Loss of N1-methylation of G37 in tRNA induces ribosome stalling and reprograms gene expression

N-1-methylation of G37 is required for a subset of tRNAs to maintain the translational reading-frame. While loss of m(1) G37 increases ribosomal +1 frameshifting, whether it incurs additional translational defects is unknown. Here, we address this question by applying ribosome profiling to gain a genome-wide view of the effects of m(1) G37 deficiency on protein synthesis. Using E coli as a model, we show that m(1) G37 deficiency induces ribosome stalling at codons that are normally translated by m(1) G37-containing tRNAs. Stalling occurs during decoding of affected codons at the ribosomal A site, indicating a distinct mechanism than that of +1 frameshifting, which occurs after the affected codons leave the A site. Enzyme- and cell-based assays show that m(1) G37 deficiency reduces tRNA aminoacylation and in some cases peptide-bond formation. We observe changes of gene expression in m(1) G37 deficiency similar to those in the stringent response that is typically induced by deficiency of amino acids. This work demonstrates a previously unrecognized function of m(1) G37 that emphasizes its role throughout the entire elongation cycle of protein synthesis, providing new insight into its essentiality for bacterial growth and survival.

Automated summary

N-1-methylation of G37 is crucial for maintaining the translational reading-frame of a subset of tRNAs, with its deficiency leading to ribosome stalling during decoding of affected codons and affecting tRNA aminoacylation and peptide-bond formation. This study highlights a previously unrecognized role of m(1) G37 throughout the elongation cycle of protein synthesis, shedding light on its essentiality for bacterial growth and survival.