Control of Pseudomonas aeruginosa algD transcription

描述（由申请人提供）：囊性纤维化（CF）患者易发生铜绿假单胞菌引起的反复呼吸道感染。这些感染引起的并发症是发病的主要原因，也是患者死亡的主要原因。最初定殖于肺的铜绿假单胞菌菌株是非粘液样的，但随着时间的推移出现粘液样变体，这与CF患者的临床状况恶化相关。粘液样表型是由于被称为藻酸盐的荚膜多糖的高水平合成，并且这种毒力因子的过量产生赋予了CF肺中铜绿假单胞菌的选择性优势。因此，本提案的长期目标是了解定植于CF患者的铜绿假单胞菌菌株产生藻酸盐的分子机制。 大多数用于藻酸盐生产的基因位于由严格控制的启动子（palgD）转录的大操纵子中。palgD在粘液型铜绿假单胞菌分离株中被激活，但在非粘液型菌株中从该启动子检测不到转录。该提案将重点关注AlgZ和AlgB，这两种蛋白质对algD激活至关重要。此外，提出了旨在定义导致类粘蛋白转化和随后的algD激活的事件的实验。生物化学和遗传学的方法将被用来解决三个核心问题，构成本建议的基础：（1）是什么机制的AIgZ介导的algD启动子的转录激活？(2)反应调节剂AlgB如何控制algD表达和藻酸盐合成？(3)在铜绿假单胞菌中控制粘液转化的分子事件是什么？由于藻酸盐的过量产生与粘液样铜绿假单胞菌定殖的CF患者的不良临床结果相关，并且由于algD活化是藻酸盐合成的先决条件，因此对algD转录的基本理解对于理解铜绿假单胞菌的发病机制至关重要。这将导致新的治疗方法，并提高生活质量的CF患者与粘液铜绿假单胞菌定殖。

DESCRIPTION (provided by applicant): Cystic fibrosis (CF) patients are predisposed to recurrent respiratory tract infections by the bacterium Pseudomonas aeruginosa. Complications arising from these infections are a major source of morbidity and the leading cause of death in those afflicted. P. aeruginosa strains that initially colonize the lungs are nonmucoid, but over time mucoid variants emerge and this is correlated with a worsening clinical condition for the CF patient. The mucoid phenotype is due to high-level synthesis of a capsular polysaccharide called alginate and overproduction of this virulence factor confers a selective advantage for P. aeruginosa in the CF lung. Thus, the long-term objective of this proposal is to understand the molecular mechanisms responsible for the production of alginate by strains of P. aeruginosa which colonize CF patients. Most of the genes for alginate production are in a large operon that is transcribed by a tightly controlled promoter (palgD). palgD is activated in mucoid P. aeruginosa isolates but no transcription is detectable from this promoter in nonmucoid strains. This proposal will focus on AlgZ and AlgB, two proteins that are essential for algD activation. In addition, experiments aimed at defining the events leading to mucoid conversion and subsequent algD activation are proposed. Biochemical and genetic approaches will be utilized to address three central questions which constitute the basis of this proposal: (1) What is the mechanism of AIgZ-mediated transcriptional activation of the algD promoter? (2) How does the response regulator AlgB controls algD expression and alginate synthesis? (3) What are the molecular events controlling mucoid conversion in P. aeruginosa? Since the overproduction of alginate correlates with a poor clinical outcome for CF patients colonized with mucoid P. aeruginosa, and since algD activation is a prerequisite for alginate synthesis, a basic understanding of algD transcription is essential for understanding the pathogenesis of P. aeruginosa. This will lead to novel therapies and improve the quality of life for CF patients colonized with mucoid P. aeruginosa.