Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA.
Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
mBio. 2018 Oct 23;9(5):e01088-18. doi: 10.1128/mBio.01088-18.
Coordination between chromosome replication and segregation is essential for equal partitioning of genetic material between daughter cells. In bacteria, this is achieved through the proximity of the origin of replication, , and the chromosome partitioning site, We report here that in , segregation but not replication is also controlled at the terminus region of the chromosome. Using the fluorescent repressor operator system (FROS), we investigated chromosome segregation in strain PAO1-UW, wherein the chromosome dimer resolution site, , is asymmetrically positioned relative to In these cells, segregation proceeded sequentially along the two chromosomal arms and terminated at In contrast, chromosome replication terminated elsewhere, opposite from We further found two large domains on the longer arm of the chromosome, wherein DNA segregated simultaneously. Notably, GC-skew, which reflects a bias in nucleotide usage between the leading and lagging strands of the chromosome, switches polarity at the locus but not necessarily at the terminus of replication. These data demonstrate that termination of chromosome replication and segregation can be physically separated without adverse effects on bacterial fitness. They also reveal the critical role of the region in defining the global layout of the chromosome and the progression of chromosome segregation and suggest that chromosome packing adapts to its subcellular layout. Segregation of genetic information is a central event in cellular life. In bacteria, chromosome segregation occurs concurrently with replication, sequentially along the two arms from to How the two processes are coordinated is unknown. We explored here chromosome segregation in an opportunistic human pathogen, , using its strain with markedly unequal chromosomal arms. We found that replication and segregation diverge in this strain and terminate at very different locations, whereas the longer chromosomal arm folds into large domains to align itself with the shorter arm. The significance of this research is in establishing that segregation and replication of bacterial chromosomes are largely uncoupled from each other and that the large-scale structure of the chromosome adapts to its subcellular layout.
染色体复制和分离之间的协调对于将遗传物质在子细胞之间均等分配至关重要。在细菌中，这是通过复制起点 和染色体分区位点 的接近来实现的。我们在此报告，在 中，染色体分离的控制不仅在染色体末端区域，而且在复制中也得到了控制。我们使用荧光阻遏操纵子系统（FROS），研究了 菌株 PAO1-UW 中的染色体分离，其中染色体二聚体分辨率位点 相对于 不对称定位。在这些细胞中，分离沿着两个染色体臂依次进行，并在 终止。相比之下，染色体复制在其他地方终止，与 相反。我们进一步在染色体的较长臂上发现了两个大的区域，其中 DNA 同时分离。值得注意的是，GC-倾斜反映了染色体前导链和滞后链之间核苷酸使用的偏向，在 位点发生极性转换，但不一定在复制末端。这些数据表明，染色体复制和分离的终止可以在不影响细菌适应性的情况下在物理上分离。它们还揭示了 区域在定义染色体全局布局和染色体分离进展方面的关键作用，并表明染色体包装适应其亚细胞布局。遗传信息的分离是细胞生命中的一个核心事件。在细菌中，染色体分离与复制同时发生，从 到 依次沿着两个臂进行。这两个过程如何协调尚不清楚。我们在这里使用具有明显不等臂的菌株，探索了机会性病原体 中的染色体分离。我们发现，在这种菌株中，复制和分离存在分歧，并在非常不同的位置终止，而较长的染色体臂折叠成大的域，以与较短的臂对齐。这项研究的意义在于，它确立了细菌染色体的分离和复制在很大程度上是相互独立的，并且染色体的大规模结构适应其亚细胞布局。
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