scholarly journals The ATP-Dependent Lon Protease of Salmonella enterica Serovar Typhimurium Regulates Invasion and Expression of Genes Carried on Salmonella Pathogenicity Island 1

2002 ◽  
Vol 184 (1) ◽  
pp. 224-232 ◽  
Author(s):  
Akiko Takaya ◽  
Toshifumi Tomoyasu ◽  
Akane Tokumitsu ◽  
Mizue Morioka ◽  
Tomoko Yamamoto
Keyword(s):  
Gene Expression ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Pathogenicity Island ◽  
Lon Protease ◽  
Environmental Signals ◽  
Regulatory Systems ◽  
Expression Of Genes ◽  
Serovar Typhimurium ◽  
Complex Manner

ABSTRACT An early step in the pathogenesis of Salmonella enterica serovar Typhimurium infection is bacterial penetration of the intestinal epithelium. Penetration requires the expression of invasion genes found in Salmonella pathogenicity island 1 (SPI1). These genes are controlled in a complex manner by regulators in SPI1, including HilA and InvF, and those outside SPI1, such as two-component regulatory systems and small DNA-binding proteins. We report here that the expression of invasion genes and the invasive phenotype of S. enterica serovar Typhimurium are negatively regulated by the ATP-dependent Lon protease, which is known to be a major contributor to proteolysis in Escherichia coli. A disrupted mutant of lon was able to efficiently invade cultured epithelial cells and showed increased production and secretion of three identified SPI1 proteins, SipA, SipC, and SipD. The lon mutant also showed a dramatic enhancement in transcription of the SPI1 genes hilA, invF, sipA, and sipC. The increases ranged from 10-fold to almost 40-fold. It is well known that the expression of SPI1 genes is also regulated in response to several environmental conditions. We found that the disruption of lon does not abolish the repression of hilA and sipC expression by high-oxygen or low-osmolarity conditions, suggesting that Lon represses SPI1 gene expression by a regulatory pathway independent of these environmental signals. Since HilA is thought to function as a central regulator of SPI1 gene expression, it is speculated that Lon may regulate SPI1 gene expression by proteolysis of putative factors required for activation of hilA expression.

scholarly journals HilE Interacts with HilD and Negatively Regulates hilA Transcription and Expression of the Salmonella enterica Serovar Typhimurium Invasive Phenotype

2003 ◽  
Vol 71 (3) ◽  
pp. 1295-1305 ◽  
Author(s):  
M. Aaron Baxter ◽  
Thomas F. Fahlen ◽  
Rebecca L. Wilson ◽  
Bradley D. Jones
Keyword(s):  
Gene Expression ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Gastrointestinal Disease ◽  
Pathogenicity Island ◽  
Specific Gene ◽  
Negative Effects ◽  
Invasive Phenotype ◽  
Serovar Typhimurium ◽  
Two Hybrid

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.

scholarly journals The fimYZ Genes Regulate Salmonella enterica Serovar Typhimurium Invasion in Addition to Type 1 Fimbrial Expression and Bacterial Motility

2005 ◽  
Vol 73 (3) ◽  
pp. 1377-1385 ◽  
Author(s):  
M. Aaron Baxter ◽  
Bradley D. Jones
Keyword(s):  
Gene Expression ◽  
Gene Regulation ◽  
Protein Interactions ◽  
Salmonella Enterica ◽  
Negative Regulator ◽  
Invasive Phenotype ◽  
Environmental Signals ◽  
Bacterial Physiology ◽  
Serovar Typhimurium

ABSTRACT An important step in Salmonella enterica serovar Typhimurium virulence is the ability to invade the intestinal epithelium. The invasion process requires a large number of genes encoded on Salmonella pathogenicity island 1 (SPI-1) at centisome 63 as well as genes located in other positions throughout the chromosome. Expression of the invasive phenotype is tightly regulated by environmental cues that are processed by a complex regulatory scheme. A central player in the invasion regulatory pathway is the HilA protein, which is transcriptional activator belonging to the OmpR/ToxR family. A number of positive regulators (hilC, hilD, fis, sirA/barA, csrAB, phoBR, fadD, envZ/ompR, and fliZ) and negative regulators (hha, hilE, lon, ams, phoP c and pag) have been identified that are able to alter expression of hilA transcription. Recent work has found that hilA transcription requires the HilD protein for activation. Other work has emphasized the importance of HilE as a negative regulator of hilA. Overexpression of hilE superrepresses hilA transcription, as well as the invasive phenotype. Two-hybrid experiments suggest that HilE exerts its regulatory influence on hilA through protein-protein interactions with HilD as the protein does not bind to the hilA promoter nor does it affect hilD transcription. As it seems likely that hilE plays an important role in translating environmental signals into invasion gene regulation, we have attempted to identify how the hilE gene itself is regulated. Our results indicate that the fimYZ genes, response regulatory proteins involved in type 1 fimbrial gene expression and recently implicated in motility gene regulation, are important activators of hilE expression. These findings indicate that invasion gene expression is coregulated with motility and adherence and provide experimental evidence that the expression of these virulence phenotypes is a subset of the overall regulation of bacterial physiology.

scholarly journals Fur Regulates Expression of the Salmonella Pathogenicity Island 1 Type III Secretion System through HilD

2007 ◽  
Vol 190 (2) ◽  
pp. 476-486 ◽  
Author(s):  
Jeremy R. Ellermeier ◽  
James M. Slauch
Keyword(s):  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Dependent Manner ◽  
Intestinal Epithelial ◽  
Environmental Signals ◽  
Type Iii ◽  
Regulatory Systems ◽  
Serovar Typhimurium

ABSTRACT The invasion of intestinal epithelial cells by Salmonella enterica serovar Typhimurium is mediated by a type III secretion system (T3SS) encoded on Salmonella pathogenicity island 1 (SPI1). Expression of the SPI1 T3SS is tightly regulated by the combined action of HilC, HilD, and RtsA, three AraC family members that can independently activate hilA, which encodes the direct regulator of the SPI1 structural genes. Expression of hilC, hilD, and rtsA is controlled by a number of regulators that respond to a variety of environmental signals. In this work, we show that one such signal is iron mediated by Fur (ferric uptake regulator). Fur activates hilA transcription in a HilD-dependent manner. Fur regulation of HilD does not appear to be simply at the transcriptional or translational level but rather requires the presence of the HilD protein. Fur activation of SPI1 is not mediated through the Fur-regulated small RNAs RfrA and RfrB, which are the Salmonella ortholog and paralog of RyhB that control expression of sodB. Fur regulation of HilD is also not mediated through the known SPI1 repressor HilE or the CsrABC system. Although understanding the direct mechanism of Fur action on HilD requires further analysis, this work is an important step toward elucidating how various global regulatory systems control SPI1.

The effect of the Salmonella genomic island 1 on in vitro global gene expression in Salmonella enterica serovar Typhimurium LT2

2007 ◽  
Vol 9 (1) ◽  
pp. 21-27 ◽  
Author(s):  
George R. Golding ◽  
Adam B. Olson ◽  
Benoît Doublet ◽  
Axel Cloeckaert ◽  
Sara Christianson ◽  
...  
Keyword(s):  
Gene Expression ◽  
Salmonella Enterica ◽  
Genomic Island ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Global Gene Expression ◽  
Serovar Typhimurium

scholarly journals Transcriptional Organization and Function of Invasion Genes within Salmonella enterica Serovar Typhimurium Pathogenicity Island 1, Including the prgH,prgI, prgJ, prgK, orgA,orgB, and orgC Genes

2000 ◽  
Vol 68 (6) ◽  
pp. 3368-3376 ◽  
Author(s):  
Joanna R. Klein ◽  
Thomas F. Fahlen ◽  
Bradley D. Jones
Keyword(s):  
Epithelial Cells ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Pathogenicity Island ◽  
Pcr Analysis ◽  
Intestinal Epithelial ◽  
Reading Frame ◽  
Bacterial Proteins ◽  
Serovar Typhimurium ◽  
And Function

ABSTRACT Salmonella enterica serovar Typhimurium initiates infection of a host by inducing its own uptake into specialized M cells which reside within the epithelium overlaying Peyer's patches. Entry of Salmonella into intestinal epithelial cells is dependent upon invasion genes that are clustered together inSalmonella pathogenicity island 1 (SPI-1). Upon contact between serovar Typhimurium and epithelial cells targeted for bacterial internalization, bacterial proteins are injected into the host cell through a type III secretion system that leads to internalization of the bacteria. Previous work has established that the prgH, -I, -J, and -K and orgAgenes reside in SPI-1, and the products of these genes are predicted to be components of the invasion secretion apparatus. We report that an error in the published orgA DNA sequence has been identified so that this region encodes two small genes rather than a single large open reading frame. These genes have been designatedorgA and orgB. Additionally, an opening reading frame downstream of orgB, which we have designatedorgC, has been identified and partially characterized. Previously published work has indicated that the prgH, -I, -J, and -K genes are transcribed from a promoter distinct from that used by the gene immediately downstream, orgA. Here, we present experiments indicating that orgA expression is driven by theprgH promoter. In addition, using reverse transcriptase PCR analysis, we have found that this polycistronic message extends downstream of prgH to include a total of 10 genes. To more fully characterize this invasion operon, we demonstrate that theprgH, prgI, prgJ, prgK,orgA, and orgB genes are each required for invasion and secretion, while orgC is not essential for the invasive phenotype.

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