Yang Ya-Chun, Feng Tzu-Hui, Chen Tse-Yao, Huang Hsiang-Hung, Hung Chen-Chia, Liu Shih-Tung, Chang Li-Kwan
Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei, 106, Taiwan, ROC.
Molecular Genetics Laboratory, Department of Microbiology and Immunology, Chang-Gung University, Taoyuan, 333, Taiwan, ROC.
J Gen Virol. 2015 Aug;96(8):2336-2348. doi: 10.1099/vir.0.000157. Epub 2015 Apr 21.
Epstein-Barr virus (EBV) expresses two immediate-early proteins, Rta and Zta, which are key transcription factors that can form a complex with MCAF1 at Zta-responsive elements (ZREs) to synergistically activate several viral lytic genes. Our previous research indicated that RanBPM interacts with Rta and enhances Rta sumoylation. Here we showed that RanBPM binds to Zta in vitro and in vivo, and acts as an intermediary protein in Rta-Zta complex formation. The Rta-RanBPM-Zta complex was observed to bind with ZREs in the transcriptional activation of key viral genes, such as BHLF1 and BHRF1, while the introduction of RanBPM short hairpin RNA (shRNA) subsequently reduced the synergistic activity of Zta and Rta. RanBPM was found to enhance Zta-dependent transcriptional activity via the inhibition of Zta sumoylation. Interestingly, Z-K12R, a sumoylation-defective mutant of Zta, demonstrated transcriptional activation capabilities that were stronger than those of Zta and apparently unaffected by RanBPM modulation. Finally, RanBPM silencing inhibited the expression of lytic proteins. Taken together, these results shed light on the mechanisms by which RanBPM regulates Zta-mediated transcriptional activation, and point to an important role for RanBPM in EBV lytic progression.
爱泼斯坦-巴尔病毒（EBV）表达两种立即早期蛋白，即Rta和Zta，它们是关键转录因子，可在Zta反应元件（ZREs）处与MCAF1形成复合物，协同激活多个病毒裂解基因。我们之前的研究表明，RanBPM与Rta相互作用并增强Rta的SUMO化。在此我们发现，RanBPM在体外和体内均与Zta结合，并在Rta-Zta复合物形成过程中充当中间蛋白。在关键病毒基因（如BHLF1和BHRF1）的转录激活过程中，观察到Rta-RanBPM-Zta复合物与ZREs结合，而引入RanBPM短发夹RNA（shRNA）随后降低了Zta和Rta的协同活性。研究发现，RanBPM通过抑制Zta的SUMO化来增强Zta依赖的转录活性。有趣的是，Z-K12R是Zta的一种SUMO化缺陷突变体，其转录激活能力比Zta更强，且明显不受RanBPM调节的影响。最后，RanBPM沉默抑制了裂解蛋白的表达。综上所述，这些结果揭示了RanBPM调节Zta介导的转录激活的机制，并指出RanBPM在EBV裂解进程中起重要作用。
