Division of Biological Sciences, University of Montana, Missoula, MT, USA.
Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
Mol Microbiol. 2020 Feb;113(2):399-417. doi: 10.1111/mmi.14427. Epub 2019 Dec 11.
6S RNA binds to RNA polymerase and regulates gene expression, contributing to bacterial adaptation to environmental stresses. In this study, we examined the role of 6S RNA in murine infectivity and tick persistence of the Lyme disease spirochete Borrelia (Borreliella) burgdorferi. B. burgdorferi 6S RNA (Bb6S RNA) binds to RNA polymerase, is expressed independent of growth phase or nutrient stress in culture, and is processed by RNase Y. We found that rny (bb0504), the gene encoding RNase Y, is essential for B. burgdorferi growth, while ssrS, the gene encoding 6S RNA, is not essential, indicating a broader role for RNase Y activity in the spirochete. Bb6S RNA regulates expression of the ospC and dbpA genes encoding outer surface protein C and decorin binding protein A, respectively, which are lipoproteins important for host infection. The highest levels of Bb6S RNA are found when the spirochete resides in unfed nymphs. ssrS mutants lacking Bb6S RNA were compromised for infectivity by needle inoculation, but injected mice seroconverted, indicating an ability to activate the adaptive immune response. ssrS mutants were successfully acquired by larval ticks and persisted through fed nymphs. Bb6S RNA is one of the first regulatory RNAs identified in B. burgdorferi that controls the expression of lipoproteins involved in host infectivity.
6S RNA 与 RNA 聚合酶结合，调节基因表达，有助于细菌适应环境压力。在这项研究中，我们研究了 6S RNA 在伯氏疏螺旋体（Borreliella）burgdorferi 感染小鼠和蜱虫持续感染中的作用。B. burgdorferi 6S RNA（Bb6S RNA）与 RNA 聚合酶结合，在培养物中独立于生长阶段或营养胁迫表达，并由 RNase Y 加工。我们发现，编码 RNase Y 的 rny（bb0504）基因对 B. burgdorferi 的生长是必需的，而编码 6S RNA 的 ssrS 基因不是必需的，这表明 RNase Y 活性在螺旋体中具有更广泛的作用。Bb6S RNA 调节分别编码外表面蛋白 C 和连接蛋白 A 的 ospC 和 dbpA 基因的表达，这两种脂蛋白对宿主感染很重要。当螺旋体存在于未喂食的若虫中时，Bb6S RNA 的水平最高。缺乏 Bb6S RNA 的 ssrS 突变体在通过针接种接种时的感染性受损，但注射小鼠血清转化，表明能够激活适应性免疫反应。ssrS 突变体被幼虫蜱成功获得并在喂食的若虫中持续存在。Bb6S RNA 是在 B. burgdorferi 中鉴定出的第一个控制宿主感染性相关脂蛋白表达的调节 RNA 之一。
