Oxidation of cellular amino acid pools leads to cytotoxic mistranslation of the genetic code.

Adil Moghal,Noah M Reynolds,Farbod Fazlollahi,Christopher Ryan,Medha Raina,Huseyin Kayadibi,Beth A Lazazzera,Nathaniel Howitz,Eleftheria Matsa,Michael Ibba,Andrei Rajkovic,Tammy J Bullwinkle,Kym F Faull

doi:10.7554/elife.02501

Adil Moghal, Noah M Reynolds + Show 11 more

Open Access

https://doi.org/10.7554/elife.02501

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Abstract

Aminoacyl-tRNA synthetases use a variety of mechanisms to ensure fidelity of the genetic code and ultimately select the correct amino acids to be used in protein synthesis. The physiological necessity of these quality control mechanisms in different environments remains unclear, as the cost vs benefit of accurate protein synthesis is difficult to predict. We show that in Escherichia coli, a non-coded amino acid produced through oxidative damage is a significant threat to the accuracy of protein synthesis and must be cleared by phenylalanine-tRNA synthetase in order to prevent cellular toxicity caused by mis-synthesized proteins. These findings demonstrate how stress can lead to the accumulation of non-canonical amino acids that must be excluded from the proteome in order to maintain cellular viability.

Highlights

The faithful translation of mRNA into the corresponding protein sequence is an essential step in gene expression
Cognate amino acids are attached to their respective transfer RNAs (tRNAs) by aminoacyl-tRNA synthetases, and the ability of these enzymes to distinguish between cognate and non-cognate substrates is a major determinant of the fidelity of the genetic code
It has long been proposed that the fidelity of aminoacyl-tRNA synthetases needs to be at or above 1 in 3,000, which is cited as an approximate overall level of error for protein synthesis (Loftfield and Vanderjagt, 1972)

Summary

Introduction

The faithful translation of mRNA into the corresponding protein sequence is an essential step in gene expression. The accuracy of translation depends on the precise pairing of mRNA codons with their cognate aminoacyl-tRNAs, containing the corresponding anticodons, during ribosomal protein synthesis (Zaher and Green, 2009; Rodnina, 2012). Cognate amino acids are attached to their respective tRNAs by aminoacyl-tRNA synthetases (aaRSs), and the ability of these enzymes to distinguish between cognate and non-cognate substrates is a major determinant of the fidelity of the genetic code. AaRSs discriminate against near- and non-cognate tRNAs at levels compatible with typical translation error rates (∼10−4) due to the structural complexity and diversity observed between tRNA isoacceptors.

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