WhiB6 regulation of ESX-1 gene expression is controlled by a negative feedback loop in Mycobacterium marinum
WhiB6 regulation of ESX-1 gene expression is controlled by a negative feedback loop in Mycobacterium marinum
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DOI：
10.1073/pnas.1710167114
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发表时间：
2017-12-12
影响因子：
11.1
通讯作者：
Champion, Patricia A.
中科院分区：
文献类型：
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作者：
Bosserman, Rachel E.;Nguyen, Tiffany T.;Champion, Patricia A.
ESX（ESAT-6系统）输出系统在分枝杆菌物种中发挥着不同的作用。有趣的是，不同物种中ESX系统的遗传破坏不会导致分枝杆菌细胞中蛋白质底物的积累。然而，这一观察结果背后的机制是难以捉摸的。我们假设ESX底物的水平受反馈控制机制的调节，将底物的水平与ESX系统的分泌状态联系起来。为了验证这一假设，我们结合使用遗传学、转录组学和蛋白质组学方法来定义调节海分枝杆菌中ESX-1底物水平的输出依赖性机制。WhiB 6是调节编码ESX-1底物的基因表达的转录因子。我们发现，在不存在编码ESX-1系统的保守膜组分的基因的情况下，whiB 6基因和编码ESX-1底物的基因的表达降低。因此，ESX-1底物水平降低，在M中未检测到WhiB 6。缺乏编码ESX-1组分的基因的海洋菌株。我们证明，在缺乏EccCb（1）（一种保守的ESX-1组分）的情况下，底物基因的表达通过whiB 6基因的组成型而非天然表达得以恢复。最后，我们发现WhiB 6的缺失导致了一种有毒的M。具有减少的ESX-1分泌的海洋细菌菌株。总之，我们的研究结果表明，M. marinum通过负反馈控制进行微调，将whiB 6基因的表达与ESX-1膜复合物的存在而非功能联系起来。
ESX (ESAT-6 system) export systems play diverse roles across mycobacterial species. Interestingly, genetic disruption of ESX systems in different species does not result in an accumulation of protein substrates in the mycobacterial cell. However, the mechanisms underlying this observation are elusive. We hypothesized that the levels of ESX substrates were regulated by a feedback-control mechanism, linking the levels of substrates to the secretory status of ESX systems. To test this hypothesis, we used a combination of genetic, transcriptomic, and proteomic approaches to define export-dependent mechanisms regulating the levels of ESX-1 substrates in Mycobacterium marinum. WhiB6 is a transcription factor that regulates expression of genes encoding ESX-1 substrates. We found that, in the absence of the genes encoding conserved membrane components of the ESX-1 system, the expression of the whiB6 gene and genes encoding ESX-1 substrates were reduced. Accordingly, the levels of ESX-1 substrates were decreased, and WhiB6 was not detected in M. marinum strains lacking genes encoding ESX-1 components. We demonstrated that, in the absence of EccCb(1), a conserved ESX-1 component, substrate gene expression was restored by constitutive, but not native, expression of the whiB6 gene. Finally, we found that the loss of WhiB6 resulted in a virulent M. marinum strain with reduced ESX-1 secretion. Together, our findings demonstrate that the levels of ESX-1 substrates in M. marinum are fine-tuned by negative feedback control, linking the expression of the whiB6 gene to the presence, not the functionality, of the ESX-1 membrane complex.