Loss of RNase R Induces Competence Development in Legionella pneumophila
Loss of RNase R Induces Competence Development in Legionella pneumophila
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DOI：
10.1128/jb.01035-08
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发表时间：
2008-12-01
影响因子：
3.2
通讯作者：
Shuman, Howard A.
中科院分区：
文献类型：
--
作者：
Charpentier, Xavier;Faucher, Sebastien P.;Shuman, Howard A.
RNase R 是一种持续进行的 3'-5' 核糖核酸外切酶，在原核生物中具有高度保守性。尽管一些细菌具有额外的水解 3'-5' 核糖核酸外切酶（例如 RNase II），但人们发现 RNase R 是兼性细胞内病原体嗜肺军团菌中唯一预测的酶。这提供了一个独特的机会来研究 RNase R 在缺乏具有类似酶活性的额外 RNase 的情况下的作用。我们研究了 RNase R 在不同条件下嗜肺军团菌生物学中的作用，并使用微阵列进行了基因表达谱分析。在最佳生长温度下，RNase R 的缺失对细菌生长没有重大影响，但对正常基因调控有中等影响。然而，在较低温度下，RNase R 的缺失对细菌生长产生显着影响，并导致结构化 RNA 降解产物的积累。同时，基因调控受到影响，特别导致能力调节子表达增加。 RNase R 核糖核酸外切酶活性的丧失足以诱导能力发展，这是一种基因编程过程，通常作为对环境刺激的反应而触发。研究发现，rnr 突变体中能力基因的温度依赖性表达与之前在嗜肺军团菌中鉴定的能力调节因子无关。我们认为 RNase R 的生理作用是消除低温稳定的结构化 RNA 分子，这反过来可能影响调节网络，损害对寒冷的适应，从而导致活力下降。
RNase R is a processive 3'-5' exoribonuclease with a high degree of conservation in prokaryotes. Although some bacteria possess additional hydrolytic 3'-5' exoribonucleases such as RNase II, RNase R was found to be the only predicted one in the facultative intracellular pathogen Legionella pneumophila. This provided a unique opportunity to study the role of RNase R in the absence of an additional RNase with similar enzymatic activity. We investigated the role of RNase R in the biology of Legionella pneumophila under various conditions and performed gene expression profiling using microarrays. At optimal growth temperature, the loss of RNase R had no major consequence on bacterial growth and had a moderate impact on normal gene regulation. However, at a lower temperature, the loss of RNase R had a significant impact on bacterial growth and resulted in the accumulation of structured RNA degradation products. Concurrently, gene regulation was affected and specifically resulted in an increased expression of the competence regulon. Loss of the exoribonuclease activity of RNase R was sufficient to induce competence development, a genetically programmed process normally triggered as a response to environmental stimuli. The temperature-dependent expression of competence genes in the rnr mutant was found to be independent of previously identified competence regulators in Legionella pneumophila. We suggest that a physiological role of RNase R is to eliminate structured RNA molecules that are stabilized by low temperature, which in turn may affect regulatory networks, compromising adaptation to cold and thus resulting in decreased viability.