Phase-variable gene expression in Pseudomonas aeruginosa

描述(申请人提供)：铜绿假单胞菌是一种重要的人类条件致病菌，是囊性纤维化患者发病和死亡的主要原因而臭名昭著。在慢性感染的CF肺中，有机体以生物膜的形式存在--一个包裹在聚合物基质中的表面附着的细菌群落。这种生物被膜的生长模式增加了铜绿假单胞菌对抗生素的抵抗力，并有助于逃避宿主的免疫反应。 在这些在铜绿假单胞菌生物被膜形成中起重要作用的基因中，突出的是CUPA基因，它编码促进表面附着的假定菌毛结构的组成部分。我们发现，MvaT是最近在铜绿假单胞菌中发现的一种全球毒力基因表达调节蛋白，它控制着CupA菌毛基因簇的相位可变(即开/关)表达。拟议的研究将确定MVaT如何实施这种控制。我们最近的发现也表明，转录终止因子Rho也参与了这一过程。因此，我们建议探索MvaT和Rho协同作用以实现对相变CUPA基因表达的有效抑制的可能性。此外，我们将试图阐明阶段可变的CUPA基因表达(第一次在铜绿假单胞菌中记录)实际发生的机制。 我们预计，这些研究将阐明MvaT控制CUPA基因表达的机制，进而控制其他与毒力有关的MvaT靶基因的表达。我们预计这些研究还将阐明铜绿假单胞菌中相变基因表达背后的分子基础。

DESCRIPTION (provided by applicant): Pseudomonas aeruginosa is an important opportunistic pathogen of humans that is notorious for being the principal cause of morbidity and mortality in Cystic Fibrosis (CF) patients. In the chronically infected CF lung the organism persists as a biofilm-a surface attached community of bacteria encased in a polymeric matrix. This biofilm mode of growth augments the resistance of P. aeruginosa to antibiotics and facilitates evasion of the host immune response. Prominent amongst those genes that play an important role in biofilm formation in P. aeruginosa are the cupA genes, which encode components of a putative fimbrial structure that facilitates surface- attachment. We have found that MvaT, a protein recently identified in P. aeruginosa as a global regulator of virulence gene expression, controls the phase-variable (i.e. ON/OFF) expression of the cupA fimbrial gene cluster. The proposed studies will determine how MvaT exerts this control. Our recent findings also implicate Rho, a transcription termination factor, in this same process. We therefore propose to explore the possibility that MvaT and Rho function synergistically to achieve efficient repression of phase-variable cupA gene expression. Moreover, we will attempt to elucidate the mechanism by which phase-variable cupA gene expression (the first of its kind documented in P. aeruginosa) actually occurs. We anticipate that these studies will illuminate the mechanism by which MvaT controls the expression of the cupA genes and, by extension, other MvaT-target genes that contribute to virulence. We anticipate further that these studies will also shed light on the molecular basis behind phase-variable gene expression in P. aeruginosa.