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 U54). Here, we uncover contributions of m U54 to both tRNA maturation and protein synthesis. Our mass spectrometry analyses demonstrate that cells lacking the enzyme that installs m U in the T-loop (TrmA in , Trm2 in ) exhibit altered tRNA modifications patterns. Furthermore, m U54 deficient tRNAs are desensitized to small molecules that prevent translocation This finding is consistent with our observations that, relative to wild-type cells, Δ cell growth and transcriptome-wide gene expression are less perturbed by translocation inhibitors. Together our data suggest a model in which m U54 acts as an important modulator of tRNA maturation and translocation of the ribosome during protein synthesis.