猪圆环病毒在猪群中的阳性率一直居高不下，给养猪业带来了巨大的经济损失。开发新的防控产品，降低病毒流行率，具有重要的意义。然而目前猪圆环病毒复制的分子机制不明，病毒编码的重要复制蛋白Rep的功能没有深入研究，给圆环病毒新的防控策略研究带来了障碍。本项目将以Rep蛋白为研究对象，通过结构生物学方法解析蛋白结构以及蛋白与底物复合物的结构，结合点突变方法阐明Rep蛋白中与DNA互作、解旋以及变构相关的关键位点，解析Rep蛋白解旋的机制；分别筛选与Rep、Rep’蛋白相互作用的细胞蛋白，阐明细胞蛋白与Rep-Rep’二聚体互作的方式，揭示猪圆环病毒复制复合物组装的机制；用过表达或者基因沉默方法，在细胞水平阐明蛋白在猪圆环病毒复制中的功能。通过上述研究，本项目将解析Rep蛋白参与猪圆环病毒复制及介导复制复合体形成的机制，为开发猪圆环病毒防控新策略提供理论支撑。

The high prevalence rate of porcine circovirus has maintained for many years and caused huge economic loss for pig industry. New antiviral strategies need to be considered in future. Rep protein, a virus encoded replication associated protein, plays crucial roles in several steps of PCV replication. But the research on Rep protein is so limited currently. The mechanisms of DNA unwinding and roles in replication of Rep are remaining unclear, hindering the development of new anti-PCV products. In this project, we will resolve the crystal structure of Rep protein as well as the structure of protein-substrate complex. The amino acids associated with DNA binding, unwinding and protein allosterism will be located by analyzing the protein structures, and then verify by site-directed mutagenesis. The Rep or Rep' binding protein in nucleus will be identified by pull-down and Co-IP assays and the interaction pattern will be discovered. By over-expression or gene silencing, the roles of cellular proteins in virus replication will be elucidated. Collectively, these researches will resolve the mechanism of DNA unwinding of Rep protein and the molecular details of PCV replication. These results will benefit the development of new anti-PCV strategies.