Identification and Characterization of a Phase-Variable Element That Regulates the Autotransporter UpaE in Uropathogenic Escherichia coli
Identification and Characterization of a Phase-Variable Element That Regulates the Autotransporter UpaE in Uropathogenic Escherichia coli
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DOI：
10.1128/mbio.01360-18
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发表时间：
2018-07-01
期刊：
影响因子：
6.4
通讯作者：
Welch, R. A.
中科院分区：
文献类型：
--
作者：
Battaglioli, E. J.;Goh, K. G. K.;Welch, R. A.
尿路致病性大肠杆菌 (UPEC) 是单纯性尿路感染 (UTI) 最常见的病原体。 UPEC 中基因调控的一个重要机制是相变，涉及通过酪氨酸重组酶的酶活性反转包含启动子的 DNA 元件，从而导致目标基因的双相、ON 或 OFF 表达。 UPEC 参考菌株 CFT073 具有五种酪氨酸位点特异性重组酶，它们在两个先前表征的启动子倒置系统 fimS 和 hyxS 中发挥作用。五种重组酶中的三种位于其同源靶元件附近，这是启动子倒位系统的典型特征。其他两种重组酶 IpuA 和 IpuB 的基因位于远离这些位点的位置。在这里，我们识别并表征了 CFT073 中的第三个相变可逆元件 ipuS，位于 ipuA 和 ipuB 附近。 ipuS 的倒转由五个 CFT073 重组酶中的四个催化。该元件的方向驱动双基因操纵子的转录，其中包含 ipuR（一种预测的 LuxR 型调节因子）和 upaE（一种预测的自转运蛋白）。我们表明，预测的自转运蛋白 UpaE 位于表面，促进生物膜形成以及 K-12 重组背景中细胞外基质蛋白的粘附。与这种表型一致，CFT073 中的 ipuS ON 条件会导致游泳运动缺陷、对人肾上皮细胞的粘附增加以及实验性小鼠 UTI 中的积极竞争性肾脏定植优势。总体而言，UPEC 中由一组共享重组酶调节的第三相开关的识别描述了 UPEC 中复杂的相变毒力网络。 重要性 尿路致病性大肠杆菌 (UPEC) 是尿路感染 (UTI) 的最常见原因。通过 UPEC 中两个染色体位点的小 DNA 元件的倒转进行 ON 与 OFF 相转换，调节重要毒力因子的表达，包括 1 型菌毛粘附细胞器。在本报告中，我们描述了 UPEC 参考菌株 CFT073 中的第三种可逆元件 ipuS。 ipuS 的反转控制着 upaE 的相变表达，upaE 是一种自转运蛋白基因，编码一种表面蛋白，参与尿路感染小鼠模型中细胞外基质蛋白的粘附和肾脏的定植。
Uropathogenic Escherichia coli (UPEC) is the most common etiologic agent of uncomplicated urinary tract infection (UTI). An important mechanism of gene regulation in UPEC is phase variation that involves inversion of a promoter-containing DNA element via enzymatic activity of tyrosine recombinases, resulting in biphasic, ON or OFF expression of target genes. The UPEC reference strain CFT073 has five tyrosine site-specific recombinases that function at two previously characterized promoter inversion systems, fimS and hyxS. Three of the five recombinases are located proximally to their cognate target elements, which is typical of promoter inversion systems. The genes for the other two recombinases, IpuA and IpuB, are located distal from these sites. Here, we identified and characterized a third phase-variable invertible element in CFT073, ipuS, located proximal to ipuA and ipuB. The inversion of ipuS is catalyzed by four of the five CFT073 recombinases. Orientation of the element drives transcription of a two-gene operon containing ipuR, a predicted LuxR-type regulator, and upaE, a predicted autotransporter. We show that the predicted autotransporter UpaE is surface located and facilitates biofilm formation as well as adhesion to extracellular matrix proteins in a K-12 recombinant background. Consistent with this phenotype, the ipuS ON condition in CFT073 results in defective swimming motility, increased adherence to human kidney epithelial cells, and a positive competitive kidney colonization advantage in experimental mouse UTIs. Overall, the identification of a third phase switch in UPEC that is regulated by a shared set of recombinases describes a complex phase-variable virulence network in UPEC.IMPORTANCE Uropathogenic Escherichia coil (UPEC) is the most common cause of urinary tract infection (UTI). ON versus OFF phase switching by inversion of small DNA elements at two chromosome sites in UPEC regulates the expression of important virulence factors, including the type 1 fimbria adhesion organelle. In this report, we describe a third invertible element, ipuS, in the UPEC reference strain CFT073. The inversion of ipuS controls the phase-variable expression of upaE, an autotransporter gene that encodes a surface protein involved in adherence to extracellular matrix proteins and colonization of the kidneys in a murine model of UTI.