The Salmonella Typhimurium InvF-SicA complex is necessary for the transcription of sopB in the absence of the repressor H-NS

PLoS One. 2020 Oct 29;15(10):e0240617. doi: 10.1371/journal.pone.0240617. eCollection 2020.

Abstract

Expression of virulence factors in non-typhoidal Salmonella enterica depends on a wide variety of general and specific transcriptional factors that act in response to multiple environmental signals. Expression of genes for cellular invasion located in the Salmonella pathogenicity island 1 (SPI-1) is tightly regulated by several transcriptional regulators arrayed in a cascade, while repression of this system is exerted mainly by H-NS. In SPI-1, H-NS represses the expression mainly by binding to the regulatory region of hilA and derepression is exercised mainly by HilD. However, the possible regulatory role of H-NS in genes downstream from HilD and HilA, such as those regulated by InvF, has not been fully explored. Here the role of H-NS on the expression of sopB, an InvF dependent gene encoded in SPI-5, was evaluated. Our data show that InvF is required for the expression of sopB even in the absence of H-NS. Furthermore, in agreement with previous results on other InvF-regulated genes, we found that the expression of sopB requires the InvF/SicA complex. Our results support that SicA is not required for DNA binding nor for increasing affinity of InvF to DNA in vitro. Moreover, by using a bacterial two-hybrid system we were able to identify interactions between SicA and InvF. Lastly, protein-protein interaction assays suggest that InvF functions as a monomer. Derived from these results we postulate that the InvF/SicA complex does not act on sopB as an anti-H-NS factor; instead, it seems to induce the expression of sopB by acting as a classical transcriptional regulator.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • DNA-Binding Proteins / genetics*
  • Gene Expression Regulation, Bacterial / genetics
  • Humans
  • Molecular Chaperones / genetics*
  • Multiprotein Complexes / genetics
  • Promoter Regions, Genetic / genetics
  • Salmonella enterica / genetics
  • Salmonella typhimurium / genetics*
  • Salmonella typhimurium / pathogenicity
  • Trans-Activators / genetics
  • Transcription Factors / genetics*

Substances

  • Bacterial Proteins
  • DNA-Binding Proteins
  • H-NS protein, bacteria
  • HilA protein, Salmonella
  • HilD protein, Salmonella typhimurium
  • Molecular Chaperones
  • Multiprotein Complexes
  • SicA protein, Salmonella typhimurium
  • Spi1 protein, Salmonella
  • Trans-Activators
  • Transcription Factors
  • invF protein, Salmonella
  • SopB protein, Salmonella

Grants and funding

This work was supported by grants from Consejo Nacional de Ciencia y Tecnología (Proyecto Apoyado por el Fondo Sectorial de Investigación para la Educación CONACYT A1-S-25438), Secretaría de Investigación y Posgrado (SIP 2020-0728) and COFAA to JAI, from Consejo Nacional de Ciencia y Tecnología (CONACYT 254531) and Dirección General de Asuntos del Personal Académico de la UNAM (IN202418) to VHB. LER-G, DC-A and EV-G obtained a grant for graduate studies from CONACYT (619402, 935269 and 618908, respectively). LER-G, DC-A and DAP-H enjoyed a BEIFI-IPN fellowship.