Conserved 5-methyluridine tRNA modification modulates ribosome translocation

While the centrality of post-transcriptional modifications to RNA biology has long been acknowledged, the function of the vast majority of modified sites remains to be discovered. Illustrative of this, there is not yet a discrete biological role assigned for one the most highly conserved modifications, 5-methyluridine at position 54 in tRNAs (m ⁵ U54). Here, we uncover contributions of m ⁵ U54 to both tRNA maturation and protein synthesis. Our mass spectrometry analyses demonstrate that cells lacking the enzyme that installs m ⁵ U in the T-loop (TrmA in E. coli , Trm2 in S. cerevisiae ) exhibit altered tRNA modifications patterns. Furthermore, m ⁵ U54 deficient tRNAs are desensitized to small molecules that prevent translocation in vitro. This finding is consistent with our observations that, relative to wild-type cells, trm2 Δ cell growth and transcriptome-wide gene expression are less perturbed by translocation inhibitors. Together our data suggest a model in which m ⁵ U54 acts as an important modulator of tRNA maturation and translocation of the ribosome during protein synthesis.