Involvement of E. coli 6S RNA in Oxidative Stress Response

Abstract

6S RNA, a small non-coding RNA present in almost all bacteria, inhibits transcription via direct binding to RNA polymerase holoenzymes. The mechanism of 6S RNA action was investigated to a large extent in <i>E. coli</i>, however, lack of 6S RNA (Δ<i>ssrS</i>) was demonstrated to be unfavorable but not essential for cell survival under various growth conditions. In the present study, we revealed, for the first time, a lethal phenotype of the Δ<i>ssrS</i> strain in the presence of high concentrations of H₂O₂. This phenotype was rescued by complementation of the <i>ssrS</i> gene on a plasmid. We performed comparative qRT-PCR analyses on an enlarged set of mRNAs of genes associated with the oxidative stress response, allowing us to identify four genes known to be involved in this pathway (<i>soxS</i>, <i>ahpC</i>, <i>sodA</i> and <i>tpx</i>) that had decreased mRNA levels in the Δ<i>ssrS</i> strain. Finally, we performed comparative proteomic analyses of the wild-type and Δ<i>ssrS</i> strains, confirming that Δ<i>ssrS</i> bacteria have reduced levels of the proteins AhpC and Tpx involved in H₂O₂ reduction. Our findings substantiate the crucial role of the riboregulator 6S RNA for bacterial coping with extreme stresses.