竞争性乙肝病毒与宿主RNA调控网络研究

During virus infection, viral RNAs and mRNAs function as blueprints for viral protein synthesis and possibly as pathogen-associated molecular patterns (PAMPs) in innate immunity. Our previous studies show that during hepatitis B virus (HBV) infection, high levels of viral RNAs harboring an miR-122 response element in their 3'-UTR competitively sponge and efficiently sequester cellular miR-122, thus blocking the binding of miR-122 to its host target mRNAs. In this manner, viral RNAs de-repress and rescue the expression of host target mRNAs. In this project, we propose a "competitive viral and host RNAs" (cvhRNAs) hypothesis. Viral RNAs and host mRNAs could competitively sequester the same miRNA pool within infected cells. The positive reciprocal regulation between virus and host mRNAs acting in this manner is termed cvhRNAs. The dynamic changes of HBV mRNA-miRNA-host mRNA, and the basis for formation of cvhRNA crosstalk will be determined in the HBV infection model. The molecular mechanisms of cvhRNAs which may be involved in the regulation of HBV replication and HCC development will be fully analyzed. In addition, the impact of HBV mRNA-mediated cvhRNA networks on the fine-tuned balance between miRNAs and host mRNA targets will be studied, which may provide further dissection of the impact of cvhRNA networks on vial persistence and HCC development. This study will facilitate the development of new antiviral and antitumor strategies.

我们前期研究发现乙肝病毒（HBV）mRNA的一个新功能，即3'-UTR上含有一个miR-122结合序列，通过与miR-122结合，以"海绵"吸附的方式隔离并抑制感染细胞中的miR-122，从而减轻了miR-122对宿主靶基因表达的抑制，引起miR-122的多个靶基因表达的上调。在此基础上，本项目提出竞争性病毒与宿主RNAs（cvhRNAs）的假设，包含有共同miRNA结合序列的病毒RNA/mRNA与宿主mRNA会竞争性地结合感染细胞中的特定miRNA，这种以miRNA为桥梁的病毒mRNA与宿主mRNA之间的直接相互正向调控称作cvhRNAs。本项目将全面分析HBV mRNA-miRNA-宿主mRNA之间的动态变化以及cvhRNAs调控网络形成的必要条件，深入研究 cvhRNAs参与调节HBV表达与复制、病毒感染引发肝癌（HCC）发生的分子机制，为设计新的抗病毒、抗肝癌策略提供线索。

本项目在前期工作基础上提出竞争性病毒RNAs（cvRNAs）的假设，包含有共同miRNA 结合序列的病毒RNA/mRNA 与宿主mRNA 会竞争性地结合感染细胞中的特定miRNA，这种以miRNA 为桥梁的病毒mRNA 与宿主mRNA 之间的直接相互正向调控称作cvRNAs。全面分析乙肝病毒（HBV）mRNA-miRNA-宿主mRNA 之间的动态变化以及cvRNAs 调控网络参与调节HBV 表达与复制、病毒感染引发肝癌（HCC）发生的分子机制， 同时我们还研究了流感病毒RNA 通过cvRNAs可参与调节流感病毒的复制。乙肝病毒RNA作为cvRNA通过吸附隔离miR-122上调cyclin G1促进病毒转录，进而形成HBV mRNA-miR-122-cyclin G1/p53正向调节病毒mRNA转录的环路，参与促进病毒复制、增强病毒适应肝细胞环境和诱导肝细胞癌发生(Scientific Reports ,2015)，为了解病毒感染病理与病毒持续性感染提供了新的线索。同时，乙肝病毒的3个RNA（包括pgRNA, Pre-S和S mRNA）均含有宿主let-7a的结合位点，HBV mRNAs通过let-7a反应元件依赖的模式吸附隔离let-7a，从而解除let-7a对其靶点(例如 c-myc、K-RAS和CCR7)及其下游通路的抑制作用，进而促进肝细胞的克隆形成和肿瘤生长，这为揭示慢性HBV感染向肝细胞癌（HCC）的转化提供了新的机制和治疗靶点（Cancer Letters，2015），并发现HER2 mRNA作为ceRNA调节HER3表达（Molecular Cancer, 2018）。同时发现流感病毒RNA聚合酶PA上存在miR-10靶点，作为cvRNA竞争性吸附miR-10，解除了miR-10对宿主蛋白camk2的抑制，从而促进了病毒的复制。通过本课题的研究我们发现了病毒RNA的新功能，即作为cvRNA直接参与调节病毒复制、感染和病理，cvRNA是流感病毒、乙肝病毒与宿主相互作用的新模式。