Baumann M, Gires O, Kolch W, Mischak H, Zeidler R, Pich D, Hammerschmidt W
GSF-National Research Center for Environment and Health, Institute of Clinical Molecular Biology and Tumor Genetics, Department of Gene Vectors, München, Germany.
Eur J Biochem. 2000 Jun;267(12):3891-901. doi: 10.1046/j.1432-1327.2000.01430.x.
Phorbol esters reactivate Epstein-Barr virus (EBV) from latently infected cells via transcriptional activation of the viral immediate-early gene BZLF1. BZLF1 is a member of the extended AP-1 family of transcription factors that binds to specific BZLF1-binding motifs within early EBV promoters and to consensus AP-1 sites. Regulation of BZLF1's activity is achieved at the transcriptional level as well as through post-translational modifications. Recently, we reported that the transcriptional activity of BZLF1 is augmented by TPA [Baumann, M., Mischak, H., Dammeier, S., Kolch, W., Gires, O., Pich, D., Zeidler, R., Delecluse, H. J. & Hammerschmidt, W., (1998) J. Virol. 72, 8105-8114]. The increase of BZLF1's activity depends on a single serine residue (S186) that is phosphorylated by protein kinase C (PKC) in vitro and in vivo after stimulation with 12-O-tetradecanoylphorbol-13-acetate (TPA). Here, we identified RACK1 as a binding partner of BZLF1 in a yeast interaction trap assay. RACK stands for receptor of activated C-kinase and is involved in targeting activated PKCs and other signaling proteins. In vivo, RACK1 binds directly to the transactivation domain of BZLF1. Although a functional relationship between BZLF1 and PKC could be mediated by RACKs, RACK1 did not have a detectable effect on the phosphorylation status of BZLF1 in in vitro or in vivo phosphorylation assays. We suggest that RACK1 may act as a scaffolding protein on BZLF1 independently of activated PKCs.
佛波酯通过病毒立即早期基因BZLF1的转录激活，从潜伏感染的细胞中重新激活爱泼斯坦-巴尔病毒（EBV）。BZLF1是转录因子扩展AP-1家族的成员，它与EBV早期启动子内的特定BZLF1结合基序以及共有AP-1位点结合。BZLF1活性的调节在转录水平以及通过翻译后修饰来实现。最近，我们报道了TPA增强了BZLF1的转录活性[鲍曼，M.，米沙克，H.，达迈尔，S.，科尔奇，W.，吉雷斯，O.，皮希，D.，蔡德勒，R.，德莱克吕斯，H. J. & 哈默施密特，W.，（1998年）《病毒学杂志》72卷，8105 - 8114页]。BZLF1活性的增加取决于单个丝氨酸残基（S186），在用12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA）刺激后，该残基在体外和体内被蛋白激酶C（PKC）磷酸化。在这里，我们在酵母相互作用陷阱试验中鉴定出RACK1是BZLF1的结合伙伴。RACK代表活化C激酶的受体，参与靶向活化的PKC和其他信号蛋白。在体内，RACK1直接与BZLF1的反式激活结构域结合。尽管BZLF1和PKC之间的功能关系可能由RACKs介导，但在体外或体内磷酸化试验中，RACK1对BZLF1的磷酸化状态没有可检测到的影响。我们认为RACK1可能作为BZLF1上的一种支架蛋白，独立于活化的PKC发挥作用。
