本项目拟依据指南重点资助方向 "（二）生物大分子动态修饰的调控机制与功能解析" 开展研究，研究重点为蛋白质泛素化调控机制与功能解析。在已知的蛋白质翻译后修饰中，泛素化是调控细胞内蛋白质水平的主要途径。主要由E1、E2、E3通过级联反应完成。其中泛素化修饰的特异性很大程度上取决于E3泛素连接酶对底物的特异识别。本研究以Cul2-FEM1 E3泛素连接酶复合物为研究对象，拟通过结构生物学、生物化学、细胞生物学、化学生物学等手段，揭示Cul2-FEM1 E3泛素连接酶与底物的相互作用分子机制及酶催化机制，阐明SIL1、CDK5R1等蛋白质寿命调控的细胞功能；在此基础上发现鉴定Cul2-FEM1 的新底物，开发化学探针干预FEM1识别底物c-degron以调控Cul2-FEM1的泛素化修饰活性，建立重要靶蛋白质泛素化动态修饰模型，为神经退行性疾病的药物开发提供研究基础。

Based on the 2nd funding direction "Molecular mechanism and function of dynamic biomacromolecular modifications", the proposal aims to study the molecular mechanism of protein ubiquitination. Among post-translational modifications (PTMs), ubiquitination is the major route in regulating protein homeostasis in vivo, which a well-defined multistep reaction catalyzed by E1, E2, and E3. The specificity of ubiquitination is conferred, to a large extent, by the interaction between E3 ligase complex and substrate. The project aims to unravel the molecular mechanisms underlining the substrate recognition mode and the catalytic specificity of Cul2-FEM1, and to investigate the function of the E3-mediated stability of SIL1 and CDK5R1, by using structural biology, biochemistry, cell biology and chemical biology. On the basis of molecular structures, the proposal further plans to identify new substrate catalyzed by Cul2-FEM1, and to develop chemical probe to mediating the E3 activity by interfering with the interaction between FEM1 and substrate, which will provide guidance on drug development and treatment of neurodegenerative disease.