Lv Xiao-Bin, Xie Fangyun, Hu Kaishun, Wu Yuanzhong, Cao Lin-Lin, Han Xia, Sang Yi, Zeng Yi-Xin, Kang Tiebang
State Key Laboratory of Oncology in South China, Department of Experimental Research, Sun Yat-Sen University Cancer Center, 510060 Guangzhou, China.
J Biol Chem. 2010 Jun 11;285(24):18234-40. doi: 10.1074/jbc.M109.094144. Epub 2010 Apr 15.
APC/C(Cdh1) plays a key role in mitotic exit and has essential targets in the G(1) phase; however, these mechanisms are poorly understood. In this report, we provide evidence that damaged DNA-binding protein 1 (DDB1) is capable of binding the WD40 domains of Cdh1, but not of Cdc20, through its BPA and BPC domains. Moreover, cells lacking DDB1 exhibit markedly elevated levels of the protein substrates of APC/C(Cdh1). Depletion of DDB1 in mitotic cells significantly delays mitotic exit, which demonstrates that the interaction between DDB1 and Cdh1 plays a critical role in regulating APC/C(Cdh1) activity. However, cells depleted of Cdh1 demonstrated no change in the UV-induced degradation of Cdt1, the main function of DDB1 as an E3 ligase. Strikingly, the APC/C(Cdh1) substrate levels are normal in cell knockdowns of Cul4A and Cul4B, which, along with DDB1, form an E3 ligase complex. This finding indicates that DDB1 modulates the function of APC/C(Cdh1) in a manner independent on the Cul4-DDB1 complex. Our results suggest that DDB1 may functionally regulate mitotic exit by modulating APC/C(Cdh1) activity. This study reveals that there may be cross-talk among DDB1, Cdh1, and Skp2 in the control of cell cycle division.
后期促进复合物/细胞周期体（Cdh1）在有丝分裂退出过程中起关键作用，并且在G1期有重要作用靶点；然而，这些机制目前还知之甚少。在本报告中，我们提供证据表明，损伤DNA结合蛋白1（DDB1）能够通过其BPA和BPC结构域与Cdh1的WD40结构域结合，但不能与Cdc20的WD40结构域结合。此外，缺乏DDB1的细胞中，后期促进复合物/细胞周期体（Cdh1）的蛋白底物水平显著升高。在有丝分裂细胞中耗尽DDB1会显著延迟有丝分裂退出，这表明DDB1与Cdh1之间的相互作用在调节后期促进复合物/细胞周期体（Cdh1）活性方面起关键作用。然而，耗尽Cdh1的细胞中，DDB1作为E3连接酶的主要功能，即紫外线诱导的Cdt1降解，没有变化。令人惊讶的是，在与DDB1一起形成E3连接酶复合物的Cul4A和Cul4B的细胞敲低实验中，后期促进复合物/细胞周期体（Cdh1）的底物水平正常。这一发现表明，DDB1以独立于Cul4 - DDB1复合物的方式调节后期促进复合物/细胞周期体（Cdh1）的功能。我们的结果表明，DDB1可能通过调节后期促进复合物/细胞周期体（Cdh1）的活性在功能上调节有丝分裂退出。这项研究揭示，在细胞周期分裂的控制中，DDB1、Cdh1和Skp2之间可能存在相互作用。
