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 (m5U54). Here, we uncover contributions of m5U54 to both tRNA maturation and protein synthesis. Our mass spectrometry analyses demonstrate that cells lacking the enzyme that installs m5U in the T-loop (TrmA inE. coli, Trm2 inS. cerevisiae) exhibit altered tRNA modifications patterns. Furthermore, m5U54 deficient tRNAs are desensitized to small molecules that prevent translocationin vitro.This finding is consistent with our observations that, relative to wild-type cells,trm2Δ cell growth and transcriptome-wide gene expression are less perturbed by translocation inhibitors. Together our data suggest a model in which m5U54 acts as an important modulator of tRNA maturation and translocation of the ribosome during protein synthesis. To investigate the impact of m5U modifications on expression we knocked out the methyltransferase Trm2 and then did RNA-seq on both WT and KO cells in the presence or absence of the elongation inhibitor hygromycin B. All experiments were performed in biological duplicate