Institute for Infectiology, Center for Molecular Biology of Inflammation (ZMBE), University of Münster, Münster, Germany.
Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany.
PLoS Pathog. 2024 Aug 19;20(8):e1011965. doi: 10.1371/journal.ppat.1011965. eCollection 2024 Aug.
RNA degradation is an essential process that allows bacteria to regulate gene expression and has emerged as an important mechanism for controlling virulence. However, the individual contributions of RNases in this process are mostly unknown. Here, we tested the influence of 11 potential RNases in the intestinal pathogen Yersinia pseudotuberculosis on the expression of its type III secretion system (T3SS) and associated effectors (Yops) that are encoded on the Yersinia virulence plasmid. We found that exoribonuclease PNPase and endoribonuclease RNase III inhibit T3SS and yop gene transcription by repressing the synthesis of LcrF, the master activator of Yop-T3SS. Loss of both RNases led to an increase in lcrF mRNA levels. Our work indicates that PNPase exerts its influence via YopD, which accelerates lcrF mRNA degradation. Loss of RNase III, on the other hand, results in the downregulation of the CsrB and CsrC RNAs, thereby increasing the availability of active CsrA, which has been shown previously to enhance lcrF mRNA translation and stability. This CsrA-promoted increase of lcrF mRNA translation could be supported by other factors promoting the protein translation efficiency (e.g. IF-3, RimM, RsmG) that were also found to be repressed by RNase III. Transcriptomic profiling further revealed that Ysc-T3SS-mediated Yop secretion leads to global reprogramming of the Yersinia transcriptome with a massive shift of the expression from chromosomal to virulence plasmid-encoded genes. A similar reprogramming was also observed in the RNase III-deficient mutant under non-secretion conditions. Overall, our work revealed a complex control system where RNases orchestrate the expression of the T3SS/Yop machinery on multiple levels to antagonize phagocytic uptake and elimination by innate immune cells.
RNA 降解是一种重要的过程，它允许细菌调节基因表达，并已成为控制毒力的重要机制。然而，该过程中 RNase 的个体贡献大多未知。在这里，我们测试了 11 种潜在的 RNase 在肠道病原体假结核耶尔森氏菌中的影响，这些 RNase 对其 III 型分泌系统（T3SS）和相关效应物（Yops）的表达有影响，这些基因编码在耶尔森氏菌毒力质粒上。我们发现，外切核酸酶 PNPase 和内切核酸酶 RNase III 通过抑制 LcrF（Yop-T3SS 的主激活剂）的合成来抑制 T3SS 和 yop 基因的转录。这两种 RNase 的缺失导致 lcrF mRNA 水平的增加。我们的工作表明，PNPase 通过 YopD 发挥其影响，YopD 加速了 lcrF mRNA 的降解。另一方面，RNase III 的缺失导致 CsrB 和 CsrC RNA 的下调，从而增加了活性 CsrA 的可用性，先前的研究表明 CsrA 增强了 lcrF mRNA 的翻译和稳定性。这种 CsrA 促进的 lcrF mRNA 翻译的增加可以得到其他促进蛋白质翻译效率的因素的支持（例如 IF-3、RimM、RsmG），这些因素也被发现受到 RNase III 的抑制。转录组谱分析进一步表明，Ysc-T3SS 介导的 Yop 分泌导致耶尔森氏菌转录组的全局重编程，从染色体基因到毒力质粒编码基因的表达发生了巨大转变。在非分泌条件下，RNase III 缺陷突变体也观察到类似的重编程。总的来说，我们的工作揭示了一个复杂的控制系统，其中 RNase 在多个层面上协调 T3SS/Yop 机制的表达，以拮抗先天免疫细胞的吞噬作用和消除作用。
