Zhu Fan Xiu, Li Xiaojuan, Zhou Fuchun, Gao Shou-Jiang, Yuan Yan
Department of Microbiology, School of Dental Medicine, University of Pennsylvania, 240 S. 40th Street, Philadelphia, PA 19104, USA.
J Virol. 2006 Dec;80(24):12187-96. doi: 10.1128/JVI.01275-06. Epub 2006 Oct 11.
Open reading frame 45 (ORF45) of Kaposi's sarcoma-associated herpesvirus (KSHV) encodes an immediate-early protein. This protein is also present in virions as a tegument protein. ORF45 protein interacts with interferon regulatory factor 7 (IRF-7) and inhibits virus-induced type I interferon production by blocking activation of IRF-7. To define further the function of ORF45 and the mechanism underlying its action, we constructed an ORF45-null recombinant virus genome (BAC-stop45) by using a bacterial artificial chromosome (BAC) system. Stable 293T cells carrying the BAC36 (wild type) and BAC-stop45 genomes were generated. When monolayers of 293T BAC36 and 293T BAC-stop45 cells were induced with 12-O-tetradecanoylphorbol-13-acetate and sodium butyrate, no significant difference was found between them in overall viral gene expression and lytic DNA replication, but induced 293T BAC-stop45 cells released 10-fold fewer virions to the medium than did 293T BAC36 cells. When ORF45-null virus was used to infect cells, lower infectivity was observed than for wild-type BAC36. These results suggest that KSHV ORF45 plays roles in both early and late stages of viral infection, probably in viral ingress and egress.
卡波西肉瘤相关疱疹病毒（KSHV）的开放阅读框45（ORF45）编码一种立即早期蛋白。该蛋白也作为一种被膜蛋白存在于病毒颗粒中。ORF45蛋白与干扰素调节因子7（IRF-7）相互作用，并通过阻断IRF-7的激活来抑制病毒诱导的I型干扰素产生。为了进一步确定ORF45的功能及其作用机制，我们使用细菌人工染色体（BAC）系统构建了一个缺失ORF45的重组病毒基因组（BAC-stop45）。产生了携带BAC36（野生型）和BAC-stop45基因组的稳定293T细胞。当用12-O-十四烷酰佛波醇-13-乙酸酯和丁酸钠诱导293T BAC36和293T BAC-stop45细胞单层时，它们在整体病毒基因表达和裂解性DNA复制方面没有显著差异，但诱导的293T BAC-stop45细胞释放到培养基中的病毒颗粒比293T BAC36细胞少10倍。当使用缺失ORF45的病毒感染细胞时，观察到其感染性低于野生型BAC36。这些结果表明，KSHV ORF45在病毒感染的早期和晚期都发挥作用，可能在病毒的进入和释放过程中起作用。
