Ku80與EB病毒Zta蛋白質的功能研究

Abstract

EB病毒 (Epstein-Barr virus；EBV)屬於一種人類疱疹病毒，當病毒進入溶裂期會表現出極早期基因BZLF1並轉譯出Zta蛋白質，Zta為一個多功能蛋白質，主要負責調控基因轉錄及將DNA複製相關的蛋白質聚集到複製起始點。為了探討Zta在細胞中是否與其它細胞內蛋白質結合，對EB病毒溶裂期機制造成影響，所以本研究利用His pull-down assay吸附細胞蛋白質並以MALDI-TOF進行蛋白質定序發現人類的ATP-dependent DNA helicase II Ku80會與Zta結合，接著進一步以共同免疫沉澱分析和GST-pull down證實了Zta會與Ku80在細胞內及細胞外結合並一起結合到oriLyt上，並且觀察到Zta以C端區域與Ku80的N端區域結合，也在Ku80缺陷的P3HR1細胞中觀察到EB病毒溶裂期DNA複製的下降，Ku80也會與Zta和EA-D在細胞內結合。此外，利用冷光分析發現Ku80會增加Zta的轉錄活性。綜合以上，Zta與Ku80結合後會進一步調控EB病毒溶裂期複製。

Epstein-Barr virus (EBV) expresses immediate-early transcription factor Zta during the lytic cycle. Zta is a multifunctional protein that regulates gene transcription and recruits a replication complex at the lytic viral origin of replication. To identify cellular proteins that associate with Zta, this study performed His-Zta pull down analysis to precipitate cellular proteins and identified by MALDI-TOF a human ATP-dependent DNA helicase II Ku80 that interacts with Zta. Furthermore, Zta interacts with Ku80 in vivo and in vitro, forming a complex that binds to ZREs at the oriLyt. Furthermore, depleting Ku80 reduces EBV lytic DNA replication, showing the involvement of Ku80 in EBV lytic development. This study shows that the C-terminal domain of Zta interacts with the N- and M-domain of Ku80. Ku80 and Zta also interact with BMRF1 polymerase processivity factor, suggesting that Ku80 facilitates viral lytic DNA replication . In addition, Ku80 enhances the transcriptional activity of Zta. Taken together, this study found Ku80 involves in EBV lytic replication through an interaction with Zta.