Not all pseudouridine synthases are potently inhibited by RNA containing 5-fluorouridine.
RNA containing 5-fluorouridine has been assumed to inhibit strongly or irreversibly the pseudouridine synthases that act on the RNA. RNA transcripts containing 5-fluorouridine in place of uridine have, therefore, been added to reconstituted systems in order to investigate the importance of particular pseudouridine residues in a given RNA by inactivating the pseudouridine synthase responsible for their generation. In sharp contradiction to the assumption of universal inhibition of pseudouridine synthases by RNA containing 5-fluorouridine, the Escherichia coli pseudouridine synthase TruB, which has physiologically critical eukaryotic homologs, is not inhibited by such RNA. Instead, the RNA containing 5-fluorouridine was handled as a substrate by TruB. The E. coli pseudouridine synthase RluA, on the other hand, forms a covalent complex and is inhibited stoichiometrically by RNA containing 5-fluorouridine. We offer a hypothesis for this disparate behavior and urge caution in interpreting results from reconstitution experiments in which RNA containing 5-fluorouridine is assumed to inhibit a pseudouridine synthase, as normal function may result from a failure to inactivate the targeted enzyme rather than from the absence of nonessential pseudouridine residues.
Spedaliere
Christopher J
CJ
Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.
Mueller
Eugene G
EG
D004926:Escherichia coli / Q000201:enzymology; D006836:Hydro-Lyases / Q000037:antagonists & inhibitors*; D019753:Intramolecular Lyases / Q000037:antagonists & inhibitors*; D019751:Intramolecular Transferases; D012313:RNA / Q000378:metabolism*; D014529:Uridine / Q000031:analogs & derivatives* / Q000378:metabolism*
C001943:5-fluorouridine; D012313:RNA; D006836:Hydro-Lyases; C022479:pseudouridylate synthetase; D019751:Intramolecular Transferases; C096995:pseudouridine synthases; D019753:Intramolecular Lyases; D014529:Uridine