title: Complementation of defective picornavirus internal ribosome entry site (IRES) elements by the coexpression of fragments of the IRES.
abstract: Mutant forms of the encephalomyocarditis virus (EMCV) internal ribosome entry site (IRES) have been produced and shown to be severely defective in directing internal initiation of protein synthesis within cells using the vaccinia/T7 RNA polymerase system. Mutants in different regions of the IRES were complemented in trans by coexpression of the intact EMCV IRES but not by coexpression of the related IRES elements from Theiler's murine encephalomyelitis virus (another cardiovirus) or from foot-and-mouth disease virus. Distinct, truncated regions of the EMCV IRES, insufficient to direct internal initiation, were also shown to complement defective EMCV IRES elements. It was necessary for the complementing molecule, whether truncated or full length, to be expressed in the positive sense orientation. RT-PCR analysis provided no support for the idea that any recombination event was responsible for the complementation. The data suggest that multiple activities are performed by distinct functional entities within the IRES in the process of internal initiation of protein synthesis. At least some of these different functions may be achieved by different molecules acting in trans.
authors.affiliation: BBSRC Institute for Animal Health, Pirbright, Woking, Surrey, GU24 ONF, United Kingdom.
authors.forename: L O
authors.initials: LO
authors.lastname: Roberts
authors.forename: G J
authors.initials: GJ
authors.lastname: Belsham
mesh_terms: D002460:Cell Line; D003673:Defective Viruses / Q000235:genetics*; D004686:Encephalomyocarditis virus / Q000235:genetics* / Q000502:physiology; D005816:Genetic Complementation Test; D009154:Mutation; D010442:Peptide Chain Initiation, Translational / Q000235:genetics* / Q000502:physiology; D010957:Plasmids; D016133:Polymerase Chain Reaction; D012367:RNA, Viral / Q000235:genetics* / Q000502:physiology; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics
chemical_list: D012367:RNA, Viral; D014764:Viral Proteins