Regulation of Bacillus subtilis tRNA synthetase genes

描述（由申请人提供）：枯草芽孢杆菌tyrS基因是一大组氨酰-tRNA合成酶、氨基酸生物合成和转运蛋白基因（称为T盒家族）的成员，其受独特的转录终止控制系统调节。每个基因的表达依赖于转录物的前导区与特定的不带电荷的tRNA的相互作用。这种相互作用促进了抗终止子结构的形成，防止了转录的过早终止。我们已经确定了超过250个转录单位，主要是从革兰氏阳性细菌，与领导人区域展示了这个家庭的成员的保守元件的特性。几种重要的病原体，包括炭疽杆菌、葡萄球菌、链球菌、肠球菌和分枝杆菌，都属于这一组。由于大多数受调控的基因编码必需蛋白质，因此该系统代表了抗生素开发的潜在靶点。该家族中每个基因的表达依赖于诱导物tRNA的反密码子与前导序列中的单个密码子（“指定序列”）的配对，以及tRNA的受体末端与抗终止子的凸出区域的配对;这些配对是必要的，但不足以有效地抗终止。对前导序列的系统发育分析揭示了许多元件，其结构可以根据与其他RNA的相似性来预测。保守的前导元件的排列上的新的变化也被发现;这些变化中的一些提示抗终止的分子机制的可变性。下一个项目期间将侧重于使用系统发育数据作为基础，努力揭示该系统的其他结构和机制特征。所使用的方法将包括我们广泛的对齐的前导RNA和tRNA数据库的计算分析，和平行于我们成功的antiterminator域的分析的前导元件的结构研究。遗传学和生物化学方法将针对所需的前导序列和tRNA元件的改进，以及可能的其他因子的鉴定。

DESCRIPTION (provided by applicant): The Bacillus subtilis tyrS gene is a member of a large group of aminoacyl-tRNA synthetase, amino acid biosynthesis and transporter genes, designated the T box family, that are regulated by a unique transcription termination control system. Expression of each gene is dependent on interaction of the leader region of the transcript with a specific uncharged tRNA. This interaction promotes formation of an antiterminator structure, preventing premature termination of transcription. We have identified over 250 transcriptional units, primarily from Gram-positive bacteria, with leader regions exhibiting the conserved elements characteristic of members of this family. Several important pathogens, including Bacillus anthracis, Staphylococcus, Streptococcus, Enterococcus and Mycobacterium, are represented in this group. Since most of the regulated genes encode essential proteins, this system represents a potential target for antibiotic development. Expression of each gene in the family is dependent on pairing of the anticodon of the inducer tRNA with a single codon, the "specifier sequence," in the leader, and on pairing of acceptor end of the tRNA with a bulged region of the antiterminator; these pairings are necessary but not sufficient for efficient antitermination. Phylogenetic analysis of the leaders has revealed a number of elements the structure of which can be predicted based on similarity to other RNAs. Novel variations on the arrangement of conserved leader elements has also been uncovered; some of these variations are suggestive of variability in the molecular mechanism of antitermination. The next project period will focus on using the phylogenetic data as a basis for efforts to uncover additional structural and mechanistic features of the system. The approaches used will include computational analyses of our extensive aligned leader RNA and tRNA database, and structural studies of leader elements in parallel to our successful analysis of the antiterminator domain. Genetic and biochemical approaches will be directed to the refinement of the required leader and tRNA elements, and for identification of possible additional factors.