Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano, Italy.
Biotechnol Adv. 2012 Jan-Feb;30(1):73-98. doi: 10.1016/j.biotechadv.2011.09.009. Epub 2011 Sep 22.
In eukaryotes DNA replication takes place in the S phase of the cell cycle. It initiates from hundreds to thousands of replication origins in a coordinated manner, in order to efficiently duplicate the genome. The sequence of events leading to the onset of DNA replication is conventionally divided in two interdependent processes: licensing-a process during which replication origins acquire replication competence but are kept inactive- and firing-a process during which licensed origins are activated but not re-licensed. In this review we investigate the evolutionary conservation of the molecular machinery orchestrating DNA replication initiation both in yeast and in mammalian cells, highlighting a remarkable conservation of the general architecture of this central biological mechanism. Many steps are conserved down to molecular details and are performed by orthologous proteins with high sequence conservation, while differences in molecular structure of the performing proteins and their interactions are apparent in other steps. Tight regulation of initiation of DNA replication is achieved through protein phosphorylation, exerted mostly by Cyclin-dependent kinases in order to ensure that each chromosome is fully replicated once, and only once, during each cycle, and to avoid the formation of aberrant DNA structures and incorrect chromosomal duplication, that in mammalian cells are a prerequisite for genome instability and tumorigenesis. We then consider a molecular mathematical model of DNA replication, recently proposed by our group in a collaborative project, as a frame of reference to discuss similarities and differences observed in the regulatory program controlling DNA replication initiation in yeast and in mammalian cells and discuss whether they may be dependent upon different functional constraints. We conclude that a systems biology approach, integrating molecular analysis with modeling and computational investigations, is the best choice to investigate the control of DNA replication in mammalian cells.
在真核生物中，DNA 复制发生在细胞周期的 S 期。它以协调的方式从数百到数千个复制起点起始，以有效地复制基因组。导致 DNA 复制起始的事件序列通常分为两个相互依赖的过程：许可-一个过程，在此过程中复制起点获得复制能力但保持非活性-和引发-一个过程，在此过程中许可的起点被激活但不再许可。在这篇综述中，我们研究了在酵母和哺乳动物细胞中协调 DNA 复制起始的分子机制的进化保守性，突出了这种核心生物机制的一般结构的惊人保守性。许多步骤都以分子细节的形式被保守下来，并且由同源蛋白执行，这些蛋白具有高度的序列保守性，而在执行蛋白的分子结构及其相互作用方面的差异在其他步骤中是明显的。DNA 复制起始的严格调节是通过蛋白磷酸化来实现的，主要是由细胞周期蛋白依赖性激酶来实现的，以确保每个染色体在每个周期中只完全复制一次，并且避免形成异常的 DNA 结构和不正确的染色体复制，这在哺乳动物细胞中是基因组不稳定和肿瘤发生的前提。然后，我们考虑了我们小组在一个合作项目中最近提出的一个分子数学模型，作为讨论控制酵母和哺乳动物细胞中 DNA 复制起始的调控程序中观察到的相似性和差异的参考框架，并讨论它们是否可能依赖于不同的功能约束。我们得出的结论是，系统生物学方法，将分子分析与建模和计算研究相结合，是研究哺乳动物细胞中 DNA 复制控制的最佳选择。
