MCM协调损伤反应的行为调控的新机理研究

It is crucial for genomic stability to co-ordinate DNA replication with DNA damage response, which otherwise leads to carcinogenesis. During DNA replication, MCM unwinds duplex DNA along the chromatin. The insight into actions of MCM in response to DNA damage will highlight new cancer methodologies. This grant will prove dephosphorylation restricts progression of MCM on the chromatin to stabilize stalled replication forks in the presence of DNA damage. The HU (hydroxyurea) sensitivity, increase of single strand DNA and accumulation of Rad52 foci in the phosphomimetic mutants will be examined. Furthermore, we will explore function of Cdc14 in dephosphorylating MCM. The study will elucidate new mechanisms of regulation of MCM and contribute to developing new cancer therapies.

DNA损伤时，DNA复制相应地协调反应，避免了癌症发生的可能。MCM在DNA复制中沿染色体解开DNA双螺旋，深入理解损伤时MCM行为的变化，能够提供癌症治疗的新思路。本项目将从HU敏感性、ssDNA的积累以及Rad52 foci的聚集证明去磷酸限制MCM在染色体上的功能行使，避免损伤时停滞复制叉的坍塌，维持基因组的稳定性，并且探索Cdc14作用于MCM进行去磷酸的功能。这将深入理解MCM行为调控的新机理，为开展癌症治疗新方法提供科学依据。

DNA损伤时，Rad53能够稳定停滞的复制叉，损伤修复后，DNA复制可以继续，确保了基因组的完整性。然而，Rad53如何调控复制体蛋白从而保证复制叉的稳定是DNA损伤反应领域的关键问题，我们发现Rad53激酶底物— Cdc14作用于DNA复制中的解旋酶Mcm4，在cdc14突变体中，Mcm4的磷酸化增强，ssDNA积聚，意味着，随着磷酸化与去磷酸化的动态平衡调控MCM的功能行使，过度的磷酸化导致MCM过度解旋，在移动或停滞的复制叉上与DNA聚合酶uncouple，产生ssDNA积聚。并且，Cdc14缺陷时，细胞对DNA损伤剂尤其敏感，说明Cdc14在DNA损伤反应时行使重要的作用。我们的研究工作深入阐明了DNA损伤反应的核心Rad53激酶稳定停滞的复制叉的作用机理。