title: HilE interacts with HilD and negatively regulates hilA transcription and expression of the Salmonella enterica serovar Typhimurium invasive phenotype.
abstract: The ability of Salmonella enterica serovar Typhimurium to traverse the intestinal mucosa of a host is an important step in its ability to initiate gastrointestinal disease. The majority of the genes required for this invasive characteristic are encoded on Salmonella pathogenicity island 1 (SPI1), and their expression is controlled by the transcriptional activator HilA, a member of the OmpR/ToxR family of proteins. A variety of genes (hilC, hilD, fis, sirA/barA, csrAB, phoB, fadD, envZ/ompR, fliZ, hilE, ams, lon, pag, and hha) have been identified that exert positive or negative effects on hilA expression, although the mechanisms by which these gene products function remain relatively unclear. Recent work indicates that the small DNA-binding protein, Hha, has a significant role in repressing hilA transcription and the invasive phenotype, particularly in response to osmolarity signals. We have characterized the Salmonella-specific gene, hilE, and found that it plays an important regulatory role in hilA transcription and invasion gene expression. Mutation of hilE causes derepression of hilA transcription, and overexpression of hilE superrepresses hilA expression and the invasive phenotype. Bacterial two-hybrid experiments indicate that the HilE protein interacts with HilD, suggesting a possible mechanism for HilE negative regulation of hilA gene expression and the Salmonella invasive phenotype. Finally, we have found that the hilE gene resides on a region of the serovar Typhimurium chromosome that has many characteristics of a pathogenicity island.
authors.affiliation: Genetics Program, University of Iowa School of Medicine, Iowa City, Iowa 52242, USA.
authors.forename: M Aaron
authors.initials: MA
authors.lastname: Baxter
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Fahlen
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Wilson
authors.forename: Bradley D
authors.initials: BD
authors.lastname: Jones
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002460:Cell Line; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D012097:Repressor Proteins / Q000502:physiology*; D012486:Salmonella typhimurium / Q000235:genetics / Q000472:pathogenicity*; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; C102236:HilA protein, Salmonella; C119660:HilD protein, Salmonella typhimurium; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C090990:invF protein, Salmonella