Duigou Stéphane, Boccard Frédéric
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France.
PLoS Genet. 2017 May 9;13(5):e1006758. doi: 10.1371/journal.pgen.1006758. eCollection 2017 May.
The Escherichia coli chromosome is organized into four macrodomains (Ori, Ter, Right and Left) and two non-structured regions. This organization influences the segregation of sister chromatids, the mobility of chromosomal DNA, and the cellular localization of the chromosome. The organization of the Ter and Ori macrodomains relies on two specific systems, MatP/matS for the Ter domain and MaoP/maoS for the Ori domain, respectively. Here by constructing strains with chromosome rearrangements to reshuffle the distribution of chromosomal segments, we reveal that the difference between the non-structured regions and the Right and Left lateral macrodomains relies on their position on the chromosome. A change in the genetic location of oriC generated either by an inversion within the Ori macrodomain or by the insertion of a second oriC modifies the position of Right and Left macrodomains, as the chromosome region the closest to oriC are always non-structured while the regions further away behave as macrodomain regardless of their DNA sequence. Using fluorescent microscopy we estimated that loci belonging to a non-structured region are significantly closer to the Ori MD than loci belonging to a lateral MD. Altogether, our results suggest that the origin of replication plays a prominent role in chromosome organization in E. coli, as it determines structuring and localization of macrodomains in growing cell.
大肠杆菌染色体被组织成四个宏观结构域（ori、ter、右臂和左臂）和两个非结构化区域。这种组织方式影响姐妹染色单体的分离、染色体DNA的移动性以及染色体的细胞定位。Ter和ori宏观结构域的组织分别依赖于两个特定系统，即用于Ter结构域的MatP/matS和用于ori结构域的MaoP/maoS。在这里，通过构建具有染色体重排的菌株来重新排列染色体片段的分布，我们发现非结构化区域与右臂和左臂侧向宏观结构域之间的差异取决于它们在染色体上的位置。oriC基因位置的改变，无论是由ori宏观结构域内的倒位还是由第二个oriC的插入引起的，都会改变右臂和左臂宏观结构域的位置，因为最接近oriC的染色体区域总是非结构化的，而较远的区域则表现为宏观结构域，无论其DNA序列如何。使用荧光显微镜，我们估计属于非结构化区域的基因座比属于侧向宏观结构域的基因座更接近ori MD。总之，我们的结果表明，复制起点在大肠杆菌的染色体组织中起着重要作用，因为它决定了生长细胞中宏观结构域的结构和定位。
