Severe oxidative stress induces protein mistranslation through impairment of an aminoacyl-tRNA synthetase editing site

Abstract

Oxidative stress arises from excessive reactive oxygen species (ROS) and affects organisms of all three domains of life. Here we present a previously unknown pathway through which ROS may impact faithful protein synthesis. Aminoacyl-tRNA synthetases are key enzymes in the translation of the genetic code; they attach the correct amino acid to each tRNA species and hydrolyze an incorrectly attached amino acid in a process called editing. We show both in vitro and in vivo in Escherichia coli that ROS reduced the overall translational fidelity by impairing the editing activity of threonyl-tRNA synthetase. Hydrogen peroxide oxidized cysteine182 residue critical for editing, leading to Ser-tRNA Thr formation and protein mistranslation that impaired growth of Escherichia coli. The presence of major heat shock proteases was required to allow cell growth in medium containing serine and hydrogen peroxide; this suggests that the mistranslated proteins were misfolded.aaRS | quality control | ROS | translational fidelity

Lipid II-independent trans Editing of Mischarged tRNAs by the Penicillin Resistance Factor MurM

“…In support of this hypothesis, it has been shown that exposure of E. coli threonyl-tRNA synthetase to hydrogen peroxide results in exacerbated production of misaminoacylated SertRNA Thr . This is due to oxidation of an editing site cysteine residue and subsequent loss of zinc ion coordination (4). Therefore, in the absence of free-standing homologues of the editing domain of AlaRS (AlaXPs proteins), pneumococcus may require MurM to maintain translation quality control, particularly if tRNA mischarging is elevated under oxidative stress as has been previously observed in other organisms (3,4).…”

“…In Escherichia coli, exposure to hydrogen peroxide causes reduction in the fidelity of translation. This effect has been directly attributed to oxidation of Cys-182 within threonyltRNA synthetase, which subsequently impairs the editing ability of the enzyme and results in the production of misaminoacylated Ser-tRNA Thr (4). How translation quality control is maintained in pneumococci, which are routinely exposed to elevated hydrogen peroxide levels, is unknown.…”

“…Pneumococci have an unusual lifestyle because they produce high levels of hydrogen peroxide that provides a competitive advantage for the organism during colonization of the nasopharynx (1,2). In other organisms, it has been reported that exposure to increased levels of hydrogen peroxide can enhance cellular mistranslation rates both in vivo and in vitro (3,4). For example, in mammalian cells, ϳ1% of protein synthesis-directed methionine residues are aminoacylated onto noncognate tRNA molecules.…”

Apoptosis and DNA damage in human spermatozoa

“…The vulnerability of spermiogenesis to oxidative stress has been ascribed to the importance of regulated protein translation in this process and the unique sensitivity of the protein translation machinery to such stress. 66 The result of this ROS-mediated disruption of spermiogenesis is not to halt the morphogenesis of spermatozoa but rather to impair this process so that the spermatozoa that are produced are imperfect. Specifically, we propose that these defective spermatozoa with their poorly compacted chromatin are particularly vulnerable to stress and respond to such adversity by defaulting to apoptosis.…”

Yeast mitochondrial threonyl-tRNA synthetase recognizes tRNA isoacceptors by distinct mechanisms and promotes CUN codon reassignment

“…For instance, a recent study on a bacterial ThrRS has revealed that its editing function is inactivated under oxidative stress conditions (33). Also, it has been proposed that mistranslation could be well tolerated, if not desired, in bacteria and eukaryotes under certain stress conditions (34)(35)(36).…”