title: Targeted mutagenesis of intergenic regions in the Neisseria gonorrhoeae gonococcal genetic island reveals multiple regulatory mechanisms controlling type IV secretion.
abstract: Gonococci secrete chromosomal DNA into the extracellular environment using a type IV secretion system (T4SS). The secreted DNA acts in natural transformation and initiates biofilm development. Although the DNA and its effects are detectable, structural components of the T4SS are present at very low levels, suggestive of uncharacterized regulatory control. We sought to better characterize the expression and regulation of T4SS genes and found that the four operons containing T4SS genes are transcribed at very different levels. Increasing transcription of two of the operons through targeted promoter mutagenesis did not increase DNA secretion. The stability and steady-state levels of two T4SS structural proteins were affected by a homolog of tail-specific protease. An RNA switch was also identified that regulates translation of a third T4SS operon. The switch mechanism relies on two putative stem-loop structures contained within the 5' untranslated region of the transcript, one of which occludes the ribosome binding site and start codon. Mutational analysis of these stem loops supports a model in which induction of an alternative structure relieves repression. Taken together, these results identify multiple layers of regulation, including transcriptional, translational and post-translational mechanisms controlling T4SS gene expression and DNA secretion.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA.
authors.forename: Meghan E
authors.initials: ME
authors.lastname: Ramsey
authors.affiliation: Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bender
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA.
authors.forename: Amy K
authors.initials: AK
authors.lastname: Klimowicz
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA.
authors.forename: Kathleen T
authors.initials: KT
authors.lastname: Hackett
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA.
authors.forename: Ami
authors.initials: A
authors.lastname: Yamamoto
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA.
authors.forename: Adrienne
authors.initials: A
authors.lastname: Jolicoeur
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA.
authors.forename: Melanie M
authors.initials: MM
authors.lastname: Callaghan
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Wassarman
authors.affiliation: Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.
authors.forename: Chris
authors.initials: C
authors.lastname: van der Does
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Dillard
mesh_terms: D020121:5' Untranslated Regions; D001426:Bacterial Proteins / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D021901:DNA, Intergenic; D010450:Endopeptidases / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D056426:Genetic Loci; D016296:Mutagenesis; D009344:Neisseria gonorrhoeae / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D059748:Proteolysis; D000069319:Type IV Secretion Systems / Q000235:genetics / Q000378:metabolism*
chemical_list: D020121:5' Untranslated Regions; D001426:Bacterial Proteins; D021901:DNA, Intergenic; D000069319:Type IV Secretion Systems; D004247:DNA; D010450:Endopeptidases; C072135:C-terminal processing peptidase