Translational bypassing without peptidyl-tRNA anticodon scanning of coding gap mRNA |
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Authors: | Wills Norma M O'Connor Michelle Nelson Chad C Rettberg Charles C Huang Wai Mun Gesteland Raymond F Atkins John F |
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Affiliation: | Department of Human Genetics, University of Utah, Salt Lake City, UT, USA. |
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Abstract: | Half the ribosomes translating the mRNA for phage T4 gene 60 topoisomerase subunit bypass a 50 nucleotide coding gap between codons 46 and 47. The pairing of codon 46 with its cognate peptidyl-tRNA anticodon dissociates, and following mRNA slippage, peptidyl-tRNA re-pairs to mRNA at a matched triplet 5' adjacent to codon 47, where translation resumes. Here, in studies with gene 60 cassettes, it is shown that the peptidyl-tRNA anticodon does not scan the intervening sequence for potential complementarity. However, certain coding gap mutants allow peptidyl-tRNA to scan sequences in the bypassed segment. A model is proposed in which the coding gap mRNA enters the ribosomal A-site and forms a structure that precludes peptidyl-tRNA scanning of its sequence. Dissipation of this RNA structure, together with the contribution of 16S rRNA anti-Shine-Dalgarno sequence pairing with GAG, facilitates peptidyl-tRNA re-pairing to mRNA. |
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Keywords: | mRNA folding ORF coupling ribosomal frameshifting ribosome translational bypassing |
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