4.8 Article

Expansion of Noncanonical V-Arm-Containing tRNAs in Eukaryotes

期刊

MOLECULAR BIOLOGY AND EVOLUTION
卷 33, 期 2, 页码 530-540

出版社

OXFORD UNIV PRESS
DOI: 10.1093/molbev/msv253

关键词

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

资金

  1. Yamagata Prefectural Government
  2. Tsuruoka City, Japan
  3. Japan Society for the Promotion of Science

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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 tRNA(Leu), tRNA(Ser), and bacterial and organellar tRNA(Tyr). However, as we have previously reported, noncanonical V-arms occur in nematode tRNA(Gly) and tRNA(Ile), 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 tRNA(Leu) but also from tRNA(Ser) 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.

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