title: Expression Regulation of Polycistronic lee3 Genes of Enterohaemorrhagic Escherichia coli.
abstract: Enterohaemorrhagic Escherichia coli O157:H7 (EHEC) carries a pathogenic island LEE that is consisted mainly of five polycistronic operons. In the lee3 operon, mpc is the first gene and has been reported to down regulate the type-3 secretion system of EHEC when its gene product is over-expressed. Furthermore, mpc has been suggested to have a regulation function via translation but the mechanism remains unclear. To clarify this hypothesis, we dissected the polycistron and examined the translated products. We conclude that translation of mpc detrimentally governs the translation of the second gene, escV, which in turn affects the translation of the third gene, escN. Then sequentially, escN affects the expression of the downstream genes. Furthermore, we located a critical cis element within the mpc open-reading frame that plays a negative role in the translation-dependent regulation of lee3. Using qRT-PCR, we found that the amount of mpc RNA transcript present in EHEC was relatively limited when compared to any other genes within lee3. Taken together, when the transcription of LEE is activated, expression of mpc is tightly controlled by a restriction of the RNA transcript of mpc, translation of which is then critical for the efficient production of the operon's downstream gene products.
authors.affiliation: Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan, R.O.C.|Taiwan International Graduate Program in Molecular Medicine, Academia Sinica, Taipei, Taiwan, R.O.C.
authors.forename: Wei-Sheng W
authors.initials: WS
authors.lastname: Sun
authors.affiliation: Department of Microbiology and Immunology, National Cheng-Kung University, Tainan, Taiwan, R.O.C.
authors.forename: Jenn-Wei
authors.initials: JW
authors.lastname: Chen
authors.affiliation: Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, R.O.C.
authors.forename: Yi-Chih
authors.initials: YC
authors.lastname: Wu
authors.affiliation: Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, R.O.C.
authors.forename: Hsing-Yuan
authors.initials: HY
authors.lastname: Tsai
authors.affiliation: Department of Medical Imaging and Radiological Sciences, Chung Shan Medical University, Taichung, Taiwan, R.O.C.|Department of Medical Imaging, Chung Shan Medical University Hospital, Taichung, Taiwan, R.O.C.
authors.forename: Yu-Liang
authors.initials: YL
authors.lastname: Kuo
authors.affiliation: Taiwan International Graduate Program in Molecular Medicine, Academia Sinica, Taipei, Taiwan, R.O.C.|Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, R.O.C.
authors.forename: Wan-Jr
authors.initials: WJ
authors.lastname: Syu
mesh_terms: D054324:Enterohemorrhagic Escherichia coli / Q000235:genetics* / Q000378:metabolism; D019453:Escherichia coli O157 / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D044404:Genomic Islands; D016366:Open Reading Frames; D009876:Operon; D010957:Plasmids / Q000235:genetics; D014176:Protein Biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic
chemical_list: D029968:Escherichia coli Proteins