Department of Microbiology, Cornell University, 370 Wing Hall, Ithaca, NY 14853-8101, USA.
Proc Natl Acad Sci U S A. 2009 Dec 15;106(50):21323-8. doi: 10.1073/pnas.0910006106. Epub 2009 Nov 25.
The sigma-like factor YvrI and coregulator YvrHa activate transcription from a small set of conserved promoters in Bacillus subtilis. We report here that these two proteins independently contribute sigma-region 2 and sigma-region 4 functions to a holoenzyme-promoter DNA complex. YvrI binds RNA polymerase (RNAP) through a region 4 interaction with the beta-subunit flap domain and mediates specific promoter recognition but cannot initiate DNA melting at the -10 promoter element. Conversely, YvrHa possesses sequence similarity to a conserved core-binding motif in sigma-region 2 and binds to the N-terminal coiled-coil element in the RNAP beta'-subunit previously implicated in interaction with region 2 of sigma-factors. YvrHa plays an essential role in stabilizing the open complex and interacts specifically with the N-terminus of YvrI. Based on these results, we propose that YvrHa is situated in the transcription complex proximal to the -10 element of the promoter, whereas YvrI is responsible for -35 region recognition. This system presents an unusual example of a two-subunit bacterial sigma-factor.
类似西格玛的因子 YvrI 和共调节因子 YvrHa 在枯草芽孢杆菌中激活一组保守启动子的转录。我们在此报告称，这两种蛋白质独立地为全酶启动子 DNA 复合物贡献了 sigma 区 2 和 sigma 区 4 的功能。YvrI 通过与 beta 亚基瓣结构域的区域 4 相互作用与 RNA 聚合酶 (RNAP) 结合，并介导特异性启动子识别，但不能在 -10 启动子元件处起始 DNA 熔解。相反，YvrHa 与 sigma 区 2 中的保守核心结合基序具有序列相似性，并与先前涉及与 sigma 因子的区域 2 相互作用的 RNAP beta'-亚基中的 N 端卷曲螺旋元件结合。YvrHa 在稳定开放复合物方面发挥着重要作用，并与 YvrI 的 N 端特异性相互作用。基于这些结果，我们提出 YvrHa 位于转录复合物中靠近启动子 -10 元件的位置，而 YvrI 负责 -35 区域识别。该系统呈现了一种不寻常的二亚基细菌 sigma 因子的例子。
