乙肝病毒的感染是严重的社会健康威胁。在感染肝细胞后，病毒在细胞核内生成一个共价闭合环状的小染色cccDNA作为病毒基因转录和复制的模板。cccDNA持续稳定存在于被感染肝细胞中，而目前所有药物无法有效的将它清除。因此，研究cccDNA小染色体、鉴定相关宿主蛋白不仅有助于了解病毒的生物学基础，还有助于研发针对cccDNA的新型抗病毒药物来治愈乙肝病毒感染。通过建立体外高效感染模型，我们分离纯化并鉴定了cccDNA相关宿主蛋白，发现了Nucleolin（核仁素）作为新的病毒感染关键因子。我们前期研究结果发现Nucleolin能与cccDNA启动子区结合调控其转录。本课题拟过ChIP-Seq、基因敲除、免疫共沉淀、邻位连接技术等方法全面系统探索Nucleolin调控HBV cccDNA转录的分子机制并在HBV病人肝穿样本中验证，以期将Nucleolin作为药物靶点筛选新的抗病毒药物。

Hepatitis B virus (HBV) remains a major public health threat worldwide. After infection, the virus infects hepatocytes and establishes a covalently closed circular DNA (cccDNA) mini-chromosome, which serves as the transcriptional template of viral replication, in the nucleus of infected cells. Its stability accounts for the long-term persistence of HBV even if viral replication is blocked by antivirals. Currently, none of the treatments have significant little or no impact on eliminating HBV infection cccDNA. Therefore, identification of cccDNA- associated host factors and their functions is not only important in understanding the basic biology of HBV but also relevant to designing novel strategies to target cccDNA for potential curative therapy. Based on the efficient in vitro infection model, we isolated and purified cccDNA associated host proteins, and identified Nucleolin as a key factor of HBV infection. Our preliminary data showed that Nucleolin binds to the promoter regions of HBV cccDNA and regulates its transcription. We will use different methods including ChIP-Seq, gene knockout, Co-Immunoprecipitation, proximity ligation assay to dissect the molecular mechanism of how Nucleolin regulate HBV cccDNA and further validate our findings in liver biopsies from chronic hepatitis B patients. Whether Nucleolin is a potential target for antiviral development will also be evaluated.