VIRUS CHROMOSOME STRUCTURE--ROLE IN DEVELOPMENT

实验研究了病毒DNA的作用机理 包装，使用噬菌体λ作为模型系统。lambda，如 T3和T7以及疱疹病毒，通过以下方式产生病毒体染色体： 在多聚体前体DNA中引入特异性切割。为每个这些 病毒，一个复杂的DNA位点阵列指示包装机器， 切割并包装病毒DNAλ DNA包装系统是最好的 了解集团。为了启动DNA包装终止酶，λ DNA包装酶，结合到cosB位点，并引入交错 邻近位点的切口，cosN，以产生病毒粒子的粘性末端 DNA.然后，终止酶结合一个空的蛋白质外壳，即前头部， DNA易位到头部，伴随着ATP 水解包装的终止发生在 包装机械遇到下一个cosN，它被切割生成 病毒体DNA的末端终止需要cosN、cosB和 新发现的网站，cosQ。 拟议的实验将详细研究的相互作用 在起始和终止过程中， 包装.这些相互作用将在分子水平上定义， 提供了关于末端酶识别DNA的信息， 参与DNA识别的末端酶结构域。一系列 包装过程中的中间体，包括末端酶-DNA复合物， 一个暂停的易位复合体，和一个暂停的终止复合体， 详细检查，以确定蛋白质的组成和结构， 复杂的。这些信息应有助于了解 包装过程中包装机械内部的结构变化 过程cosQ如何参与改变易位的模型 将测试复合物转化为终止复合物。ATP具有多个角色 在DNA包装中作为效应分子和能量来源。研究 两种ATP酶活性的突变体末端的改变将定义 ATP在切口、粘性末端分离和易位中的作用 终止酶的活性。DNA包装，像其他DNA蛋白质一样 诸如转录、重组和复制的事务， 涉及蛋白质组装体和DNA之间复杂的相互作用。 在分子水平上理解这些过程是一个主要目标， 生物学

Experiments are proposed to investigate the mechanism of virus DNA packaging, using bacteriophage lambda as a model system. lambda, like phages T3 and T7 and the herpesviruses, generates virion chromosomes by introducing specific cuts in multimeric precursor DNA. For each of these viruses, a complex array of DNA sites instructs the packaging machinery to cut and package the viral DNA. The lambda DNA packaging system is the best understood of the group. To initiate DNA packaging terminase, the lambda DNA packaging enzyme, binds to the cosB site, and introduces staggered nicks in the adjacent site, cosN, to generate the cohesive ends of virion DNA. Terminase then binds an empty protein shell, the prohead, and translocation of the DNA into the head ensues, accompanied by ATP hydrolysis. Termination of packaging occurs when the translocating packaging machinery encounters the next cosN, which is nicked to generate the terminus of the virion DNA. Termination requires cosN, cosB and the newly discovered site, cosQ. The proposed experiments will examine in detail the interactions of terminase with the cos sites during initiation and termination of packaging. These interactions will be defined at the molecular level, giving information about DNA recognition by terminase, and about the domains of terminase involved in DNA recognition. A series of intermediates in the packaging process, including a terminase-DNA complex, a paused translocating complex, and a paused termination complex will be examined in detail to determine the protein composition and structures of the complexes. This information should lead to an understanding of structural changes within the packaging machinery during the packaging process. A model for how cosQ participates in changing the translocating complex into a termination complex will be tested. ATP has multiple roles in DNA packaging as an effector molecule and an energy source. Studies of mutant terminases altered for the two ATPase activities will define the role of ATP in the nicking, cohesive end separation, and translocation activities of terminase. DNA packaging, like other DNA-protein transactions such as transcription, recombination and replication, involves complex interactions between a protein assembly and the DNA. Understanding these processes at the molecular level is a major goal of biology.