title: Environmental response and autoregulation of Clostridium difficile TxeR, a sigma factor for toxin gene expression.
abstract: TxeR, a sigma factor that directs Clostridium difficile RNA polymerase to recognize the promoters of two major toxin genes, was shown to stimulate its own synthesis. Whether expressed in C. difficile, Clostridium perfringens, or Escherichia coli, TxeR stimulated transcription of fusions of the txeR promoter region to reporter genes. As is the case for the tox genes, txeR expression was responsive to the cellular growth phase and the constituents of the medium. That is, the level of expression in broth culture was low during the exponential growth phase, but rapidly increased as cells approached the stationary phase. In the presence of excess glucose, expression from the txeR promoter was repressed. The results support a model for toxin gene expression in which synthesis of TxeR is induced by specific environmental signals. The increased level of TxeR then permits high-level expression of the toxin genes. The study of txeR gene regulation in C. difficile was made possible by introduction of a mobilizable, replicative plasmid via conjugation with E. coli.
authors.affiliation: Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
authors.forename: Nagraj
authors.initials: N
authors.lastname: Mani
authors.forename: Dena
authors.initials: D
authors.lastname: Lyras
authors.forename: Lisa
authors.initials: L
authors.lastname: Barroso
authors.forename: Pauline
authors.initials: P
authors.lastname: Howarth
authors.forename: Tracy
authors.initials: T
authors.lastname: Wilkins
authors.forename: Julian I
authors.initials: JI
authors.lastname: Rood
authors.forename: Abraham L
authors.initials: AL
authors.lastname: Sonenshein
authors.forename: Bruno
authors.initials: B
authors.lastname: Dupuy
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D016360:Clostridioides difficile / Q000235:genetics*; D003016:Clostridium perfringens / Q000235:genetics / Q000254:growth & development; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004777:Environment; D004926:Escherichia coli; D015964:Gene Expression Regulation, Bacterial; D006706:Homeostasis; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D001426:Bacterial Proteins; D012808:Sigma Factor; D012321:DNA-Directed RNA Polymerases