Insights into the mechanism regulating the differential expression of the P28-OMP outer membrane proteins in obligatory intracellular pathogen <i>Ehrlichia chaffeensis</i>

<i>Ehrlichia chaffeensis</i> causes human monocytic ehrlichiosis (HME), which is one of the most prevalent, life-threatening emerging infectious zoonoses. The life cycle of <i>E. chaffeensis</i> includes ticks and mammals, in which <i>E. chaffeensis</i> proteins are expressed differentially contributing to bacterial survival and infection. Among the <i>E. chaffeensis</i> P28-OMP outer membrane proteins, OMP-1B and P28 are predominantly expressed in tick cells and mammalian macrophages, respectively. The mechanisms regulating this differential expression have not been comprehensively studied. Here, we demonstrate that the transcriptional regulators EcxR and Tr1 regulate the differential expression of <i>omp-1B</i> and <i>p28</i> in <i>E. chaffeensis.</i> Recombinant <i>E. chaffeensis</i> Tr1 bound to the promoters of <i>omp-1B</i> and <i>p28,</i> and transactivated <i>omp-1B</i> and <i>p28</i> promoter-EGFP fusion constructs in <i>Escherichia coli</i>. The consensus sequence of Tr1 binding motifs was A^C/_TTATA as determined with DNase I footprint assay. Tr1 showed a higher affinity towards the <i>p28</i> promoter than the <i>omp-1B</i> promoter as determined with surface plasmon resonance. EcxR activated the <i>tr1</i> expression in response to a temperature decrease. At 37°C low level of Tr1 activated the <i>p28</i> expression. At 25°C high level of Tr1 activated the <i>omp-1B</i> expression, while repressing the <i>p28</i> expression by binding to an additional site upstream of the <i>p28</i> gene. Our data provide insights into a novel mechanism mediated by Tr1 regulating <i>E. chaffeensis</i> differential gene expression, which may aid in the development of new therapeutics for HME.

查菲埃立克体（Ehrlichia chaffeensis）可引发人类单核细胞埃立克体病（human monocytic ehrlichiosis, HME），该病是当前流行最为广泛、危及生命的新发传染性人畜共患病之一。查菲埃立克体的生活周期涉及蜱类与哺乳动物，在此过程中，该菌表达的蛋白会出现差异，这一差异有助于细菌的存活与感染。在查菲埃立克体的P28-OMP外膜蛋白家族中，OMP-1B与P28分别主要在蜱细胞和哺乳动物巨噬细胞中表达。目前，调控这种差异表达的机制尚未得到全面研究。本研究证实，转录调节因子EcxR与Tr1可调控查菲埃立克体中omp-1B与p28的差异表达。重组查菲埃立克体Tr1可结合omp-1B与p28的启动子区域，并在大肠杆菌（Escherichia coli）中反式激活omp-1B与p28启动子-增强绿色荧光蛋白（EGFP）融合构建体。通过DNase I足迹试验确定，Tr1结合基序的保守序列为A^C/_TTATA。表面等离子体共振（surface plasmon resonance）检测结果显示，相较于omp-1B启动子，Tr1对p28启动子具有更高的亲和力。EcxR可在温度降低时激活tr1的表达。在37℃条件下，低水平的Tr1可激活p28的表达。在25℃条件下，高水平的Tr1可激活omp-1B的表达，并通过结合p28基因上游的额外结合位点抑制p28的表达。本研究揭示了Tr1介导的查菲埃立克体差异基因表达的新型调控机制，可为人类单核细胞埃立克体病的新型治疗手段开发提供参考。

搜集汇总

背景与挑战

背景概述

该数据集研究专性细胞内病原体Ehrlichia chaffeensis中P28-OMP外膜蛋白的差异表达调控机制，重点揭示转录调节因子EcxR和Tr1如何在不同温度下调控omp-1B和p28基因的表达。数据集包含实验数据（如DNase I足迹测定、表面等离子共振等），旨在为开发人单核细胞埃立克体病的新疗法提供理论基础。