Organization of the <i>LEE1</i> operon regulatory region of enterohaemorrhagic <i>Escherichia coli</i> O157:H7 and activation by GrlA

Islam, Md. Shahidul; Bingle, Lewis; Pallen, Mark J.; Busby, Stephen J. W.

doi:10.1111/j.1365-2958.2010.07460.x

Cited by 38 publications

(57 citation statements)

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“…In this manner, expression of nleA will be induced mostly under conditions that allow the expression of Ler and, thus, of the LEE genes, where it overcomes H-NS repression by competitively binding to a region that overlaps the H-NS binding sites at the LEE promoters. Consistent with a recent report (82), GrlA was also required for full activation of nleA, most likely in an indirect manner as GrlA's role in the regulation of LEE genes is due to its function as a positive regulator of ler expression (2,18,37,39,42,50).…”

Section: Discussionsupporting

confidence: 88%

A Distinct Regulatory Sequence Is Essential for the Expression of a Subset of nle Genes in Attaching and Effacing Escherichia coli

et al. 2012

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Enteropathogenic Escherichia coli uses a type III secretion system (T3SS), encoded in the locus of enterocyte effacement (LEE) pathogenicity island, to translocate a wide repertoire of effector proteins into the host cell in order to subvert cell signaling cascades and promote bacterial colonization and survival. Genes encoding type III-secreted effectors are located in the LEE and scattered throughout the chromosome. While LEE gene regulation is better understood, the conditions and factors involved in the expression of effectors encoded outside the LEE are just starting to be elucidated. Here, we identified a highly conserved sequence containing a 13-bp inverted repeat (IR), located upstream of a subset of genes coding for different non-LEE-encoded effectors in A/E pathogens. Site-directed mutagenesis and deletion analysis of the nleH1 and nleB2 regulatory regions revealed that this IR is essential for the transcriptional activation of both genes. Growth conditions that favor the expression of LEE genes also facilitate the activation of nleH1 and nleB2; however, their expression is independent of the LEE-encoded positive regulators Ler and GrlA but is repressed by GrlR and the global regulator H-NS. In contrast, GrlA and Ler are required for nleA expression, while H-NS silences it. Consistent with their role in the regulation of nleA, purified Ler and H-NS bound to the regulatory region of nleA upstream of its promoter. This work shows that at least two modes of regulation control the expression of effector genes in attaching and effacing (A/E) pathogens, suggesting that a subset of effector functions may be coordinately expressed in a particular niche or time during infection. Enteropathogenic Escherichia coli (EPEC) is the leading cause of severe watery diarrhea in children in developing countries. This Gram-negative bacterium belongs to the attaching and effacing (A/E) family of pathogens, which includes enterohemorrhagic E. coli (EHEC) and the murine pathogen Citrobacter rodentium. A/E pathogens colonize the intestinal tract of their host and use a type III secretion system (T3SS) to translocate an assortment of proteins called effectors into the cytosol of the enterocyte which subvert cell signaling pathways in order to promote bacterial colonization and proliferation. The characteristic A/E lesion caused by these pathogens consists of epithelial microvillus depletion and the formation of actin-rich pedestals beneath adhering bacteria (reviewed in references 17, 33, 45, 67, and 93).The genes required for assembly of the T3SS in A/E pathogens are encoded by the locus of enterocyte effacement (LEE) pathogenicity island. Besides the structural T3SS genes, the LEE also encodes regulatory proteins, effectors, chaperones, and proteins involved in the hierarchical regulation of secretion (18,29). Substrate effectors of the T3SS are encoded in the LEE, as well as in prophages and integrative elements scattered throughout the chromosome. LEE-encoded effectors include Tir, EspF, Map, EspH, EspG, and EspZ. These eff...

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Section: Discussionsupporting

confidence: 88%

A Distinct Regulatory Sequence Is Essential for the Expression of a Subset of nle Genes in Attaching and Effacing Escherichia coli

et al. 2012

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“…Differential regulation of the LEE among EHEC strains 86-24, EDL933, and Sakai has been observed in studies examining the roles of RpoS and GrlA in EHEC virulence (18,37,38,49,80,86). Moreover, Islam et al reported that the ler P1 promoter was the major promoter activating LEE expression in EHEC strains Sakai and EDL933 (37), whereas other studies have found that the ler P2 promoter was the major promoter in EHEC strain 86-24 (74, 78). Islam et al suggested that the differences are likely due to the genetic backgrounds of the strains and/or the exact fusions and measurement conditions used in the experimental design (37).…”

Section: Discussionmentioning

confidence: 93%

Hfq Virulence Regulation in Enterohemorrhagic Escherichia coli O157:H7 Strain 86-24

et al. 2011

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Enterohemorrhagic Escherichia coli O157:H7 (EHEC) causes bloody diarrhea and hemolytic-uremic syndrome. EHEC encodes the sRNA chaperone Hfq, which is important in posttranscriptional regulation. In EHEC strain EDL933, Hfq acts as a negative regulator of the locus of enterocyte effacement (LEE), which encodes most of the proteins involved in type III secretion and attaching and effacing (AE) lesions. Here, we deleted hfq in the EHEC strain 86-24 and compared global transcription profiles of the hfq mutant and wild-type (WT) strains in exponential growth phase. Deletion of hfq affected transcription of genes common to nonpathogenic and pathogenic strains of E. coli as well as pathogen-specific genes. Downregulated genes in the hfq mutant included ler, the transcriptional activator of all the LEE genes, as well as genes encoded in the LEE2 to -5 operons. Decreased expression of the LEE genes in the hfq mutant occurred at middle, late, and stationary growth phases. We also confirmed decreased regulation of the LEE genes by examining the proteins secreted and AE lesion formation by the hfq mutant and WT strains. Deletion of hfq also caused decreased expression of the two-component system qseBC, which is involved in interkingdom signaling and virulence gene regulation in EHEC, as well as an increase in expression of stx 2AB , which encodes the deadly Shiga toxin. Altogether, these data indicate that Hfq plays a regulatory role in EHEC 86-24 that is different from what has been reported for EHEC strain EDL933 and that the role of Hfq in EHEC virulence regulation extends beyond the LEE.Enterohemorrhagic Escherichia coli O157:H7 (EHEC) is a food-borne pathogen that causes severe bloody diarrhea and is often associated with complications, including hemolytic-uremic syndrome (HUS), seizures, cerebral edema, and/or coma (42). EHEC attaches intimately to intestinal epithelial cells and triggers extensive cytoskeletal rearrangements, resulting in attaching and effacing (AE) lesions and formation of a characteristic pedestal structure (40,41,46). Most of the genes involved in AE lesion formation are carried within a chromosomal pathogenicity island called the locus of enterocyte effacement (LEE) (53). The LEE contains five major operons (LEE1 to -5) that encode a type III secretion (TTS) system and effector proteins. EHEC's arsenal of virulence factors also includes non-LEE-encoded effector proteins that increase adherence or mediate colonization of host epithelial cells (8,16,26,27,32,84,87,88).The mortality associated with EHEC infections is due to the production and release of a Shiga toxin (Stx) by these bacteria. EHEC expresses Stx, and this potent inhibitor of protein synthesis can be absorbed systemically, where it binds to receptors found in the kidneys and the central nervous system, thus causing the complications associated with EHEC disease (42).Regulation of EHEC virulence genes is extremely complex and involves interkingdom signaling (12). EHEC senses the host-derived signals epinephrine and norepinephrine as well...

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“…GrlA is a positive regulator of LEE1, and GrlR binds directly to GrlA to block its activity (24). Under inducing conditions, the GrlR repression is removed, likely by its targeting to degradation by ClpXP (25), allowing the establishment of a positive feedback loop between GrlA and Ler (9,10). This mechanism provides a rationale for the relatively high level of basal expression of LEE7 (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…P LEE1 is repressed by H-NS at 27°C, but upon shifting of the culture to 37°C, P LEE1 is activated and no longer repressed by H-NS. This LEE1 activation is mediated by PerC and/or GrlA, which are redundant positive regulators of P LEE1 (8,9). PerC is encoded by a large plasmid, and GrlA is encoded by a bicistronic operon within the LEE (LEE7) (10).…”

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confidence: 99%

Dynamics of Expression and Maturation of the Type III Secretion System of Enteropathogenic Escherichia coli

et al. 2014

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Enteropathogenic Escherichia coli (EPEC) is a major cause of food poisoning, leading to significant morbidity and mortality. EPEC virulence is dependent on a type III secretion system (T3SS), a molecular syringe employed by EPEC to inject effector proteins into host cells. The injected effector proteins subvert host cellular functions to the benefit of the infecting bacteria. The T3SS and related genes reside in several operons clustered in the locus of enterocyte effacement (LEE). We carried out simultaneous analysis of the expression dynamics of all the LEE promoters and the rate of maturation of the T3SS. The results showed that expression of the LEE1 operon is activated immediately upon shifting the culture to inducing conditions, while expression of other LEE promoters is activated only ϳ70 min postinduction. Parallel analysis showed that the T3SS becomes functional around 100 min postinduction. The T3SS core proteins EscS, EscT, EscU, and EscR are predicted to be involved in the first step of T3SS assembly and are therefore included among the LEE1 genes. However, interfering with the temporal regulation of EscS, EscT, EscU, and EscR expression has only a marginal effect on the rate of the T3SS assembly. This study provides a comprehensive description of the transcription dynamics of all the LEE genes and correlates it to that of T3SS biogenesis.

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Organization of the LEE1 operon regulatory region of enterohaemorrhagic Escherichia coli O157:H7 and activation by GrlA

Cited by 38 publications

References 50 publications

A Distinct Regulatory Sequence Is Essential for the Expression of a Subset of nle Genes in Attaching and Effacing Escherichia coli

A Distinct Regulatory Sequence Is Essential for the Expression of a Subset of nle Genes in Attaching and Effacing Escherichia coli

Hfq Virulence Regulation in Enterohemorrhagic Escherichia coli O157:H7 Strain 86-24

Dynamics of Expression and Maturation of the Type III Secretion System of Enteropathogenic Escherichia coli

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