The H-NS protein represses transcription of the eltAB operon, which encodes heat-labile enterotoxin in enterotoxigenic Escherichia coli, by binding to regions downstream of the promoter

Yang, Jiyeon; Tauschek, Marija; Strugnell, Richard A.; Robins-Browne, Roy M.

doi:10.1099/mic.0.27734-0

Cited by 46 publications

(58 citation statements)

References 45 publications

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“…H-NS and StpA repress the expression of genes encoding the type II secretory system required for secretion of E. coli heat-labile enterotoxin (LT) [34] by inhibiting open complex formation. H-NS also represses eltAB encoding the enterotoxin itself [35]. H-NS can act synergistically as co-repressor with LRP, the leucine-responsive regulatory protein, to inhibit expression of the ribosomal RNA promoter [36], although no direct interaction between LRP and H-NS has been reported.…”

Section: Interactions Between H-ns and Other Nucleoid Proteinsmentioning

confidence: 99%

New insights into transcriptional regulation by H-NS

Fang

Rimsky

2008

Current Opinion in Microbiology

186

173

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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: Interactions Between H-ns and Other Nucleoid Proteinsmentioning

confidence: 99%

New insights into transcriptional regulation by H-NS

Fang

Rimsky

2008

Current Opinion in Microbiology

186

173

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“…The global transcriptional regulator H-NS is known to bind to curved and AT-rich DNA sequences upstream of several defined UPEC virulence genes (85), including genes encoding toxins (86)(87)(88)(89) and autotransporter proteins (8,10,90). To investigate the effect of H-NS on vat transcription, the levels of Vat expression were compared by Western blot analysis of supernatant fractions prepared from WT CFT073, CFT073 vat, CFT073 vatX, CFT073 hns, and a CFT073 vatX hns double mutant (Fig.…”

Section: Transcription Of the Vat Gene Is Directly Repressed By H-nsmentioning

confidence: 99%

Molecular Characterization of the Vacuolating Autotransporter Toxin in Uropathogenic Escherichia coli

et al. 2016

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The vacuolating autotransporter toxin (Vat) contributes to uropathogenic Escherichia coli (UPEC) fitness during systemic infection. Here, we characterized Vat and investigated its regulation in UPEC. We assessed the prevalence of vat in a collection of 45 UPEC urosepsis strains and showed that it was present in 31 (68%) of the isolates. The isolates containing the vat gene corresponded to three major E. coli sequence types (ST12, ST73, and ST95), and these strains secreted the Vat protein. Further analysis of the vat genomic locus identified a conserved gene located directly downstream of vat that encodes a putative MarR-like transcriptional regulator; we termed this gene vatX. The vat-vatX genes were present in the UPEC reference strain CFT073, and reverse transcriptase PCR (RT-PCR) revealed that the two genes are cotranscribed. Overexpression of vatX in CFT073 led to a 3-fold increase in vat gene transcription. The vat promoter region contained three putative nucleation sites for the global transcriptional regulator histone-like nucleoid structuring protein (H-NS); thus, the hns gene was mutated in CFT073 (to generate CFT073 hns). Western blot analysis using a Vat-specific antibody revealed a significant increase in Vat expression in CFT073 hns compared to that in wild-type CFT073. Direct H-NS binding to the vat promoter region was demonstrated using purified H-NS in combination with electrophoresis mobility shift assays. Finally, Vat-specific antibodies were detected in plasma samples from urosepsis patients infected by vat-containing UPEC strains, demonstrating that Vat is expressed during infection. Overall, this study has demonstrated that Vat is a highly prevalent and tightly regulated immunogenic serine protease autotransporter protein of Enterobacteriaceae (SPATE) secreted by UPEC during infection. IMPORTANCEUropathogenic Escherichia coli (UPEC) is the major cause of hospital-and community-acquired urinary tract infections. The vacuolating autotransporter toxin (Vat) is a cytotoxin known to contribute to UPEC fitness during murine sepsis infection. In this study, Vat was found to be highly conserved and prevalent among a collection of urosepsis clinical isolates and was expressed at human core body temperature. Regulation of vat was demonstrated to be directly repressed by the global transcriptional regulator H-NS and upregulated by the downstream gene vatX (encoding a new MarR-type transcriptional regulator). Additionally, increased Vat-specific IgG titers were detected in plasma from corresponding urosepsis patients infected with vatpositive isolates. Hence, Vat is a highly conserved and tightly regulated urosepsis-associated virulence factor. U rinary tract infections (UTIs) are one of the most common human infections, affecting 40 to 50% of women and approximately 12% of men globally (1). UTIs are ascending infections and can involve infection of the bladder (cystitis), kidneys (pyelonephritis), or dissemination into the bloodstream (urosepsis). Uropathogenic Escherichia coli (UPEC) strains ...

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“…When interacting with DNA, H-NS initially binds to a curved, AT-rich sequence, followed by oligomerization and subsequent alteration of the DNA structure (11,41). As a repressor, H-NS can prevent the RNAP from binding to the promoter (39,49), trap RNAP at the promoter through DNA bridging (8,47), or block transcription initiation or elongation when bound to the downstream sequences of the promoters (10,25,50). It has been shown that the disruption of the repressive nucleoprotein structures mediated by H-NS requires activation signals or positively acting transcription factors (reviewed in reference 11), even though little is known about the mechanisms involved in this process.…”

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confidence: 99%

Role of Nucleoid-Associated Proteins Hha and H-NS in Expression of Salmonella enterica Activators HilD, HilC, and RtsA Required for Cell Invasion

Olekhnovich

Kadner

2007

J Bacteriol

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The coordinate expression of Salmonella enterica invasion genes on Salmonella pathogenicity island 1 is under the control of the complex circuits of regulation that involve the AraC/XylS family transcriptional activators HilD, HilC, and RtsA and nucleoid-associated proteins. Single-copy transcription fusions were used to assess the effects of nucleoid-associated proteins Hha and H-NS on hilD, hilC, and rtsA expression. The data show that all three genes, hilD, hilC, and rtsA, were repressed by H-NS and/or Hha. The repression of rtsA was the highest among tested genes. The level of rtsA-lac was equally elevated in hns and hha mutants and was further enhanced in the hns hha double mutant under low-osmolarity conditions. Electrophoretic mobility shift experiments showed that H-NS and Hha directly bind to the rtsA promoter. In addition to the negative control that was exerted by H-NS/Hha under low-osmolarity conditions, the homologous virulence activators HilD, HilC, and RtsA (Hil activators) induced rtsA-lac expression in a high-salt medium. A DNase footprinting assay of the rtsA promoter revealed one common DNA-binding site for all three Hil activators centered at position ؊54 relative to the transcriptional start site. In the absence of Hha and H-NS, however, osmoregulation of the rtsA promoter was lost, and Hil activators were not required for rtsA transcription. These results taken together suggest that the HilD, HilC, and RtsA proteins induce the transcription of the rtsA promoter by counteracting H-NS/Hhamediated repression.

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The H-NS protein represses transcription of the eltAB operon, which encodes heat-labile enterotoxin in enterotoxigenic Escherichia coli, by binding to regions downstream of the promoter

Cited by 46 publications

References 45 publications

New insights into transcriptional regulation by H-NS

New insights into transcriptional regulation by H-NS

Molecular Characterization of the Vacuolating Autotransporter Toxin in Uropathogenic Escherichia coli

Role of Nucleoid-Associated Proteins Hha and H-NS in Expression of Salmonella enterica Activators HilD, HilC, and RtsA Required for Cell Invasion

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