Coordination of Growth, Chromosome Replication/Segregation, and Cell Division in E. coli.
Coordination of Growth, Chromosome Replication/Segregation, and Cell Division in E. coli.
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DOI：
10.3389/fmicb.2018.01469
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发表时间：
2018
影响因子：
5.2
通讯作者：
Stouf M
中科院分区：
文献类型：
--
作者：
Kleckner NE;Chatzi K;White MA;Fisher JK;Stouf M
在稳定状态下生长的细菌细胞在适当的质量增加、一轮DNA复制加上姐妹染色体分离和细胞分裂之间保持着1:1:1的关系。这是在没有真核细胞中发现的细胞周期引擎的情况下完成的。我们在这里提出了一种形式逻辑，以及一种伴随的机制，来解释这种协调如何在大肠杆菌中提供。染色体和分裂体相关事件的完成将相互作用地导致“进展控制复合体”（PCC）， PCC在姊妹端区和新生隔膜之间提供综合的物理耦合。当一个细胞(i)达到足够的质量增加，（ii） PCC已经形成时，PCC的构象就会发生变化。这种变化导致“进展许可”，从而触发细胞分裂的开始和末端区域的释放。末端区的释放，反过来，通过通过类核传递的物理变化，直接使下一轮复制起始成为可能。然后，根据目前的条件，以各自的速度和时间进行分割和起始。重要的是：(i)进展许可的限制步骤可能是完成生长要求或PCC组装所需的染色体/分裂过程；（ii）拟议工艺的结果是授予进度许可，而不是确定下游事件的绝对或相对时间。这个基本逻辑和伴随的机制可以解释慢速和快速增长条件下事件的协调；能适应细胞事件的各种变化和扰动；并且与大肠杆菌细胞周期的现有数学描述相容。此外，虽然我们的主张是专门设计为在“每个细胞周期”的基础上提供1:1:1的基本事件协调，但进一步设想许可进度也是基本增长率控制的目标，这是一小步。在这种情况下，质量积累速率（或同等速率）将决定连续许可事件之间的间隔长度，从而决定连续的细胞分裂和连续的复制起始。
Bacterial cells growing in steady state maintain a 1:1:1 relationship between an appropriate mass increase, a round of DNA replication plus sister chromosome segregation, and cell division. This is accomplished without the cell cycle engine found in eukaryotic cells. We propose here a formal logic, and an accompanying mechanism, for how such coordination could be provided in E. coli. Completion of chromosomal and divisome-related events would lead, interactively, to a “progression control complex” (PCC) which provides integrated physical coupling between sister terminus regions and the nascent septum. When a cell has both (i) achieved a sufficient mass increase, and (ii) the PCC has developed, a conformational change in the PCC occurs. This change results in “progression permission,” which triggers both onset of cell division and release of terminus regions. Release of the terminus region, in turn, directly enables a next round of replication initiation via physical changes transmitted through the nucleoid. Division and initiation are then implemented, each at its own rate and timing, according to conditions present. Importantly: (i) the limiting step for progression permission may be either completion of the growth requirement or the chromosome/divisome processes required for assembly of the PCC; and, (ii) the outcome of the proposed process is granting of permission to progress, not determination of the absolute or relative timings of downstream events. This basic logic, and the accompanying mechanism, can explain coordination of events in both slow and fast growth conditions; can accommodate diverse variations and perturbations of cellular events; and is compatible with existing mathematical descriptions of the E. coli cell cycle. Also, while our proposition is specifically designed to provide 1:1:1 coordination among basic events on a “per-cell cycle” basis, it is a small step to further envision permission progression is also the target of basic growth rate control. In such a case, the rate of mass accumulation (or its equivalent) would determine the length of the interval between successive permission events and, thus, successive cell divisions and successive replication initiations.
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发表时间：
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期刊：
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影响因子：
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