Graduate Institute of Clinical Medical Sciences, Chang-Gung University, Taoyuan, Taiwan.
Virology. 2010 Feb 20;397(2):311-21. doi: 10.1016/j.virol.2009.11.031. Epub 2009 Dec 6.
The ORF61 and ORF60 genes of Kaposi's sarcoma-associated herpesvirus (KSHV) encode the ribonucleotide reductase large and small subunits, respectively. Here we show that ORF50 protein, a latent-lytic switch transactivator, activates the transcription of these two early-lytic genes through different mechanisms. Activation of the ORF61 promoter by ORF50 protein is dependent on an intact RBP-Jkappa-binding site within the identified responsive element and the expression of RBP-Jkappa protein in cells. The critical element in the ORF60 promoter in response to ORF50 was mapped to a 40-bp region. Binding of YY1, Sp1/Sp3 or unknown proteins to this element may contribute to repression or activation of the ORF60 promoter. Although ORF50 protein does not directly bind to the ORF61 and ORF60 promoters in vitro, we show the association of ORF50 protein with these two promoters in vivo. Our results provide further insights into the regulatory network of the viral lytic genes in KSHV reactivation.
卡波济肉瘤相关疱疹病毒 (KSHV) 的 ORF61 和 ORF60 基因分别编码核苷酸还原酶的大亚基和小亚基。在这里，我们发现潜伏-裂解开关转录激活物 ORF50 蛋白通过不同的机制激活这两个早期裂解基因的转录。ORF50 蛋白对 ORF61 启动子的激活依赖于鉴定出的反应元件内完整的 RBP-Jkappa 结合位点和细胞中 RBP-Jkappa 蛋白的表达。ORF50 响应的 ORF60 启动子的关键元件被映射到一个 40 个碱基对的区域。YY1、Sp1/Sp3 或未知蛋白与该元件的结合可能有助于 ORF60 启动子的抑制或激活。尽管 ORF50 蛋白在体外不能直接结合到 ORF61 和 ORF60 启动子上，但我们在体内显示了 ORF50 蛋白与这两个启动子的关联。我们的结果为 KSHV 再激活过程中病毒裂解基因的调控网络提供了进一步的见解。
