is not known, duplication of this proline-rich motif could improve assembly and packaging at membrane locations, resulting in the observed phenotype of increased infectivity and drug resistance.
Januka S Athukoralage - One of the best experts on this subject based on the ideXlab platform.
-
The dynamic interplay of host and Viral Enzymes in type III CRISPR-mediated cyclic nucleotide signalling
eLife, 2020Co-Authors: Januka S Athukoralage, Shirley Graham, Christophe Rouillon, Sabine Grüschow, Clarissa M. Czekster, Malcolm F. WhiteAbstract:Cyclic nucleotide second messengers are increasingly implicated in prokaryotic anti-Viral defence systems. Type III CRISPR systems synthesise cyclic oligoadenylate (cOA) upon detecting foreign RNA, activating ancillary nucleases that can be toxic to cells, necessitating mechanisms to remove cOA in systems that operate via immunity rather than abortive infection. Previously, we demonstrated that the Sulfolobus solfataricus type III-D CRISPR complex generates cyclic tetra-adenylate (cA4), activating the ribonuclease Csx1, and showed that subsequent RNA cleavage and dissociation acts as an 'off-switch' for the cyclase activity. Subsequently, we identified the cellular ring nuclease Crn1, which slowly degrades cA4 to reset the system (Rouillon et al., 2018), and demonstrated that viruses can subvert type III CRISPR immunity by means of a potent anti-CRISPR ring nuclease variant AcrIII-1. Here, we present a comprehensive analysis of the dynamic interplay between these Enzymes, governing cyclic nucleotide levels and infection outcomes in virus-host conflict.
