Post-Transcriptional Regulation of RseA by Small RNAs RyhB and FnrS in Escherichia coli

Abstract

RseA is the critical central regulator of the σE-dependent stress response in E. coli and other related bacteria. The synthesis of RseA is controlled at the transcriptional level by several promoters and transcriptional regulators, including σE itself at two σE-dependent promoters: rpoEP and rseAP3. The presence of these two independent polycistrons encoding rseA is potentially redundant. We hypothesized that post-transcriptional control of the rseAP3 transcript was necessary to overcome this redundancy. However, to date, nothing is known about the post-transcriptional control of the rseAP3 transcript. We executed a targeted genetic screen to identify small RNA regulators of the rseAP3 transcript and identified RyhB and FnrS as small RNA activators of the RseA P3 transcript. Through genetic analysis, we confirmed that a direct interaction occurs between RyhB and RseA. We also identified sequences within the 5′ untranslated region (UTR) of RseA that were inhibitory for RseA expression. Point mutations predicted to prevent an interaction between RyhB and RseA resulted in increased RseA expression. Taken together, this suggests that the 5’ UTR of the RseAP3 transcript prevents optimal expression of RseA, preventing redundancy due to RseA expression from the σE-dependent rpoEP, and this is overcome by the stimulatory activity of RyhB and FnrS.

Post-transcriptional regulation of the MiaA prenyl transferase by CsrA and the small RNA CsrB inE. coli

“…It was used for screening a plasmid-based small RNA library containing 30 Escherichia coli small RNAs that were cloned downstream of an IPTG inducible promoter (Mandin and Gottesman, 2009). The screening was carried out on Mac-Lac-Amp plates supplemented with arabinose to a final concentration of 0.002% to induce basal transcription from the P BAD promoter without producing a strong Lac + phenotype, as previously described (76). This facilitated the identification of sRNA repressors more easily through our genetic screen.…”