Global translational impacts of the loss of the tRNA modification t 6 A in yeast

• Published in: Microbial cell Vol. 3; no. 1; p. 29
• Main Authors: Thiaville, Patrick C, Legendre, Rachel, Rojas-Benítez, Diego, Baudin-Baillieu, Agnès, Hatin, Isabelle, Chalancon, Guilhem, Glavic, Alvaro, Namy, Olivier, de Crécy-Lagard, Valérie
• Format: Journal Article
• Language: English
• Published: Austria 01.01.2016
• Subjects: ribosome profiling; tRNA; translation; modified nucleosides; t6A
• ISSN: 2311-2638

The universal tRNA modification t A is found at position 37 of nearly all tRNAs decoding ANN codons. The absence of t A leads to severe growth defects in baker's yeast, phenotypes similar to those caused by defects in mcm s U synthesis. Mutants in mcm s U can be suppressed by overexpression of tRNA , but we show t A phenotypes could not be suppressed by expressing any individual ANN decoding tRNA, and t A and mcm s U are not determinants for each other's formation. Our results suggest that t A deficiency, like mcm s U deficiency, leads to protein folding defects, and show that the absence of t A led to stress sensitivities (heat, ethanol, salt) and sensitivity to TOR pathway inhibitors. Additionally, L-homoserine suppressed the slow growth phenotype seen in t A-deficient strains, and proteins aggregates and Advanced Glycation End-products (AGEs) were increased in the mutants. The global consequences on translation caused by t A absence were examined by ribosome profiling. Interestingly, the absence of t A did not lead to global translation defects, but did increase translation initiation at upstream non-AUG codons and increased frame-shifting in specific genes. Analysis of codon occupancy rates suggests that one of the major roles of t A is to homogenize the process of elongation by slowing the elongation rate at codons decoded by high abundance tRNAs and I :C pairs while increasing the elongation rate of rare tRNAs and G :U pairs. This work reveals that the consequences of t A absence are complex and multilayered and has set the stage to elucidate the molecular basis of the observed phenotypes.