Regulation of transcription by the activity of the Shigella flexneri type III secretion apparatus
Regulation of transcription by the activity of the Shigella flexneri type III secretion apparatus
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DOI：
10.1046/j.1365-2958.2002.02836.x
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发表时间：
2002-03-01
影响因子：
3.6
通讯作者：
Parsot, C
中科院分区：
文献类型：
--
作者：
Mavris, M;Page, AL;Parsot, C
福氏志贺氏菌毒力质粒编码的 III 型分泌系统由 Mxi-Spa 分泌装置、参与细菌进入上皮细胞的分泌蛋白 IpaA-D 和 IpgD、细胞质伴侣 IpgC 和 IpgE 以及 15 种其他功能未知的分泌蛋白组成，包括 VirA 和 IpaH 家族的成员。 Mxi-Spa装置的活性受外部信号调节，virA和ipaH基因的转录在主动分泌的条件下被特异性诱导。我们提出的遗传证据表明，这些基因的调节涉及 MxiE（由 mxi 操纵子编码的 AraC 家族的转录激活子）和 IpgC（IpaB 和 IpaC 的伴侣）。我们还表明，MxiE 和 IpgC 一起足以激活大肠杆菌中的 virA 和 ipaH9.8 启动子。在弗氏链霉菌中，增加 IpgC 的表达导致在非分泌条件下 IpaH 产量随之增加。这表明分泌活性是通过游离 IpgC 的存在来感知的，IpgC 作为共激活剂，允许 MxiE 在其目标启动子处激活转录。
The virulence plasmid-encoded type III secretion system of Shigella flexneri consists of the Mxi-Spa secretion apparatus, secreted proteins IpaA-D and IpgD involved in entry of bacteria into epithelia] cells, cytoplasmic chaperones IpgC and IpgE and 15 other secreted proteins of unknown function, including VirA and members of the IpaH family. The activity of the Mxi-Spa apparatus is regulated by external signals, and transcription of virA and ipaH genes is specifically induced in conditions of active secretion. We present genetic evidence that regulation of these genes involves both MxiE, the transcriptional activator of the AraC family encoded by the mxi operon, and IpgC, the chaperone for IpaB and IpaC. We also show that together MxiE and IpgC are sufficient to activate virA and ipaH9.8 promoters in Escherichia coli. In S. flexneri, increasing the expression of IpgC led to a concomitant increase in IpaH production in conditions of non-secretion. This suggests that the activity of secretion is sensed by the presence of free IpgC, which acts as a coactivator to allow MxiE to activate transcription at its target promoters.