江西农业大学研究生院，江西农业大学研究生院官网
近日， Journal of Virology 杂志在线发表了 江西农业大学动科院 最 新 研究 进展，报道 IBDV 聚合酶蛋白 VP1 磷酸 化 修饰的分子机制。该研究首次揭示了磷酸化修饰促进IBDV聚合酶蛋白VP1稳定性从而促进病毒复制，加深了对该病毒聚合酶调节方面的认识，也为抗该病毒药物的研发提供了潜在靶点。
传染性法氏囊病病毒（ Infectious Bursa Diseases Virus, IBDV ）是双 RNA 病毒科 ( Birnaviridae ) ，禽双 RNA 病毒属 ( avibirnavirus ) 的唯一代表成员， IBDV 属于禽类高度接触性传染病，主要危害 5 周龄左右的雏鸡，雏鸡中枢免疫器官法氏囊为 该病毒的主要靶器官，造成雏鸡免疫抑制性疾病。 IBDV 基因组为双节段双链 RNA (dsRNA) ，分别为 A 片段和 B 片段， B 片段编码病毒聚合酶蛋白 VP1 ， 负责 基因组的复制和转录。 目前， IBDV 依然呈部分流行趋势，给我国乃至全球养禽业造成很大的经济损失 ，聚合酶蛋白磷酸化修饰对其功能及病毒复制至关重要 。
本研究通过免疫沉淀联合质谱发现VP1与CDK1存在互作，并经细胞内外实验给予了验证，CDK1抑制剂以及沉默都显著抑制IBDV复制，质谱鉴定发现CDK1-Cyclin B1磷酸化VP1 Ser7位点，聚合酶实验发现，CDK1抑制剂、CDK1-Cyclin B1沉默下调VP1聚合酶活性，S7A突变后VP1聚合酶活性显著下降，最后通过病毒拯救获得S7A突变IBDV，比较分析发现，S7A突变体IBDV复制能力显著低于野生型（WT） IBDV。该研究首次揭示了磷酸化修饰促进IBDV聚合酶蛋白VP1稳定性从而促进病毒复制，加深了对该病毒聚合酶调节方面的认识，也为抗该病毒药物的研发提供了潜在靶点。
附文献信息：
Title：Phosphorylation of VP1 Mediated by CDK1-Cyclin B1 Facilitates Infectious Bursal Disease Virus Replication
DOI：10.1128/jvi.01941-22
ABSTRACT：Infectious bursal disease virus (IBDV) is a double-stranded RNA (dsRNA) virus belonging to the genus Avibirnavirus in the family Birnaviridae. It can cause serious failure of vaccination in young poultry birds with impaired immune systems. Post-translational modifications of the VP1 protein are essential for viral RNA transcription, genome replication, and viral multiplication. Little information is available so far regarding the exact mechanism of phosphorylation of IBDV VP1 and its significance in the viral life cycle. Here, we provide several lines of evidence that the cyclin-dependent kinase 1 (CDK1)-cyclin B1 complex phosphorylates VP1, which facilitates viral replication. We show that the CDK1-cyclin B1 specifically interacts with VP1 and phosphorylates VP1 on the serine 7 residue, located in the N-terminal 7SPAQ10 region, which follows the optimal phosphorylation motif of CDK1, p-S/T-P. Additionally, IBDV infection drives the cytoplasmic accumulation of CDK1-cyclin B1, which co-localizes with VP1, supporting the kinase activity of CDK1-cyclin B1. Treatment with CDK1 inhibitor RO3306 and knockdown of CDK1-cyclin B1 severely disrupts the polymerase activity of VP1, resulting in diminished viral replication. Moreover, the replication of S7A mutant recombinant IBDV was significantly decreased compared to that of wild-type (WT) IBDV. Thus, CDK1-cyclin B1 is a crucial enzyme which phosphorylates IBDV VP1 on serine 7, which is necessary both for the polymerase activity of VP1 and for viral replication.
IMPORTANCE：Infectious bursal disease virus still poses a great economic threat to the global poultry farming industry. Detailed information on the steps of viral genome replication is essential for the development of antiviral therapeutics. Phosphorylation is a common post-translational modification in several viral proteins. There is a lack of information regarding the significance of VP1 phosphorylation and its role in modulating the viral life cycle. In this study, we found that CDK1-cyclin B1 accumulates in the cytoplasm and phosphorylates VP1 on serine 7. The presence of a CDK1 inhibitor and the silencing of CDK1-cyclin B1 decrease IBDV replication. The mutation of VP1 serine 7 to alanine reduces VP1 polymerase activity, disrupting the viral life cycle, which suggests that this residue serves an essential function. Our study offers novel insights into the regulatory mechanism of VP1 phosphorylation.
江西农业大学动科院预防兽医学2020级硕士研究生胡西凤为第一作者，青年教师吴欢生为通讯作者。该研究得到了国家自然基金、江西省自然科学基金的支持。
江西农业大学研究生院(江西农业大学研究生院官网)
