MacLellan Shawn R, Wecke Tina, Helmann John D
Department of Microbiology, Cornell University, Ithaca, NY 14853, USA.
Mol Microbiol. 2008 Aug;69(4):954-67. doi: 10.1111/j.1365-2958.2008.06331.x. Epub 2008 Jun 28.
We have investigated the function of a cell envelope stress-inducible gene, yvrI, which encodes a 22.5 kDa protein that includes a predicted sigma(70) region 4 domain, but lacks an apparent region 2 domain. YvrI interacts with RNA polymerase and overexpression of YvrI results in induction of OxdC, an oxalate decarboxylase maximally expressed under low-pH conditions. We have used microarray-based analyses to define the YvrI regulon. YvrI is required for the transcription of three operons (oxdC-yvrL, yvrJ and yvrI-yvrHa) each of which is preceded by a highly similar promoter sequence. Activation of these promoters requires both YvrI and the product of the second gene in the yvrI-yvrHa operon, YvrHa. YvrI and YvrHa together allow recognition of the oxdC promoter, stimulate DNA melting and activate transcription by core RNA polymerase. Together, these results suggest that YvrI is a previously unrecognized sigma factor in Bacillus subtilis and that the 9.5 kDa YvrHa protein acts as a required co-activator of transcription. A yvrL deletion results in the upregulation of YvrI activity suggesting that YvrL is a negative regulator of YvrI-dependent transcription, possibly functioning as an anti-sigma factor.
我们研究了一种细胞包膜应激诱导基因yvrI的功能，该基因编码一种22.5 kDa的蛋白质，其中包含一个预测的σ⁷⁰ 4区结构域，但缺乏明显的2区结构域。YvrI与RNA聚合酶相互作用，YvrI的过表达导致OxdC的诱导，OxdC是一种在低pH条件下最大程度表达的草酸脱羧酶。我们使用基于微阵列的分析来定义YvrI调控子。YvrI是三个操纵子（oxdC - yvrL、yvrJ和yvrI - yvrHa）转录所必需的，每个操纵子之前都有一个高度相似的启动子序列。这些启动子的激活需要YvrI和yvrI - yvrHa操纵子中第二个基因的产物YvrHa。YvrI和YvrHa共同作用可识别oxdC启动子，刺激DNA解链并通过核心RNA聚合酶激活转录。总之，这些结果表明YvrI是枯草芽孢杆菌中一个以前未被识别的σ因子，并且9.5 kDa的YvrHa蛋白作为转录所需的共激活因子发挥作用。yvrL缺失导致YvrI活性上调，这表明YvrL是YvrI依赖性转录的负调节因子，可能作为一种抗σ因子发挥作用。
