Structural basis of the ubiquitination dependent modulation of XPC DNA repair protein.

XPC蛋白在核苷酸切除修复（NER）过程中特异性识别受损DNA的某种二级结构。泛素连接酶（E3）复合物（cullin 4A、DDB1、DDB2和Roc 1）通过紫外线损伤催化XPC的泛素化而刺激其活性。XPC的泛素化修饰促进其自身对DNA损伤的识别。然而，XPC的泛素修饰在NER途径中的作用尚不清楚。在这项研究中，我试图阐明通过泛素化XPC的生化和结构分析的DNA损伤识别的调节。采用生物化学方法鉴定XPC中泛素化的主要区域。另一方面，为了结构分析的目的，我试图制备XPC几个区域的表达构建体。然而，我没有成功地制备用于XPC结构分析的表达构建体，因为在纯化过程中蛋白质表达水平低和蛋白质沉淀。

XPC protein specifically recognizes a certain secondary structure of the damaged DNA during the NER (Nucleotide excision repair). The ubiquitin ligase (E3) complex (cullin 4A, DDB1, DDB2 and Roc1) stimulated its activity by UV damage catalyzes ubiquitination of XPC. The ubiquitin modification of XPC promotes the DNA damage recognition by itself. However, the role of the ubiquitin modification of XPC in the NER pathway is not clear. In this study, I have attempted to elucidate the regulation of DNA damage recognition through ubiquitination of XPC using biochemical and structural analysis. Biochemical approaches was taken to identify main region of ubiquitination in XPC. On the other hand, I have tried to prepare expression constructs of several regions of XPC for the purpose of structural analysis. However, I did not succeed in preparing expression constructs for structural analysis of XPC because of low level of protein expression and protein precipitation during purification.