Recent insights into the general stress response regulatory network in Escherichia coli

Many bacterial species exhibit a general stress response that can be induced by numerous very different stress conditions and, phenotypically, renders the cells broadly stress resistant. In Escherichia coli, this response is dependent on the sigmaS (RpoS) subunit of RNA polymerase. SigmaS is a close relative of the vegetative sigma factor sigma70 (RpoD) and recognizes very similar promoter sequences. In recent years, significant progress has been made with respect to elucidating (i) the molecular mechanisms that control the cellular sigmaS level, which include translational regulation as well as intricate control of sigmaS proteolysis, and (ii) the molecular function of sigmaS as a transcription initiation factor, where a number of sigmaS-dependent promoters have been studied in great detail, and the mechanisms that generate sigmaS selectivity are now becoming apparent.