Anti-silencing: overcoming H-NS-mediated repression of transcription in Gram-negative enteric bacteria

Stoebel, Daniel M.; Free, Andrew; Dorman, Charles J.

doi:10.1099/mic.0.2008/020693-0

Cited by 231 publications

(269 citation statements)

References 149 publications

Supporting

Mentioning

264

Contrasting

Order By: Relevance

“…well-characterized process that overcomes H-NS-mediated repression of several operons under specific physiological conditions (Stoebel et al, 2008). The RovA and Ler proteins have been shown to counteract H-NS-mediated silencing in Yersinia enterocolitica and E. coli, respectively (Bustamante et al, 2001;Ellison & Miller, 2006).…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2011

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionmentioning

confidence: 99%

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

et al. 2011

View full text Add to dashboard Cite

show abstract

“…silencing of virulence-associated genes must be relieved. In E. coli and Salmonella enterica serovar Typhimurium, a number of mechanisms of relieving silencing by H-NS have been described (reviewed by Stoebel et al, 2008). These include altering the secondary structure of DNA in response to changing environmental conditions, binding of regulatory proteins that can disrupt H-NS-mediated silencing and/or directly stimulate transcription by interacting with RNA polymerase, and the formation of heteromeric complexes between H-NS and H-NS paralogues, which lack DNAbinding motifs and disrupt H-NS function.…”

Section: Introductionmentioning

confidence: 99%

Ler of pathogenic Escherichia coli forms toroidal protein–DNA complexes

et al. 2011

View full text Add to dashboard Cite

Enteropathogenic and enterohaemorrhagic Escherichia coli are related pathotypes of bacteria that cause acute watery diarrhoea and haemorrhagic colitis, respectively, and enterohaemorrhagic E. coli can lead to a serious complication known as haemolytic uraemic syndrome. In both bacteria the global regulatory protein Ler controls virulence. The ler gene is found within the locus of enterocyte effacement, or LEE, encoding a type III secretion system necessary for injecting effector proteins into intestinal epithelial cells and causing net secretory diarrhoea. The nucleoidassociated protein H-NS silences, whereas Ler serves as an anti-silencer of, multiple LEE operons. Although Ler has a higher affinity for DNA than does H-NS, the precise molecular mechanism by which Ler increases LEE transcription remains to be determined. In this report we investigate the oligomerization activity of Ler. In solution, Ler forms dimers and soluble aggregates of up to 5000 kDa molecular mass, and appears to oligomerize more readily than the related protein H-NS. An insertional mutation into the Ler linker region diminished oligomerization activity. Despite being proteins of similar mass and having homologous DNA-binding domains, Ler and H-NS complexed to DNA migrated to distinct locations, as determined by an electrophoretic mobility shift assay, implying that the related proteins form different 3D shapes in the presence of DNA. Lastly, we present electron microscopy images of toroidal Ler-DNA structures that are predicted to be involved in stimulating gene expression.

show abstract

“…Binding of H-NS to DNA results in several structural (including supercoiling) alterations that have been variously referred to as bending, bridging, coating, looping, and stiffening of the DNA (16,20,23,32,39,61). YdgT and Hha bear structural resemblance to, and also interact with, the N-terminal oligomerization domains of H-NS and StpA; in this manner, YdgT and Hha are believed to modulate the DNA-binding and nucleoid-organizing properties of H-NS and StpA even though they do not bind DNA by themselves (23,30,33,38,42,55).…”

mentioning

confidence: 99%

“…(Amino acid residues in H-NS are numbered here beginning from the N-terminal methionine as 1 [65], even though this residue is posttranslationally removed from the mature protein.) The presence of the two dimerization interfaces allows H-NS to assemble (either alone or with its paralogous partner StpA [53,55,60,65,67]) into a helical polymeric scaffold around which DNA is bound (3,22). Binding of H-NS to DNA results in several structural (including supercoiling) alterations that have been variously referred to as bending, bridging, coating, looping, and stiffening of the DNA (16, 20,…”

mentioning

confidence: 99%

Modulation of Rho-Dependent Transcription Termination in Escherichia coli by the H-NS Family of Proteins

Saxena

Gowrishankar

2011

J Bacteriol

View full text Add to dashboard Cite

Nascent transcripts in Escherichia coli that fail to be simultaneously translated are subject to a factordependent mechanism of termination (also termed a polarity) that involves the proteins Rho and NusG. In this study, we found that overexpression of YdgT suppressed the polarity relief phenotypes and restored the efficiency of termination in rho or nusG mutants. YdgT and Hha belong to the H-NS and StpA family of proteins that repress a large number of genes in Gram-negative bacteria. Variants of H-NS defective in one or the other of its two dimerization domains, but not those defective in DNA binding alone, also conferred a similar suppression phenotype in rho and nusG mutants. YdgT overexpression was associated with derepression of proU, a prototypical H-NS-silenced locus. Polarity relief conferred by rho or nusG was unaffected in a derivative completely deficient for both H-NS and StpA, although the suppression effects of YdgT or the oligomerizationdefective H-NS variants were abolished in this background. Transcription elongation rates in vivo were unaffected in any of the suppressor-bearing strains. Finally, the polarity defects of rho and nusG mutants were exacerbated by Hha and YdgT deficiency. A model is proposed that invokes a novel role for the polymeric architectural scaffold formed on DNA by H-NS and StpA independent of the gene-silencing functions of these nucleoid proteins, in modulating Rho-dependent transcription termination such that interruption of the scaffold (as obtained by expression either of the H-NS oligomerization variants or of YdgT) is associated with improved termination efficiency in the rho and nusG mutants.Translation is a cotranscriptional process in both eubacteria and archaebacteria (1,9,25,45,50), and it has been proposed that such coupling is a defining characteristic of prokaryotic life (34, 64). The maintenance of transcription-translation coupling in a prokaryotic cell would require dynamic inter-regulation between the binding and progression of a pioneer ribosome on the nascent transcript on the one hand and the rate of transcription elongation on the other (9, 45); however, the detailed mechanisms by which such regulation is achieved are not known. Furthermore, in bacteria such as Escherichia coli, nascent transcripts that are not simultaneously translated are subject to a mechanism of factor-dependent transcription termination (also referred to as transcriptional polarity) (reviewed in references 1, 6, 15, 40, 44, 47, and 52), so that the occurrence of translation-uncoupled transcription is minimized within the cells (11, 43).Factor-dependent (also called Rho-dependent) transcription termination is mediated by, among others, the Rho and NusG proteins (1,6,15,39,40,44,47,52). Although the structures of the two proteins have been determined and several of their biochemical properties have been characterized, the precise mechanisms of their action in transcription termination remain unclear, even controversial. Rho is an RNAbinding protein and possesses RNA-dependent ATPa...

show abstract

Anti-silencing: overcoming H-NS-mediated repression of transcription in Gram-negative enteric bacteria

Cited by 231 publications

References 149 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

Ler of pathogenic Escherichia coli forms toroidal protein–DNA complexes

Modulation of Rho-Dependent Transcription Termination in Escherichia coli by the H-NS Family of Proteins

Contact Info

Product

Resources

About