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Role of the histone-like nucleoid structuring protein in the regulation of rpoS and RpoS-dependent genes in Vibrio cholerae.

ABSTRACT: Production of the Zn-metalloprotease hemagglutinin (HA)/protease by Vibrio cholerae has been reported to enhance enterotoxicity in rabbit ileal loops and the reactogenicity of live cholera vaccine candidates. Expression of HA/protease requires the alternate sigma factor sigma(S) (RpoS), encoded by rpoS. The histone-like nucleoid structuring protein (H-NS) has been shown to repress rpoS expression in Escherichia coli. In V. cholerae strains of the classical biotype, H-NS has been reported to silence virulence gene expression. In this study we examined the role of H-NS in the expression of HA/protease and motility in an El Tor biotype strain by constructing a Deltahns mutant. The Deltahns mutant exhibited multiple phenotypes, such as production of cholera toxin in nonpermissive LB medium, reduced resistance to high osmolarity, enhanced resistance to low pH and hydrogen peroxide, and reduced motility. Depletion of H-NS by overexpression of a dominant-negative allele or by deletion of hns resulted in diminished expression of HA/protease. Epistasis analysis of HA/protease expression in Deltahns, DeltarpoS, and Deltahns DeltarpoS mutants, analysis of RpoS reporter fusions, quantitative reverse transcription-PCR measurements, and ectopic expression of RpoS in DeltarpoS and DeltarpoS Deltahns mutants showed that H-NS posttranscriptionally enhances RpoS expression. The Deltahns mutant exhibited a lower degree of motility and lower levels of expression of flaA, flaC, cheR-2, and motX mRNAs than the wild type. Comparison of the mRNA abundances of these genes in wild-type, Deltahns, DeltarpoS, and Deltahns DeltarpoS strains revealed that deletion of rpoS had a more severe negative effect on their expression. Interestingly, deletion of hns in the rpoS background resulted in higher expression levels of flaA, flaC, and motX, suggesting that H-NS represses the expression of these genes in the absence of sigma(S). Finally, we show that the cyclic AMP receptor protein and H-NS act along the same pathway to positively affect RpoS expression.

SUBMITTER: Silva AJ

PROVIDER: S-EPMC2576668 | biostudies-literature | 2008 Nov

REPOSITORIES: biostudies-literature

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Role of the histone-like nucleoid structuring protein in the regulation of rpoS and RpoS-dependent genes in Vibrio cholerae.

Silva Anisia J AJ Sultan Syed Zafar SZ Liang Weili W Benitez Jorge A JA

Journal of bacteriology 20080912 22

Production of the Zn-metalloprotease hemagglutinin (HA)/protease by Vibrio cholerae has been reported to enhance enterotoxicity in rabbit ileal loops and the reactogenicity of live cholera vaccine candidates. Expression of HA/protease requires the alternate sigma factor sigma(S) (RpoS), encoded by rpoS. The histone-like nucleoid structuring protein (H-NS) has been shown to repress rpoS expression in Escherichia coli. In V. cholerae strains of the classical biotype, H-NS has been reported to sile ...[more]

PMID: 18790865

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Project description:The cholera disease bacterium V. cholerae, can adopt planktonic or biofilm lifestyles depending on the intracellular concentration of the second messenger cyclic diguanylic acid (c-di-GMP). Biofilm formation protects Vibrios from stressful conditions and facilitates disease transmission by enhancing infectivity. The histone-like nucleoid structuring protein (H-NS) is a global regulator of genes associated with pathogenicity and responses to environmental stresses. H-NS represses the transcription of genes vpsT, vpsA and vpsL, which are required for the biosynthesis of the biofilm exopolysacchide matrix. Here we demonstrate that the c-di-GMP-binding protein VpsT disrupts H-NS nucleoprotein complexes at the vpsA and vpsL promoters and that this effect is enhanced by c-di-GMP. We used ChIP coupled with Next Generation Sequencing (ChIP-Seq) and transcriptome analysis (RNA-Seq) to identify additional loci repressed by H-NS affecting biofilm formation. This study showed that H-NS directly represses the transcription of genes encoding proteins present in the biofilm matrix such as the rbmA-F cluster, hemolysin and chitinase. Similar to vpsA and vpsL, the promoter region of vpsU, rbmA and rbmF exhibited overlapping H-NS and VpsT binding motifs. Deletion of vpsT increased H-NS occupancy at the vpsU, vpsA, vpsL, rbmA and rbmF promoters. Conversely, artificially increasing the c-di-GMP pool diminished H-NS occupancy at the above promoters. Deletion of vpsT did not affect H-NS occupancy at its own promoter. However, deletion of genes encoding the regulators AphA and VpsR significantly increased H-NS occupancy at the vpsT promoter. In sum, our study shows that c-di-GMP enhances biofilm formation by acting through VpsT to activate an H-NS anti-repression cascade. The Binding profile of V. cholerae H-NS to the genome was determined by ChIP followed by Next Generation Sequencing (ChIP-Seq) using the Illumina HiSeq2000 platform. V. cholerae C7258 cells expressing H-NS-FLAG fusion protein from the hns transcription and translation signals were collected from LB cultures grown to mid-exponential phase (OD600 0.5). An anti-FLAG Immunoprecipitation (IP) and an Input samples were used for the analysis.

Project description:Cholera is a diarrheal disease caused by Vibrio cholerae of serogroups O1 and O139 that affects impoverished populations worldwide. The histone-like nucleoid structuring protein (H-NS) is a global regulator of environmentally-regulated gene expression that plays a fundamental role in V. cholerae adaptation to disparate ecological niches. We used RNA-seq to characterize the hns transcriptome of El Tor biotype V. cholerae. H-NS affected the expression of 18% of all predicted genes in a growth phase-dependent manner. It silenced the transcription of genes encoding virulence regulators and cytotoxic factors such as the VieSAB regulatory system, the repeat in toxin (RTX) and hemolysin. H-NS was 10 times more effective in silencing the vieSAB promoter in El Tor compared to classical biotype V. cholerae. In the El Tor biotype hns mutant, VieSAB significantly enhanced the expression of cholera toxin genes. For the RTX and hemolysin, we found that overexpression of the transcription activator HlyU diminished H-NS occupancy at the hlyA promoter but not at the rtxCA and rtxBDE promoters. H-NS had a significant impact on the cell envelope and the mutant expressed elevated rpoE encoding the extracytoplamic sigma factor E (sE), though this effect was indirect. A remarkable feature of the hns transcriptome was the down-regulation of numerous methyl-accepting chemotaxis proteins in early stationary phase that translated into diminished chemotaxis toward the amino acids glycine and serine. Our study suggests that H-NS transcriptional silencing can contribute to multiple phenotypic differences observed between V. cholerae biotypes, mainly by differentially repressing the VieSAB sensory pathway. Transcriptome profiles of wild type and M-NM-^Thns mutant cells of the V. cholerae strain C7258 grown in LB medium were generated by Next Generation Sequencing using the Illumina HiSeq2000 platform. Samples from mid-exponential phase (OD600 0.5) and early stationary phase (OD600 2.0) were analyzed in duplicate

Dataset Information

Role of the histone-like nucleoid structuring protein in the regulation of rpoS and RpoS-dependent genes in Vibrio cholerae.

Publications

Role of the histone-like nucleoid structuring protein in the regulation of rpoS and RpoS-dependent genes in Vibrio cholerae.

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