Targeted ubiquitination of CDT1 by the DDB1-CUL4A-ROC1 ligase in response to DNA damage
Targeted ubiquitination of CDT1 by the DDB1-CUL4A-ROC1 ligase in response to DNA damage
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DOI：
10.1038/ncb1172
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发表时间：
2004-10-01
影响因子：
21.3
通讯作者：
Xiong, Y
中科院分区：
文献类型：
--
作者：
Hu, J;McCall, CM;Xiong, Y
Cullins通过与RING蛋白ROC1结合来组装潜在的大量泛素连接酶，催化多泛素化，并与各种特异性因子结合以招募底物（1-4）。Cul4A基因在人类乳腺癌和肝癌中被扩增，Cul4的功能缺失导致秀丽隐杆线虫胚胎和紫外线照射的人类细胞中复制许可因子CDT1的积累。在这里，我们报道了人类紫外线损伤的dna结合蛋白DDB1在体内与CUL4A化学计量相关，并以类似于SKP1、SOCS和BTB分别与CUL1、CUL2和CUL3结合的方式结合到CUL4A的氨基末端区域。与SKP1-CUL1一样，DDB1-CUL4A关联受到cullin相关和类木化解离蛋白CAND1的负调控。重组DDB1和CDT1在体外直接结合，而异位表达的DDB1在体内架起CDT1与CUL4A的桥梁。在体外，沉默DDB1可阻止紫外线诱导的CDT1快速降解和cul4a介导的CDT1泛素化。我们认为，在紫外线照射下，DDB1通过cul4a依赖的泛素连接酶CDL4A（DDB1）靶向CDT1使其泛素化。
Cullins assemble a potentially large number of ubiquitin ligases by binding to the RING protein ROC1 to catalyse polyubiquitination, as well as binding to various specificity factors to recruit substrates(1-4). The Cul4A gene is amplified in human breast and liver cancers, and loss-of-function of Cul4 results in the accumulation of the replication licensing factor CDT1 in Caenorhabditis elegans embryos and ultraviolet ( UV)-irradiated human cells. Here, we report that human UV-damaged DNA-binding protein DDB1 associates stoichiometrically with CUL4A in vivo, and binds to an amino-terminal region in CUL4A in a manner analogous to SKP1, SOCS and BTB binding to CUL1, CUL2 and CUL3, respectively. As with SKP1-CUL1, the DDB1-CUL4A association is negatively regulated by the cullin-associated and neddylation-dissociated protein, CAND1. Recombinant DDB1 and CDT1 bind directly to each other in vitro, and ectopically expressed DDB1 bridges CDT1 to CUL4A in vivo. Silencing DDB1 prevented UV-induced rapid CDT1 degradation in vivo and CUL4A-mediated CDT1 ubiquitination in vitro. We suggest that DDB1 targets CDT1 for ubiquitination by a CUL4A-dependent ubiquitin ligase, CDL4A(DDB1), in response to UV irradiation.