Activity of sRNAs in the general stress response. (A) Together with Hfq, the sRNAs DsrA, ArcZ and RprA activate translation of the rpoS transcript by alleviating a self-inhibitory structure within the 5’ UTR of the mRNA. The sRNA OxyS functions as an indirect, negative regulator of rpoS expression. The major alternative sigma factor RpoS governs the general stress response, and directly controls more than 400 genes in E. coli and related enterobacteria, including at least four sRNAs (SdsR, SdsN, GadY and SraL). (B) Transcription factors with restricted functions as activators or repressors, respectively, utilize sRNAs to facilitate opposite regulation.