The bipartite structure of the tRNA m¹A58 methyltransferase from S. cerevisiae is conserved in humans

Abstract

Among all types of RNA, tRNA is unique given that it possesses the largest assortment and abundance of modified nucleosides. The methylation at N 1 of adenosine 58 is a conserved modification, occurring in bacterial, archaeal, and eukaryotic tRNAs. In the yeast Saccharomyces cerevisiae, the tRNA 1-methyladenosine 58 (m 1 A58) methyltransferase (Mtase) is a two-subunit enzyme encoded by the essential genes TRM6 (GCD10) and TRM61 (GCD14). While the significance of many tRNA modifications is poorly understood, methylation of A58 is known to be critical for maintaining the stability of initiator tRNA Met in yeast. Furthermore, all retroviruses utilize m 1 A58-containing tRNAs to prime reverse transcription, and it has been shown that the presence of m 1 A58 in human tRNA 3 Lys is needed for accurate termination of plus-strand strong-stop DNA synthesis during HIV-1 replication. In this study we have identified the human homologs of the yeast m

Genome-wide analysis of N1-methyl-adenosine modification in human tRNAs

“…To examine the consequence of m 1 A58 hypomodification and further establish our array method as a suitable tool for functional studies, we performed siRNA experiments on either of the human m 1 A58 methyltransferase subunits, TRM6 or TRM61 (Ozanick et al 2005). We chose to carry out this experiment with MDA-MB-231 cells because tRNAs are known to be overexpressed in these cells (Pavon-Eternod et al 2009), and this high amount of tRNA may be more sensitive to variations in this modification enzyme.…”

“…Among the over 30 tRNAs sequenced, only two, rat tRNA Asp and tRNA Glu , have been reported to be unmodified at position 58 (Kuchino et al 1981;Chan et al 1982). The human homolog of the yeast tRNA m 1 A methyltransferase has been identified and it has been shown to have the same two subunit composition as the methyltransferase from yeast (Ozanick et al 2005).…”

Publisher's Note

“…The situation in human is strikingly similar, and the human homologs TRMT6 and TRMT61A show 20% and 30% similarity to the yeast enzymes at the amino acid level, respectively. 17,54 Supporting this conserved role, ALKBH1 was recently reported to demethylate m 1 A58 in human tRNA iMet as well as several other tRNA species. 55 Loss of ALKBH1 increases the cellular tRNA iMet level, corroborating the idea that m 1 A58 methylation is essential for tRNA iMet stability.…”

“…16 However, numerous other modifications have been added to the mRNA repertoire. m 1 A has been described in tRNA and rRNA, 17,18 but we now know that it is also present in mRNA, albeit at levels approximately 10-fold lower than m 6 A. 19,20 In the studies that first described its distribution in mRNA, one identified 7,154 peaks in 4,151 coding genes, 19 while the other identified 887 peaks in 600 genes.…”

Epitranscriptomics for Biomedical Discovery

“…The tRNA T-loop at position 58 commonly contains a m 1 A modiication [50], along with position 9 of metazoan mitochondrial tRNAs [51] and eukaryotic rRNAs [52]. Initiator tRNA C marks stabilize the secondary structure of tRNA, alter aminoacylation and codon recognition [56], and regulate translational idelity [57].…”