Banks Damon, Wu Min, Higa Leigh Ann, Gavrilova Nadia, Quan Junmin, Ye Tao, Kobayashi Ryuji, Sun Hong, Zhang Hui
Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Cell Cycle. 2006 Aug;5(15):1719-29. doi: 10.4161/cc.5.15.3150. Epub 2006 Aug 1.
The CUL4-ROC1 E3 ligase complex regulates genome stability, replication and cell cycle progression. A novel WD40 domain-containing protein, L2DTL/CDT2 and PCNA were identified as proteins associated with CUL4/DDB1 complexes. Inactivation of CUL4A, L2DTL, PCNA, DDB1 or ROC1 induced p53 stabilization and growth arrest. L2DTL, PCNA and DDB1/CUL4A complexes were found to physically interact with p53 tumor suppressor and its regulator MDM2/HDM2. The isolated CUL4A complexes display potent and robust polyubiquitination activity towards p53 and this activity is dependent on L2DTL, PCNA, DDB1, ROC1 and MDM2/HDM2. We also found that the interaction between p53 and CUL4 complex is regulated by DNA damage. Our data further showed that MDM2/HDM2 is rapidly proteolyzed in response to UV irradiation and this process is regulated by CUL4/DDB1 and PCNA. Our studies demonstrate that PCNA, L2DTL and the DDB1-CUL4A complex play critical and differential roles in regulating the protein stability of p53 and MDM2/HDM2 in unstressed and stressed cells.
CUL4-ROC1 E3连接酶复合物调控基因组稳定性、复制及细胞周期进程。一种含新型WD40结构域的蛋白L2DTL/CDT2以及增殖细胞核抗原（PCNA）被鉴定为与CUL4/DDB1复合物相关的蛋白。CUL4A、L2DTL、PCNA、DDB1或ROC1的失活诱导p53稳定化及生长停滞。发现L2DTL、PCNA以及DDB1/CUL4A复合物与p53肿瘤抑制因子及其调节因子MDM2/HDM2发生物理相互作用。分离得到的CUL4A复合物对p53显示出强大且稳定的多聚泛素化活性，且该活性依赖于L2DTL、PCNA、DDB1、ROC1以及MDM2/HDM2。我们还发现p53与CUL4复合物之间的相互作用受DNA损伤调控。我们的数据进一步表明，MDM2/HDM2在紫外线照射后迅速被蛋白酶解，且该过程受CUL4/DDB1和PCNA调控。我们的研究表明，PCNA、L2DTL以及DDB1-CUL4A复合物在未受应激和受应激细胞中对p53和MDM2/HDM2的蛋白质稳定性调控中发挥关键且不同的作用。
