Department of Molecular & Medical Pharmacology,University of California at Los Angeles, Los Angeles, California, USA.
J Virol. 2014 Mar;88(6):3411-22. doi: 10.1128/JVI.01374-13. Epub 2014 Jan 8.
Infection with the human gammaherpesviruses, Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV), is associated with several cancers. During lytic replication of herpesviruses, viral genes are expressed in an ordered cascade. However, the mechanism by which late gene expression is regulated has not been well characterized in gammaherpesviruses. In this study, we have investigated the cis element that mediates late gene expression during de novo lytic infection with murine gammaherpesvirus 68 (MHV-68). A reporter system was established and used to assess the activity of viral late gene promoters upon infection with MHV-68. It was found that the viral origin of lytic replication, orilyt, must be on the reporter plasmid to support activation of the late gene promoter. Furthermore, the DNA sequence required for the activation of late gene promoters was mapped to a core element containing a distinct TATT box and its neighboring sequences. The critical nucleotides of the TATT box region were determined by systematic mutagenesis in the reporter system, and the significance of these nucleotides was confirmed in the context of the viral genome. In addition, EBV and KSHV late gene core promoters could be activated by MHV-68 lytic replication, indicating that the mechanisms controlling late gene expression are conserved among gammaherpesviruses. Therefore, our results on MHV-68 establish a solid foundation for mechanistic studies of late gene regulation.
人类γ疱疹病毒（EBV 和卡波西肉瘤相关疱疹病毒[KSHV]）感染与几种癌症有关。在疱疹病毒的裂解复制过程中，病毒基因按顺序级联表达。然而，γ疱疹病毒中晚期基因表达的调控机制尚未得到很好的描述。在这项研究中，我们研究了介导新发生的裂解感染期间鼠γ疱疹病毒 68（MHV-68）的晚期基因表达的顺式元件。建立了报告系统，用于评估感染 MHV-68 后病毒晚期基因启动子的活性。结果发现，裂解复制的病毒起点 orilyt 必须位于报告质粒上，才能支持晚期基因启动子的激活。此外，激活晚期基因启动子所需的 DNA 序列被映射到一个核心元件，该元件包含一个独特的 TATT 框及其相邻序列。在报告系统中通过系统诱变确定了 TATT 框区域的关键核苷酸，并在病毒基因组的背景下证实了这些核苷酸的重要性。此外，EBV 和 KSHV 晚期基因核心启动子可以被 MHV-68 裂解复制激活，表明控制晚期基因表达的机制在γ疱疹病毒中是保守的。因此，我们对 MHV-68 的研究结果为晚期基因调控的机制研究奠定了坚实的基础。
