Mani Nagraj, Lyras Dena, Barroso Lisa, Howarth Pauline, Wilkins Tracy, Rood Julian I, Sonenshein Abraham L, Dupuy Bruno
Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
J Bacteriol. 2002 Nov;184(21):5971-8. doi: 10.1128/JB.184.21.5971-5978.2002.
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.
TxeR是一种sigma因子，可引导艰难梭菌RNA聚合酶识别两个主要毒素基因的启动子，研究表明它能刺激自身的合成。无论在艰难梭菌、产气荚膜梭菌还是大肠杆菌中表达，TxeR都能刺激txeR启动子区域与报告基因融合体的转录。与tox基因的情况一样，txeR的表达对细胞生长阶段和培养基成分有反应。也就是说，在肉汤培养中，指数生长期的表达水平较低，但随着细胞接近稳定期，表达迅速增加。在葡萄糖过量的情况下，txeR启动子的表达受到抑制。这些结果支持了一种毒素基因表达模型，即TxeR的合成由特定环境信号诱导。然后，TxeR水平的增加使得毒素基因能够高水平表达。通过与大肠杆菌接合引入可移动的复制性质粒，使得对艰难梭菌中txeR基因调控的研究成为可能。
