title: The human tRNA-modifying protein, TRIT1, forms amyloid fibers in vitro.
abstract: TRIT1 is a highly conserved tRNA isopentenyl transferase that modifies a subset of tRNAs in human cells and is a candidate tumor suppressor in lung cancer in certain ethnic populations. The yeast homologue, Mod5, has similar tRNA-modifying functions in the cytoplasm and is required for the transcriptional silencing activity of RNA polymerase II promoters near tRNA genes in the nucleus, a phenomenon termed tRNA gene mediated (tgm) silencing. Furthermore, Mod5 can fold into amyloid fibers in vitro and in vivo, which confers resistance to certain fungicides in yeast. Since TRIT1 complements both tRNA modifying and tgm-silencing activities in yeast where the Mod5 gene has been deleted, it seemed possible that TRIT1 might also have amyloid-forming capabilities. Here we show that TRIT1, like Mod5, directly binds to tRNAs that are both substrate and non-substrates for modification with similar affinity, and to an unstructured, non-tRNA. Binding appears to involve distinct protein-RNA multimers which decrease in electrophoretic mobility as the protein to RNA ratio increases. Furthermore, we characterize TRIT1 as a novel human amyloid fiber forming protein. We discuss these data in light of TRIT1's functional roles and possible implications for disease.
authors.affiliation: Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, United States.
authors.forename: T J
authors.initials: TJ
authors.lastname: Waller
authors.affiliation: Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, United States.
authors.forename: D F
authors.initials: DF
authors.lastname: Read
authors.affiliation: Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, United States; University of Denver, Aurora, CO 80045, United States. Electronic address: david.engelke@ucdenver.edu.
authors.forename: D R
authors.initials: DR
authors.lastname: Engelke
authors.affiliation: Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, United States; Biology, Ball State University, Muncie, IN 47306, United States. Electronic address: pjsmaldino@bsu.edu.
authors.forename: P J
authors.initials: PJ
authors.lastname: Smaldino
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000682:Amyloid / Q000096:biosynthesis*; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D012343:RNA, Transfer / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D000682:Amyloid; D012343:RNA, Transfer; D019883:Alkyl and Aryl Transferases; C000595656:TRIT1 protein, human
keywords: Amyloid fibers; Isopentenyl transferase; Mod5; Prion; RNA binding; TRIT1; tRNA gene mediated silencing; tRNA modification