Trm7/FTSJ1-Mediated tRNA Anticodon-Loop 2′-O-Methylation: From Structural Mechanisms to Translational Dysfunction and Disease

Transfer RNAs (tRNAs) are chemically matured decoding molecules that are central to protein synthesis. Their post-transcriptional modifications, especially those in the anticodon stem-loop (ASL), shape local RNA structure, codon recognition and translational fidelity at the tRNA-mRNA decoding interface. 2′-O-methylation (Nm) is a conserved ribose modification installed at selected ASL positions, particularly positions 32 and 34, by the modular Trm7/FTSJ1 methyltransferase system. Rather than directly changing base-pairing identity, these marks help prepare the decoder for efficient translation and function within an interconnected 32–34–37 modification network, best illustrated by tRNAPhe. Loss of Trm7/FTSJ1-mediated Nm may impair selected codon–tRNA decoding pairs; in yeast, Trm7 deficiency is additionally associated with GAAC activation and phenotypes consistent with reduced functional tRNAPhe availability. In humans, mutations in FTSJ1 are associated with nonsyndromic X-linked intellectual disability (NSXLID), suggesting that disruption of tRNA chemical maturation can affect neuronal translation programs. In this review, we integrate anticodon-loop modifications at positions 32, 34, and 37 into a decoder-centered framework and compare the conserved enzymatic logic of yeast Trm7 and human FTSJ1 with their divergent substrate repertoires. By synthesizing structural, biochemical, genetic, and translational evidence, we distinguish established mechanisms from working models and unresolved questions concerning tRNA modification hierarchies and neuronal vulnerability.