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. Author manuscript; available in PMC: 2021 Nov 23.
Published in final edited form as: Annu Rev Genet. 2020 Sep 1;54:237–264. doi: 10.1146/annurev-genet-112618-043822

Figure 1. uORF-mediated control of bacterial gene expression.

Figure 1.

Transcriptional Off: Rho-dependent termination of transcription in the mRNA 5’-leader occurs when Rho has access to its binding site in the RNA (rut site) as occurs when there is no uORF-mediated ribosome stalling. RNA polymerase pauses at a GC-rich stem structure; if Rho binds to the RNA and by moving 5’ to 3’ on the mRNA catches up to the paused RNA polymerase, transcription will terminate in the 5’-leader. On: Ribosome stalling on the uORF blocks access of Rho to the rut site. RNA polymerase is not impacted by Rho and, therefore, can resume transcription of the downstream protein-coding regions after pausing. Translational Off: Elements (SD, Shine-Dalgarno region) important for downstream translation initiation are masked in RNA secondary structure as occurs when there is no uORF-mediated ribosome stalling. On: Ribosome stalling on the uORF changes RNA secondary structure to unmask the SD and enable downstream translation initiation.