Yasumura Ayako, Abe Sadanobu, Tanaka Teruo
Institute of Oceanic Research and Development, Tokai University, Orido 3-20-1, Shimizu-ku, Shizuoka 424-8610, Japan.
J Bacteriol. 2008 Aug;190(15):5162-71. doi: 10.1128/JB.00368-08. Epub 2008 May 23.
Bacillus subtilis DegS-DegU belongs to a bacterial two-component system that controls many processes, including the production of exocellular proteases and competence development. It was found that when the glutamine synthetase gene glnA, which is involved in nitrogen regulation, was disrupted, the expression of the response regulator degU gene was increased. Deletion analysis and 5'-end mapping of the degU transcripts showed that the increase was caused by induction of a promoter (P2) located before the degU gene. Disruption of tnrA, a global regulator of nitrogen regulation, eliminated the P2 promoter induction by the glnA mutation. The fact that the P2 promoter is under nitrogen regulation was demonstrated by an increase in P2 expression with nitrogen-limited growth. It was also found by primer extension analysis that degU was transcribed by another promoter, P3, that is located downstream of P2. Efficient expression of P3 was dependent on phosphorylated DegU, as inactivation of the sensor kinase gene, degS, resulted in the loss of degU expression, although less efficient stimulation of degU expression was also observed with an enhanced level of DegU in a degS-deficient mutant. The promoter located upstream of the degSU operon, designated the P1 promoter here, was insensitive to glnA and degU mutations. These results suggest that degU expression is controlled by the three promoters under different growth conditions.
枯草芽孢杆菌DegS - DegU属于一种细菌双组分系统，该系统控制着许多过程，包括胞外蛋白酶的产生和感受态发育。研究发现，当参与氮调节的谷氨酰胺合成酶基因glnA被破坏时，反应调节因子degU基因的表达会增加。对degU转录本的缺失分析和5'端定位表明，这种增加是由位于degU基因之前的一个启动子（P2）的诱导引起的。氮调节全局调节因子tnrA的破坏消除了glnA突变对P2启动子的诱导作用。通过在氮限制生长条件下P2表达的增加证明了P2启动子受氮调节。通过引物延伸分析还发现，degU由另一个位于P2下游的启动子P3转录。P3的有效表达依赖于磷酸化的DegU，因为传感器激酶基因degS的失活导致degU表达丧失，尽管在degS缺陷突变体中DegU水平增强时也观察到对degU表达的低效刺激。位于degSU操纵子上游的启动子，在此处称为P1启动子，对glnA和degU突变不敏感。这些结果表明，degU的表达在不同生长条件下受这三个启动子的控制。
