Guo Lijuan, Zhao Yilin, Zhang Qian, Feng Ying, Bi Lulu, Zhang Xia, Wang Teng, Liu Cong, Ma Hanhui, Sun Bo
School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China.
CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai 200031, China.
Nucleic Acids Res. 2022 Sep 9;50(16):9294-9305. doi: 10.1093/nar/gkac651.
The tripartite ParABS system mediates chromosome segregation in a wide range of bacteria. Dimeric ParB was proposed to nucleate on parS sites and spread to neighboring DNA. However, how properly distributed ParB dimers further compact chromosomal DNA into a higher-order nucleoprotein complex for partitioning remains poorly understood. Here, using a single-molecule approach, we show that tens of Bacillus subtilis ParB (Spo0J) proteins can stochastically multimerize on and stably bind to nonspecific DNA. The introduction of CTP promotes the formation and diffusion of the multimeric ParB along DNA, offering an opportunity for ParB proteins to further forgather and cluster. Intriguingly, ParB multimers can recognize parS motifs and are more inclined to remain immobile on them. Importantly, the ParB multimer features distinct capabilities of not only bridging two independent DNA molecules but also mediating their transportation, both of which are enhanced by the presence of either CTP or parS in the DNA. These findings shed new light on ParB dynamics in self-multimerization and DNA organization and help to better comprehend the assembly of the ParB-DNA partition complex.
三方ParABS系统介导多种细菌中的染色体分离。二聚体ParB被认为在parS位点成核并扩散到邻近的DNA上。然而，分布适当的ParB二聚体如何进一步将染色体DNA压缩成更高阶的核蛋白复合物以进行分配，目前仍知之甚少。在这里，我们使用单分子方法表明，数十个枯草芽孢杆菌ParB（Spo0J）蛋白可以在非特异性DNA上随机多聚化并稳定结合。CTP的引入促进了多聚体ParB沿DNA的形成和扩散，为ParB蛋白进一步聚集提供了机会。有趣的是，ParB多聚体可以识别parS基序，并且更倾向于在其上保持不动。重要的是，ParB多聚体不仅具有桥接两个独立DNA分子的独特能力，还具有介导其运输的能力，DNA中CTP或parS的存在都会增强这两种能力。这些发现为ParB在自我多聚化和DNA组织中的动态变化提供了新的见解，并有助于更好地理解ParB-DNA分配复合物的组装。
