Shaping the landscape of the Escherichia coli chromosome: replication-transcription encounters in cells with an ectopic replication origin.
Shaping the landscape of the Escherichia coli chromosome: replication-transcription encounters in cells with an ectopic replication origin.
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DOI：
10.1093/nar/gkv704
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发表时间：
2015-09-18
影响因子：
14.9
通讯作者：
Rudolph CJ
中科院分区：
文献类型：
--
作者：
Ivanova D;Taylor T;Smith SL;Dimude JU;Upton AL;Mehrjouy MM;Skovgaard O;Sherratt DJ;Retkute R;Rudolph CJ
每次细胞分裂都需要解开数百万个DNA碱基对，以允许染色体复制和基因转录。由于DNA复制和转录共享相同的模板，两个过程之间的冲突是不可避免的，正面碰撞被认为是特别有问题的。令人惊讶的是，最近的一项研究报告了具有异位复制起源的大肠杆菌细胞中未受干扰的细胞周期进程，其中高度转录的rrn操纵子被迫以与正常相反的方式复制。在这项研究中，我们再生了一个类似的菌株，发现倍增时间是正常细胞的两倍。与野生型相比，这种背景的复制谱显示出明显的偏差，特别是在高转录区和终止区。突变可以使终止区失活或使RNA聚合酶复合物不稳定，从而使它们更容易被复制叉取代，从而减轻了这些偏差。我们的数据表明，正面的复制-转录冲突是非常有问题的。事实上，对先前发表的大肠杆菌结构的复制谱的分析显示，染色体重排以一种有趣的简单方式减轻了复制-转录冲突。我们的数据支持这样一种观点，即避免正面碰撞对形成细菌染色体的独特结构有重要贡献。
Each cell division requires the unwinding of millions of DNA base pairs to allow chromosome duplication and gene transcription. As DNA replication and transcription share the same template, conflicts between both processes are unavoidable and head-on collisions are thought to be particularly problematic. Surprisingly, a recent study reported unperturbed cell cycle progression in Escherichia coli cells with an ectopic replication origin in which highly transcribed rrn operons were forced to be replicated opposite to normal. In this study we have re-generated a similar strain and found the doubling time to be twice that of normal cells. Replication profiles of this background revealed significant deviations in comparison to wild-type profiles, particularly in highly transcribed regions and the termination area. These deviations were alleviated by mutations that either inactivate the termination area or destabilise RNA polymerase complexes and allow their easier displacement by replication forks. Our data demonstrate that head-on replication-transcription conflicts are highly problematic. Indeed, analysis of the replication profile of the previously published E. coli construct revealed a chromosomal rearrangement that alleviates replication-transcription conflicts in an intriguingly simple way. Our data support the idea that avoiding head-on collisions has significantly contributed to shaping the distinct architecture of bacterial chromosomes.