Function of type1A topoisomerases in bacterial chromosome segregation

细菌细胞生命的关键一步是分裂产生两个相同的子细胞。这一事件使其得以代代相传。然而，在细胞分裂之前，一个关键的过程是将复制的遗传物质（染色体）分离到细胞的两端，这样每个子细胞在分裂后就能得到一条染色体。有了母细胞的全套基因，每个子细胞就能生长和分裂。由于DNA的双螺旋性质，在复制过程中不可避免地会发生DNA链缠结。如果不能正确和迅速地去除，这些缠结将最终阻碍复制复合体的进展，结果，染色体分离将不可能。DNA拓扑异构酶，通过切割DNA和允许链通道和宗教解决与复制复合体进展相关的拓扑问题。大肠杆菌的拓扑异构酶在体外的催化性能和复制过程中的工作能力已经得到了很好的表征。然而，人们对它们在细胞中的实际功能及其与细胞周期的调节知之甚少。我们研究项目的主要目的是表征各种DNA拓扑异构酶在大肠杆菌细胞染色体复制和分离中的作用。现代显微技术使活细胞中的染色体和蛋白质可视化，并结合分子生物学、遗传学和生化方法，将用于表征各种拓扑异构酶在细胞周期中的作用。我们研究项目的最终目标是了解细菌如何调节其细胞周期的主要事件，以便将其遗传物质忠实地传递给子细胞。

A key step in the life of a bacterial cell is its division to generate two identical daughter cells. This event allows its perpetuation from generation to generation. However, one key event that most be faithfully accomplish before cell division, is the segregation of the replicated genetic material (chromosomes) to each end of the cell, so that each daughter cell can receive one chromosome following division. With a full set of the genes from the mother cell, each daughter cell will be able to grow and divide. Because of the double-helical nature of the DNA, entanglement of the DNA strands inevitably occurs during replication. If not properly and rapidly removed, these intertwines will eventually block the progression of the replication complex and, as a consequence, chromosome segregation will not be possible. DNA topoisomerases, by cutting DNA and by allowing strand passage and religation solve the topological problem associated with the progression of replication complexes. Topoisomerases from the bacterium Escherichia coli have been well characterized in vitro in term of their catalytic properties and their ability to work during replication. However, little is known about their actual function in the cell and their regulation with the cell cycle. The main goal of our research project is to characterize the roles of the various DNA topoisomerases in chromosome replication and segregation in E. coli cells. Modern microscopic techniques allowing the visualization of chromosomes and proteins in living cells together with molecular biology, genetic and biochemical approaches will be used to characterize the roles of the various topoisomerases in the cell cycle. The ultimate goal of our research program is to understand how bacteria regulate the major events of their cell cycle to allow the faithful transmission of their genetic material to daughter cells.