Lim Sangyong, Kim Byeongkwan, Choi Hyun-Sook, Lee Younghoon, Ryu Sangryeol
Radiation Food Science & Biotechnology Team, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185, Korea.
Microb Pathog. 2006 Jul;41(1):33-42. doi: 10.1016/j.micpath.2006.03.005. Epub 2006 Jun 13.
Salmonella pathogenicity island 2 (SPI2) encodes a type III secretion system (TTSS) necessary for bacterial survival and replication in intracellular environment of host cells. SPI2 genes are transcribed preferentially after Salmonella enters the host cells. Transcriptional regulation of ssaG encoding the component of SPI2-TTSS apparatus was studied in vivo and in vitro. Fis, one of the major components of bacterial nucleoid, activated the stationary phase-specific expression of ssaG when Salmonella was grown in LB media. Gel-shift and footprinting analysis showed Fis bound to four distinct sites of the ssaG promoter region with different affinities. All four Fis-binding sites were required for timely transcription activation of ssaG after Salmonella entered macrophage cells. Gentamicin protection experiments using bacteria grown to stationary phase prior to infection showed that the ability of the fis mutant strain to replicate within the RAW264.7 macrophage cells was lower than the wild type. These observations confirm that Fis plays an important role in regulations of SPI2 as well as SPI1 for an efficient regulation of the virulence genes.
沙门氏菌致病岛2（SPI2）编码一种III型分泌系统（TTSS），这是细菌在宿主细胞内环境中存活和复制所必需的。SPI2基因在沙门氏菌进入宿主细胞后优先转录。对编码SPI2-TTSS装置组件的ssaG进行了体内和体外转录调控研究。Fis是细菌类核的主要成分之一，当沙门氏菌在LB培养基中生长时，它激活了ssaG的稳定期特异性表达。凝胶迁移和足迹分析表明，Fis以不同亲和力结合到ssaG启动子区域的四个不同位点。沙门氏菌进入巨噬细胞后，ssaG的及时转录激活需要所有四个Fis结合位点。使用感染前生长至稳定期的细菌进行的庆大霉素保护实验表明，fis突变株在RAW264.7巨噬细胞内复制的能力低于野生型。这些观察结果证实，Fis在SPI2以及SPI1的调控中发挥重要作用，以有效调控毒力基因。
