Origins Left, Right, and Centre: Increasing the Number of Initiation Sites in the Escherichia coli Chromosome.
Origins Left, Right, and Centre: Increasing the Number of Initiation Sites in the Escherichia coli Chromosome.
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DOI：
10.3390/genes9080376
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发表时间：
2018-07-27
期刊：
影响因子：
3.5
通讯作者：
Rudolph CJ
中科院分区：
文献类型：
--
作者：
Dimude JU;Stein M;Andrzejewska EE;Khalifa MS;Gajdosova A;Retkute R;Skovgaard O;Rudolph CJ
大肠埃希氏菌含有一条具有特定结构的单一环形染色体。DNA复制始于称为ORIC的单一起始点。两个复制叉子被组装在一起，并朝着相反的方向前进，直到它们在与原点相对的专用区融合。这个终止区的两侧是极复制叉子停顿区域，允许叉子进入，但不能离开。因此，染色体被分成两个复制柄，每个复制柄由一个复制叉复制。最近，我们分析了大肠杆菌细胞中的复制参数，其中一个名为ORIZ的异位起始点整合在右侧的复制体中。复制的两个主要障碍被发现：(1)高转录的RRN操纵子上的迎头复制-转录冲突，(2)复制叉陷阱。在这里，我们描述了具有异位起源的细胞中的复制参数，称为Orix和oriY，整合到左侧的复制体中，以及一个三重起源结构，其中Orix整合在左侧，ORIZ在右侧的复制体中。我们的数据再次强调了复制-转录冲突和复制叉陷阱是DNA复制的重要障碍，我们描述了一些自发的大型基因组重排，这些重排成功地缓解了由于在异位位置有额外起始点而产生的一些问题。然而，我们的数据揭示了影响有效染色体复制的其他因素，突出了染色体结构的复杂性。
The bacterium Escherichia coli contains a single circular chromosome with a defined architecture. DNA replication initiates at a single origin called oriC. Two replication forks are assembled and proceed in opposite directions until they fuse in a specialised zone opposite the origin. This termination area is flanked by polar replication fork pause sites that allow forks to enter, but not to leave. Thus, the chromosome is divided into two replichores, each replicated by a single replication fork. Recently, we analysed the replication parameters in E. coli cells, in which an ectopic origin termed oriZ was integrated in the right-hand replichore. Two major obstacles to replication were identified: (1) head-on replication–transcription conflicts at highly transcribed rrn operons, and (2) the replication fork trap. Here, we describe replication parameters in cells with ectopic origins, termed oriX and oriY, integrated into the left-hand replichore, and a triple origin construct with oriX integrated in the left-hand and oriZ in the right-hand replichore. Our data again highlight both replication–transcription conflicts and the replication fork trap as important obstacles to DNA replication, and we describe a number of spontaneous large genomic rearrangements which successfully alleviate some of the problems arising from having an additional origin in an ectopic location. However, our data reveal additional factors that impact efficient chromosome duplication, highlighting the complexity of chromosomal architecture.
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