Nordström Kurt, Dasgupta Santanu
Department of Cell and Molecular Biology, Uppsala University, Biomedical Centre, Box 596, S-751 24 Uppsala, Sweden.
EMBO Rep. 2006 May;7(5):484-9. doi: 10.1038/sj.embor.7400681.
The homeostatic system that sets the copy number, and corrects over-replication and under-replication, seems to be different for chromosomes and plasmids in bacteria. Whereas plasmid replication is random in time, chromosome replication is tightly coordinated with the cell cycle such that all origins are initiated synchronously at the same cell mass per origin once per cell cycle. In this review, we propose that despite their apparent differences, the copy-number control of the Escherichia coli chromosome is similar to that of plasmids. The basic mechanism that is shared by both systems is negative-feedback control of the availability of a protein or RNA positive initiator. Superimposed on this basic mechanism are at least three systems that secure the synchronous initiation of multiple origins; however, these mechanisms are not essential for maintaining the copy number.
设定拷贝数并校正过度复制和复制不足的稳态系统，在细菌的染色体和质粒中似乎有所不同。质粒复制在时间上是随机的，而染色体复制与细胞周期紧密协调，以至于每个细胞周期中，所有的复制起点都会在每个起点相同的细胞质量时同步启动。在这篇综述中，我们提出，尽管存在明显差异，但大肠杆菌染色体的拷贝数控制与质粒的拷贝数控制相似。这两个系统共有的基本机制是对蛋白质或RNA正性起始子可用性的负反馈控制。叠加在这个基本机制之上的至少有三个确保多个起点同步启动的系统；然而，这些机制对于维持拷贝数并非必不可少。
