Staphylococcus aureus capsule polysaccharide is an important antiphagocytic virulence factor. The cap genes are regulated at the promoter element (Pcap) upstream of the cap operon. Pcap, which consists of a dominant SigB-dependent promoter and a weaker upstream SigA-dependent promoter, is activated by global regulator MgrA. How MgrA activates capsule is unclear. Here, we showed that MgrA directly bound to the Pcap region and affected the SigA-dependent promoter. Interestingly, an electrophoretic mobility shift assay showed that MgrA bound to a large region of Pcap, mainly downstream of the SigA-dependent promoter. We further showed that the ArlRS two-component system and the Agr quorum sensing system activated capsule primarily through MgrA in the early growth phases.

中文翻译：

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MgrA通过依赖SigA的启动子激活葡萄球菌胶囊

金黄色葡萄球菌荚膜多糖是重要的抗吞噬毒力因子。所述帽的基因都以启动子元件（P调节帽）上游的帽操纵子。P cap由总体SigB依赖型启动子和较弱的上游SigA依赖型启动子组成，由全局调节剂MgrA激活。MgrA如何激活胶囊尚不清楚。在这里，我们表明MgrA直接绑定到P帽区域并影响SigA依赖的启动子。有趣的是，电泳迁移率变动分析表明MgrA与P cap的较大区域结合，主要在SigA依赖性启动子的下游。我们进一步表明，在生长早期，ArlRS两组分系统和Agr群体感应系统主要通过MgrA激活了胶囊。