Dynamic organization of chromosomal DNA in Escherichia coli.

我们利用荧光原位杂交技术（FISH）揭示了大肠杆菌染色体上约230-kb间隔的不同DNA片段的亚细胞定位。染色体片段序列在细胞内以与染色体图谱相同的顺序定位。包括oriC在内的大染色体区域显示出类似的定位模式，我们称之为Ori结构域。此外，包括dif在内的大片段的定位模式是复制末端区域的特征。该片段也显示出类似的定位模式，我们称之为Ter域。在新生细胞中，染色体的Ori和Ter结构域不同地定位在相反的细胞极附近。随后，在B期，在开始复制之前，Ori结构域向细胞中部移动，Ter结构域倾向于在细胞中部重新定位。一个倒置突变体，其Ter结构域位于oriC附近，显示ori和不同片段的异常亚细胞定位，导致无核细胞的频繁产生。因此，这些研究表明，大肠杆菌染色体组织形成一个紧密的环结构域Ori和Ter；这些结构域参与细胞周期依赖的染色体定位。

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.