Distinct Cdc7 functions in the context of DNA replication and mitosis

Cdc7 在 DNA 复制和有丝分裂中的独特功能

• 批准号: 203528-2013
• 负责人: Lee, Hoyun
• 金额: $ 3.13万
• 依托单位: Laurentian University of Sudbury
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=593830
• 关键词: Distinct; Cdc7; functions; context; DNA

The cell division process is tightly regulated and closely coordinated with copying of its genetic material (DNA). In mammalian cells, the genome must replicate only once in its entirety during a single cell division cycle. Derangement of this process can be fatal for the cell or result in genetic instability. The once-per-cell cycle replication is achieved mainly by strictly regulating the stepwise formation and activation of pre-replication complex (pre-RC). At final stage of this regulation, Cdc7 protein functions as a 'molecular switch' for the activation of DNA replication by phosphorylating critical licensing components of the pre-RC. It is well known that Cdc7 itself is regulated by Dbf4 protein. However, it is not well-understood the mechanism how Cdc7 and the Dbf4 regulatory subunit bind each other to activate the pre-RC at the replication start-site. Our recent data shows that the Cdk1-mediated Cdc7 phosphorylation causes an increase in Cdc7 affinity to CRM1 protein. As a result, phosphorylated Cdc7 is dissociated from replication start-sites and bound by CRM1, by which Cdc7 is sequestered in the cytoplasm. Thus, Cdc7 phosphorylation prevents DNA re-replication during G2-M, which is critical for maintaining genetic stability. As a cell progresses from G1 to S phase during the next round of cell division cycle, the function of Cdc7 as replication activator is 'restored' by removing its phosphate group by an enzyme called phosphatase. In effect, the enzyme responsible for Cdc7 dephosphorylation functions as a key molecular switch toward the activation of DNA replication by Cdc7-Dbf4. Our main objective is to identify and characterize this important dephosphorylation enzyme. In addition, we also plan to determine whether phosphorylated Cdc7 has other functions. Data from this proposed work will shed exciting new light on the regulation of DNA replication in the context of cell cycle progression. Our data will also provide tremendous insight into the control mechanism about how a cell maintains its genetic stability. If successful, this work can have very significant and lasting impact on the DNA replication and cell cycle research fields.

细胞分裂过程受到严格调节，并通过复制其遗传物质（DNA）密切协调。在哺乳动物细胞中，基因组必须在单个细胞分裂周期中仅重复一次。该过程的危险可能对细胞致命，也可能导致遗传不稳定。一个每cell循环的复制主要是通过严格调节逐步形成和复制复合物（PRE-RC）的激活来实现的。在该调节的最后阶段，CDC7蛋白通过磷酸化PRE-RC的临界许可成分来激活DNA复制的“分子开关”。众所周知，CDC7本身受DBF4蛋白的调节。但是，CDC7和DBF4调节亚基如何相互结合以在复制起始位置激活前RC的机制并不是很好地理解。我们最近的数据表明，CDK1介导的CDC7磷酸化导致CDC7与CRM1蛋白的亲和力增加。结果，磷酸化的CDC7与复制起始位置分离，并由CRM1绑定，CDC7在细胞质中被隔离。因此，CDC7磷酸化阻止了G2-M期间的DNA再复制，这对于维持遗传稳定性至关重要。随着细胞在下一轮细胞分裂周期中从G1发展到S相，Cdc7作为复制激活剂的功能通过一种称为磷酸酶的酶去除其磷酸基团来“恢复”。实际上，负责CDC7去磷酸化的酶是朝着Cdc7-DBF4激活DNA复制激活的关键分子转换。我们的主要目标是识别和表征这种重要的去磷酸化酶。此外，我们还计划确定磷酸化的CDC7是否具有其他功能。这项提出的工作的数据将为细胞周期进程中的DNA复制调节提供令人兴奋的新启示。我们的数据还将提供有关细胞如何保持其遗传稳定性的控制机制的深入了解。如果成功，这项工作可能会对DNA复制和细胞周期研究领域产生非常重要的影响。