病毒感染所激活的固有免疫通路,在多步骤受到严格调控。Cbx4/Pc2 是多梳蛋白家族成员，具SUMO E3 连接酶活性，但至今其在抗病毒固有免疫反应中的调节作用还完全未知。我们的前期研究发现过表达 Cbx4 可抑制仙台病毒以及 poly (I:C) 所诱导的 ISRE 和 IFN-beta 的激活，本研究将进一步通过过表达或 敲低 Cbx4 的表达，或利用 Cbx4 基因敲除的 MEF 细胞，通过报告基因、下游靶基因表达水平检测等多种手段确实 Cbx4 的负向调节作用。同时通过免疫共沉淀、报告基因检测等找到 Cbx4 作用的信号节点。机制分析构建 Cbx4的SIM 区缺失突变体，探讨其抑制作用是否依赖于其SUMO E3 连接酶活性，对作用的靶蛋白是否有促进其 SUMO 化修饰，以及对靶蛋白泛素化修饰和蛋白稳定性的影响，转录活性的影响。最后将通过Cbx4条件敲除小鼠体内观察其抗病毒免疫反应.

Innate immune response initiated by virus infection is strictly regulated by multiple negative and positive regulators.Cbx4/Pc2, a member of the polycomb group proteins, has been identified as a SUMO E3 ligase. Until now, the regulatory function of Cbx4 on antiviral innate immune response has not been characterized. Our previous studies found that overexpression of Cbx4 inhibited Sendai virus and poly (I: C) induced ISRE and IFN-beta activation. In this study, we will confirm the negative regulatory roles of Cbx4 by reporter assay or detection of downstream target gene expression levels in cells with overexpression or knockdown of Cbx4 expression or in Cbx4 gene knockout MEFs induced by Sendai virus or poly (I:C). We will try to find the target signal molecules of Cbx4 by coimmunoprecipitation and reporter assays. By the SIM motif mutants, we will answer whether the regulatory functions of Cbx4 is dependent on its SUMO E3 ligase activity. We will also detect whether Cbx4 promote the sumoylation of the target proteins ,as well as its influence on the ubiquitination and stability of the target protein and its transcriptional activity. Finally, we will confirm the regulatory function on antiviral immune response in conditional Cbx4 knockout mice.