Regulation of EHEC virulence genes by QseA and small RNA molecules

描述（由申请人提供）：肠出血性大肠杆菌（EHEC） O157:H7在世界各地引起血性腹泻和溶血性尿毒症系统（HUS）。肠出血性大肠杆菌的感染剂量很低，因此很难在流行病学上加以控制。肠出血性大肠杆菌在大肠中定植，引起附着和消退（AE）病变，并产生志贺毒素，导致溶血性尿毒综合征的主要症状。每年，仅在美国，肠出血性大肠杆菌就导致7万多人患病，2000人住院，7万人死亡。肠出血性大肠杆菌感知正常胃肠道菌群产生的细菌自诱导剂（AI-3），以及宿主产生的肾上腺素和去甲肾上腺素激素来激活其毒力基因的表达。毒力基因的其他调控通过转录因子QseA和小RNA分子（sRNAs）发生。然而，关于QseA和sRNA基因调控的许多方面，对毒力至关重要，仍然知之甚少。该应用程序代表了在肠出血性大肠杆菌中探索QseA和负责毒力基因调控的sRNAs功能的全面努力。具体目的是：(1)确定QseA激活和抑制靶基因的机制；(2)表征QseA在肠出血性大肠杆菌毒力基因调控中的作用；(3)阐明小RNA （sRNA）分子在肠出血性大肠杆菌转录后基因调控中的作用。提出的实验方法将更好地理解肠出血性大肠杆菌激活其毒力基因的机制，并可能揭示肠出血性大肠杆菌发病机制的潜在新方面。这些数据可能最终导致开发出肠出血性大肠杆菌感染的独特治疗策略。

DESCRIPTION (provided by applicant): Enterohemorrhagic E. coli (EHEC) O157:H7 causes bloody diarrhea and hemolytic uremic system (HUS) throughout the world. EHEC has a very low infectious dose, making it difficult to control epidemiologically. EHEC colonizes the large intestine where it causes attaching and effacing (AE) lesions and also produces Shiga toxins that are responsible for the major symptoms of HUS. Each year, EHEC causes more than 70,000 illnesses, 2000 hospitalizations, and 70,000 deaths in the United States alone. EHEC senses a bacterial autoinducer (AI-3) produced by the normal gastrointestinal flora, as well as the hormones epinephrine and norepinephrine produced by the host to activate expression of its virulence genes. Additional regulation of virulence genes occurs through the transcription factor QseA and small RNA molecules (sRNAs). However, many aspects concerning QseA and sRNA gene regulation, which are critical for virulence, remain poorly understood. This application represents a comprehensive effort to explore the functions of QseA and of sRNAs responsible for virulence gene regulation in EHEC. The Specific Aims are (1) To determine the mechanism of QseA activation and repression of target genes, (2) To characterize the role of QseA in EHEC virulence gene regulation, and (3) To elucidate the roles of small RNA (sRNA) molecules in post-transcriptional gene regulation in EHEC. The proposed experimental approaches will achieve a better understanding of the mechanisms employed by EHEC to activate its virulence genes and may reveal potentially novel aspects of EHEC pathogenesis. These data may ultimately lead to the development of unique treatment strategies for EHEC infection.