Laboratory of Molecular Biology, Intercollegiate Faculty of Biotechnology of University of Gdansk and Medical University of Gdansk, University of Gdansk, ul. Abrahama 58, 80-307 Gdansk, Poland.
Nucleic Acids Res. 2020 Jun 4;48(10):5457-5466. doi: 10.1093/nar/gkaa217.
The decision whether to replicate DNA is crucial for cell survival, not only to proliferate in favorable conditions, but also to adopt to environmental changes. When a bacteria encounters stress, e.g. starvation, it launches the stringent response, to arrest cell proliferation and to promote survival. During the stringent response a vast amount of polymer composed of phosphate residues, i.e. inorganic polyphosphate (PolyP) is synthesized from ATP. Despite extensive research on PolyP, we still lack the full understanding of the PolyP role during stress. It is also elusive what is the mechanism of DNA replication initiation arrest in starved Escherichia coli cells. Here, we show that during stringent response PolyP activates Lon protease to degrade selectively the replication initiaton protein DnaA bound to ADP, but not ATP. In contrast to DnaA-ADP, the DnaA-ATP does not interact with PolyP, but binds to dnaA promoter to block dnaA transcription. The systems controlling the ratio of nucleotide states of DnaA continue to convert DnaA-ATP to DnaA-ADP, which is proteolysed by Lon, thereby resulting in the DNA replication initiation arrest. The uncovered regulatory mechanism interlocks the PolyP-dependent protease activation with the ATP/ADP cycle of dual-functioning protein essential for bacterial cell proliferation.
决定是否复制 DNA 对细胞存活至关重要，不仅要在有利条件下增殖，还要适应环境变化。当细菌遇到压力，例如饥饿时，它会启动严格响应，以停止细胞增殖并促进生存。在严格响应过程中，大量由磷酸盐残基组成的聚合物，即无机多聚磷酸盐 (PolyP) 会从 ATP 合成。尽管对 PolyP 进行了广泛的研究，但我们仍然缺乏对 PolyP 在压力下作用的全面理解。饥饿大肠杆菌细胞中 DNA 复制起始抑制的机制也不清楚。在这里，我们表明在严格响应期间 PolyP 激活 Lon 蛋白酶，选择性降解与 ADP 结合的复制起始蛋白 DnaA，但不与 ATP 结合。与 DnaA-ADP 不同，DnaA-ATP 不与 PolyP 相互作用，而是与 dnaA 启动子结合以阻止 dnaA 转录。控制 DnaA 核苷酸状态比的系统继续将 DnaA-ATP 转化为 DnaA-ADP，Lon 对其进行蛋白水解，从而导致 DNA 复制起始抑制。揭示的调节机制将依赖 PolyP 的蛋白酶激活与双功能蛋白的 ATP/ADP 循环相互关联，该蛋白对细菌细胞增殖至关重要。
