Peng R, Gordadze A V, Fuentes Pananá E M, Wang F, Zong J, Hayward G S, Tan J, Ling P D
Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030, USA.
J Virol. 2000 Jan;74(1):379-89. doi: 10.1128/jvi.74.1.379-389.2000.
The Epstein-Barr virus (EBV) EBNA-LP and EBNA2 proteins are the first to be synthesized during establishment of latent infection in B lymphocytes. EBNA2 is a key transcriptional regulator of both viral and cellular gene expression and is essential for EBV-induced immortalization of B lymphocytes. EBNA-LP is also important for EBV-induced immortalization of B lymphocytes, but far less is known about the functional domains and cellular cofactors that mediate EBNA-LP function. While recent studies suggest that serine phosphorylation of EBNA-LP and coactivation of EBNA2-mediated transactivation are important, more detailed mutational and genetic studies are complicated by the repeat regions that comprise the majority of the EBNA-LP sequence. Therefore, we have used a comparative approach by studying the EBNA-LP homologues from baboon and rhesus macaque lymphocryptoviruses (LCVs) (baboon LCV and rhesus LCV). The predicted baboon and rhesus LCV EBNA-LP amino acid sequences are 61 and 64% identical to the EBV EBNA-LP W1 and W2 exons and 51% identical to the EBV EBNA-LP Y1 and Y2 exons. Five evolutionarily conserved regions can be defined, and four of eight potential serine residues are conserved among all three EBNA-LPs. The major internal repeat sequence also revealed a highly conserved Wp EBNA promoter with strong conservation of upstream activating sequences important for Wp transcriptional regulation. To test whether transcriptional coactivating properties were common to the rhesus LCV EBNA-LP, a rhesus LCV EBNA2 homologue was cloned and expressed. The rhesus LCV EBNA2 transcriptionally transactivates EBNA2-responsive promoters through a CBF1-dependent mechanism. The rhesus LCV EBNA-LP was able to further enhance rhesus LCV or EBV EBNA2 transactivation 5- to 12-fold. Thus, there is strong structural and functional conservation among the simian EBNA-LP homologues. Identification of evolutionarily conserved serine residues and regions in EBNA-LP homologues provides important clues for identifying the cellular cofactors and molecular mechanisms mediating these conserved viral functions.
爱泼斯坦-巴尔病毒（EBV）的EBNA-LP和EBNA2蛋白是B淋巴细胞潜伏感染建立过程中最早合成的蛋白。EBNA2是病毒和细胞基因表达的关键转录调节因子，对EBV诱导的B淋巴细胞永生化至关重要。EBNA-LP对EBV诱导的B淋巴细胞永生化也很重要，但关于介导EBNA-LP功能的功能结构域和细胞辅因子知之甚少。虽然最近的研究表明EBNA-LP的丝氨酸磷酸化和EBNA2介导的反式激活的共激活很重要，但由于构成EBNA-LP序列大部分的重复区域，更详细的突变和遗传学研究变得复杂。因此，我们采用了一种比较方法，研究来自狒狒和恒河猴淋巴细胞隐性病毒（LCV）（狒狒LCV和恒河猴LCV）的EBNA-LP同源物。预测的狒狒和恒河猴LCV EBNA-LP氨基酸序列与EBV EBNA-LP的W1和W2外显子分别有61%和64%的同一性，与EBV EBNA-LP的Y1和Y2外显子有51%的同一性。可以定义五个进化保守区域，并且在所有三种EBNA-LP中，八个潜在丝氨酸残基中的四个是保守的。主要的内部重复序列还揭示了一个高度保守的Wp EBNA启动子，其上游激活序列对于Wp转录调节具有很强的保守性。为了测试转录共激活特性是否是恒河猴LCV EBNA-LP所共有的，克隆并表达了一种恒河猴LCV EBNA2同源物。恒河猴LCV EBNA2通过一种依赖CBF1的机制转录反式激活EBNA2反应性启动子。恒河猴LCV EBNA-LP能够将恒河猴LCV或EBV EBNA2的反式激活进一步增强5至12倍。因此，猿猴EBNA-LP同源物之间存在很强的结构和功能保守性。鉴定EBNA-LP同源物中进化保守的丝氨酸残基和区域为鉴定介导这些保守病毒功能的细胞辅因子和分子机制提供了重要线索。
