泛素连接酶FBXW7靶向降解RPAP2动态调控基因转录影响肝癌发生的作用及机制研究

本项目研究重点为结合测序等新技术解析动态化学修饰对三维基因组的调控机制。RPAP2是负责去磷酸化修饰RNA聚合酶II大亚基RPB1的磷酸酶，它在动态调节基因转录过程中发挥重要作用。我们前期研究表明RPAP2可能是泛素连接酶FBXW7的新底物；它在肝癌组织中表达增加，且与患者不良预后正相关；敲降RPAP2显著抑制肝癌细胞的生长和存活。但是，RPAP2能否通过动态调控基因转录影响肝癌发生还不清楚，且抑癌蛋白FBXW7能否通过靶向降解RPAP2，动态调节RNA聚合酶II活性和基因转录，从而抑制肝癌的发生发展也还完全未知。本项目拟利用生化、分子和细胞生物学、大规模测序、基因修饰鼠和临床样品等手段研究FBXW7靶向降解RPAP2动态调控基因转录，抑制肝癌发生的作用，并揭示RPAP2在肝癌发生中的作用及机制，为开发FBXW7-RPAP2成为肝癌的诊断和预后标志物、及治疗新靶点提供理论基础和实验依据。

The proposal is focused on the regulation of three-dimensional genome by dynamic chemical modification via new technologies, like sequencing. RPAP2 (RNA Pol II-associated protein 2) is responsible for dephosphorylating RPB1, the largest subunit of RNA polymerase II complex, thereby playing important roles in dynamic regulation of gene expression. Our preliminary data showed that RPAP2 appears to be a novel substrate of ubiquitin ligase FBXW7, and is overexpressed in human liver cancer tissues, which is correlated with poor prognosis of patients with liver cancer. In addition, silencing of RPAP2 significantly suppressed the growth and survival of liver cancer cells. However, whether RPAP2 regulates liver tumorigenesis by dynamic regulation of gene transcription is totally unknown. Further, whether FBXW7 regulates the activity of RNA polymerase II and gene expression to suppress liver tumorigenesis by targeting RPAP2 for degradation also remains elusive. In this proposed study, we are going to investigate the role of FBXW7 in the dynamic regulation of gene expression to suppress liver tumorigenesis by targeting RPAP2 for degradation via a variety of approaches, including biochemical, molecular and cellular biology, large scale sequencing, genetically modified mouse tumor models and human clinical specimens. We will also evaluate the role of RPAP2 in liver tumorigenesis and its mechanism of action. Our study would provide the proof-of-concept evidence in developing FBXW7 and/or RPAP2 as biomarkers for the diagnosis and prognosis of liver cancer and selectively targeting the FBXW7-RPAP2 axis for anti-liver cancer therapy.