title: The MogR transcriptional repressor regulates nonhierarchal expression of flagellar motility genes and virulence in Listeria monocytogenes.
abstract: Flagella are surface structures critical for motility and virulence of many bacterial species. In Listeria monocytogenes, MogR tightly represses expression of flagellin (FlaA) during extracellular growth at 37 degrees C and during intracellular infection. MogR is also required for full virulence in a murine model of infection. Using in vitro and in vivo infection models, we determined that the severe virulence defect of MogR-negative bacteria is due to overexpression of FlaA. Specifically, overproduction of FlaA in MogR-negative bacteria caused pleiotropic defects in bacterial division (chaining phenotype), intracellular spread, and virulence in mice. DNA binding and microarray analyses revealed that MogR represses transcription of all known flagellar motility genes by binding directly to a minimum of two TTTT-N5-AAAA recognition sites positioned within promoter regions such that RNA polymerase binding is occluded. Analysis of MogR protein levels demonstrated that modulation of MogR repression activity confers the temperature-specificity to flagellar motility gene expression. Epistasis analysis revealed that MogR repression of transcription is antagonized in a temperature-dependent manner by the DegU response regulator and that DegU further regulates FlaA levels through a posttranscriptional mechanism. These studies provide the first known example to our knowledge of a transcriptional repressor functioning as a master regulator controlling nonhierarchal expression of flagellar motility genes.
authors.affiliation: Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Aimee
authors.initials: A
authors.lastname: Shen
authors.forename: Darren E
authors.initials: DE
authors.lastname: Higgins
mesh_terms: D000818:Animals; D002460:Cell Line; D005407:Flagella / Q000502:physiology*; D005408:Flagellin / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D007928:Lethal Dose 50; D008089:Listeria monocytogenes / Q000235:genetics* / Q000472:pathogenicity*; D051379:Mice; D046228:Microarray Analysis; D009068:Movement / Q000502:physiology; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics*; D014774:Virulence / Q000235:genetics
chemical_list: D012097:Repressor Proteins; D005408:Flagellin; C067138:flaA protein, bacteria