Temperature- and H-NS-Dependent Regulation of a Plasmid-Encoded Virulence Operon Expressing
            <i>Escherichia coli</i>
            Hemolysin

Madrid, Cristina; Nieto, J. M.; Paytubi, Sònia; Falconi, Maurizio; Gualerzi, Claudio O.; Juárez, Antonio

doi:10.1128/jb.184.18.5058-5066.2002

Cited by 95 publications

(129 citation statements)

References 44 publications

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“…Negative modulation of hilA is also accomplished by global modulators such as Hha (Fahlen et al, 2001) and H-NS (Olekhnovich & Kadner, 2006;Schechter et al, 2003). Both belong to the superfamily of the nucleoid-associated proteins (Dorman, 2004;Madrid et al, 2007) and have been shown to interact to modulate gene expression (Ellison & Miller, 2006;Madrid et al, 2002;Nieto et al, 1991Nieto et al, , 2002. The nucleoid-associated protein H-NS is a well-characterized example of a modulator that influences gene expression in response to environmental stimuli such as osmolarity, pH and temperature (Hulton et al, 1990;Hommais et al, 2001;Ono et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Integration host factor alleviates H-NS silencing of the Salmonella enterica serovar Typhimurium master regulator of SPI1, hilA

et al. 2011

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Coordination of the expression of Salmonella enterica invasion genes on Salmonella pathogenicity island 1 (SPI1) depends on a complex circuit involving several regulators that converge on expression of the hilA gene, which encodes a transcriptional activator (HilA) that modulates expression of the SPI1 virulence genes. Two of the global regulators that influence hilA expression are the nucleoid-associated proteins Hha and H-NS. They interact and form a complex that modulates gene expression. A chromosomal transcriptional fusion was constructed to assess the effects of these modulators on hilA transcription under several environmental conditions as well as at different stages of growth. The results obtained showed that these proteins play a role in silencing hilA expression at both low temperature and low osmolarity, irrespective of the growth phase. H-NS accounts for the main repressor activity. At high temperature and osmolarity, H-NS-mediated silencing completely ceases when cells enter the stationary phase, and hilA expression is induced. Mutants lacking IHF did not induce hilA in cells entering the stationary phase, and this lack of induction was dependent on the presence of H-NS. Band-shift assays and in vitro transcription data showed that for hilA induction under certain growth conditions, IHF is required to alleviate H-NS-mediated silencing.

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Section: Introductionmentioning

confidence: 99%

Integration host factor alleviates H-NS silencing of the Salmonella enterica serovar Typhimurium master regulator of SPI1, hilA

et al. 2011

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“…These low mobility complexes seem not to be very efficient in repressing hly expression. Specific repression seems to be related to the formation of DNA loops in which H-NS oligomers bridge two sites separated by a region of intrinsic curvature [22]. Stiff rods of DNA covered by H-NS oligomers could be less mobile than DNA loops due to the different shape and also to the smaller number of H-NS molecules per DNA.…”

Section: Discussionmentioning

confidence: 99%

“…The 2.8 kbp DNA fragment used, corresponding to the regulatory region of the hly operon of E. coli, was obtained by PCR amplification from plasmid pHly152 [22].…”

Section: Band Shift Assaysmentioning

confidence: 99%

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N9L and L9N mutations toggle Hha binding and hemolysin regulation by Escherichia coli and Vibrio cholerae H‐NS

et al. 2009

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a b s t r a c tProteins of the Hha/YmoA family co-regulate with H-NS the expression of virulence factors in Enterobacteriaceae. Vibrio cholerae lacks Hha-like proteins and its H-NS (vcH-NS) is unable to bind Hha, in spite of the conservation of a key residue for Hha binding by Escherichia coli H-NS (ecH-NS). Exchange of the residues in position 9 between vcH-NS and ecH-NS strongly reduces Hha binding by ecH-NS and introduces it in vcH-NS. These mutations strongly affect the repression of the hemolysin operon in E. coli and the electrophoretic mobility of complexes formed with a DNA fragment containing its regulatory region.

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“…Thus, these Western blot data taken together with the hemolytic phenotype of 34.7 noted on SRBC agar and in tube assays indicate that hemolysin production is deregulated in 34.7. Similarly, H-NS in complex with Hha, a protein that belongs to a relatively new family of modulators, controls the expression of the thermoregulated a-hemolysin operon encoded by uropathogenic Escherichia coli [25].…”

Section: Phenotypic Analysis and Complementation Of Mutant 347 With mentioning

confidence: 99%

Mutations in hns reduce the adherence of Shiga toxin-producing E. coli 091:H21 strain B2F1 to human colonic epithelial cells and increase the production of hemolysin

Scott

Melton‐Celsa

O'Brien

2003

Microbial Pathogenesis

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Shiga toxin-producing Escherichia coli (STEC) 091:H21 strain B2F1, an isolate from a patient with the hemolytic uremic syndrome (HUS), produces elastase-activatable Shiga toxin (Stx) type 2d and adheres well to human colonic epithelial T84 cells. This adherence phenotype occurs even though B2F1 does not contain the locus of enterocyte effacement (LEE) that encodes the primary adhesin for E. coli O157:H7. To attempt to identify genes involved in binding of B2F1 to T84 cells a bank of mini-Tn5phoACm r transposon mutants of this strain was generated. Several of these mutants exhibited a reduced adherence phenotype, but none of the insertions in these mutants were within putative adhesin genes. Rather, insertional mutations within hns resulted in the loss of adherence. Moreover, the hns mutant also displayed an increase in the production of hemolysin and alkaline phosphatase and a loss of motility with no change in Stx2d-activatable expression levels. When B2F1 was cured of the large plasmid that encodes the hemolysin, the resulting strain adhered well to T84 cells. However, an hns mutant of the plasmid-cured B2F1 strain exhibited a reduction in adherence to T84 cells. Taken together, these results indicate that H-NS regulates the expression of several genes and some potential virulence factors in the intimin-negative B2F1 STEC strain and that the large plasmid is not required for T84 cell colonization. Published by Elsevier Science Ltd.

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Temperature- and H-NS-Dependent Regulation of a Plasmid-Encoded Virulence Operon Expressing Escherichia coli Hemolysin

Cited by 95 publications

References 44 publications

Integration host factor alleviates H-NS silencing of the Salmonella enterica serovar Typhimurium master regulator of SPI1, hilA

Integration host factor alleviates H-NS silencing of the Salmonella enterica serovar Typhimurium master regulator of SPI1, hilA

N9L and L9N mutations toggle Hha binding and hemolysin regulation by Escherichia coli and Vibrio cholerae H‐NS

Mutations in hns reduce the adherence of Shiga toxin-producing E. coli 091:H21 strain B2F1 to human colonic epithelial cells and increase the production of hemolysin

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