Competition between SsrA tagging and translational termination at weak stop codons in Escherichia coli.
SsrA is a tmRNA involved in tagging polypeptides on stalled ribosomes. The resulting fusion proteins are then degraded. We purified endogenous SsrA-tagged proteins by means of a genetically engineered SsrA and identified some of them. Analysis of the proteins suggested that they are tagged at their C-terminal extremities. One of them, ribokinase, is expressed from a messenger with a poorly efficient stop codon, leading to translational recoding events. A change in the ribokinase coding sequence from a weak to a strong translational stop sequence (UGAc to UAAu) annihilated SsrA tagging. Translational termination by UGA recruits the translational release factor (RF) 2. We observed that SsrA tagging of ribokinase was inversely correlated with RF2 activity, revealing a dynamic competition between translational termination and SsrA tagging.
Laboratoire des Réseaux de Régulations, Institut de Génétique et Microbiologie, Université Paris-Sud, CNRS/UMR 8621, Orsay, France. Justine.Collier@igmors.u-psud.fr
Justine
J
Collier
Emmanuelle
E
Binet
Philippe
P
Bouloc
D018388:Codon, Terminator; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D014176:Protein Biosynthesis; D012323:RNA Processing, Post-Transcriptional; D012329:RNA, Bacterial / Q000235:genetics* / Q000502:physiology; D012333:RNA, Messenger; D012045:Regulatory Sequences, Nucleic Acid; D012270:Ribosomes / Q000378:metabolism
D018388:Codon, Terminator; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; C096222:tmRNA; D017853:Phosphotransferases (Alcohol Group Acceptor); C022534:ribokinase