title: Biological evidence for the world's smallest tRNAs.
abstract: Due to their function as adapters in translation, tRNA molecules share a common structural organization in all kingdoms and organelles with ribosomal protein biosynthesis. A typical tRNA has a cloverleaf-like secondary structure, consisting of acceptor stem, D-arm, anticodon arm, a variable region, and T-arm, with an average length of 73 nucleotides. In several mitochondrial genomes, however, tRNA genes encode transcripts that show a considerable deviation of this standard, having reduced D- or T-arms or even completely lack one of these elements, resulting in tRNAs as small as 66 nts. An extreme case of such truncations is found in the mitochondria of Enoplea. Here, several tRNA genes are annotated that lack both the D- and the T-arm, suggesting even shorter transcripts with a length of only 42 nts. However, direct evidence for these exceptional tRNAs, which were predicted by purely computational means, has been lacking so far. Here, we demonstrate that several of these miniaturized armless tRNAs consisting only of acceptor- and anticodon-arms are indeed transcribed and correctly processed by non-encoded CCA addition in the mermithid Romanomermis culicivorax. This is the first direct evidence for the existence and functionality of the smallest tRNAs ever identified so far. It opens new possibilities towards exploration/assessment of minimal structural motifs defining a functional tRNA and their evolution.
authors: University of Leipzig, Institute for Biochemistry, Leipzig, Germany.
authors: Sandra
authors: S
authors: Wende
authors: University of California, Riverside, Department of Nematology, Riverside, CA 92521, USA.
authors: Edward G
authors: EG
authors: Platzer
authors: University of Leipzig, Bioinformatics Group, Department of Computer Science and Interdisciplinary Center for Bioinformatics, Leipzig, Germany.
authors: Frank
authors: F
authors: Jühling
authors: Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC, 67084 Strasbourg, France.
authors: Joern
authors: J
authors: Pütz
authors: Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC, 67084 Strasbourg, France.
authors: Catherine
authors: C
authors: Florentz
authors: University of Leipzig, Bioinformatics Group, Department of Computer Science and Interdisciplinary Center for Bioinformatics, Leipzig, Germany; Max Planck Institute for Mathematics in the Sciences, Leipzig, Germany; Fraunhofer Institut für Zelltherapie und Immunologie - IZI, Leipzig, Germany; Department of Theoretical Chemistry, University of Vienna, Vienna, Austria; Center for Non-coding RNA in Technology and Health, University of Copenhagen, Frederiksberg C, Denmark; Santa Fe Institute, Santa Fe, NM, USA.
authors: Peter F
authors: PF
authors: Stadler
authors: University of Leipzig, Institute for Biochemistry, Leipzig, Germany. Electronic address: moerl@uni-leipzig.de.
authors: Mario
authors: M
authors: Mörl
mesh_terms: D000818:Animals; D001483:Base Sequence; D054629:Genome, Mitochondrial; D008632:Mermithoidea / Q000235:genetics* / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D012343:RNA, Transfer / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D012343:RNA, Transfer
keywords: Armless tRNA; CCA addition; Enoplea; Mitochondria; Processing; tRNA structure