McLeod Brett N, Allison-Gamble Gina E, Barge Madhuri T, Tonthat Nam K, Schumacher Maria A, Hayes Finbarr, Barillà Daniela
Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK.
Department of Biochemistry, Duke University Medical Center, Duke University, Durham, NC 27710, USA.
Nucleic Acids Res. 2017 Apr 7;45(6):3158-3171. doi: 10.1093/nar/gkw1302.
Genome segregation is a fundamental step in the life cycle of every cell. Most bacteria rely on dedicated DNA partition proteins to actively segregate chromosomes and low copy-number plasmids. Here, by employing super resolution microscopy, we establish that the ParF DNA partition protein of the ParA family assembles into a three-dimensional meshwork that uses the nucleoid as a scaffold and periodically shuttles between its poles. Whereas ParF specifies the territory for plasmid trafficking, the ParG partner protein dictates the tempo of ParF assembly cycles and plasmid segregation events by stimulating ParF adenosine triphosphate hydrolysis. Mutants in which this ParG temporal regulation is ablated show partition deficient phenotypes as a result of either altered ParF structure or dynamics and indicate that ParF nucleoid localization and dynamic relocation, although necessary, are not sufficient per se to ensure plasmid segregation. We propose a Venus flytrap model that merges the concepts of ParA polymerization and gradient formation and speculate that a transient, dynamic network of intersecting polymers that branches into the nucleoid interior is a widespread mechanism to distribute sizeable cargos within prokaryotic cells.
基因组分离是每个细胞生命周期中的一个基本步骤。大多数细菌依靠专门的DNA分配蛋白来主动分离染色体和低拷贝数质粒。在这里，通过使用超分辨率显微镜，我们确定了ParA家族的ParF DNA分配蛋白组装成一个三维网络，该网络以类核为支架，并在其两极之间周期性穿梭。虽然ParF指定了质粒运输的区域，但ParG伴侣蛋白通过刺激ParF三磷酸腺苷水解来决定ParF组装周期和质粒分离事件的节奏。这种ParG时间调控被消除的突变体由于ParF结构或动力学的改变而表现出分配缺陷表型，这表明ParF类核定位和动态重新定位虽然是必要的，但本身并不足以确保质粒分离。我们提出了一个捕蝇草模型，该模型融合了ParA聚合和梯度形成的概念，并推测一个分支进入类核内部的相交聚合物的瞬态动态网络是在原核细胞内分配大量货物的一种广泛机制。
