title: A dynamic competition between release factor 2 and the tRNA(Sec) decoding UGA at the recoding site of Escherichia coli formate dehydrogenase H.
abstract: Factors affecting competition between termination and elongation in vivo during translation of the fdhF selenocysteine recoding site (UGA) were studied with wild-type and modified fdhF sequences. Altering sequences surrounding the recoding site UGA without affecting RNA secondary structure indicated that the kinetics of stop signal decoding have a significant influence on selenocysteine incorporation efficiency. The UGA in the wild-type fdhF sequence remains 'visible' to the factor and forms a site-directed cross-link when mRNA stem-loop secondary structure is absent, but not when it is present. The timing of the secondary structure unfolding during translation may be a critical feature of competition between release factor 2 and tRNA(Sec) for decoding UGA. Increasing the cellular concentration of either of these decoding molecules for termination or selenocysteine incorporation showed that they were able to compete for UGA by a kinetic competition that is dynamic and dependent on the Escherichia coli growth rate. The tRNA(Sec)-mediated decoding can compete more effectively for the UGA recoding site at lower growth rates, consistent with anaerobic induction of fdhF expression.
authors.affiliation: Department of Biochemistry and Centre for Gene Research, University of Otago, PO Box 56, Dunedin, New Zealand.
authors.forename: J B
authors.initials: JB
authors.lastname: Mansell
authors.forename: D
authors.initials: D
authors.lastname: Guévremont
authors.forename: E S
authors.initials: ES
authors.lastname: Poole
authors.forename: W P
authors.initials: WP
authors.lastname: Tate
mesh_terms: D001483:Base Sequence; D004926:Escherichia coli / Q000201:enzymology*; D005560:Formate Dehydrogenases / Q000235:genetics*; D006864:Hydrogenase / Q000235:genetics*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D009690:Nucleic Acid Conformation; D010454:Peptide Termination Factors / Q000378:metabolism*; D014176:Protein Biosynthesis; D012345:RNA, Transfer, Amino Acid-Specific / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D009097:Multienzyme Complexes; D010454:Peptide Termination Factors; D012345:RNA, Transfer, Amino Acid-Specific; C041460:peptide chain termination release factor 2; C036928:tRNA, selenocysteine-; D006864:Hydrogenase; D005560:Formate Dehydrogenases; C054017:formate hydrogenlyase