Mechanisms of Virulence Gene Regulation in Streptococcus mutans

龋齿是人类最常见的细菌感染之一，许多人仍未得到治疗。 不发达国家。根据生化、流行病学和动物实验，链球菌 变形杆菌被认为是龋病的主要病原体。新陈代谢的能力 碳水化合物以及在牙齿表面附着和形成坚韧的生物膜被认为是至关重要的 与这种人类病原体的致龋性有关。变形链球菌通过以下途径从蔗糖中合成葡聚糖 三种葡萄糖转移酶(GTF)，并在它们的合作下牢固地附着在牙齿表面。它还生产 葡聚糖结合蛋白(GBP)在毒力中起主要作用。治理的具体机制 变形链球菌胞外多糖合成的调控尚不清楚。然而，最近它是 发现一个孤儿反应调节因子GcrR调节至少一个GTF和一个GBP的表达 吉恩。值得注意的是，gcrR的失活显著减少了大鼠生物膜的形成和龋病的发生。 因此，GcrR在该菌的发病机制中起着重要作用。此外，GcrR还展示了 与致病性A组链球菌(GAS)COVR的广泛序列同源性(&gt；80%)，回应 控制多达15%的GAS基因的调节器，包括许多重要的毒力因子。vt.给出 与COVR的高度相似性及其在生物被膜和龋病发生中的作用，人们可以预料到GcrR 可能是变形链球菌的全球监管者。因此，我们选择关注GcrR对基因的调控 具体目标如下。在目标1中，我们将通过dna微阵列和体外鉴定gcrR调节子。 用纯化的GcrR蛋白进行DNA结合分析。我们将用蛋白质组学的方法来证实我们的结果。在……里面 目的：探讨GcrR基因调控的机制。我们将确定和描述 GcrR基因启动子上的GcrR结合基序(S)。在《目标3》中，我们将 研究gcrR的表达调控。由于GcrR的同源感受器激酶在附近的 GcrR基因座，使用生化和遗传学方法，我们将识别同源感受器激酶以 了解gcrR法规。 这项研究将促进我们对基因调控和信号的分子机制的理解 在变形链球菌中转导并促进旨在控制的治疗方法的发展 菌斑生物膜的形成和随后的龋病发生。

Dental caries is one of the most common bacterial infections in humans and remains untreated in many underdeveloped countries. Based on biochemical, epidemiological and animal experiments, Streptococcus mutans is considered to be the principal etiological agent of dental caries. The ability to metabolize carbohydrates and to adhere to and form tenacious biofilms on the tooth surfaces are believed to be critically associated with the cariogenicity of this human pathogen. S. mutans synthesizes glucans from sucrose by three glucosyltransferases (Gtf), and adheres firmly to tooth surfaces with their cooperation. It also produces glucan-binding proteins (Gbps) which play major roles in virulence. The specific mechanisms governing regulation of exopolysaccharide synthesis in S. mutans have yet to be discovered. However, recently it was found that an orphan response regulator, GcrR, modulates the expression of at least one Gtf and one Gbp gene. Remarkably, inactivation of gcrR drastically reduces biofilm formation and cariogenesis in rat. Therefore, GcrR appears to be very important for pathogenesis of this organism. In addition, GcrR shows extensive sequence homology (>80%) with the pathogenic group A streptococcus (GAS) CovR, a response regulator that controls as much as 15% of the GAS genes including many important virulence factors. Given the high degree of similarity with CovR and its effect in biofilm and cariogenesis, one would expect that GcrR may be a global regulator of S. mutans. Therefore, we have chosen to focus on gene regulation by GcrR with the following Specific Aims. In Aim 1, we will identify the gcrR regulon by DNA microarray and in vitro DNA binding assays using purified GcrR protein. We will confirm our results with proteomics approach. In Aim 2, we will determine the mechanisms of gene regulation by GcrR. We will identify and characterize the GcrR binding motif(s) on the promoters of genes (such as gtfD, gbpC) regulated by GcrR. In Aim 3, we will study the regulation of gcrR expression. Since the cognate sensor kinase of GcrR is absent in the nearby gcrR locus, using both biochemical and genetic approaches we will identify the cognate sensor kinase to understand gcrR regulation. This (investigationwill promote our understanding of molecular mechanisms of gene regulation and signal transduction in S. mutans and facilitate the development of therapeutic approaches aimed at controlling formation of plaque biofilm and subsequent cariogenesis.