Regulation of methionine metabolism in Bacillus subtilis

描述（由申请人提供）：S盒系统是一种新型的全局调控机制，用于控制革兰氏阳性菌中参与甲硫氨酸代谢的基因。S盒家族中的基因含有一组复杂的保守的一级序列和编码序列起始上游的结构元件。这些元件在新生RNA中起作用以结合S-腺苷甲硫氨酸（SAM），并且与SAM的相互作用导致RNA中的结构转换，其促进转录的过早终止。赖氨酸生物合成基因使用类似的机制，赖氨酸与L盒家族中的新生RNA结合以终止转录或阻止翻译起始。一种新的SAM结合RNA元件现已被确定在某些革兰氏阳性生物的SAM合成酶基因的上游区域中，并且该元件，如S盒元件，被预测为响应SAM而调节下游编码序列的表达。这些系统和相关系统广泛用于调节革兰氏阳性细菌（包括重要病原体）中的基因表达。该项目的总体目标是研究新生RNA对效应分子的特异性识别的分子基础，以及校准每类RNA对生理相关浓度的效应物的亲和力。将采用各种遗传、生物化学和结构生物学方法来阐明RNA-效应物相互作用和对效应物结合的适当调节反应所必需的结构重排。甲硫氨酸基因调控和严格的反应之间的相互作用也将进行探讨。工作将集中在枯草芽孢杆菌作为这些系统的分析模型，也将包括新的SAM结合元件从粪肠球菌的分析。该项目将提供有关新的基于RNA的基因调控机制的基本信息，并将提供对使用这些机制的致病生物体的代谢调控的见解。革兰氏阳性病原体通常使用与枯草芽孢杆菌中发现的那些密切相关的调节机制。致病性决定因子的表达通常受到生理信号的调节，了解细胞如何监测这些信号对于了解细菌毒力非常重要。

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.