title: Fis is required for proper regulation of ssaG expression in Salmonella enterica serovar Typhimurium.
abstract: Salmonella pathogenicity island 2 (SPI2) encodes a type III secretion system (TTSS) necessary for bacterial survival and replication in intracellular environment of host cells. SPI2 genes are transcribed preferentially after Salmonella enters the host cells. Transcriptional regulation of ssaG encoding the component of SPI2-TTSS apparatus was studied in vivo and in vitro. Fis, one of the major components of bacterial nucleoid, activated the stationary phase-specific expression of ssaG when Salmonella was grown in LB media. Gel-shift and footprinting analysis showed Fis bound to four distinct sites of the ssaG promoter region with different affinities. All four Fis-binding sites were required for timely transcription activation of ssaG after Salmonella entered macrophage cells. Gentamicin protection experiments using bacteria grown to stationary phase prior to infection showed that the ability of the fis mutant strain to replicate within the RAW264.7 macrophage cells was lower than the wild type. These observations confirm that Fis plays an important role in regulations of SPI2 as well as SPI1 for an efficient regulation of the virulence genes.
authors.affiliation: Radiation Food Science & Biotechnology Team, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185, Korea.
authors.forename: Sangyong
authors.initials: S
authors.lastname: Lim
authors.forename: Byeongkwan
authors.initials: B
authors.lastname: Kim
authors.forename: Hyun-Sook
authors.initials: HS
authors.lastname: Choi
authors.forename: Younghoon
authors.initials: Y
authors.lastname: Lee
authors.forename: Sangryeol
authors.initials: S
authors.lastname: Ryu
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D035021:Factor For Inversion Stimulation Protein / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000235:genetics; D012486:Salmonella typhimurium / Q000235:genetics* / Q000254:growth & development
chemical_list: D001426:Bacterial Proteins; D035021:Factor For Inversion Stimulation Protein; D008565:Membrane Proteins; C440638:SPI-2 protein, Salmonella