YdgT, the Hha paralogue in Escherichia coli, forms heteromeric complexes with H‐NS and StpA

Abstract

SummaryIn enteric bacteria, proteins of the Hha/YmoA family play a role in the regulation of gene expression in response to environmental factors. Interaction of both Hha and YmoA with H-NS has been reported, and an Hha/H-NS complex has been shown to modulate expression in Escherichia coli of the haemolysin operon of plasmid pHly152. In addition to the hns gene, the chromosome of E. coli and other enteric bacteria also includes the stpA gene that encodes the StpA protein, an H-NS paralogue. We report here the identification of the Hha paralogue in E. coli , the YdgT protein. As Hha paralogue, YdgT appears to fulfil some of the functions reported for StpA as H-NS paralogue: YdgT is overexpressed in hha mutants and can compensate, at least partially, some of the hhainduced phenotypes. We also demonstrate that YdgT interacts both with H-NS and with StpA. Protein crosslinking studies showed that YdgT/H-NS heteromeric complexes are generated within the bacterial cell. The StpA protein, which is subjected to Lon-mediated turnover, was less stable in the absence of Hha or YdgT. Our findings suggest that Hha, YdgT and StpA may form complexes in vivo .

Structural Insights into the Regulation of Foreign Genes in Salmonella by the Hha/H-NS Complex

“…The loss of ydgT has minimal effects on Salmonella strains encoding a functional Hha protein; however, hha/ydgT double mutants display greater losses in fitness and virulence than the additive effects of the single mutants (24,25). Hha and YdgT appear to be highly redundant with regard to their function, and given that hha mutations result in more dramatic phenotypes than deleting ydgT, Hha is thought to play a more dominant regulatory role, and YdgT is considered as a "backup" molecule (26), although it is unclear what the purpose of such a backup would be.…”

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

“…The ydgT gene codes for an Hha-like protein in E. coli and Salmonella, and it can interact with H-NS and the H-NS paralogue, the StpA protein (Paytubi et al, 2004). The YdgT protein is important in Salmonella enterica for the proper contextual regulation of the virulence genes in the SPI2 pathogenicity island: in the absence of YdgT, the bacterium upregulates its SPI2 genes too early during infection, leading ultimately to a loss of virulence (Coombes et al, 2005).…”

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

“…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).…”

“…on April 7, 2019 by guest http://jb.asm.org/ suppressors of rho and nusG (27) and, since YdgT is an interacting partner of H-NS (30,33,42), we tested whether it is the presence of YdgT in the plasmid derivatives that was responsible for the suppression phenotype. The minimal ydgT construct, as well as the gene fragment encoding H-NS⌬64 as a positive control, was cloned downstream of the IPTG-inducible trc promoter in the ColE1-plasmid vector pTrc99A.…”