The alternative sigma factor katF (rpoS) regulates Salmonella virulence.

Fang, Ferric C.; Libby, Stephen J.; Buchmeier, Nancy A.; Loewen, P.C.; Switala, Jacek; Harwood, Julia; Guiney, Donald G.

doi:10.1073/pnas.89.24.11978

Cited by 474 publications

(470 citation statements)

References 34 publications

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“…Interestingly, H-NS also appears to be required for the normal proteolytic turnover of σ s [43]. Circumvention of H-NS silencing provides an explanation for σ s involvement in the regulation of horizontallyacquired virulence genes [44,45], and complex interactions between σ s and H-NS are responsible for their co-involvement in the expression of certain osmoregulated genes [41,46,47].…”

Section: Counter-silencing Of H-ns and Its Functional Consequencesmentioning

confidence: 99%

New insights into transcriptional regulation by H-NS

Fang

Rimsky

2008

Current Opinion in Microbiology

182

172

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H-NS, a nucleoid-associated DNA-binding protein of enteric bacteria, was discovered thirty-five years ago and subsequently found to exert widespread and highly pleiotropic effects on gene regulation. H-NS binds to high-affinity sites and spreads along adjacent AT-rich DNA to silence transcription. Preferential binding to sequences with higher AT-content than the resident genome allows H-NS to repress the expression of foreign DNA in a process known as "xenogeneic silencing." Counter-silencing by a variety of mechanisms facilitates the evolutionary acquisition of horizontally transferred genes and their integration into pre-existing regulatory networks. This review will highlight recent insights into the mechanism and biological importance of H-NS-DNA interactions. H-NS--A Nucleoid ProteinH-NS is an abundant DNA-binding protein implicated in the organization of the bacterial chromosome [1]. H-NS and other nucleoid-associated proteins can affect DNA topology at specific loci, thereby modulating gene transcription. Binding by these proteins is proposed to selectively direct supercoiling effects to promoters [2•]. Mutation of hns alters the responsiveness of transcription to changes in DNA superhelicity. Regulatory effects of supercoiling are linked to metabolic and environmental conditions. Thus, H-NS has been viewed as a nucleoid structuring protein with global effects on gene expression [3].H-NS exists primarily as a dimer at low concentrations but can multimerize into higher order complexes [4,5] that form bridges between adjacent DNA helices [6]. Optical tweezers have been used to demonstrate that H-NS dimers or multimers can simultaneously interact with separate DNA binding sites [7••]. H-NS-coated DNA is not self-interactive, suggesting that dimerization or oligomerization must precede DNA binding for bridging to occur. Force measurements suggest that transcription barriers created by H-NS binding are weak (∼7 pN) and readily overcome, so that H-NS oligomers pose only a relative barrier to translocating RNA polymerase. DNA bridging is a conserved feature of H-NS homologs found in most gram-negative bacteria [8] that appears to constrain large DNA loops [9••] and helps to account for the effects of H-NS on transcription. However, it must be noted that the relationship between bridging as a general effect and the silencing of specific promoters is not yet clear.H-NS is more appropriately viewed as a determinant of chromosomal architecture rather than as a general structural component. The analysis of nucleoids treated with urea suggests that *Corresponding Author : Tel 206-275-0966, Fax 206-616-1575, e-mail : fcfang@u.washington.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production proce...

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Section: Counter-silencing Of H-ns and Its Functional Consequencesmentioning

confidence: 99%

New insights into transcriptional regulation by H-NS

Fang

Rimsky

2008

Current Opinion in Microbiology

182

172

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“…Starvation for certain nutrients renders S. Typhimurium more resilient than nutrient-replete cells to a variety of stresses (the starvation stress response) and this is also mediated by both s E and s S (Spector & Cubitt, 1992;Kenyon et al, 2002). Both sigma factors also participate in the pathogenesis of S. Typhimurium infection (Fang et al, 1992;Nickerson & Curtiss, 1997;Humphreys et al, 1999;Testerman et al, 2002;Rowley et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Role of the alternative sigma factors σ E and σ S in survival of Salmonella enterica serovar Typhimurium during starvation, refrigeration and osmotic shock

et al. 2007

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The ability of Salmonella enterica serovar Typhimurium to survive environmental stress requires specific, coordinated, responses, which induce resistance to the stress condition. This study investigated the relative contribution of s E and s S , the sigma factors regulating extracytoplasmic and general stress response functions, respectively, to survival at low temperature and also in media of differing osmotic strength, conditions relevant to food preservation. To determine if low-temperature storage is a signal for s E -and s S -mediated survival, the ability of S. Typhimurium rpoE, rpoS and rpoE/rpoS mutants to survive in a saline starvation-survival model at a refrigeration temperature (4.5 6C) was examined. Under these conditions, the rpoE mutant was significantly (P<0.05) compromised compared to the parent and to an rpoS mutant. The double mutant in rpoE and rpoS displayed a cumulative defect in survival. In hyperosmotic environments (low a w ) containing 6 % NaCl and at refrigeration temperature, both sigma factors were important for maximum survival but s S played the dominant role. Analysis of the metabolic activity of starved populations at 4.5 and 37 6C revealed significantly (P<0.001) elevated electron-transport system activity in mutants in rpoE and rpoS, indicating a role for s E -and s S -regulated genes in maintaining energy homeostasis. Together these data demonstrate that s E and s S are important for survival of S. Typhimurium in conditions encountered during food processing and that the relative contribution of s E and s S is critically dependent on the precise nature of the stress.

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“…Also known as 38 or s , RpoS regulates expression of Ϸ10% of Escherichia coli genes (3), including katE and xthA, which encode hydroperoxidase II catalase and exonuclease III, respectively (4,5). In Salmonella enterica serovar Typhimurium, RpoS plays a major role in virulence by controlling expression of the spv plasmid genes (6,7), which govern Salmonella's growth rate in deep organs and are required for systemic infection in mice (8)(9)(10).…”

mentioning

confidence: 99%

“…Inactivation of either the phoP or rpoS genes results in Salmonella strains that are highly attenuated for virulence in mice (6,(25)(26)(27)34). The PhoP and RpoS regulons are both activated inside macrophages (35)(36)(37) and by sublethal concentrations of the cationic antimicrobial peptide polymyxin (38).…”

mentioning

confidence: 99%

The PhoP/PhoQ two-component system stabilizes the alternative sigma factor RpoS in Salmonella enterica

Latifi²,

Bougdour³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

109

121

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The sigma factor RpoS regulates the expression of many stress response genes and is required for virulence in several bacterial species. We now report that RpoS accumulates when Salmonella enterica serovar Typhimurium is growing logarithmically in media with low Mg 2؉ concentrations. This process requires the twocomponent regulatory system PhoP͞PhoQ, which is specifically activated in low Mg 2؉ . We show that PhoP controls RpoS protein turnover by serving as a transcriptional activator of the iraP (yaiB) gene, which encodes a product that enhances RpoS stability by interacting with RssB, the protein that normally delivers RpoS to the ClpXP protease for degradation. Mutation of the phoP gene rendered Salmonella as sensitive to hydrogen peroxide as an rpoS mutant after growth in low Mg 2؉ . In Escherichia coli, low Mg 2؉ leads to only modest RpoS stabilization, and iraP is not regulated by PhoP͞PhoQ. These findings add the sigma factor RpoS to the regulatory proteins and two-component systems that are elevated in a PhoP͞PhoQ-dependent fashion when Salmonella face low Mg 2؉ environments. Our data also exemplify the critical differences in regulatory circuits that exist between the closely related enteric bacteria Salmonella and E. coli.IraP ͉ magnesium ͉ Escherichia coli

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The alternative sigma factor katF (rpoS) regulates Salmonella virulence.

Cited by 474 publications

References 34 publications

New insights into transcriptional regulation by H-NS

New insights into transcriptional regulation by H-NS

Role of the alternative sigma factors σ E and σ S in survival of Salmonella enterica serovar Typhimurium during starvation, refrigeration and osmotic shock

The PhoP/PhoQ two-component system stabilizes the alternative sigma factor RpoS in Salmonella enterica

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