Lu J, Chen S Y, Chua H H, Liu Y S, Huang Y T, Chang Y, Chen J Y, Sheen T S, Tsai C H
Graduate Institute of Microbiology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China.
J Virol. 2000 Aug;74(16):7391-9. doi: 10.1128/jvi.74.16.7391-7399.2000.
The Zta protein is a key transactivator involved in initiating the Epstein-Barr virus (EBV) lytic cascade. In addition to transactivating many viral genes, Zta has the capacity to influence host cellular signals by binding to promoter regions or by interacting with several important cellular factors. Based on the observation that tyrosine kinases play central roles in determining the fate of cells, a kinase display assay was used to investigate whether cells expressing Zta have an altered pattern of kinase expression. The assay revealed that TRK-related tyrosine kinase (TKT) is expressed at significant levels in Zta transfectants but not in control cells. Additional evidence was obtained from Northern and Western blotting. Importantly, the upregulation of phosphorylated TKT and TKT downstream effector matrix metalloproteinase 1 in Zta transfectants hinted that TKT might initiate a signaling cascade in Zta-expressing cells. In addition, deletion analysis of the Zta protein revealed that the transactivation and dimerization domains were both essential for the upregulation of TKT transcription. Moreover, correlation of expression levels of Zta and TKT transcripts in nasopharyngeal carcinoma biopsy specimens was clearly demonstrated by quantitative PCR (Q-PCR), which provides the first evidence for an effect of Zta on cellular gene expression in vivo. These findings offer insight into the virus-cell interactions and may help us elucidate the role of EBV in tumorigenesis.
Zta蛋白是一种关键的反式激活因子，参与启动爱泼斯坦-巴尔病毒（EBV）的裂解级联反应。除了反式激活许多病毒基因外，Zta还能够通过与启动子区域结合或与几种重要的细胞因子相互作用来影响宿主细胞信号。基于酪氨酸激酶在决定细胞命运中起核心作用这一观察结果，采用激酶展示分析来研究表达Zta的细胞是否具有改变的激酶表达模式。该分析显示，TRK相关酪氨酸激酶（TKT）在Zta转染细胞中高水平表达，而在对照细胞中不表达。通过Northern印迹和Western印迹获得了额外的证据。重要的是，Zta转染细胞中磷酸化TKT和TKT下游效应物基质金属蛋白酶1的上调暗示TKT可能在表达Zta的细胞中启动信号级联反应。此外，对Zta蛋白的缺失分析表明，反式激活结构域和二聚化结构域对于TKT转录的上调都是必不可少的。此外，定量PCR（Q-PCR）清楚地证明了鼻咽癌活检标本中Zta和TKT转录本表达水平的相关性，这为Zta在体内对细胞基因表达的影响提供了首个证据。这些发现为病毒-细胞相互作用提供了见解，并可能帮助我们阐明EBV在肿瘤发生中的作用。
