The HilA box and sequences outside it determine the magnitude of HilA-dependent activation of P(prgH) from Salmonella pathogenicity island 1.
Salmonella requires genes on the Salmonella pathogenicity island 1 (SPI1) for the intestinal phase of infection in several models of pathogenesis. In Salmonella enterica serovar Typhimurium, most SPI1 genes are arranged in operons that are coordinately regulated by the SPI1-encoded protein HilA. In the past, it has been shown that HilA directly activates two promoters on SPI1, P(invF-1) and P(prgH). P(invF-1) contains a HilA binding site, termed a HilA box, that is necessary and sufficient for activation by HilA. The HilA box is 17 nucleotides long and contains a direct repeat comprised of two hexamers separated by 5 nucleotides, centered at -45 relative to the start site of transcription. P(prgH) also contains a HilA box, and here we investigate its role at P(prgH). We have found that the HilA box is necessary, but not sufficient, for HilA-dependent activation of P(prgH). Instead, half-site-like hexamers outside the HilA box appear to be required for HilA-dependent activation of P(prgH), even though HilA binds to the HilA box in the absence of these hexamers. Thus, although HilA-dependent activation of P(invF-1) and P(prgH) coordinates the expression of the structural genes for a type III secretion apparatus and the effectors secreted by that apparatus, it is also possible that mechanisms not apparent under in vitro inducing conditions could separate the expression of invFGEABC-spaMNOPQRS-sicA-sipBCDA-iacP-sicP-sptP and prgHIJK-orgABC.
Lostroh
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CP
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Lee
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CA
D001089:Arabinose / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D017930:Genes, Reporter; D006801:Humans; D007422:Intestines / Q000382:microbiology; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis; D019779:Salmonella enterica / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors; D014774:Virulence / Q000235:genetics
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C102236:HilA protein, Salmonella; D009838:Oligodeoxyribonucleotides; C079790:PrgH protein, Salmonella typhimurium; D011994:Recombinant Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C090990:invF protein, Salmonella; D001089:Arabinose