Bacteriophage Mu Transposition and the Role of Gyrase Binding Sites

细菌病毒Mu由于同时是病毒和转座子，其体积大，转座子频率高，在转座子中是不寻常的。尽管受到细菌类核复杂结构的限制，但在裂解周期中，37.2 kb Mu DNA的扩增是通过发生在细菌类核内的一系列复制转位事件进行的。由于担心在类核内连接前噬菌体DNA末端的潜在问题，这是转位过程的早期步骤，研究发现Mu基因组中心有一个强旋酶结合位点（SGS），这是有效复制所必需的。我们进行了广泛的搜索，以寻找在Mu复制中可以替代SGS的染色体或质粒位点。没有发现其他网站，集中关注什么是不寻常的SGS。本项目主要关注该模型提出的两个重要问题：1)Mu位点如何促进Mu噬菌体末端的突触；2)为什么需要一种新的机制来促进突触？第一个问题将通过确定Mu遗址的特殊或独特之处来解决。对SGS和其他强回转酶结合位点进行了详细的遗传和生化分析，目的是确定SGS在Mu DNA复制中起作用的元件。第二个问题正在通过探索因素来解决，例如转座酶分子与Mu噬菌体末端的结合，这是在没有SGS的情况下Mu复制长时间延迟的原因。这些研究旨在深入了解病毒DNA复制的机制和DNA结构在生物功能中的重要性。特别令人感兴趣的是DNA拓扑结构在功能调节中的作用。

Pato 9727991 The bacterial virus Mu, by virtue of its being both a virus and a transposon, is unusual among transposons in its large size and its high frequency of transposition. Amplification of the 37.2 kb Mu DNA during the lytic cycle occurs by a series of replicative transposition events which take place within the bacterial nucleoid, despite the constraints imposed by the complex structure of that body. Concerns about potential problems with synapsing the ends of prophage DNA within the nucleoid, an early step in the transposition process, led to studies which uncovered a strong gyrase binding site (SGS) in the center of the Mu genome that is required for efficient replication. An extensive search was undertaken to find chromosomal or plasmid sites which could replace the SGS in Mu replication. No other sites have been found, focusing attention on what is unusual about the SGS. This project focuses on two important questions raised by the model: 1) How does the Mu site promote synapsis of the Mu prophage ends and 2) Why is a novel mechanism required for promoting the synapsis? The first question will be addressed by determining what is special or unique about the Mu site. A detailed genetic and biochemical analysis of the SGS and of other strong gyrase binding sites is being performed with the goal of defining the elements of the SGS that are responsible for its ability to function in Mu DNA replication. The second question is being addressed by exploring the factors, such as the binding of transposase molecules to the ends of a Mu prophage, that are responsible for the long delay in Mu replication in the absence of the SGS. These studies are designed to provide insights into the mechanism of viral DNA replication and the importance of DNA structure in biological function. Of particular interest is the role of DNA topology in the modulation of function.