Modulation of Escherichia coli Translation by the Specific Inactivation of tRNAGly Under Oxidative Stress

Abstract

Bacterial oxidative stress responses are generally controlled by transcription factors that modulate the synthesis of RNAs with the aid of some sRNAs that control the stability, and in some cases the translation, of specific mRNAs. Here, we report that oxidative stress additionally leads to inactivation of tRNA Gly in Escherichia coli, inducing a series of physiological changes. The observed inactivation of tRNA Gly correlated with altered efficiency of translation of Gly codons, suggesting a possible mechanism of translational control of gene expression under oxidative stress. Changes in translation also depended on the availability of glycine, revealing a mechanism whereby bacteria modulate the response to oxidative stress according to the prevailing metabolic state of the cells.

Oxidative Stress in Bacteria and the Central Dogma of Molecular Biology

“…The opposite was true, when the tRNA pool was enriched by addition of a plasmid carrying extra copies of rare tRNA genes, cells became more resistant to oxidative stress (Zhu and Dai, 2019). Surprisingly, Leiva et al published somewhat contradictory results to the two previous reports (Leiva et al, 2020). Instead of a global reduction of the tRNA pool, the authors found that from ten tested tRNA species only one specific tRNA (tRNA Gly ) was downregulated under both H 2 O 2 and paraquat stress.…”

“…Leiva et al also investigated whether the tRNA modification pattern was altered in response to the oxidative stress. They found no change at all known modification sites for the tRNA Gly isoacceptors before and after addition of the stress ( Leiva et al, 2020 ). However, the authors also pointed out that abasic sites and unknown oxidation products of modified tRNA Gly nucleotides might have escaped their analysis.…”

Enhanced translation of leaderless mRNAs under oxidative stress in Escherichia coli

“…In order to get some insights about the effects of paraquat on translation, we analyzed the sedimentation coefficient of ribosomes from E. coli cultured in M9r media in the presence of 250 µM paraquat. Previous assays have shown that under these conditions bacterial replication and protein synthesis are greatly decreased (Leiva et al, 2020). Also, for this strain, the decreased translation produced by this lower concentration of paraquat seems to depend mainly on steps different from elongation (Leiva et al, 2020).…”

“…In addition to this global repression of translation, we and other authors have described important alterations in translation elongation. For instance, an increased error rate in the incorporation of some amino acids (Ling & Soll, 2010;Steiner et al, 2019;Wu et al, 2014) or decreased elongation rates during translation have been observed (Leiva et al, 2020;Zhong et al, 2015;Zhu & Dai, 2019). The relative contribution of each of these effects is not completely understood.…”

“…In effect, we have not observed this tRNA degradation using another strain of E. coli (K-12 MG1655). When using 250 µM of paraquat to induce oxidative stress, the decreased translation seems to derive mainly from steps different than elongation, probably translation initiation (Leiva et al, 2020). In order to better understand the regulation of translation under this concentration of paraquat, we analyzed a ribosome sedimentation profile (Figure 1).…”