Mechanisms of Theta Plasmid Replication in Enterobacteria and Implications for Adaptation to Its Host.
Mechanisms of Theta Plasmid Replication in Enterobacteria and Implications for Adaptation to Its Host.
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DOI：
10.1128/ecosalplus.esp-0026-2019
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发表时间：
2020-11
期刊：
影响因子：
--
通讯作者：
Camps M
中科院分区：
文献类型：
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作者：
Kim JW;Bugata V;Cortés-Cortés G;Quevedo-Martínez G;Camps M
质粒是自主复制的序列，可以帮助细胞适应不同的压力。Theta质粒是肠杆菌中最常见的质粒类别。它们采用两种宿主复制机制：在oriC上复制，这是一种依赖dna的途径，导致复制体组装（theta类a）；和复制叉重新启动，这是一种依赖pria的途径，通过引物延伸和D环形成（θ类B， C和D）导致引物体组装。为了确保不受宿主复制的影响并促进拷贝数调节，theta质粒在质粒复制起始点（ori）具有独特的复制起始机制。质粒拷贝数的严格调控是必要的，因为质粒基因剂量对基因表达有重大而直接的影响。质粒复制和分离的时机也是优化质粒基因表达的关键。因此，我们提出，质粒复制需要在其生物学背景下理解，其中复杂的复制起源（冗余起源，镶嵌和协整复制子），质粒分离和毒素-抗毒素系统经常存在。在大肠杆菌质粒的大量收集中，我们强调了它们与ori功能的紧密功能整合，表明分区系统和毒素-抗毒素系统倾向于在靠近ori的物理位置进行编码。我们还提出，质粒对宿主的适应优化了它们对宿主适应性的贡献，同时限制了获得广泛的遗传多样性，并认为对宿主的适应和获得遗传多样性之间的权衡可能是塑造肠杆菌群体中复制子分布的决定性因素。
Plasmids are autonomously-replicating sequences that help cells adapt to diverse stresses. Theta plasmids are the most frequent plasmid class in enterobacteria. They co-opt two host replication mechanisms: replication at oriC, a DnaA-dependent pathway leading to replisome assembly (theta class A); and replication fork restart, a PriA-dependent pathway leading to primosome assembly through primer extension and D-loop formation (theta classes B, C and D). To ensure autonomy from the host’s replication and to facilitate copy number regulation, theta plasmids have unique mechanisms of replication initiation at the plasmid origin of replication (ori). Tight plasmid copy number regulation is essential because of the major and direct impact plasmid gene dosage has on gene expression. The timing of plasmid replication and segregation are also critical for optimizing plasmid gene expression. Therefore we propose, that plasmid replication needs to be understood in its biological context, where complex origins of replication (redundant origins, mosaic and co-integrated replicons), plasmid segregation and toxin-antitoxin systems are often present. Highlighting their tight functional integration with ori function, we show that both partition and toxin-antitoxin systems tend to be encoded in close physical proximity to the ori in a large collection of Escherichia coli plasmids. We also propose that adaptation of plasmids to their host optimizes their contribution to the host’s fitness while restricting access to broad genetic diversity, and argue that this trade-off between adaptation to host and access to genetic diversity is likely a determinant factor shaping the distribution of replicons in populations of enterobacteria.