Rosenthal Adam Z, Kim Youngbae, Gralla Jay D
Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA.
J Mol Biol. 2008 Feb 29;376(4):938-49. doi: 10.1016/j.jmb.2007.12.037. Epub 2008 Jan 16.
Bacteria must adapt their transcription to overcome the osmotic stress associated with the gastrointestinal tract of their host. This requires the sigma 38 (rpoS) form of RNA polymerase. Here, chromatin immunoprecipitation experiments show that activation is associated with a poise-and-release mechanism in vivo. A C-terminal tail unique among sigma factors is shown to be required for in vivo recruitment of RNA polymerase to the promoter region prior to osmotic shock. C-terminal domain tail-dependent transcription in vivo can be mimicked by using the intracellular signaling molecule potassium glutamate in vitro. Following signaling, the barrier to elongation into the gene body is overcome and RNA polymerase is released to produce osmY mRNA.
细菌必须调整其转录过程,以克服与宿主胃肠道相关的渗透应激。这需要RNA聚合酶的σ38(rpoS)形式。在这里,染色质免疫沉淀实验表明,激活与体内的一种 poised-and-release 机制有关。在渗透休克之前,σ因子中独特的C末端尾巴被证明是RNA聚合酶在体内募集到启动子区域所必需的。在体外使用细胞内信号分子谷氨酸钾可以模拟体内C末端结构域尾巴依赖性转录。信号传导后,延伸进入基因体的障碍被克服,RNA聚合酶被释放以产生osmY mRNA。