title: Mitochondrial tRNA 5'-editing in Dictyostelium discoideum and Polysphondylium pallidum.
abstract: Mitochondrial tRNA (mt-tRNA) 5'-editing was first described more than 20 years ago; however, the first candidates for 5'-editing enzymes were only recently identified in a eukaryotic microbe (protist), the slime mold Dictyostelium discoideum. In this organism, eight of 18 mt-tRNAs are predicted to be edited based on the presence of genomically encoded mismatched nucleotides in their aminoacyl-acceptor stem sequences. Here, we demonstrate that mt-tRNA 5'-editing occurs at all predicted sites in D. discoideum as evidenced by changes in the sequences of isolated mt-tRNAs compared with the expected sequences encoded by the mitochondrial genome. We also identify two previously unpredicted editing events in which G-U base pairs are edited in the absence of any other genomically encoded mismatches. A comparison of 5'-editing in D. discoideum with 5'-editing in another slime mold, Polysphondylium pallidum, suggests organism-specific idiosyncrasies in the treatment of U-G/G-U pairs. In vitro activities of putative D. discoideum editing enzymes are consistent with the observed editing reactions and suggest an overall lack of tRNA substrate specificity exhibited by the repair component of the editing enzyme. Although the presence of terminal mismatches in mt-tRNA sequences is highly predictive of the occurrence of mt-tRNA 5'-editing, the variability in treatment of U-G/G-U base pairs observed here indicates that direct experimental evidence of 5'-editing must be obtained to understand the complete spectrum of mt-tRNA editing events in any species.
authors.affiliation: From the Department of Chemistry and Biochemistry, Center for RNA Biology and.
authors.forename: Maria G
authors.initials: MG
authors.lastname: Abad
authors.affiliation: From the Department of Chemistry and Biochemistry, Center for RNA Biology and Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio 43210 and.
authors.forename: Yicheng
authors.initials: Y
authors.lastname: Long
authors.affiliation: From the Department of Chemistry and Biochemistry, Center for RNA Biology and.
authors.forename: R Dimitri
authors.initials: RD
authors.lastname: Kinchen
authors.affiliation: Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Elinor T
authors.initials: ET
authors.lastname: Schindel
authors.affiliation: Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Gray
authors.affiliation: From the Department of Chemistry and Biochemistry, Center for RNA Biology and Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio 43210 and jackman.14@osu.edu.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Jackman
mesh_terms: D020137:Base Pair Mismatch; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004023:Dictyostelium / Q000201:enzymology / Q000235:genetics*; D008928:Mitochondria / Q000235:genetics; D009235:Myxomycetes / Q000235:genetics; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry / Q000235:genetics*; D017393:RNA Editing / Q000235:genetics*; D000077278:RNA, Mitochondrial; D012343:RNA, Transfer / Q000737:chemistry / Q000235:genetics*
chemical_list: D000077278:RNA, Mitochondrial; D012313:RNA; D012343:RNA, Transfer; D012321:DNA-Directed RNA Polymerases
keywords: 3′–5′ Polymerase; Dictyostelium; Enzyme; Mitochondria; RNA Editing; Transfer RNA (tRNA); tRNA Repair
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