title: Evolution from possible primitive tRNA-viroids to early poly-tRNA-derived mRNAs: a new approach from the poly-tRNA theory.
abstract: Poly-tRNA theory have revealed that the tRNA gene-clusters in the Bacillus subtilis trrnD- and rrnB-operons are relics of early peptide-synthesizing RNA apparatus. The trrnD-type and rrnB-type poly-tRNA models were re-analyzed by using recent databases. The results elucidated that the 16 amino acid (aa)-trrnD- and the 21 aa-rrnB-peptides (whose aa sequences are in the order of aa specificities of tRNAs in the respective tRNA cluster) are really relics of earliest peptides encoded by most primitive mRNAs, trrnD-mRNA and rrnB-mRNA, which are homologous to tRNA(Gly) and tRNA(His), respectively. Genes encoding various protein superfamilies (including pgtB protein, glycyl-tRNA synthetase alpha, C-type lectin, F1-ATP-synthase gamma, etc) were concluded to have derived from tRNA(Gly)-tRNA(Cys)-tRNA(Leu) region (including trrnD-mRNA region) in the trrnD-poly-tRNA. Genes for another group of protein superfamilies (including adenylate kinase, glyceraldehyde-3-phosphate dehydrogenase, helix-turn-helix DNA-binding domains, etc.) were found to have derived rrnB-mRNA, which is most plausibly homologous to a region containing the tRNA(His) of the rrnB-poly-tRNA. Thus Proto-tRNA((Gly)) reconstructed from tRNA(Gly) and other tRNAs strongly suggested that proto-tRNA was most plausibly a viroid-like possibly self-cleavable replicable ribozyme possessing a possible hammerhead-like structure.
authors.affiliation: Department of Biology, Faculty of Science, Niigata University, Ikarashi-2, Niigata 950-2181, Japan. ohnishi@sc.niigata-u.ac.jp.
authors.forename: Koji
authors.initials: K
authors.lastname: Ohnishi
authors.forename: Madoka
authors.initials: M
authors.lastname: Ohshima
authors.forename: Naotaka
authors.initials: N
authors.lastname: Furuichi
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D019295:Computational Biology / Q000379:methods* / Q000639:trends*; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D005810:Multigene Family; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics*; D012343:RNA, Transfer / Q000737:chemistry / Q000235:genetics*; D014772:Viroids / Q000737:chemistry / Q000235:genetics*
chemical_list: D012333:RNA, Messenger; D012343:RNA, Transfer