Dynamic organization of chromosomal DNA in Escherichia coli.

我们用荧光原位杂交技术(FISH)揭示了不同DNA片段的亚细胞定位，这些DNA片段位于大肠杆菌染色体上大约230-kb的间隔。一系列染色体片段以与染色体图谱相同的顺序定位在细胞内。包括ORIC在内的大染色体区域显示出相似的定位模式，我们称之为ORI结构域。此外，包括dif的大片段的定位模式是复制终止区的特征。该片段也显示出类似的本地化模式，我们称之为Ter域。在新生细胞中，染色体的ORI和Ter结构域在相对的细胞极点附近有差异地定位。随后，在B期，在复制开始之前，ORI结构域向中间细胞移动，而Ter结构域倾向于在中间细胞重新定位。Ter结构域位于ORIC附近的倒位突变体，表现出OrI和dif片段的亚细胞定位异常，导致频繁产生无核细胞。因此，这些研究表明，大肠杆菌染色体被组织成与ORI和Ter结构域形成紧凑的环结构；这些结构域参与了染色体依赖于细胞周期的定位。

We have revealed the subcellular localization of different DNA segments that are located at approximately 〜230-kb intervals on the Escherichia coli chromosome using fluorescence in situ hybridization (FISH). The series of chromosome segments is localized within the cell in the same order as the chromosome map. The large chromosome region including oriC shows similar localization patterns, which we call the Ori domain. In addition, the localization pattern of the large segment including dif is characteristic of the replication terminus region. The segment also shows similar localization patterns, which we call the Ter domain. In newborn cells, Ori and Ter domains of the chromosome are differentially localized near opposite cell poles. Subsequently, in the B period, the Ori domain moves toward mid-cell before the initiation of replication, and the Ter domain tends to relocate at mid-cell. An inversion mutant, in which the Ter domain is located close to oriC, shows abnormal subcellular localization of ori and dif segments, resulting in frequent production of anucleate cells. These studies thus suggest that the E. coli chromosome is organized to form a compacted ring structure with the Ori and Ter domains; these domains participate in the cell cycle- dependent localization of the chromosome.