title: Co-ordinate regulation of Salmonella typhimurium invasion genes by environmental and regulatory factors is mediated by control of hilA expression.
abstract: During infection of their hosts, salmonellae enter intestinal epithelial cells. It has been proposed that when Salmonella typhimurium is present in the intestinal lumen, several environmental and regulatory conditions modulate the expression of invasion factors required for bacterial entry into host cells. We report here that the expression of six different S. typhimurium invasion genes encoded on SPI1 (Salmonella pathogenicity island 1) is co-ordinately regulated by oxygen, osmolarity, pH, PhoPQ, and HilA. HilA is a transcriptional activator of the OmpR/ToxR family that is also encoded on SPI1. We have found that HilA plays a central role in the co-ordinated regulation of invasion genes by environmental and regulatory conditions. HilA can activate the expression of two invasion gene-lacZY fusions on reporter plasmids in Escherichia coll, suggesting that HilA acts directly at invasion-gene promoters in S. typhimurium. We have found that the regulation of invasion genes by oxygen, osmolarity, pH, and PhoPQ is indirect and is mediated by regulation of hilA expression by these environmental and regulatory factors. We hypothesize that the complex and co-ordinate regulation of Invasion genes by HilA is an important feature of salmonella pathogenesis and allows salmonellae to enter intestinal epithelial cells.
authors.affiliation: Department of Microbiology and Molecular Genetios, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: V
authors.initials: V
authors.lastname: Bajaj
authors.forename: R L
authors.initials: RL
authors.lastname: Lucas
authors.forename: C
authors.initials: C
authors.lastname: Hwang
authors.forename: C A
authors.initials: CA
authors.lastname: Lee
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D010100:Oxygen; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012486:Salmonella typhimurium / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C102236:HilA protein, Salmonella; C088960:OrgA protein, Salmonella typhimurium; C079792:PhoQ protein, Bacteria; C079790:PrgH protein, Salmonella typhimurium; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C090990:invF protein, Salmonella; C061064:PhoP protein, Bacteria; D010100:Oxygen