Methylated nucleosides in tRNA and tRNA methyltransferases

Abstract

To date, more than 90 modified nucleosides have been found in tRNA and the biosynthetic pathways of the majority of tRNA modifications include a methylation step(s). Recent studies of the biosynthetic pathways have demonstrated that the availability of methyl group donors for the methylation in tRNA is important for correct and efficient protein synthesis. In this review, I focus on the methylated nucleosides and tRNA methyltransferases. The primary functions of tRNA methylations are linked to the different steps of protein synthesis, such as the stabilization of tRNA structure, reinforcement of the codon-anticodon interaction, regulation of wobble base pairing, and prevention of frameshift errors. However, beyond these basic functions, recent studies have demonstrated that tRNA methylations are also involved in the RNA quality control system and regulation of tRNA localization in the cell. In a thermophilic eubacterium, tRNA modifications and the modification enzymes form a network that responses to temperature changes. Furthermore, several modifications are involved in genetic diseases, infections, and the immune response. Moreover, structural, biochemical, and bioinformatics studies of tRNA methyltransferases have been clarifying the details of tRNA methyltransferases and have enabled these enzymes to be classified. In the final section, the evolution of modification enzymes is discussed.

S-Adenosylmethionine Synthetase 3 Is Important for Pollen Tube Growth

“…Moreover, it was reported that radical SAM enzymes function in tRNA modification (Pierrel et al, 2004;Hernández et al, 2007). The methylation of tRNA is important for correct and efficient protein synthesis (Hori, 2014). It was suggested that tRNA is the only RNA methylated in pollen tubes (Steffensen, 1971) Here, we present evidence that MAT3, a SAMS expressed in pollen, plays an important role during pollen germination and pollen tube growth.…”

NSUN 3 and ABH 1 modify the wobble position of mt‐t RNA Met to expand codon recognition in mitochondrial translation

“…The large majority of rRNA modifications are already installed co‐transcriptionally by small nucleolar (sno)RNPs, and only few base modifications require the action of lone‐standing enzymes (Watkins & Bohnsack, 2012; Sharma & Lafontaine, 2015). tRNAs contain the largest variety of nucleoside modifications, and many of them are suggested to affect tRNA biogenesis and nuclear export, tRNA structure, interaction with aminoacyl‐tRNA‐sythetases or codon recognition during translation (Agris et al , 2007; Leisegang et al , 2012; Hori, 2014; Duechler et al , 2016; Ranjan & Rodnina, 2016). Many tRNAs contain base modifications of the nucleoside at position 34 of the tRNA anticodon (the “wobble position”).…”

NSUN6 is a human RNA methyltransferase that catalyzes formation of m5C72 in specific tRNAs

“…The most heavily modified types of RNA are transfer (tRNAs) and ribosomal RNAs (rRNAs). The majority of rRNA modifications are introduced cotranscriptionally by small nucleolar RNA-protein particles (snoRNPs) (Watkins and Bohnsack 2012), while modifications in tRNAs occur post-transcriptionally and are mainly mediated by lonestanding enzymes (Motorin and Helm 2011;Hopper 2013;Hori 2014). tRNA genes are transcribed by polymerase III as precursor molecules (pre-tRNA) that undergo end processing and numerous modification steps to mature.…”