EspR, a regulator of the ESX-1 secretion system in Mycobacterium tuberculosis, is directly regulated by the two-component systems MprAB and PhoPR
EspR, a regulator of the ESX-1 secretion system in Mycobacterium tuberculosis, is directly regulated by the two-component systems MprAB and PhoPR
复制标题
EspR 是结核分枝杆菌 ESX-1 分泌系统的调节因子，直接受双组分系统 MprAB 和 PhoPR 调节
DOI：
10.1099/mic.0.000023
复制
发表时间：
2015-03-01
期刊：
影响因子：
2.8
通讯作者：
Pang, Xiuhua
中科院分区：
文献类型：
--
作者：
Cao, Guangxiang;Howard, Susan T.;Pang, Xiuhua
控制ESX-1分泌系统的调节机制，结核分枝杆菌的发病机制的关键球员，尚未完全阐明。然而，调节ESX-1底物EspA的因素通常会影响ESX-1的功能。以前的研究表明espA是直接调控的核相关蛋白EspR和双组分系统（TCS）MprAB。PhoPR TCS也激活espA，但PhoP的直接目标未知。在这份报告中，我们揭示了EspR是由MprA和PhoP-Rv直接调节，而不是由PhoP-Ra。通过凝胶移位和DNA酶I足迹测定法确定了espR启动子中的PhoP-Rv和MprA结合位点，所述DNA酶I足迹测定法鉴定了在espR起始密码子之前以约205 bp为中心的PhoP保护区，并且所述PhoP保护区包括MprA区域-1，两个MprA保护区之一。MprA区域-2位于MprA区域-1的下游约60 bp处，并与已知的EspR结合位点重叠。通过定点DNA诱变鉴定PhoP和/或MprA结合所必需的核苷酸。我们的研究还表明，MprA Region-2，而不是MprA Region-1/PhoP区域，是espR的完整表达所必需的。在MprA区域-2处携带突变的重组菌株表现出espR、espA和espD的较低转录水平，并且在细胞裂解物中具有降低的EspR和EspA水平。这些发现表明EspR可能介导PhoPR和MprAB的调节作用，并为ESX-1控制的机制提供了更多的见解。
The regulatory mechanisms that control the ESX-1 secretion system, a key player in the pathogenesis of Mycobacterium tuberculosis, have not been fully elucidated. However, factors that regulate the ESX-1 substrate EspA usually affect ESX-1 function. Previous studies showed that espA is directly regulated by the nucleoid-associated protein EspR and the two-component system (TCS) MprAB. The PhoPR TCS also activates espA, but the direct target of PhoP was unknown. In this report, we reveal that EspR is directly regulated by MprA and PhoP-Rv, but not by PhoP-Ra. PhoP-Rv and MprA binding sites in the espR promoter were determined by gel-shift and DNase I footprinting assays, which identified a PhoP-protected region centred approximately 205 bp before the espR start codon and that encompasses MprA Region-1, one of two MprA-protected regions. MprA Region-2 is located approximately 60 bp downstream of MprA Region-1 and overlaps a known EspR binding site. Nucleotides essential for the binding of PhoP and/or MprA were identified through site-directed DNA mutagenesis. Our studies also indicate that MprA Region-2, but not MprA Region-1/PhoP region, is required for the full expression of espR. Recombinant strains carrying mutations at MprA Region-2 exhibited lower transcription levels for espR, espA and espD, and had reduced EspR and EspA levels in cell lysates. These findings indicate that EspR may mediate the regulatory effect of PhoPR and MprAB, and provide more insight into the mechanisms underlying ESX-1 control.