title: Drop-off during ribosome hopping.
abstract: Ribosomes bypass a 50 nucleotide non-coding segment of mRNA between the two open reading frames of bacteriophage T4 gene 60 in order to synthesize a topoisomerase subunit. While nearly all ribosomes appear to initiate bypassing, only 50 % resume translation in the second open reading frame. Failure to bypass is shown here to be independent of the stop codon at the end of the first open reading frame and to be amplified by mutant variants of tRNA(Gly)(2) known to diminish bypassing efficiency. Unproductive bypassing may result from premature dissociation of peptidyl-tRNAs from ribosomes (drop-off) or resumption of translation at inappropriate sites. Assessment of the influence of factors known to induce drop-off reveals that ribosome recycling factor accounts for a small fraction of unproductive bypassing products, but none of the other known factors appear to play a significant role. Resumption of translation at inappropriate sites appears to be minimal, which suggests that spontaneous release of the peptidyl-tRNA may account for the remaining unproductive bypassing products and may be inherent to the gene 60 bypassing mechanism.
authors.affiliation: Department of Human Genetics, University of Utah, 2030 E. 15N., Salt Lake City, UT 84112-5330, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Herr
authors.forename: N M
authors.initials: NM
authors.lastname: Wills
authors.forename: C C
authors.initials: CC
authors.lastname: Nelson
authors.forename: R F
authors.initials: RF
authors.lastname: Gesteland
authors.forename: J F
authors.initials: JF
authors.lastname: Atkins
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D017122:Bacteriophage T4 / Q000235:genetics; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D003062:Codon / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D005814:Genes, Viral / Q000235:genetics; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames / Q000235:genetics; D011485:Protein Binding; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000235:genetics; D012353:RNA, Transfer, Gly / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D012270:Ribosomes / Q000378:metabolism*; D013879:Thioredoxins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D003062:Codon; D058619:Maltose-Binding Proteins; D012329:RNA, Bacterial; D012353:RNA, Transfer, Gly; D011993:Recombinant Fusion Proteins; C096222:tmRNA; D013879:Thioredoxins