Misacylation of tRNA with methionine in Saccharomyces cerevisiae

Department of Chemistry, Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, 60637, USA and Institute of Molecular Life Sciences, University of Zurich, CH-8057 Zurich, Switzerland.
Nucleic Acids Research (Impact Factor: 9.11). 08/2012; 40(20). DOI: 10.1093/nar/gks805
Source: PubMed


Accurate transfer RNA (tRNA) aminoacylation by aminoacyl-tRNA synthetases controls translational fidelity. Although tRNA synthetases are generally highly accurate, recent results show that the methionyl-tRNA synthetase (MetRS) is an exception. MetRS readily misacylates non-methionyl tRNAs at frequencies of up to 10% in mammalian cells; such mismethionylation may serve a beneficial role for cells to protect their own proteins against oxidative damage. The Escherichia coli MetRS mismethionylates two E. coli tRNA species in vitro, and these two tRNAs contain identity elements for mismethionylation. Here we investigate tRNA mismethionylation in Saccharomyces cerevisiae. tRNA mismethionylation occurs at a similar extent in vivo as in mammalian cells. Both cognate and mismethionylated tRNAs have similar turnover kinetics upon cycloheximide treatment. We identify specific arginine/lysine to methionine-substituted peptides in proteomic mass spectrometry, indicating that mismethionylated tRNAs are used in translation. The yeast MetRS is part of a complex containing the anchoring protein Arc1p and the glutamyl-tRNA synthetase (GluRS). The recombinant Arc1p-MetRS-GluRS complex binds and mismethionylates many tRNA species in vitro. Our results indicate that the yeast MetRS is responsible for extensive misacylation of non-methionyl tRNAs, and mismethionylation also occurs in this evolutionary branch.

    • "Filter-based aminoacylation reactions and aminoacylation reactions for microarray analysis were performed as previously described (Netzer et al., 2009; Wiltrout et al., 2012). "
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    • "Codon 'capture' and reassignment have been reported in mitochondria and other obligate bacterial symbionts (Knight et al. 2001b; McCutcheon et al. 2009), while mischarging of various tRNAs as methionyl-tRNA is found in representatives from each branch of the tree of life (Jones et al. 2011; Wiltrout et al. 2012). These tRNA transformations (mischarging, post-transcriptional modification , etc.) are protein mediated and do not involve codon–anticodon remodeling or changes in core ribosome structure or function (Knight et al. 2001a). "
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    • "Indeed, it has been shown, from fungi to mammals, that MRS methionylates non-cognate tRNAs under oxidative stress. In S. cerevisiae, mismethionylated tRNAs can be used by translating ribosomes [60]. This mechanism is conserved in human cells [100]. "
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