title: Gene Activation through the Modulation of Nucleoid Structures by a Horizontally Transferred Regulator, Pch, in Enterohemorrhagic Escherichia coli.
abstract: The horizontally transferred chromosomal segments, which are the main source of genetic diversity among bacterial pathogens, are bound by the nucleoid protein H-NS, resulting in the formation of a nucleoprotein complex and the silencing of gene expression. The de-silencing or activation of virulence genes necessary for the colonization of enterohemorrhagic Escherichia coli is achieved mainly by the action of two regulators, Pch and Ler, which are encoded by horizontally transferred elements. Although Ler has been shown to activate transcription by counteracting H-NS silencing, the mechanism for Pch is poorly understood. We show here that Pch activates the LEE1 promoter and also enhances the Ler-mediated activation of other LEE promoters. Transcriptional activation was completely dependent on repression by the H-NS/StpA/Hha/YdgT complex, indicating that Pch-derived activation was achieved by alleviating H-NS-mediated silencing. Expression of pch reduced the binding of H-NS at LEE1 promoter and altered the nucleoprotein complex. Furthermore, in vitro reconstruction of the protein-DNA complex on LEE1 promoter DNA confirmed the exclusive effect of Pch on H-NS binding. These results demonstrated that Pch is another anti-silencing regulator and a modulator of H-NS-containing nucleoprotein complexes. Thus, the anti-silencing mechanism plays a key role in the coordinated regulation of virulence genes in EHEC.
authors.affiliation: Department of Biomedical Informatics, Graduate School of Medicine Osaka University, 1-7 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Fukui
authors.affiliation: Graduate School of Biological Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0101, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Oshima
authors.affiliation: Graduate School of Biological Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0101, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ueda
authors.affiliation: Graduate School of Biological Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0101, Japan.
authors.forename: Naotake
authors.initials: N
authors.lastname: Ogasawara
authors.affiliation: Department of Biomedical Informatics, Graduate School of Medicine Osaka University, 1-7 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Tobe
mesh_terms: D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D022761:Gene Transfer, Horizontal; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology*; D000097796:Nucleolin
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D046912:Multiprotein Complexes; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D015534:Trans-Activators; D000097796:Nucleolin; C465556:Ler protein, E coli