Carroll Kyla Driscoll, Bu Wei, Palmeri Diana, Spadavecchia Sophia, Lynch Stephen J, Marras Salvatore A E, Tyagi Sanjay, Lukac David M
Department of Microbiology and Molecular Genetics, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, NJ 07101, USA.
J Virol. 2006 Oct;80(19):9697-709. doi: 10.1128/JVI.00746-06.
Kaposi's sarcoma-associated herpesvirus (KSHV) lytic switch protein, Rta, is a ligand-independent inducer of the Notch signal transduction pathway, and KSHV cannot reactivate from latency in cells null for the Notch target protein RBP-Jk. Here we show that Rta promotes DNA binding of RBP-Jk, a mechanism that is fundamentally different from that established for the RBP-Jk-activating proteins, Notch intracellular domain (NICD) and Epstein-Barr virus EBNA2. Although constitutively active RBP-Jk and NICD do not transactivate KSHV promoters independently, cotransfection of an Rta mutant lacking its transactivation domain robustly restores transcriptional activation. Cooperation requires intact DNA binding sites for Rta and RBP-Jk and trimeric complex formation between the three molecules in vitro. In infected cells, RBP-Jk is virtually undetectable on a series of viral and cellular promoters during KSHV latency but is significantly enriched following Rta expression during viral reactivation. Accordingly, Rta, but not EBNA2 and NICD, reactivates the complete viral lytic cycle.
卡波西肉瘤相关疱疹病毒（KSHV）的裂解开关蛋白Rta是Notch信号转导通路的一种不依赖配体的诱导剂，并且在Notch靶蛋白RBP-Jk缺失的细胞中，KSHV无法从潜伏状态重新激活。在此我们表明，Rta促进RBP-Jk的DNA结合，这一机制与已确立的RBP-Jk激活蛋白Notch细胞内结构域（NICD）和爱泼斯坦-巴尔病毒EBNA2的机制根本不同。尽管组成型激活的RBP-Jk和NICD不能独立反式激活KSHV启动子，但共转染缺乏其反式激活结构域的Rta突变体可有力地恢复转录激活。这种协同作用需要Rta和RBP-Jk完整的DNA结合位点以及三者在体外形成三聚体复合物。在受感染细胞中，在KSHV潜伏期间，在一系列病毒和细胞启动子上几乎检测不到RBP-Jk，但在病毒重新激活期间Rta表达后，RBP-Jk会显著富集。因此，是Rta而非EBNA2和NICD重新激活了完整的病毒裂解周期。
