An antibiotic-sensing leader peptide regulates translation and premature Rho-dependent transcription termination of thetopAIgene inEscherichia coli

Abstract

AbstractLong 5′ UTRs in bacteria often contain regulatory elements that modulate expression of the downstream gene in response to environmental stimuli. In most examples of such regulation, the mechanism involves switching between alternative 5′ UTR RNA structures that impact transcription, stability, or translation of the mRNA. Here, we show that transcription of theEscherichia coli topAIgene is prematurely terminated by the termination factor Rho under standard laboratory growth conditions, and that this occurs as a result of translational repression. Regulation oftopAItranslation is controlled by a sensory ORF,toiL, located within thetopAI5′ UTR. We show that ribosomes translatingtoiLstall in a sequence-specific manner in the presence of specific ribosome-targeting antibiotics. Ribosome stalling attoiLinduces conformational changes in the RNA structure of thetopAI5′ UTR, unmasking thetopAIribosome-binding site, thereby relieving translational repression and preventing premature transcription termination. Thus,toiLacts as a sensor of translation stress, leading to regulation oftopAIat both the translational and transcriptional levels.