BIOCHEMICAL STUDIES OF PHAGE MU

基因转座的过程彻底改变了人们对 真核生物和原核生物染色体的进化和形成 一模一样。 虽然转座子的遗传影响越来越明显， 剪接基因的酶及其调控机制 在细胞中的表达和活性是未知的。 只有少数系统 目前可用的方法允许对这些基因进行遗传和生物化学分析， 问题 我们的长期目标是剖析 调节Mu转录和复制。 噬菌体Mu使用转座来 整合并复制它的DNA 它是最活跃的自然 已知的转座因子：在裂解周期中，Mu使用E。杆菌 复制机器转座到染色体中的100个位点， 小时 控制病毒发展的主要元素位于 在基因的左边 我们正在开发一种技术， 反义RNA生产，允许噬菌体的表征 体外和体内的转录模式。 Mu利用聚合 启动子合成裂解功能或Mu阻遏物。 这 操纵子与宿主酶相互作用。 超螺旋刺激溶解性 转录并减少阻遏物转录;因此，病毒是 对宿主的DNA促旋酶活性敏感。 II型的结合位点 E.大肠杆菌（IHF）中的启动子位于DDNA附近 含有序列诱导的弯曲的位点。 IHF增强了超级线圈调制 的启动子强度。 这种类型的增强子控制50倍 调控 穆换位是高效的，也因为一套附件 蛋白质是由病毒的一个可分配区域编码的。 一种蛋白质来自 这一区域是由Mu gam基因编码的一种不寻常的DNA结合蛋白， 被大量提纯。 pgam阻断核酸外切酶和聚集体 超螺旋DNA 概述了体外和体内实验， 这种蛋白质修饰Mu的生化机制 换位过程

The process of genetic transposition has revolutionized ideas about evolution and the formation of chromosomes in eukaryotes and prokaryotes alike. While the genetic impact of transposons is becoming evident, the enzymes that splice genes and the regulatory mechanisms controlling their expression and activity in the cell are unknown. Only a few systems are currently available which permit genetic and biochemical analysis of these problems. Our long range objective is to dissect the biochemical mechanisms that regulate Mu transcription and replication. Phage Mu uses transposition to integrate and replicate its DNA. It is the most active natural transposable element known: during the lytic cycle Mu uses the E. coli replication machinery to transpose to 100 sites in the chromosome within an hour. The principle elements controlling virus development are located near the left genetic end. We are developing a technology based on anti-sense RNA production that allows the characterization of phage transcription patterns in vitro as well as in vivo. Mu utilizes converging promoters to synthesixe either lytic functions or Mu repressor. This operator is interactive wiht host enzymes. Supercoiling stimulates lytic transcription and decreases repressor transcription; thus, the virus is sensitive to DNA gyrase activity of the host. A binding site for a type II DNA binding protein of E. coli (IHF) is located in the promoter near a DDNA site containing a sequence induced bend. IHF enhances supercoil-modulation of promoter strength in vitro. This type of enhancer controls 50-fold regulation. Mu transposition is efficient also because a set of accessory proteins is encoded by a dispensible region of the virus. One protein from this region, an unusual DNA binding protein encoded by the Mu gam gene, has been purified in large amounts. pgam blocks exonucleases and aggregates supercoiled DNA. In vitro and in vivo experiments are outlined to define the biochemical mechanisms by which this protein modifies the Mu transposition process.