Li Yuling, Webster-Cyriaque Jennifer, Tomlinson Christine C, Yohe Marielle, Kenney Shannon
Department of Microbiology and Immunology and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, North Carolina 27599, USA.
J Virol. 2004 Apr;78(8):4197-206. doi: 10.1128/jvi.78.8.4197-4206.2004.
The Epstein-Barr virus (EBV) immediate-early (IE) protein BRLF1 (R) is a transcription factor that induces the lytic form of EBV infection. R activates certain early viral promoters through a direct binding mechanism but induces transcription of the other EBV IE gene, BZLF1 (Z), indirectly through cellular factors binding to a CRE motif in the Z promoter (Zp). Here we demonstrate that R activates expression of the fatty acid synthase (FAS) cellular gene through a p38 stress mitogen-activated protein kinase-dependent mechanism. B-cell receptor engagement of Akata cells also increases FAS expression. The FAS gene product is required for de novo synthesis of the palmitate fatty acid, and high-level FAS expression is normally limited to liver, brain, lung, and adipose tissue. We show that human epithelial tongue cells lytically infected with EBV (from oral hairy leukoplakia lesions) express much more FAS than uninfected cells. Two specific FAS inhibitors, cerulenin and C75, prevent R activation of IE (Z) and early (BMRF1) lytic EBV proteins in Jijoye cells. In addition, cerulenin and C75 dramatically attenuate IE and early lytic gene expression after B-cell receptor engagement in Akata cells and constitutive lytic viral gene expression in EBV-positive AGS cells. However, FAS inhibitors do not reduce lytic viral gene expression induced by a vector in which the Z gene product is driven by a strong heterologous promoter. In addition, FAS inhibitors do not reduce R activation of a naked DNA reporter gene construct driven by the Z promoter (Zp). These results suggest that cellular FAS activity is important for induction of Z transcription from the intact latent EBV genome, perhaps reflecting the involvement of lipid-derived signaling pathways or palmitoylated proteins. Furthermore, using FAS inhibitors may be a completely novel approach for blocking the lytic form of EBV replication.
爱泼斯坦-巴尔病毒（EBV）即刻早期（IE）蛋白BRLF1（R）是一种转录因子，可诱导EBV感染的裂解形式。R通过直接结合机制激活某些早期病毒启动子，但通过细胞因子与Z启动子（Zp）中的CRE基序结合间接诱导另一个EBV IE基因BZLF1（Z）的转录。在此，我们证明R通过p38应激丝裂原活化蛋白激酶依赖性机制激活脂肪酸合酶（FAS）细胞基因的表达。Akata细胞的B细胞受体参与也会增加FAS表达。FAS基因产物是棕榈酸脂肪酸从头合成所必需的，高水平的FAS表达通常仅限于肝脏、大脑、肺和脂肪组织。我们发现，被EBV裂解感染的人上皮舌细胞（来自口腔毛状白斑病变）比未感染的细胞表达更多的FAS。两种特异性FAS抑制剂，浅蓝菌素和C75，可阻止Jijoye细胞中IE（Z）和早期（BMRF1）EBV裂解蛋白的R激活。此外，浅蓝菌素和C75可显著减弱Akata细胞中B细胞受体参与后的IE和早期裂解基因表达以及EBV阳性AGS细胞中的组成性裂解病毒基因表达。然而，FAS抑制剂不会降低由强异源启动子驱动Z基因产物的载体诱导的裂解病毒基因表达。此外，FAS抑制剂不会降低由Z启动子（Zp）驱动的裸DNA报告基因构建体的R激活。这些结果表明，细胞FAS活性对于从完整的潜伏EBV基因组诱导Z转录很重要，这可能反映了脂质衍生信号通路或棕榈酰化蛋白的参与。此外，使用FAS抑制剂可能是一种全新的阻断EBV复制裂解形式的方法。
