The DDB1-CUL4ADDB2 ubiquitin ligase is deficient in xeroderma pigmentosum group E and targets histone H2A at UV-damaged DNA sites
The DDB1-CUL4ADDB2 ubiquitin ligase is deficient in xeroderma pigmentosum group E and targets histone H2A at UV-damaged DNA sites
复制标题
DOI：
10.1073/pnas.0511160103
复制
发表时间：
2006-02-21
影响因子：
11.1
通讯作者：
Levine, AS
中科院分区：
文献类型：
--
作者：
Kapetanaki, MG;Guerrero-Santoro, J;Levine, AS
着色性干皮病（XP）是一种可遗传的人类疾病，其特征在于核磷脂切除修复（NER）缺陷和皮肤癌的发展。来自XP E组（XP-E）患者的细胞在UV损伤的DNA结合蛋白复合物（UV-DDB）中存在缺陷，参与NER的损伤识别步骤。UVDDB包含两个亚基，分别是DDB 1和DDB 2基因的产物。DDB 2基因的突变解释了XP-E的潜在缺陷。UV-DDB复合物是新鉴定的基于cullin 4A的泛素E3连接酶DDB 1-CUL 4A（DDB 2）的组分。E3泛素连接酶识别特异性底物并介导其泛素化以调节蛋白质活性或靶蛋白通过蛋白酶体途径降解。在这项研究中，我们已经解决了基于UV-DDB的E3在NER中的作用，并寻求一种生理底物。我们证明，monoubiquitinated组蛋白H2 A在天然染色质coimmunoprecipitates与内源性DDB 1-CUL 4A（DDB 2）复合物响应于紫外线照射。此外，DDB 2中的突变改变了DDB 1-CUL 4A（DDB 2）连接酶的形成和结合活性，与修复熟练的细胞相比，伴随着UV处理XP-E细胞后H2 A的单泛素化受损。这一发现表明DDB 2作为DDB 1-CUL 4A连接酶的底物受体，以光解结合依赖性方式特异性靶向组蛋白H2 A进行单泛素化。考虑到在紫外线损伤DNA的位点上单泛素化组蛋白H2 A的丢失与XP-E细胞中全局基因组修复的减少有关，这项研究表明，由XPE因子介导的组蛋白修饰促进了NER的启动。
Xeroderma pigmentosum (XP) is a heritable human disorder characterized by defects in nuclecitide excision repair (NER) and the development of skin cancer. Cells from XP group E (XP-E) patients have a defect in the UV-damaged DNA-binding protein complex (UV-DDB), involved in the damage recognition step of NER. UVDDB comprises two subunits, products of the DDB1 and DDB2 genes, respectively. Mutations in the DDB2 gene account for the underlying defect in XP-E. The UV-DDB complex is a component of the newly identified cullin 4A-based ubiquitin E3 ligase, DDB1-CUL4A(DDB2). The E3 ubiquitin ligases recognize specific substrates and mediate their ubiquitination to regulate protein activity or target proteins for degradation by the proteasomal pathway. In this study, we have addressed the role of the UV-DDB-based E3 in NER and sought a physiological substrate. We demonstrate that monoubiquitinated histone H2A in native chromatin coimmunoprecipitates with the endogenous DDB1-CUL4A(DDB2) complex in response to UV irradiation. Further, mutations in DDB2 alter the formation and binding activity of the DDB1-CUL4A(DDB2) ligase, accompanied by impaired monoubiquitination of H2A after UV treatment of XP-E cells, compared with repair-proficient cells. This finding indicates that DDB2, as the substrate receptor of the DDB1-CUL4A-based ligase, specifically targets histone H2A for monoubiquitination in a photolesion-binding-dependent manner. Given that the loss of monoubiquitinated histone H2A at the sites of UV-damaged DNA is associated with decreased global genome repair in XP-E cells, this study suggests that histone modification, mediated by the XPE factor, facilitates the initiation of NER.