The DNA-binding protein from starved cells (Dps) plays a crucial role in maintaining bacterial cell viability during periods of stress. Dps is a nucleoid-associated protein that interacts with DNA to create biomolecular condensates in live bacteria. Purified Dps protein can also rapidly form large complexes when combined with DNA in vitro. However, the mechanism that allows these complexes to nucleate on DNA remains unclear. Here, we examine how DNA topology influences the formation of Dps–DNA complexes. We find that DNA supercoils offer the most preferred template for the nucleation of condensed Dps structures. More generally, bridging contacts between different regions of DNA can facilitate the nucleation of condensed Dps structures. In contrast, Dps shows little affinity for stretched linear DNA before it is relaxed. Once DNA is condensed, Dps forms a stable complex that can form inter-strand contacts with nearby DNA, even without free Dps present in solution. Taken together, our results establish the important role played by bridging contacts between DNA strands in nucleating and stabilizing Dps complexes.

中文翻译：

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桥接 DNA 触点使大肠杆菌的 Dps 能够浓缩 DNA

来自饥饿细胞 (Dps) 的 DNA 结合蛋白在应激期间维持细菌细胞活力方面发挥着至关重要的作用。 Dps 是一种类核相关蛋白，可与 DNA 相互作用，在活细菌中产生生物分子凝聚物。纯化的 Dps 蛋白在体外与 DNA 结合时也能快速形成大型复合物。然而，这些复合物在 DNA 上成核的机制仍不清楚。在这里，我们研究 DNA 拓扑结构如何影响 Dps-DNA 复合物的形成。我们发现 DNA 超螺旋为缩合 Dps 结构的成核提供了最优选的模板。更一般地说，DNA 不同区域之间的桥接接触可以促进凝聚的 Dps 结构的成核。相比之下，Dps 在松弛之前对拉伸的线性 DNA 几乎没有亲和力。一旦 DNA 被浓缩，Dps 就会形成稳定的复合物，即使溶液中没有游离的 Dps，也可以与附近的 DNA 形成链间接触。总而言之，我们的结果证实了 DNA 链之间的桥接接触在 Dps 复合物成核和稳定中发挥的重要作用。