Gene Regulation Lab, Department of Biosciences and Bioengineering, Indian Institute of Technology (IIT) Bombay, Powai, Mumbai 400 076, India.
J Biosci. 2013 Jun;38(2):291-9. doi: 10.1007/s12038-013-9309-8.
Bacillus subtilis under nutritional deprivation exhibits several physiological responses such as synthesis of degradative enzymes, motility, competence, sporulation, etc. At the onset of post-exponential phase the global response regulator, Spo0A, directly or indirectly activates the expression of genes involved in the above processes. These genes are repressed during the exponential phase by a group of proteins called transition state regulators, e.g. AbrB, ScoC and SinR. One such post-exponentially expressed gene is epr, which encodes a minor extracellular serine protease and is involved in the swarming motility of B. subtilis. Deletion studies of the upstream region of epr promoter revealed that epr is co-repressed by transition state regulators, SinR and ScoC. Our study shows that Spo0A positively regulates epr expression by nullifying the repressive effect of co-repressors, SinR and ScoC. We demonstrate via in vitro mobility shift assays that Spo0A binds to the upstream region of epr promoter and in turn occludes the binding site of one of the co-repressor, SinR. This explains the mechanism behind the positive regulatory effect of Spo0A on epr expression.
在营养剥夺的情况下，枯草芽孢杆菌会表现出几种生理反应，如合成降解酶、运动性、感受态、孢子形成等。在指数后期开始时，全局调控因子 Spo0A 直接或间接地激活了上述过程中涉及的基因的表达。在指数期，一组称为过渡态调控因子的蛋白质会抑制这些基因的表达，例如 AbrB、ScoC 和 SinR。epr 就是这样一个在指数后期表达的基因，它编码一种次要的细胞外丝氨酸蛋白酶，参与枯草芽孢杆菌的 swarm 运动。epr 启动子上游区域的缺失研究表明，SinR 和 ScoC 共同抑制 epr 的表达。我们的研究表明，Spo0A 通过消除共同抑制因子 SinR 和 ScoC 的抑制作用来正向调控 epr 的表达。我们通过体外迁移率变动分析证明，Spo0A 结合在 epr 启动子的上游区域，从而阻断了其中一个共同抑制因子 SinR 的结合位点。这解释了 Spo0A 对 epr 表达的正向调控作用的机制。
