title: Comparisons among the larger genome segments of six nodaviruses and their encoded RNA replicases.
abstract: The Nodaviridae are a family of isometric RNA viruses that infect insects and fish. Their genomes, which are among the smallest known for animal viruses, consist of two co-encapsidated positive-sense RNA segments: RNA1 encodes the viral contribution to the RNA-dependent RNA polymerase (RdRp) which replicates the viral genome, whereas RNA2 encodes the capsid protein precursor. In this study, the RNA1 sequences of two insect nodaviruses - Nodamura virus (the prototype of the genus) and Boolarra virus - are reported as well as detailed comparisons of their encoded RdRps with those of three other nodaviruses of insects and one of fish. Although the 5' and 3' untranslated regions did not reveal common features of RNA sequence or secondary structure, these divergent viruses showed similar genome organizations and encoded RdRps that had from 26 to 99% amino acid sequence identity. All six RdRp amino acid sequences contained canonical RNA polymerase motifs in their C-terminal halves and conserved elements of predicted secondary structure throughout. A search for structural homologues in the protein structure database identified the poliovirus RdRp, 3D(pol), as the best template for homology modelling of the RNA polymerase domain of Pariacoto virus and allowed the construction of a congruent three-dimensional model. These results extend our understanding of the relationships among the RNA1 segments of nodaviruses and the predicted structures of their encoded RdRps.
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, BBRB 373/17, 845 19th Street South, Birmingham, AL 35294-2170, USA1.
authors.forename: Karyn N
authors.initials: KN
authors.lastname: Johnson
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, BBRB 373/17, 845 19th Street South, Birmingham, AL 35294-2170, USA1.
authors.forename: Kyle L
authors.initials: KL
authors.lastname: Johnson
authors.affiliation: Department of Animal Health and Biomedical Science, University of Wisconsin-Madison, Madison, WI 53706, USA2.
authors.forename: Ranjit
authors.initials: R
authors.lastname: Dasgupta
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, BBRB 373/17, 845 19th Street South, Birmingham, AL 35294-2170, USA1.
authors.forename: Theresa
authors.initials: T
authors.lastname: Gratsch
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, BBRB 373/17, 845 19th Street South, Birmingham, AL 35294-2170, USA1.
authors.forename: L Andrew
authors.initials: LA
authors.lastname: Ball
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D020121:5' Untranslated Regions / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D016679:Genome, Viral; D007304:Insect Viruses / Q000201:enzymology / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D012328:RNA Viruses / Q000201:enzymology / Q000235:genetics*; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D014764:Viral Proteins; D012324:RNA-Dependent RNA Polymerase