Regulation of Bacillus subtilis tRNA synthetase genes

描述(申请人提供)：枯草芽孢杆菌TyrS基因是一大组氨基酰-tRNA合成酶、氨基酸生物合成和转运蛋白基因的成员，被称为T盒家族，受独特的转录终止控制系统调控。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，防止了转录的提前终止。我们已经确定了超过250个转录单位，主要来自革兰氏阳性细菌，其前导区显示了该家族成员特有的保守元件。其中包括炭疽杆菌、葡萄球菌、链球菌、肠球菌和分枝杆菌等几种重要的病原菌。由于大多数受调控的基因都编码必要的蛋白质，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的配对，以及tRNA的受体端与反终止子的凸起区域的配对；这些配对对于有效的抗终止是必要的，但不是充分的。对领导者的系统发育分析揭示了许多元件，这些元件的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也发现了新的变化；其中一些变化暗示了抗终止的分子机制的可变性。下一个项目期将侧重于利用系统发育数据作为努力揭示该系统的其他结构和机械特征的基础。所使用的方法将包括对我们广泛的比对的前导RNA和tRNA数据库的计算分析，以及在我们成功分析反终止子结构域的同时对前导元件的结构研究。遗传和生化方法将用于提炼所需的先导分子和tRNA元件，并确定可能的额外因素。

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.