Release factor competition is equivalent at strong and weakly suppressed nonsense codons |
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Authors: | Robin Martin Mark Hearn Patrick Jenny and Jonathan Gallant |
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Institution: | (1) Department of Genetics, University of Washington, 98195 Seattle, WA, USA;(2) Present address: University of Sussex, Biology Building, BN1 9QG Brighton, UK |
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Abstract: | Summary We have compared the competition between strong or weak suppressor tRNAs and translational release factors (RF) at nonsense codons in the lacI gene of Escherichia coli. Using the F'lacIZ fusions developed by Miller and coworkers, UAG, UAA, and UGA codons at positions 189 and 220 were efficiently suppressed by plasmid-borne tRNAtrp suppressors cognate to each nonsense triplet. Introduction of a compatible RF 1 plasmid competed at UAG and UAA but not UGA codons. An RF2 expressing plasmid competed at UAA and UGA but had little effect at UAG. Release factor competition against weak suppressors was measured using combinations of noncognate suppressors and nonsense codons. In each case, release factor plasmids behaved identically towards poorly suppressed codons as they did when the same codons were efficiently suppressed. The implications for these studies on the role of release factors in nonsense suppression context effects are discussed. |
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Keywords: | Nonsense suppressor Release factor Noncognate tRNA |
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