REGULATION OF BACILLUS SUBTILIS TRNA SYNTHETASE GENES

本项目的目标是分析 枯草芽孢杆菌tyrS基因，编码酪氨酰-tRNA合成酶。 氨基酰基 tRNA合成酶是翻译机器的关键组成部分 催化tRNA与同源物的准确充电， 氨基酸 tRNA合成酶基因的表达响应细胞内的 合成酶的要求。tRNA的调控机制 合成酶基因的部分特点是在克兰氏阴性 细菌大肠杆菌，并已被发现是复杂的;没有 关于这些基因在其它细胞中调控信息是可获得的。 系统. B。枯草杆菌是一种革兰氏阳性的、孢子形成的土壤细菌， 进化上与E.大肠杆菌，但具有发达的遗传 该系统极大地方便了基因分析。 B。枯草杆菌酪氨酸酶 基因已被克隆，其DNA序列已被确定。 对tyrS调控的初步研究表明，该基因可能是 由转录抗终止机制调节， 到因酪氨酸而饥饿 一个潜在的调控靶位点是 鉴定了在许多芽孢杆菌tRNA合成酶中保守的 基因，以及在ilv-leu生物合成操纵子;删除这个 序列导致不可诱导的表型。 保护这个 位点，在所有情况下都在前导区转录的上游 终止子，这表明这些基因可能是受 一个共同的机制。提出的转录抗终止机制 将通过体内转录作图测试tyrS调控， 体外 tyrS响应的生理条件将是 进一步探索。 对tyrS调控重要的顺式作用序列 将被检查，和反式作用因子所需的抗终止 将通过遗传和生化分析进行鉴定。 本研究 预期提供有关转录的一般信息 抗终止系统。 这是第一份关于抗终止的报告 系统提出了大量的基因操作;分析的 该系统的作用机制是针对特定的基因， 对适当的生理信号的响应将提供一般的 对调节系统特异性生成的洞察。

The goal of this project is the analysis of the regulation of the Bacillus subtilis tyrS gene, encoding tyrosyl-tRNA synthetase. Aminoacyl tRNA synthetases are critical components of the translational machinery of all cells, catalyzing the accurate charging of tRNA with the cognate amino acid. Expression of tRNA synthetase genes responds to the cellular requirement for the synthetases. The mechanisms for regulation of tRNA synthetase genes has been partially characterized in the Cram-negative bacterium Escherichia coli, and have been found to be complex; no information is available about regulation of these genes in other systems. B. subtilis is a Gram-positive, spore-forming soil bacterium, evolutionarily distant from E. coli, but with a well-developed genetic system which greatly facilitates genetic analysis. The B. subtilis tyrS gene has been cloned, and its DNA sequence has been determined. Preliminary studies on tyrS regulation indicated that this gene is likely to be regulated by a transcription antitermination mechanism, in response to starvation for tyrosine. A potential regulatory target site was identified which is conserved in a number of Bacillus tRNA synthetase genes, as well as in the ilv-leu biosynthetic operon; deletion of this sequence results in an uninducible phenotype. The conservation of this site, in all cases upstream of a leader region transcriptional terminator, suggests the possibility that these genes are regulated by a common mechanism. The proposed transcription antitermination mechanism for tyrS regulation will be tested by transcriptional mapping in vivo and in vitro. The physiological conditions to which tyrS responds will be further explored. The cis-acting sequences important for tyrS regulation will be examined, and trans-acting factors required for antitermination will be identified by genetic and biochemical analysis. This study is expected to provide general information about transcription antitermination systems. This is the first report of an antitermination system proposed to operate on a large number of genes; analysis of the mechanisms by which this system is directed to act on specific genes in response to appropriate physiological signals will provide general insight into the generation of specificity in regulatory system.