Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France.
Genes (Basel). 2022 May 13;13(5):877. doi: 10.3390/genes13050877.
Partition systems are widespread among bacterial chromosomes. They are composed of two effectors, ParA and ParB, and cis acting sites, , located close to the replication origin of the chromosome (). ParABS participate in chromosome segregation, at least in part because they serve to properly position sister copies of . A fourth element, located at cell poles, is also involved in some cases, such as HubP for the ParABS1 system of chromosome 1 (ch1). The polar anchoring of of ch1 () is lost when HubP or ParABS1 are inactivated. Here, we report that in the absence of HubP, ParABS1 actively maintains at mid-cell, leading to the subcellular separation of the two ch1 replication arms. We further show that sites ectopically inserted in chromosome 2 (ch2) stabilize the inheritance of this replicon in the absence of its endogenous partition system, even without HubP. We also observe the positioning interference between and of ch2 regions when their positionings are both driven by ParABS1. Altogether, these data indicate that ParABS1 remains functional in the absence of HubP, which raises questions about the role of the polar anchoring of in the cell cycle.
分区系统在细菌染色体中广泛存在。它们由两个效应器 ParA 和 ParB 以及顺式作用位点组成，这些位点位于染色体复制原点附近（）。ParABS 参与染色体分离，至少部分原因是它们有助于正确定位染色体的姐妹拷贝（）。在某些情况下，还涉及第四个元素，位于细胞两极，例如 ParABS1 系统的 HubP 对于染色体 1（ch1）。当 HubP 或 ParABS1 失活时，ch1 的（）的极性锚定会丢失。在这里，我们报告说，在没有 HubP 的情况下，ParABS1 会主动将 ParABS1 维持在细胞中部，导致两个 ch1 复制臂的亚细胞分离。我们进一步表明，当它们的定位都由 ParABS1 驱动时，异位插入染色体 2（ch2）的 位点稳定了该复制子的遗传，即使没有 HubP 也是如此。我们还观察到 ch2 区域的 与 的定位干扰，当它们的定位都由 ParABS1 驱动时。总的来说，这些数据表明，在没有 HubP 的情况下，ParABS1 仍然具有功能，这引发了关于染色体定位在细胞周期中的作用的问题。
