Interplay between chromosomal architecture and termination of DNA replication in bacteria.
Interplay between chromosomal architecture and termination of DNA replication in bacteria.
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DOI：
10.3389/fmicb.2023.1180848
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发表时间：
2023
影响因子：
5.2
通讯作者：
中科院分区：
文献类型：
--
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基因组从一代到下一代的忠实传递是所有细胞生物生命的关键。在大多数细菌中，基因组由单个环状染色体组成，通常从单个来源复制，尽管额外的遗传信息可能编码在称为质粒的更小的染色体外元件中。相比之下，真核生物的基因组分布在多个线性染色体上，每个线性染色体都是从多个来源复制的。古细菌物种的基因组是圆形的，但主要是从多个来源复制。在所有三种情况下，复制是双向的，并且当聚合的复制叉复合物合并并随着染色体DNA的复制完成而“融合”时终止。虽然复制起始的机制已经被很好地理解，但在终止过程中到底发生了什么还远不清楚，尽管近年来对细菌和真核生物模型的研究已经开始提供一些见解。具有环状染色体和单个双向起点的细菌模型提供了明显的优势，即当合成终止时，两个复制叉复合物之间通常只有一个融合事件。此外，尽管在许多细菌中，复制的终止似乎发生在叉碰巧相遇的地方，但在一些细菌物种中，包括经过充分研究的细菌大肠杆菌和枯草芽孢杆菌，终止更具限制性，并局限于“复制叉陷阱”区域，使终止更容易处理。该区域由多个基因组终止子（ter）位点限定，如果被特定的终止子蛋白结合，则形成单向叉屏障。在这篇综述中，我们讨论了一系列的实验结果，突出了叉融合过程如何触发干扰DNA复制成功结束的显著病理，这些病理如何在没有叉陷阱系统的细菌中解决，以及叉陷阱的获得如何提供了一种替代和更清洁的解决方案，从而解释了为什么在已经获得叉陷阱系统的细菌物种中，这个系统维护得非常好。最后，我们考虑如何真核细胞可以科普大量增加的终止事件。
Faithful transmission of the genome from one generation to the next is key to life in all cellular organisms. In the majority of bacteria, the genome is comprised of a single circular chromosome that is normally replicated from a single origin, though additional genetic information may be encoded within much smaller extrachromosomal elements called plasmids. By contrast, the genome of a eukaryote is distributed across multiple linear chromosomes, each of which is replicated from multiple origins. The genomes of archaeal species are circular, but are predominantly replicated from multiple origins. In all three cases, replication is bidirectional and terminates when converging replication fork complexes merge and ‘fuse’ as replication of the chromosomal DNA is completed. While the mechanics of replication initiation are quite well understood, exactly what happens during termination is far from clear, although studies in bacterial and eukaryotic models over recent years have started to provide some insight. Bacterial models with a circular chromosome and a single bidirectional origin offer the distinct advantage that there is normally just one fusion event between two replication fork complexes as synthesis terminates. Moreover, whereas termination of replication appears to happen in many bacteria wherever forks happen to meet, termination in some bacterial species, including the well-studied bacteria Escherichia coli and Bacillus subtilis, is more restrictive and confined to a ‘replication fork trap’ region, making termination even more tractable. This region is defined by multiple genomic terminator (ter) sites, which, if bound by specific terminator proteins, form unidirectional fork barriers. In this review we discuss a range of experimental results highlighting how the fork fusion process can trigger significant pathologies that interfere with the successful conclusion of DNA replication, how these pathologies might be resolved in bacteria without a fork trap system and how the acquisition of a fork trap might have provided an alternative and cleaner solution, thus explaining why in bacterial species that have acquired a fork trap system, this system is remarkably well maintained. Finally, we consider how eukaryotic cells can cope with a much-increased number of termination events.
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