Expansion of noncanonical V-Arm-containing tRNAs in eukaryotes

Kiyofumi Hamashima, Masaru Tomita, Akio Kanai

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


Transfer RNA (tRNA) is essential for the translation of genetic information into proteins, and understanding its molecular evolution is important if we are to understand the genetic code. In general, long variable-arm (V-arm) structures form in tRNALeu, tRNASer, and bacterial and organellar tRNATyr. However, as we have previously reported, noncanonical V-arms occur in nematode tRNAGly and tRNAIle, and potentially affect translational fidelity. Here, we comprehensively analyzed 69 eukaryotic genome sequences and examined the evolutionary divergence of the V-arm-containing tRNAs. In total, 253 V-arm-containing tRNAs, with neither leucine nor serine anticodons, were identified in organisms ranging from nematodes to fungi, plants, and vertebrates. We defined them as "noncanonical V-arm-containing tRNAs" (nov-tRNAs). Moreover, 2,415 nov-tRNA-like sequences lacking some of the conserved features of tRNAs were also identified, largely in vertebrate genomes. These nov-tRNA/nov-tRNA-like sequences can be categorized into three types, based on differences in their possible evolutionary origins. The type A nov-tRNAs in nematodes probably evolved not only from tRNALeu but also from tRNASer and other isotypes on several independent occasions. The type B nov-tRNAs are dispersed abundantly throughout vertebrate genomes, and seem to have originated from retrotransposable elements. The type C nov-tRNAs may have been acquired from plant chloroplasts or from bacteria through horizontal transfer. Our findings provide unexpected insight into the evolution of the tRNA molecule, which was diverse and occurred independently in nematodes, vertebrates, and plants.

Original languageEnglish
Pages (from-to)530-540
Number of pages11
JournalMolecular Biology and Evolution
Issue number2
Publication statusPublished - 2016 Feb 1


  • chloroplast
  • molecular evolution
  • phylogenetics
  • retrotransposable element
  • transfer RNA
  • variable arm

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Molecular Biology
  • Genetics


Dive into the research topics of 'Expansion of noncanonical V-Arm-containing tRNAs in eukaryotes'. Together they form a unique fingerprint.

Cite this