Glycine tRNA mutants with normal anticodon loop size cause -1 frameshifting

  • O 'mahony D
  • Mimst B
  • Thompsont S
 et al. 
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Abstract

Mutations in the acceptor stem, the 5-methyluridine-pseudouridine-cytidine (TFC) arm, and the an-ticodon of Salmonella tRNAG'Y can cause -1 frameshifting. The potential for standard base pairing between acceptor stem positions 1 and 72 is disrupted in the mutant sujS627. This disruption may interfere with the interaction of the tRNA with elongation factor-Tu-GTP or an as-yet-unspecified domain of the ribosome. The potential for standard base pairing in part of the TFC stem is disrupted in mutant suJS625. The nearly universal C-61 base of the TFC stem is altered in mutant suJS617, and the TFC loop is extended in mutant suJS605. These changes are expected to interfere with the stability of the TFC loop and its interaction with the D arm. The mutation in mutant suJS605, and possibly other mutants, alters nucleoside modification in the D arm. Three mutants, sufS601, sufS607, and suJS609, have a cytidine substituted for the modified uridine at position 34, the first anticodon position. None of the alterations grossly disrupts in-frame triplet decoding by the mutant tRNAs. The results show that -1 frameshifting in vivo can be caused by tRNAs with normal anticodon loop size and suggest that alternative conformational states of the mutant tRNAs may allow them to read a codon in frame or to shift reading frame. The normal triplet progression oftranslation can be perturbed by ribosomes shifting reading frame. The phenomenon was initially detected as frameshift mutant leakiness, but there are examples in which the phenomenon is seen in the decoding of normal cellular or viral genes. Several examples have shifts into the + 1 frame (1-5). Shifts to the -1 frame have

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Authors

  • Daniel J O 'mahony

  • Betsy H Mimst

  • Shahla Thompsont

  • Emanuel J Murgolat

  • John F Atkins

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