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A horizontally acquired Legionella genomic island encoding a LuxR type regulator and effector proteins displays variation in gene content and regulation
Molecular Microbiology ( IF 3.6 ) Pub Date : 2021-06-13 , DOI: 10.1111/mmi.14770
Marika Linsky 1 , Gil Segal 1
Affiliation  

The intracellular pathogen Legionella pneumophila translocates >300 effector proteins into host cells, many of which are regulated at the transcriptional level. Here, we describe a novel L. pneumophila genomic island, which undergoes horizontal gene transfer within the Legionella genus. This island encodes two Icm/Dot effectors: LegK3 and a previously uncharacterized effector which we named CegK3, as well as a LuxR type regulator, which we named RegK3. Analysis of this island in different Legionella species revealed a conserved regulatory element located upstream to the effector-encoding genes in the island. Further analyses, including gene expression analysis, mutagenesis of the RegK3 regulatory element, controlled expression studies, and gel-mobility shift assays, all demonstrate that RegK3 directly activates the expression levels of legK3 and cegK3 effector-encoding genes. Additionally, the expression of all the components of the island is silenced by the Fis repressors. Comparison of expression profiles of these three genes among different Legionella species revealed variability in the activation levels mediated by RegK3, which were positively correlated with the Fis-mediated repression. Furthermore, LegK3 and CegK3 effectors moderately inhibit yeast growth, and importantly, they have a strong synergistic inhibitory effect on yeast growth, suggesting these two effectors are not only co-regulated but also might function together.

中文翻译:

编码 LuxR 型调节剂和效应蛋白的水平获得的军团菌基因组岛显示出基因含量和调节的变化

细胞内病原体嗜肺军团菌将 >300 种效应蛋白转运到宿主细胞中,其中许多在转录水平受到调节。在这里,我们描述了一部小说L。pneumophila基因组岛,在军团菌属内进行水平基因转移。这个岛编码了两个 Icm/Dot 效应器:LegK3 和我们命名为 CegK3 的先前未表征的效应器,以及我们命名为 RegK3 的 LuxR 型调节器。不同军团菌对该岛的分析物种揭示了位于岛上效应子编码基因上游的保守调节元件。进一步的分析,包括基因表达分析、RegK3 调控元件的诱变、受控表达研究和凝胶迁移率测定,都表明 RegK3 直接激活legK3cegK3效应子编码基因的表达水平。此外,岛上所有成分的表达都被 Fis 阻遏物沉默了。这三个基因在不同军团菌中的表达谱比较物种揭示了 RegK3 介导的激活水平的变异性,这与 Fis 介导的抑制呈正相关。此外,LegK3 和 CegK3 效应子适度抑制酵母生长,重要的是,它们对酵母生长具有很强的协同抑制作用,这表明这两种效应子不仅是共同调节的,而且可能一起发挥作用。
更新日期:2021-06-13
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