Praetorius-Ibba Mette, Wang Qi-En, Wani Gulzar, El-Mahdy Mohamed A, Zhu Qianzheng, Qin Song, Wani Altaf A
Department of Radiology, The Ohio State University, Columbus, OH 43240, United States.
DNA Repair (Amst). 2007 May 1;6(5):578-87. doi: 10.1016/j.dnarep.2006.11.009. Epub 2006 Dec 28.
The replication checkpoint protein Claspin is important for maintenance of genomic stability and is required for cells to overcome genotoxic stress. Upon UV-induced DNA damage, Claspin is required for activation of the ATR-mediated DNA damage checkpoint response, leading to arrest of DNA replication and inhibition of cell cycle progression. Located at the DNA replication fork, Claspin is also suggested to monitor replication and sense damage. Our present studies in HeLa cells demonstrate associations between the Claspin/ATR-related DNA damage checkpoint response and the global genomic nucleotide excision repair pathway. siRNA-mediated knockdown of Claspin abolishes the UV-induced degradation of DDB2 and impairs the co-localization of DDB2 to DNA damage sites. Thus, the presence of Claspin is required for the total turnover of DNA damage binding protein DDB2, as well as for its functionality in DNA damage recognition. Claspin, however, seems not to be required for maintaining the cellular level of the NER factor XPC and its UV-induced post-translational modifications. Co-localization of XPC with DNA lesions is also intact in the absence of Claspin as is the repair of the UV-induced lesions CPD and 6-4PP. Claspin itself may be directly responsible for physical interaction between the two pathways since Claspin is able to associate with DDB1, DDB2 and XPC. Taken together, these findings reveal physical and functional interplay between Claspin and NER-related proteins and demonstrate crosstalk between the DNA damage checkpoint control and DNA damage repair pathways.
复制检查点蛋白Claspin对于维持基因组稳定性很重要，并且是细胞克服基因毒性应激所必需的。在紫外线诱导的DNA损伤后，Claspin是激活ATR介导的DNA损伤检查点反应所必需的，导致DNA复制停滞和细胞周期进程的抑制。位于DNA复制叉处的Claspin也被认为可监测复制并感知损伤。我们目前在HeLa细胞中的研究表明，Claspin/ATR相关的DNA损伤检查点反应与全球基因组核苷酸切除修复途径之间存在关联。siRNA介导的Claspin敲低消除了紫外线诱导的DDB2降解，并损害了DDB2与DNA损伤位点的共定位。因此，Claspin的存在是DNA损伤结合蛋白DDB2完全周转及其在DNA损伤识别中的功能所必需的。然而，Claspin似乎不是维持NER因子XPC的细胞水平及其紫外线诱导的翻译后修饰所必需的。在没有Claspin的情况下，XPC与DNA损伤的共定位也是完整的，紫外线诱导的损伤CPD和6-4PP的修复也是如此。Claspin本身可能直接负责这两种途径之间的物理相互作用，因为Claspin能够与DDB1、DDB2和XPC结合。综上所述，这些发现揭示了Claspin与NER相关蛋白之间的物理和功能相互作用，并证明了DNA损伤检查点控制与DNA损伤修复途径之间的串扰。
