RNF6自身泛素化的调控机制及其在多发性骨髓瘤中的作用研究

泛素连接酶RNF6在多发性骨髓瘤（MM）中异常高表达，并与MM细胞增殖和地塞米松耐药密切相关。我们前期发现RNF6发生自身泛素化后经蛋白酶体途径降解，由于蛋白质的泛素-蛋白酶体途径降解可以被其特异性的去泛素化酶逆转，而目前尚不清楚RNF6的去泛素化酶有哪些。因此我们采用亲和纯化偶联串联质谱学技术分析了RNF6泛素化相关酶，发现USP7可以与RNF6结合并抑制其泛素化，可能是RNF6的去泛素化酶，但具体机制尚不明确。为了进一步探讨RNF6自身泛素化的调控机制，本项目将分析USP7抑制RNF6泛素化的类型和位点、研究USP7与RNF6结合的特点、分析USP7对RNF6诱导的MM细胞凋亡和地塞米松耐药的影响以及USP7抑制剂对克服MM化疗耐药的作用。本项目有助于深入理解RNF6自身泛素化的机制、USP7的功能及USP7调控RNF6自身泛素化对MM发生发展的影响，为MM的治疗提供新的思路。

RNF6, a ubiquitin ligase, is over-expressed in multiple myeloma（MM） and is found closely associated with MM cell proliferation and dexamethasone resistance. Our preliminary work showed that RNF6 could be auto-ubiquitinated and degraded via the ubiquitin-proteasome pathway, which is a process that can be reversed by specific deubiquitinases. However, it is not known yet about the deubiquitinase of RNF6. Thus, we applied the affinity purification/tandem mass spectrometry assay to find RNF6 ubiquitiantion-associated proteins and found that the ubiquitin-specific protease USP7 was present in the RNF6 interactome, suggesting USP7 might be a deubiquitinase of RNF6, but the mechanism is still elusive. To investigate the mechanism of RNF6 auto-ubiquitination, we will analyze RNF6 ubiquitination manners and lysine sites inhibited by USP7, and explore the critical domain of USP7 and RNF6 interaction. Moreover, we will elucidate how USP7 affect MM cell proliferation and dexamethasone resistance induced by RNF6, as well as whether USP7 inhibitors could overcome MM cell dexamethasone resistance. This project will help provide more details in understanding the mechanism of RNF6 auto-ubiquitination, USP7 function and its possible implications for MM pathophysiology， presenting new insights for MM treatment.