PMID:21219458

Citation	Dong, T, Yu, R and Schellhorn, H (2011) Antagonistic regulation of motility and transcriptome expression by RpoN and RpoS in Escherichia coli. Mol. Microbiol. 79:375-86
Abstract	Bacteria generally possess multiple σ factors that, based on structural and functional similarity, divide into two families: σ(70) and σ(N) . Many studies have revealed σ factor competition within the σ(70) family, while the competition between σ(N) and σ(70) families has yet to be fully explored. Here we report a global antagonistic effect on gene expression between two alternative σ factors, σ(N) (RpoN) and a σ(70) family protein σ(S) (RpoS). Mutations in rpoS and rpoN were found to inversely affect a number of cellular traits, such as the expression of flagellar genes, σ(N) -controlled growth on poor nitrogen sources, and σ(S) -directed expression of acid phosphatase AppA. Transcriptome analysis reveals that about 60% of genes in the RpoN regulon are under reciprocal RpoS control. Furthermore, loss of RpoN led to increased levels of RpoS, while RpoN levels were unaffected by the rpoS mutation. Expression of the flagellar σ(F) factor (FliA), another σ(70) family protein, is controlled positively by RpoN but negatively by RpoS. This positive control by RpoN is likely mediated through the flagellar regulator FlhDC, whose expression is RpoN-dependent. These findings unveil a complex regulatory interaction among σ(N) , σ(S) and σ(F) , which modulates motility, nitrogen utilization, stress response and many other cellular functions.
Links	PubMed Online version:10.1111/j.1365-2958.2010.07449.x
Keywords	Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Escherichia coli/genetics; Escherichia coli/physiology; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Gene Deletion; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Locomotion; Nitrogen/metabolism; RNA Polymerase Sigma 54/genetics; RNA Polymerase Sigma 54/metabolism; Regulon; Sigma Factor/biosynthesis; Sigma Factor/genetics; Sigma Factor/metabolism; Stress, Physiological
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:RP54	Contributes to	GO:0006355 : regulation of transcription, DNA-dependent	ECO:0000270:		P		Fig. 4: The expression of motility genes fliA, flhC and flhD genes are reduced in rpoN mutants compared to wild type E. coli.	complete CACAO 4278

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