Regulation of methionine metabolism in Bacillus subtilis

描述(申请人提供)：S盒系统是一种新型的全球调控机制，用于控制革兰氏阳性细菌中涉及蛋氨酸代谢的基因。S盒家族的基因包含一组复杂的保守初级序列和编码序列上游的结构元件。这些元件作用于新生的核糖核酸，与S-腺苷甲硫氨酸(SAM)结合，与SAM相互作用，导致核糖核酸的结构转换，促进转录的提前终止。赖氨酸生物合成基因使用类似的机制，通过将赖氨酸与L盒家族中新生的RNA结合来终止转录或阻止翻译启动。目前在某些革兰氏阳性菌的SAM合成酶基因的上游区域发现了一个新的与SAM结合的RNA元件，该元件与S盒元件一样，被预测为调节下游编码序列对SAM的响应。这些系统和相关系统被广泛用于调节革兰氏阳性细菌的基因表达，包括重要的病原体。该项目的总体目标是研究新生RNA对效应器分子的特异性识别的分子基础，并校准每类RNA对效应器的生理相关浓度的亲和力。将使用各种遗传、生化和结构生物学的方法来阐明RNA与效应器的相互作用和对效应器结合的适当调控反应所必需的结构重排。甲硫氨酸基因调控和严格反应之间的相互作用也将被探索。工作将集中在枯草杆菌作为分析这些系统的模型，还将包括分析来自粪肠球菌的新的SAM结合元件。该项目将提供关于基于RNA的新的基因调控机制的基本信息，并将提供对使用这些机制的病原体的代谢调控的洞察。革兰氏阳性病原体通常使用与枯草芽孢杆菌密切相关的调节机制。致病性决定因素的表达经常受到生理信号的调节，了解细胞如何监控这些信号对于了解细菌的毒力很重要。

DESCRIPTION (provided by applicant): The S box system is a novel global regulatory mechanism for control of genes involved in methionine metabolism in Gram-positive bacteria. Genes in the S box family contain a complex set of conserved primary sequence and structural elements upstream of the start of the coding sequence. These elements act in the nascent RNA to bind S-adenosylmethionine (SAM), and interaction with SAM results in a structural switch in the RNA that promotes premature termination of transcription. Lysine biosynthesis genes use a similar mechanism, with binding of lysine to nascent RNAs in the L box family to terminate transcription or prevent translation initiation. A new SAM-binding RNA element has now been identified in the upstream region of SAM synthetase genes of certain Gram-positive organisms, and this element, like the S box element, is predicted to regulate expression of the downstream coding sequence in response to SAM. These and related systems are widely used to regulate gene expression in Gram-positive bacteria, including important pathogens. The overall goals of this project are to investigate the molecular basis for specific recognition of effector molecules by the nascent RNA, and for calibration of the affinity of each class of RNA to physiologically relevant concentrations of the effector. A variety of genetic, biochemical, and structural biology approaches will be employed to elucidate both the RNA-effector interaction and the structural rearrangement necessary for the appropriate regulatory response to effector binding. The interaction between methionine gene regulation and the stringent response will also be explored. Work will focus on Bacillus subtilis as a model for analysis of these systems, and will also include analysis of the new SAM binding element from Enterococcus faecalis. This project will provide basic information about novel RNA-based mechanisms of gene regulation, and will also provide insight into metabolic regulation in pathogenic organisms that use these mechanisms. Gram-positive pathogens generally use regulatory mechanisms closely related to those found in Bacillus subtilis. Expression of determinants for pathogenicity are often regulated in response to physiological signals, and understanding how the cell monitors these signals is important for understanding bacterial virulence.