The Mycobacterium tuberculosis phoPR Operon Is Positively Autoregulated in the Virulent Strain H37Rv
The Mycobacterium tuberculosis phoPR Operon Is Positively Autoregulated in the Virulent Strain H37Rv
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DOI：
10.1128/jb.00712-08
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发表时间：
2008-11-01
影响因子：
3.2
通讯作者：
Martin, Carlos
中科院分区：
文献类型：
--
作者：
Gonzalo-Asensio, Jesus;Soto, Carlos Y.;Martin, Carlos
减毒结核分枝杆菌 H37Ra 菌株是强毒力范例菌株 H37Rv 的同基因对应物。最近，PhoP 转录调节因子的点突变与 H37Ra 的无毒力之间存在联系。值得注意的是，之前的一项研究表明 H37Ra 中 phoP 基因的负向自动调节。这些发现促使我们研究强毒 H37Rv 菌株中 PhoP 的转录自动调节。与之前针对 H37Ra 发表的 PhoP 的负向自动调节相反，我们使用 phoP 启动子-lacZ 融合的实验表明，与本研究中构建的 H37Rv phoP 缺失突变体相比，PhoP 在 H37Rv 和 H37Ra 中均呈正向自动调节。通过定量逆转录 PCR (RT-PCR) 分析，我们发现 phoP 基因在 H37Rv 和 H37Ra 中的转录水平相似。凝胶迁移率变化和 DNase I 足迹分析使我们能够识别 PhoP 从 H37Rv 到 phoP 启动子的精确结合区域。我们还进行了 RT-PCR 研究，以证明 phoP 与相邻基因 phoR 一起转录，后者编码 phoPR 双组分系统的同源组氨酸激酶。此外，定量RT-PCR研究表明phoR是从可能受PhoP调节的启动子独立转录的。最后，我们讨论了在 H37Ra 减毒株的 phoP 基因中发现的单点突变对毒力的可能作用，但在结核分枝杆菌复合体的强毒成员中却没有。
The attenuated Mycobacterium tuberculosis H37Ra strain is an isogenic counterpart of the virulent paradigm strain H37Rv. Recently, a link between a point mutation in the PhoP transcriptional regulator and avirulence of H37Ra was established. Remarkably, a previous study demonstrated negative autoregulation of the phoP gene in H37Ra. These findings led us to study the transcriptional autoregulation of PhoP in the virulent H37Rv strain. In contrast to the negative autoregulation of PhoP previously published for H37Ra, our experiments using a phoP promoter-lacZ fusion showed that PhoP is positively autoregulated in both H37Rv and H37Ra compared with an H37Rv phoP deletion mutant constructed in this study. Using quantitative reverse transcription-PCR (RT-PCR) analysis, we showed that the phoP gene is transcribed at similar levels in H37Rv and H37Ra. Gel mobility shift and DNase I footprinting assays allowed us to identify the precise binding region of PhoP from H37Rv to the phoP promoter. We also carried out RT-PCR studies to demonstrate that phoP is transcribed together with the adjacent gene phoR, which codes for the cognate histidine kinase of the phoPR two-component system. In addition, quantitative RT-PCR studies showed that phoR is independently transcribed from a promoter possibly regulated by PhoP. Finally, we discuss the possible role in virulence of a single point mutation found in the phoP gene from the attenuated H37Ra strain but not in virulent members of the M. tuberculosis complex.