The Effects of the H-NS Protein on PhoP-dependent Transcriptional Regulation of the mgtCBRU-cigR Operon in Salmonella enterica serovar Typhimurium

Description

<p>  </p>
<p>PhoQP is a two-component system that regulates the transcription of ~5% of the genes of <em>Salmonella enterica</em>. The membrane-bound PhoQ protein is phosphorylated in response to low extracellular Mg²⁺ concentration, acid pH, and a number of antimicrobial peptides. The inorganic phosphate bound to PhoQ is transferred to PhoP, which according to the classical model, acts as a typical transcriptional activator of its target genes. However, Will et al. (doi.org/10.1038/ncomms6270) proposed an alternate “counter-silencing” model, according to which genes in the PhoP regulon that were acquired by <em>Salmonella</em> via horizontal transfer are repressed by the generalized DNA-binding protein H-NS at high [Mg²⁺] and are induced at low [Mg²⁺] because the phosphorylated PhoP displaces the H-NS from the promoters and lifts repression. We evaluated this model by examining the transcriptional regulation of the <em>mgtCBRU-cigR </em>operon, which encodes the virulence protein MgtC and the Mg²⁺ transport protein MgtB and is in the SPI-3 pathogenesis island that has been acquired by <em>Salmonella</em> via horizontal transfer. Our main finding was that in the non-pathogenic strain of <em>S</em>. Typhimurium (LT2), induction of the <em>mgtCBRU-cigR</em> operon by Mg²⁺ limitation requires a functional PhoP protein, regardless of the presence or absence of H-NS. Interestingly, the pathogenic strain of <em>S</em>. Typhimurium (ATCC 14028s) revealed PhoP-independent transcription in the absence of H-NS, but only under inducing conditions. Thus, our results do not support the counter-silencing model and are consistent with the canonical view that PhoP is needed as a transcriptional activator of genes in the PhoP regulon.</p>

Links & Downloads

1. 10.25394/pgs.19666398.v1

Tags

Microbiology

Bacteriology

Microbial Genetics

Salmonella typhimurium LT 2

Salmonella typhimurium ATCC 14028

magnesium homeostasis

phoq-phop

H-NS-mediated gene

Enhanced Heat Resistance

MgtB

phop-regulated

Additional Fields

Identifer	oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/19666398
Date	27 April 2022
Creators	Jazmin L Marks-Burns (12468483)
Source Sets	Purdue University
Detected Language	English
Type	Text, Thesis
Rights	CC BY 4.0
Relation	https://figshare.com/articles/thesis/The_Effects_of_the_H-NS_Protein_on_PhoP-dependent_Transcriptional_Regulation_of_the_mgtCBRU-cigR_Operon_in_Salmonella_enterica_serovar_Typhimurium/19666398