title: Regulation of -1 ribosomal frameshifting directed by cocksfoot mottle sobemovirus genome.
abstract: The polyprotein of Cocksfoot mottle virus (CfMV) is encoded by two overlapping open reading frames (ORFs). The putative replicase of CfMV is produced as a part of the polyprotein from ORF2b by the -1 ribosomal frameshifting mechanism. The signals leading to -1 ribosomal frameshifting directed by CfMV RNA are the slippery heptamer UUUAAAC and a stem-loop structure starting seven nucleotides downstream from the heptamer. We studied the effect of different parts of the CfMV genome on the -1 ribosomal frameshifting efficiency using a wheat germ extract transcription/translation system. A point mutation in the slippery heptamer and a mutation deleting the stem-loop structure prevented frameshifting. Seventy nucleotides of CfMV sequence, including the slippery sequence and the stem-loop structure, was found to act as a minimal region for frameshifting. Interestingly, a termination codon introduced into the -1-frame 27 nucleotides downstream of the stem-loop structure increased frameshift efficiency threefold, while a similarly located termination codon in the 0-frame had no effect. Even fourfold to fivefold efficiencies were observed when the polyprotein encoding ORFs were fused together, which led simultaneously to the formation of a termination codon downstream of the frameshift signal. Possible reasons underlying these observations are discussed.
authors.affiliation: Institute of Biotechnology, Program for Plant Molecular Biology, Viikki Biocentre, University of Helsinki, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Lucchesi
authors.forename: K
authors.initials: K
authors.lastname: Mäkeläinen
authors.forename: A
authors.initials: A
authors.lastname: Merits
authors.forename: T
authors.initials: T
authors.lastname: Tamm
authors.forename: K
authors.initials: K
authors.lastname: Mäkinen
mesh_terms: D001483:Base Sequence; D018388:Codon, Terminator; D018965:Frameshifting, Ribosomal; D016679:Genome, Viral; D008969:Molecular Sequence Data; D009154:Mutation; D010942:Plant Viruses / Q000235:genetics*
chemical_list: D018388:Codon, Terminator