流感病毒是引起人畜共患病的重要病原之一，流感病毒PB2蛋白在病毒的复制周期和跨种传播过程中扮演重要角色。本课题组前期研究发现，PB2蛋白742位丝氨酸（PB2-S742）为潜在磷酸化位点，经质谱验证，此位点可以发生磷酸化。磷酸化修饰对病毒蛋白功能有重要影响，然而上述磷酸化位点对PB2蛋白功能及流感病毒生物学特性的影响尚未被解析。本研究拟通过对此位点进行去磷酸化与模拟磷酸化突变，研究其对流感病毒聚合酶活性、体外和体内复制力的影响。在此基础上，评价该位点磷酸化修饰对PB2蛋白与PB1蛋白结合能力的影响、与核输入蛋白结合能力的影响，以及鉴定催化其发生磷酸化的宿主蛋白激酶，以探究该磷酸化修饰发挥作用的分子机理。上述研究将深入揭示PB2蛋白磷酸化修饰对流感病毒复制性的影响及其分子机理，以期为研究流感病毒复制机理及新型抗病毒药物设计提供理论基础。

Influenza virus is one of the most important zoonotic pathogens, posing great threat to both humans and animals, and the PB2 protein of the causative agent is crucial to virus replication and cross-species transmission. In previous studies, we found that there was a potential phosphorylation site in 742S on the PB2 protein (PB2-S742), and our further investigations using Liquid Chromatography-Mass Spectrometry(MS-LC) verified that 742S could be phosphorylated. In general, phosphorylation plays an important role in the function of protein, however the role of the phosphorylation at the site described above in the function of PB2 protein and virus replication has remained elusive. Toward this end, in this study the effects of phosphorylation of the 742S on virus polymerase activity, in vitro replication kinetics and in vivo replication will be investigated by means of de-phosphorylation and mimicking phosphorylation. Furthermore, the molecular mechanism of phosphorylation of 742S on its binding ability with PB1, and the binding ability of importins, and the identification of host protein kinase catalyzed by phosphorylation will be studied. Taken together, this proposal will investigate the effect and the molecular mechanism of PB2 phosphorylation to virus replication, which would provide theoretical bases for investigations on replication of influenza virus and design of novel antivirals.