title: Doing it in reverse: 3'-to-5' polymerization by the Thg1 superfamily.
abstract: The tRNA(His) guanylyltransferase (Thg1) family of enzymes comprises members from all three domains of life (Eucarya, Bacteria, Archaea). Although the initial activity associated with Thg1 enzymes was a single 3'-to-5' nucleotide addition reaction that specifies tRNA(His) identity in eukaryotes, the discovery of a generalized base pair-dependent 3'-to-5' polymerase reaction greatly expanded the scope of Thg1 family-catalyzed reactions to include tRNA repair and editing activities in bacteria, archaea, and organelles. While the identification of the 3'-to-5' polymerase activity associated with Thg1 enzymes is relatively recent, the roots of this discovery and its likely physiological relevance were described ≈ 30 yr ago. Here we review recent advances toward understanding diverse Thg1 family enzyme functions and mechanisms. We also discuss possible evolutionary origins of Thg1 family-catalyzed 3'-to-5' addition activities and their implications for the currently observed phylogenetic distribution of Thg1-related enzymes in biology.
authors.affiliation: Department of Biochemistry and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA. jackman.14@osu.edu
authors.forename: Jane E
authors.initials: JE
authors.lastname: Jackman
authors.forename: Jonatha M
authors.initials: JM
authors.lastname: Gott
authors.forename: Michael W
authors.initials: MW
authors.lastname: Gray
mesh_terms: D001105:Archaea / Q000201:enzymology / Q000235:genetics; D001419:Bacteria / Q000201:enzymology / Q000235:genetics; D019143:Evolution, Molecular; D009696:Nucleic Acids / Q000096:biosynthesis*; D009711:Nucleotides / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D012313:RNA / Q000378:metabolism; D017393:RNA Editing; D000077278:RNA, Mitochondrial; D012343:RNA, Transfer / Q000378:metabolism; D015003:Yeasts / Q000201:enzymology / Q000235:genetics
chemical_list: D009696:Nucleic Acids; D009711:Nucleotides; D000077278:RNA, Mitochondrial; D012313:RNA; D012343:RNA, Transfer; D009713:Nucleotidyltransferases; C065307:tRNA guanylyltransferase