Lin Ammy, Wang Shan, Nguyen Tin, Shire Kathy, Frappier Lori
Department of Molecular Genetics, University of Toronto, 1 Kings College Circle, Toronto, Canada M5S 1A8.
J Virol. 2008 Dec;82(24):12009-19. doi: 10.1128/JVI.01680-08. Epub 2008 Oct 15.
The EBNA1 protein of Epstein-Barr virus (EBV) is essential for EBV latent infection in ensuring the replication and stable segregation of the EBV genomes and in activating the transcription of other EBV latency genes. We have tested the ability of four host proteins (Brd2, Brd4, DEK, and MeCP2) implicated in the segregation of papillomavirus and Kaposi's sarcoma-associated herpesvirus to support EBNA1-mediated segregation of EBV-based plasmids in Saccharomyces cerevisiae. We found that Brd4 enabled EBNA1-mediated segregation while Brd2 and MeCP2 had a general stimulatory effect on plasmid maintenance. EBNA1 interacted with Brd4 in both yeast and human cells through N-terminal sequences previously shown to mediate transcriptional activation but not segregation. In keeping with this interaction site, silencing of Brd4 in human cells decreased transcriptional activation by EBNA1 but not the mitotic chromosome attachment of EBNA1 that is required for segregation. In addition, Brd4 was found to be preferentially localized to the FR enhancer element regulated by EBNA1, over other EBV sequences, in latently EBV-infected cells. The results indicate that EBNA1 can functionally interact with Brd4 in native and heterologous systems and that this interaction facilitates transcriptional activation by EBNA1 from the FR element.
爱泼斯坦-巴尔病毒（EBV）的EBNA1蛋白对于EBV潜伏感染至关重要，它能确保EBV基因组的复制和稳定分离，并激活其他EBV潜伏基因的转录。我们测试了四种与乳头瘤病毒和卡波西肉瘤相关疱疹病毒分离有关的宿主蛋白（Brd2、Brd4、DEK和MeCP2）在酿酒酵母中支持EBNA1介导的基于EBV的质粒分离的能力。我们发现Brd4能够实现EBNA1介导的分离，而Brd2和MeCP2对质粒维持具有普遍的刺激作用。EBNA1在酵母和人类细胞中均通过先前显示可介导转录激活而非分离的N端序列与Brd4相互作用。与该相互作用位点一致，在人类细胞中沉默Brd4会降低EBNA1介导的转录激活，但不会降低分离所需的EBNA1的有丝分裂染色体附着。此外，在潜伏感染EBV的细胞中，相较于其他EBV序列，发现Brd4优先定位于受EBNA1调控的FR增强子元件。结果表明，EBNA1在天然和异源系统中均可与Brd4发生功能相互作用，且这种相互作用有助于EBNA1从FR元件进行转录激活。
