Poster abstracts
Poster number 126 submitted by Amelia Cochran
Pseudouridine synthase 4 exhibits a broad substrate scope in vitro
Amelia Cochran (Chemistry, University of Michigan), Jacqueline Anthenien (Chemistry, University of Michigan), David Muzyka (Chemistry, University of Michigan), Fiona Tillyer (Chemistry, University of Michigan), Markos Koutmos (Chemistry, University of Michigan), Kristin Koutmou (Chemistry, University of Michigan)
Abstract:
Pseudouridine synthase (Pus) enzymes catalyze the isomerization of uridine to pseudouridine, a common modification that impacts RNA stability and structure. Though these enzymes were originally characterized as modifiers of non-coding RNAs, over the last decade it has become apparent that some Pus enzymes also target mRNA. Because pseudouridine has been shown to impact mRNA processing, translation, and stability, these mRNA-modifying Pus enzymes have the potential to contribute to regulation of gene expression. Nonetheless, how and why specific mRNA targets are modified remains an open question. Pus4, which modifies U55 in the T-loop of most tRNAs, is one of the major mRNA-modifying enzymes in eukaryotic cells. Contrary to the initial hypothesis that Pus4 selects its mRNA targets based on their sequence and structural similarity to its tRNA targets, we show that Pus4 can modify a structurally diverse set of RNAs in vitro. Similarly, we demonstrate that TruB, the bacterial homolog of Pus4, also modifies some of these structurally diverse RNAs in vitro. These findings highlight a conserved lack of specificity in vitro and point to the potential for a broad substrate scope in vivo governed by factors such as protein localization and substrate availability in addition to protein-RNA recognition.
Keywords: pseudouridine, RNA modifications, RNA binding proteins