title: Transcribing and replicating particles in a double-stranded RNA virus from Leishmania.
abstract: During the replicative cycle of many double-stranded RNA viruses, transcription of particles with a double-stranded RNA genome alternates with replication of particles containing a single-stranded genome. In virions infecting some strains of Leishmania guyanensis the putative transcriptase and replicase activities of the RNA-dependent RNA polymerase were previously detected in vitro. Northern hybridization to RNA of known polarity demonstrates that the single-stranded RNA products are of positive polarity and, by definition, are the products of the viral transcriptase. Re-evaluation of previously published data in the light of these findings suggests that transcription in Leishmania viruses is conservative. Sedimentation in sucrose gradients revealed two types of viral particles; single-stranded RNA particles comprised a small fraction of the virus population and sedimented more slowly than the peak of double-stranded RNA particles. In agreement with the replicative model of other dsRNA viruses, these single-stranded particles co-purified with the viral replicase activity that resulted in double-stranded RNA synthesis. In virus-infected promastigote extracts replicase activity decreased with increasing parasite density in culture, suggesting a correlation between cell division and viral replication.
authors.affiliation: Seattle Biomedical Research Institute, WA.
authors.forename: R S
authors.initials: RS
authors.lastname: Weeks
authors.forename: J L
authors.initials: JL
authors.lastname: Patterson
authors.forename: K
authors.initials: K
authors.lastname: Stuart
authors.forename: G
authors.initials: G
authors.lastname: Widmer
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D002499:Centrifugation, Density Gradient; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D007892:Leishmania braziliensis / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D012328:RNA Viruses / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D012330:RNA, Double-Stranded / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics*; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics; D014779:Virus Replication / Q000235:genetics*
chemical_list: D012330:RNA, Double-Stranded; D012367:RNA, Viral; D012324:RNA-Dependent RNA Polymerase; D012321:DNA-Directed RNA Polymerases