Poster abstracts

Poster number 43 submitted by Kirk Gaston

Life without tRNA Ile-lysidine synthetase: Translation of the isoleucine codon AUA in Bacillus subtilis lacking the canonical tRNA Ile

Kirk W. Gaston (Department of Chemistry, University of Cincinnati), Caroline Kohrer (Department of Biology, Massachusetts Institute of Technology), Debabrata Mandal (Department of Biology, Massachusetts Institute of Technology), Henri Grosjean (Centre de Gntique Molculaire, CNRS), Patrick A. Limbach (Department of Chemistry, University of Cincinnati), Uttam L. RajBhandary (Department of Biology, Massachusetts Institute of Technology)

Abstract:
In almost all bacteria and archaea, translation of the isoleucine codon AUA requires a modified C (lysidine or agmatidine) at the wobble position of tRNA Ile to base pair specifically with the A of the AUA codon but not with the G of AUG. Recently, a Bacillus subtilis strain was isolated in which the gene encoding tRNAIle-lysidine synthetase was deleted. Consequently, the wobble base C34 of tRNA Ile remains unmodified and cells depend on a mutant tRNA derived from tRNA Ile, in which G34 at the wobble position has been changed to U34. Here, we show (i) that unlike U34 in the wobble position of most other tRNAs, U34 of the mutant tRNA is not modified, and (ii) that the mutant tRNA binds preferentially to the AUA codon on B. subtilis ribosomes but only weakly to AUG. These in vitro data are consistent with the finding that the suppressor strain displays only a low level of misreading AUG codons in vivo and grows at a rate comparable to that of the wild type strain.

Keywords: tRNA, Mass Spectrometry, RNA modification