Regulation of a Plasmid Gene in Bacillus Subtilis

氯霉素（Cm）通过阻断 在70 S核糖体上翻译过程中的肽延伸。 Cm 也作为cat基因表达的诱导物 （编码氯霉素乙酰转移酶） 细菌一个基因cat-86的诱导已经被证明是 这是由于mRNA翻译的激活。 这似乎导致 从Cm阻止核糖体翻译cat-86的能力 调节前导肽;停滞的核糖体被认为 破坏下游RNA茎环， 核糖体结合位点。 本提案的长期目标是 为了解释Cm激活cat-86的机制， 和其他可诱导的猫基因 预计这些 研究将澄清和扩展我们对 核糖体靶向抗生素的作用机制。 它 预计这些研究也将显示 衰减调节模型的原理 控制基因表达。 通过使用网站指导 诱变和重组DNA技术， 以确定所提出的Cm失速位点是否是mRNA或 蛋白质序列和该位点的序列。 空间 失速位点与调控RNA之间的关系 二级结构将被识别。 不常见的例子 在细菌中存在明显的Cm不敏感翻译。 做 这些都是由于碰巧没有一个CM摊位造成的？ 土壤细菌芽孢杆菌属的某些物种是 对抗生素氯霉素具有天然抗性， 由于它们能够合成一种酶， 使药物失效。 失活酶的合成 是由药物特异性诱导的，即，这些细菌 只有在遇到药物时才能释放酶。 洛维特医生 早期的研究表明，药物引起的 核糖体的行为， 蛋白质，是诱导机制的关键部分， 失活酶。 这是一个非常不寻常的机制 基因表达的调节，洛维特博士提出， 在这项研究中，许多仍然模糊的细节， 这个机制。 除了深入了解一种新的监管机制外， 机制，这项工作也应该产生新的见解如何 核糖体的功能受到控制。

Chloramphenicol (Cm) inhibits bacterial growth by blocking peptide elongation during translation on 70S ribosomes. Cm also acts as an inducer of the expression of cat genes (encoding chloramphenicol acetyltransferase) in Gram-positive bacteria. Induction of one gene, cat-86, has been shown to be due to activation of mRNA translation. This appears to result from the ability of Cm to stall ribosomes translating a cat-86 regulatory leader peptide; a stalled ribosome is thought to disrupt a downstream RNA stem-loop that sequesters the cat-86 ribosome binding site. The long term goal of this proposal is to explain the mechanism which allows Cm to activate cat-86, and other inducible cat genes. It is anticipated that these studies will clarify and extend our understanding of the mechanism of action of a ribosomally targeted antibiotic. It is also expected that these studies will show the breath of the principles of the attenuation regulatory model in controlling gene expression. By use of site directed mutagenesis and recombinant DNA technology it is now possible to determine whether the proposed Cm stall site is an mRNA or protein sequence, and the sequence of the site. The spatial relationship between the stall site and the regulated RNA secondary structure will be identified. Uncommon examples of apparently Cm-insensitive translation exit in bacteria. Do these result from the fortuitous absence of a Cm stall site? Certain species of the soil bacterium genus Bacillus are naturally resistant to the antibiotic chloramphenicol by virtue of their ability to synthesize an enzyme which inactivates the drug. The synthesis of the inactivating enzyme is specifically inducible by the drug, i.e., the bacteria make the enzyme only when they encounter the drug. Dr. Lovett's earlier studies have shown that a drug-induced change in the behavior of ribosomes, the organelles which synthesize proteins, is a critical part of the mechanism of the induction of the inactivating enzyme. This is a very unusual mechanism for the regulation of gene expression, and Dr. Lovett proposes in this study to work out many of the still obscure details of this mechanism. Apart from insight into a novel regulatory mechanism, this work should also yield new insight into how the function of ribosomes is controlled.