Replication termination without a replication fork trap
Replication termination without a replication fork trap
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DOI：
10.1038/s41598-019-43795-2
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发表时间：
2019-06-05
影响因子：
4.6
通讯作者：
Possoz, Christophe
中科院分区：
文献类型：
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作者：
Galli, Elisa;Ferat, Jean-Luc;Possoz, Christophe
细菌染色体具有双向复制的独特起源，即ORIC。它们几乎总是环形的，复制终止于与ORIC(末端)完全相反的区域。ORIC末端组织通过基因的定位和DNA结合蛋白基序的处理反映出来，DNA结合蛋白基序与染色体复制和分离与细胞分裂的协调有关。相应地，大肠杆菌和枯草杆菌模式菌分别具有复制分叉陷阱系统TUS/TER和RTP/TER，该系统在末端区域强制终止复制。在这里，我们发现TUS和RTP被限制在四个细菌分支上，这表明TUS最近是从一个质粒基因驯化而来的。我们进一步证明在霍乱弧菌中没有复制分叉系统，霍乱弧菌是一种与大肠杆菌密切相关的细菌。标记频率分析表明，来自异位起源的复制叉在两条霍乱弧菌染色体的末端区域没有被阻断，但正常进行，直到它们遇到相反的叉子。正如预期的那样，两条染色体的终止同步性被这些异位起源打乱。最后，我们发现，初级染色体复制的过早完成并没有改变其末端区域分离的编排。
Bacterial chromosomes harbour a unique origin of bidirectional replication, oriC. They are almost always circular, with replication terminating in a region diametrically opposite to oriC, the terminus. The oriC-terminus organisation is reflected by the orientation of the genes and by the disposition of DNA-binding protein motifs implicated in the coordination of chromosome replication and segregation with cell division. Correspondingly, the E. coli and B. subtilis model bacteria possess a replication fork trap system, Tus/ter and RTP/ter, respectively, which enforces replication termination in the terminus region. Here, we show that tus and rtp are restricted to four clades of bacteria, suggesting that tus was recently domesticated from a plasmid gene. We further demonstrate that there is no replication fork system in Vibrio cholerae, a bacterium closely related to E. coli. Marker frequency analysis showed that replication forks originating from ectopic origins were not blocked in the terminus region of either of the two V. cholerae chromosomes, but progressed normally until they encountered an opposite fork. As expected, termination synchrony of the two chromosomes is disrupted by these ectopic origins. Finally, we show that premature completion of the primary chromosome replication did not modify the choreography of segregation of its terminus region.