title: Identification of distinct biological functions for four 3'-5' RNA polymerases.
abstract: The superfamily of 3'-5' polymerases synthesize RNA in the opposite direction to all other DNA/RNA polymerases, and its members include eukaryotic tRNA(His) guanylyltransferase (Thg1), as well as Thg1-like proteins (TLPs) of unknown function that are broadly distributed, with family members in all three domains of life. Dictyostelium discoideum encodes one Thg1 and three TLPs (DdiTLP2, DdiTLP3 and DdiTLP4). Here, we demonstrate that depletion of each of the genes results in a significant growth defect, and that each protein catalyzes a unique biological reaction, taking advantage of specialized biochemical properties. DdiTLP2 catalyzes a mitochondria-specific tRNA(His) maturation reaction, which is distinct from the tRNA(His) maturation reaction typically catalyzed by Thg1 enzymes on cytosolic tRNA. DdiTLP3 catalyzes tRNA repair during mitochondrial tRNA 5'-editing in vivo and in vitro, establishing template-dependent 3'-5' polymerase activity of TLPs as a bona fide biological activity for the first time since its unexpected discovery more than a decade ago. DdiTLP4 is cytosolic and, surprisingly, catalyzes robust 3'-5' polymerase activity on non-tRNA substrates, strongly implying further roles for TLP 3'-5' polymerases in eukaryotes.
authors.affiliation: Department of Chemistry and Biochemistry, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Yicheng
authors.initials: Y
authors.lastname: Long
authors.affiliation: Department of Chemistry and Biochemistry, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Maria G
authors.initials: MG
authors.lastname: Abad
authors.affiliation: Department of Chemistry and Biochemistry, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Erik D
authors.initials: ED
authors.lastname: Olson
authors.affiliation: Department of Chemistry and Biochemistry, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Elisabeth Y
authors.initials: EY
authors.lastname: Carrillo
authors.affiliation: Department of Chemistry and Biochemistry, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA Jackman.14@osu.edu.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Jackman
mesh_terms: D055162:Biocatalysis; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004023:Dictyostelium / Q000201:enzymology* / Q000254:growth & development; D015800:Protozoan Proteins / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D017393:RNA Editing / Q000235:genetics; D034622:RNA Interference; D000077278:RNA, Mitochondrial; D012354:RNA, Transfer, His / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D015800:Protozoan Proteins; D000077278:RNA, Mitochondrial; D012354:RNA, Transfer, His; D012313:RNA; D012321:DNA-Directed RNA Polymerases