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首页> 外文期刊>Journal of bacteriology >SpoT Regulates DnaA Stability and Initiation of DNA Replication in Carbon-Starved Caulobacter crescentus
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SpoT Regulates DnaA Stability and Initiation of DNA Replication in Carbon-Starved Caulobacter crescentus

机译：SpoT调节碳饥饿的新月形Caulobacter crescentus中的DnaA稳定性和DNA复制的启动。

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Cell cycle progression and polar differentiation are temporally coordinated in Caulobacter crescentus. This oligotrophic bacterium divides asymmetrically to produce a motile swarmer cell that represses DNA replication and a sessile stalked cell that replicates its DNA. The initiation of DNA replication coincides with the proteolysis of the CtrA replication inhibitor and the accumulation of DnaA, the replication initiator, upon differentiation of the swarmer cell into a stalked cell. We analyzed the adaptive response of C. crescentus swarmer cells to carbon starvation and found that there was a block in both the swarmer-to-stalked cell polar differentiation program and the initiation of DNA replication. SpoT is a bifunctional synthase/hydrolase that controls the steady-state level of the stress-signaling nucleotide (p)ppGpp, and carbon starvation caused a SpoT-dependent increase in (p)ppGpp concentration. Carbon starvation activates DnaA proteolysis (B. Gorbatyuk and G. T. Marczynski, Mol. Microbiol. >55:1233-1245, 2005). We observed that SpoT is required for this phenomenon in swarmer cells, and in the absence of SpoT, carbon-starved swarmer cells inappropriately initiated DNA replication. Since SpoT controls (p)ppGpp abundance, we propose that this nucleotide relays carbon starvation signals to the cellular factors responsible for activating DnaA proteolysis, thereby inhibiting the initiation of DNA replication. SpoT, however, was not required for the carbon starvation block of the swarmer-to-stalked cell polar differentiation program. Thus, swarmer cells utilize at least two independent signaling pathways to relay carbon starvation signals: a SpoT-dependent pathway mediating the inhibition of DNA replication initiation, and a SpoT-independent pathway(s) that blocks morphological differentiation.
机译：在新月形杆菌中，细胞周期进程和极分化在时间上是协调的。这种贫营养细菌不对称分裂，产生能抑制DNA复制的运动型群体细胞和能复制其DNA的无柄茎细胞。 DNA的复制起始与CtrA复制抑制剂的蛋白水解以及复制子DnaA的积累（在将Swarmer细胞分化为茎细胞时）一致。我们分析了 C的自适应响应。新月形的成虫细胞使碳饥饿，发现成虫到茎的细胞极性分化程序和DNA复制的启动均受阻。 SpoT是一种双功能合酶/水解酶，可控制压力信号核苷酸（p）ppGpp的稳态水平，碳饥饿导致（p）ppGpp浓度引起SpoT依赖性增加。碳饥饿会激活DnaA蛋白水解作用（B. Gorbatyuk和G. T. Marczynski，分子微生物学，> 55： 1233-1245，2005）。我们观察到SpoT是在蜂群细胞中此现象所必需的，并且在没有SpoT的情况下，碳饥饿的蜂群细胞会不适当地引发DNA复制。由于SpoT控制（p）ppGpp丰度，我们建议该核苷酸将碳饥饿信号传递给负责激活DnaA蛋白水解的细胞因子，从而抑制DNA复制的启动。但是，SwarT到茎秆的细胞极性分化程序的碳饥饿块不需要SpoT。因此，成群细胞利用至少两个独立的信号传导途径来传递碳饥饿信号：介导DNA复制起始抑制的SpoT依赖性途径和阻断形态分化的SpoT非依赖性途径。

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