ParB spreading requires DNA bridging.
ParB spreading requires DNA bridging.
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DOI：
10.1101/gad.242206.114
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发表时间：
2014-06-01
影响因子：
10.5
通讯作者：
Loparo JJ
中科院分区：
文献类型：
--
作者：
Graham TG;Wang X;Song D;Etson CM;van Oijen AM;Rudner DZ;Loparo JJ
细菌的parABS系统用于质粒分配和染色体分离。ParB结合到parS位点，并与相邻DNA的大片段区域相关联，这种现象被称为扩散。然而，扩散的分子基础尚不清楚。通过单分子方法，格雷厄姆等人证明了枯草芽孢杆菌ParB（Spo0J）对DNA的桥接作用。破坏DNA桥接的Spo0J突变会导致扩散缺陷以及SMC凝聚素复合物招募异常。这项研究提出了一种新的、保守的机制，即ParB蛋白在染色体组织和分离中发挥作用的机制。
parABS系统是细菌中广泛应用的一种用于质粒分配和染色体分离的机制。ParB结合到质粒和染色体上的parS位点，并与相邻DNA的大片段区域相关联，这种现象被称为扩散。尽管对ParB的功能至关重要，但扩散的机制仍知之甚少。通过单分子方法，我们发现枯草芽孢杆菌ParB（Spo0J）能够捕获DNA环。体内实验中，破坏DNA桥接的Spo0J点突变体在扩散以及染色体结构维持（SMC）凝聚素复合物的招募方面存在缺陷。DNA桥接有助于解释每个parS位点数量有限的Spo0J分子（约20个）如何能够在数千个碱基对上扩散，并提出了ParB蛋白促进SMC复合物装载的一种机制。我们表明DNA桥接是多种ParB同源物的一种特性，这表明其在进化上具有广泛的保守性。
The bacterial parABS system is employed for plasmid partitioning and chromosome segregation. ParB binds to parS sites and associates with broad regions of adjacent DNA, a phenomenon known as spreading. However, the molecular basis for spreading is unknown. Using single-molecule approaches, Graham et al. demonstrate DNA bridging by B. subtilis ParB (Spo0J). Spo0J mutations that disrupt DNA bridging lead to defective spreading and SMC condensin complex recruitment. This study suggests a novel, conserved mechanism by which ParB proteins function in chromosome organization and segregation. The parABS system is a widely employed mechanism for plasmid partitioning and chromosome segregation in bacteria. ParB binds to parS sites on plasmids and chromosomes and associates with broad regions of adjacent DNA, a phenomenon known as spreading. Although essential for ParB function, the mechanism of spreading remains poorly understood. Using single-molecule approaches, we discovered that Bacillus subtilis ParB (Spo0J) is able to trap DNA loops. Point mutants in Spo0J that disrupt DNA bridging are defective in spreading and recruitment of structural maintenance of chromosomes (SMC) condensin complexes in vivo. DNA bridging helps to explain how a limited number of Spo0J molecules per parS site (∼20) can spread over many kilobases and suggests a mechanism by which ParB proteins could facilitate the loading of SMC complexes. We show that DNA bridging is a property of diverse ParB homologs, suggesting broad evolutionary conservation.
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