title: The polymerase gene of corona- and toroviruses: evidence for an evolutionary relationship.
abstract: In this paper we demonstrate that the organization of the polymerase gene of toroviruses and coronaviruses is similar. The polymerase gene of both virus families consists of at least two large ORFs (1a and 1b). Four domains of conserved amino acid sequences have been identified in nearly identical positions in the 3' ORF of the pol gene of toroviruses and coronaviruses. The most 3' conserved domain which is still unique for these viruses encodes a 33-kDA protein in MHV-A59, which is cleaved from a precursor protein. Expression of ORF1b of the pol gene of both virus families occurs by ribosomal frameshifting. A predicted stem-loop structure and pseudoknot are conserved in the ORF1a/ORF1b overlap of toro- and coronaviruses. On the basis of these results we postulate that toro- and coronaviruses are ancestrally more related to each other than to other families of positive stranded RNA viruses.
authors.affiliation: Department of Infectious Diseases and Immunology, State University of Utrecht, The Netherlands.
authors.forename: P J
authors.initials: PJ
authors.lastname: Bredenbeek
authors.forename: E J
authors.initials: EJ
authors.lastname: Snijder
authors.forename: F H
authors.initials: FH
authors.lastname: Noten
authors.forename: J A
authors.initials: JA
authors.lastname: den Boon
authors.forename: W M
authors.initials: WM
authors.lastname: Schaaper
authors.forename: M C
authors.initials: MC
authors.lastname: Horzinek
authors.forename: W J
authors.initials: WJ
authors.lastname: Spaan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D005075:Biological Evolution; D002151:Calorimetry; D003332:Coronaviridae / Q000201:enzymology / Q000235:genetics*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D008969:Molecular Sequence Data; D006517:Murine hepatitis virus / Q000201:enzymology / Q000235:genetics*; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames; D014176:Protein Biosynthesis; D012328:RNA Viruses / Q000201:enzymology / Q000235:genetics*; D012367:RNA, Viral / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
chemical_list: D012367:RNA, Viral; D012321:DNA-Directed RNA Polymerases