Use of tRNA suppressors to probe regulation of Escherichia coli release factor 2.
It has been suggested that Escherichia coli release factor 2 (RF-2) translation is autoregulated. Mature RF-2 protein can terminate its own nascent synthesis at an intragenic, in-phase UGA codon, or alternatively, a +1 frameshift can occur that leads to completion of the RF-2 polypeptide. Translational termination presumably increases with RF-2 concentration, providing negative regulatory feedback. We now show, in lacZ/RF-2 fusions, that translation of a UAG codon at the position of the UGA competes with frameshifting, which proves one postulate of the translational autoregulatory model. We also identify a nearby sequence that is required for high-frequency frameshifting and suggest a constraint for the codon preceding the shift point. Both these sequences are incorporated into a model for frameshifting. Our measurements allow us to compute the relative rates in vivo of these reactions: release factor action, frameshifting and tRNA selection at an amber codon.
D003062:Codon; D004926:Escherichia coli; D005786:Gene Expression Regulation; D007763:Lac Operon; D009154:Mutation; D010454:Peptide Termination Factors / Q000235:genetics*; D012343:RNA, Transfer / Q000235:genetics*; D013489:Suppression, Genetic
D003062:Codon; D010454:Peptide Termination Factors; C041460:peptide chain termination release factor 2; D012343:RNA, Transfer