title: Template requirements for recognition and copying by Sindbis virus RNA-dependent RNA polymerase.
abstract: The Sindbis virus (SIN) nonstructural protein nsP4 possesses the RNA-dependent RNA polymerase activity required for the replication of the SIN genome and transcription of a subgenomic mRNA during infection. Isolation of this protein from other viral components of the RNA synthetic complex allowed the characterization of template requirements for nsP4-mediated genome replication. The major findings of this study are: (i) in the absence of other viral proteins nsP4 is capable of copying SIN plus- and minus-strand templates, but does not transcribe subgenomic RNA; (ii) mutations in the 3' conserved sequence element and poly(A) tail of the plus-strand template prevent nsP4-mediated de novo initiation of minus-strand RNA synthesis; (iii) nsP4-dependent terminal addition of nucleotides occurs on template RNA possessing certain mutations in the 3'CSE and polyadenylate tail ; (iv) nsP4 is capable of minus-strand synthesis independent of the sequence at the 5' end of the template; (v) an A-U rich sequence in the 3'CSE represents a binding site for a replicase component, probably nsP4; (vi) plus-strand genomic RNA synthesis is dependent on the 3' end of the minus-strand template. These studies begin to define the specific interactions with the viral RNA templates mediated by individual components of the viral replication complex and suggest a model for ternary complex formation during the initiation of minus-strand RNA synthesis.
authors.affiliation: Department of Biology, Indiana University, 1001 E. Third Street, Bloomington, IN 47405, USA.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Thal
authors.forename: Brian R
authors.initials: BR
authors.lastname: Wasik
authors.forename: Jessica
authors.initials: J
authors.lastname: Posto
authors.forename: Richard W
authors.initials: RW
authors.lastname: Hardy
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D020121:5' Untranslated Regions / Q000235:genetics; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D006224:Cricetinae; D009154:Mutation; D009711:Nucleotides / Q000378:metabolism; D012367:RNA, Viral / Q000096:biosynthesis; D012845:Sindbis Virus / Q000502:physiology*; D013698:Templates, Genetic; D014158:Transcription, Genetic; D017361:Viral Nonstructural Proteins / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D009711:Nucleotides; D012367:RNA, Viral; D017361:Viral Nonstructural Proteins; C499947:nsP4 protein, Sindbis virus