Genetic and biochemical studies of competence regulation by the hdrRM operon

项目描述（由申请人提供）：本研究旨在研究新发现的高密度响应性hdrRM操纵子在突变链球菌中调控能力的遗传和生化机制。本项目的目标将通过两个方面来实现：1)确定hdrRM调控的能力级联的步骤；2)确定hdrRM调控基因的机制。1)为了分析hdrRM操纵子如何与能力级联的基因相互作用，将进行转录、上位性和突变分析的组合。这些研究将为hdrRM作为能力负向调节因子的作用提供遗传学基础。2)为了描述HdrR作为能力调节因子的机制，HdrR将用于能力基因启动子的DNA结合分析。此外，HdrR和HdrM之间的体内蛋白质相互作用研究将表征两种蛋白质之间可能的相互作用。这些数据有望为Aim 1中产生的遗传和转录数据提供生化证据，并确定HdrRM系统中信号转导的机制。本项目的目标是利用能力调控作为模型来研究hdrRM操纵子调控变形链球菌其他重要毒力因子的机制。由于该操纵子在高细胞密度条件下受到强烈的诱导，预计它将在牙菌斑的高细胞密度环境中对生存和致病性起关键作用。

DESCRIPTION (provided by applicant): The proposed research Aims to investigate the genetic and biochemical mechanisms of competence regulation in Streptococcus mutans by the newly discovered high cell density responsive hdrRM operon. The goals of this project will be achieved in two Aims by: 1) Determining the steps of the competence cascade that are regulated by hdrRM 2) Determining the mechanism of gene regulation by HdrRM. 1) To analyze how the hdrRM operon interacts with the genes of the competence cascade, a combination of transcription, epistatic, and mutation analysis will be performed. These studies will provide the genetic basis for the role of hdrRM as a negative regulator of competence. 2) To characterize the mechanism of HdrR as a regulator of competence, HdrR will be used for DNA binding assays of competence gene promoters. In addition, in vivo protein interaction studies between HdrR and HdrM will characterize possible interactions between the two proteins. These data are expected to provide biochemical evidence for the genetic and transcriptional data generated in Aim 1 as well as determine the mechanism of signal transduction in the HdrRM system. The goal of this project is to use competence regulation as a model for the mechanism by which the hdrRM operon is able to regulate other important virulence factors of Streptococcus mutans. Since this operon is strongly induced by conditions of high cell density, it is expected that it will play a crucial role for both survival and pathogenicity in the high cell density environment of the dental plaque. Project Narrative: Dental caries is the most common human bacterial disease and is largely correlated with the overgrowth of Streptococcus mutans. Since its ability to cause disease requires it to function in the high cell density conditions of dental plaque, studies of gene regulators that function in high cell density conditions may yield novel treatment strategies to control the pathogenesis of S. mutans.