Phosphorylation by cellular casein kinase II is essential for transcriptional activity of vesicular stomatitis virus phosphoprotein P.

We have previously shown that phosphorylation of vesicular stomatitis virus (VSV) phosphoprotein P by cellular protein kinase activity is an essential prerequisite for its transcriptional function. We have now purified this protein kinase by monitoring its ability to phosphorylate bacterially expressed, unphosphorylated P protein. Biochemical studies showed that the kinase is indistinguishable from casein kinase II, a ubiquitous cyclic AMP-independent protein kinase present in a wide variety of eukaryotic cells and tissues. Functional VSV transcription could be reconstituted with viral L protein, N-RNA template, and P protein phosphorylated by either purified cellular protein kinase or purified casein kinase II. The unusual role of casein kinase II in the transcription process of a nonsegmented negative-strand RNA virus would have important implications in host-virus interactions and antiviral therapy. IMAGES:

本研究团队此前已证实，细胞蛋白激酶对水疱性口炎病毒（vesicular stomatitis virus, VSV）磷蛋白P的磷酸化修饰，是该磷蛋白发挥转录功能的必要前提。本研究通过监测其磷酸化细菌表达的未磷酸化P蛋白的能力，成功纯化得到了该蛋白激酶。生化分析结果显示，该激酶与酪蛋白激酶II（casein kinase II）完全一致——后者是一类广泛分布于多种真核细胞与组织中的、不依赖环腺苷酸（cyclic AMP）的泛在蛋白激酶。借助病毒L蛋白、N-RNA模板以及经纯化细胞蛋白激酶或纯化酪蛋白激酶II磷酸化的P蛋白，即可重建具有功能的VSV转录体系。酪蛋白激酶II在不分节段负链RNA病毒的转录过程中所承担的异常作用，对于宿主-病毒互作研究以及抗病毒治疗均具有重要的启示意义。图片：