In:
Microbiology and Molecular Biology Reviews, American Society for Microbiology, Vol. 66, No. 3 ( 2002-09), p. 373-395
Abstract:
The σ S (RpoS) subunit of RNA polymerase is the master regulator of the general stress response in Escherichia coli and related bacteria. While rapidly growing cells contain very little σ S , exposure to many different stress conditions results in rapid and strong σ S induction. Consequently, transcription of numerous σ S -dependent genes is activated, many of which encode gene products with stress-protective functions. Multiple signal integration in the control of the cellular σ S level is achieved by rpoS transcriptional and translational control as well as by regulated σ S proteolysis, with various stress conditions differentially affecting these levels of σ S control. Thus, a reduced growth rate results in increased rpoS transcription whereas high osmolarity, low temperature, acidic pH, and some late-log-phase signals stimulate the translation of already present rpoS mRNA. In addition, carbon starvation, high osmolarity, acidic pH, and high temperature result in stabilization of σ S , which, under nonstress conditions, is degraded with a half-life of one to several minutes. Important cis-regulatory determinants as well as trans-acting regulatory factors involved at all levels of σ S regulation have been identified. rpoS translation is controlled by several proteins (Hfq and HU) and small regulatory RNAs that probably affect the secondary structure of rpoS mRNA. For σ S proteolysis, the response regulator RssB is essential. RssB is a specific direct σ S recognition factor, whose affinity for σ S is modulated by phosphorylation of its receiver domain. RssB delivers σ S to the ClpXP protease, where σ S is unfolded and completely degraded. This review summarizes our current knowledge about the molecular functions and interactions of these components and tries to establish a framework for further research on the mode of multiple signal input into this complex regulatory system.
Type of Medium:
Online Resource
ISSN:
1092-2172
,
1098-5557
DOI:
10.1128/MMBR.66.3.373-395.2002
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2002
detail.hit.zdb_id:
2026768-X
SSG:
12
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