2011年1月20日，国际学术杂志 PLoS ONE 在线发表了上海巴斯德研究所蓝柯研究组关于肿瘤疱疹病毒--卡波济肉瘤病毒（Kaposi’s Sarcoma associated herpesvirus，KSHV）周期调控研究的最新成果。该研究通过利用不同于之前的实验系统，验证了其他研究组报导的miR-K12-9能够下调RTA的表达。该研究还报导了一个新的KSHV编码miRNA能够通过直接抑制裂解期主要调控基因RTA，并影响RTA对下游裂解期基因和病毒粒子复制来维持病毒潜伏感染状态。
KSHV是一种重要的人类肿瘤病毒，它能够引起卡波济肉瘤（KS）、原发性渗出性淋巴瘤（PEL）和部分多中心性卡斯特曼病（MCD）等恶性肿瘤。自从KSHV发现以来，潜伏-裂解周期调控就成为国际研究热点。
博士研究生林先志等在蓝柯研究员指导下，通过构建含RTA3’UTR的报告基因，对所有KSHV编码的pre-miRNA表达质粒进行筛选，发现KSHV编码的多个miRNA能够下调报告基因的表达。其中miR-K12-9和miR-K12-7对报告基因的下调在不同细胞系中重复验证。RTA3’UTR中miRNA靶位点突变实验和miRNA特异抑制剂揭示miR-K12-7对报告基因的下调作用是由其产生的miR-K12-7-5p来实现的。在KSHV阳性细胞系中过表达miR-K12-7能够下调RTA蛋白水平的表达，却不能下调其mRNA水平，说明miR-K12-7对RTA的抑制发生在翻译水平上。进一步实验表明，miR-K12-7不仅能够下调RTA的表达，还能下调RTA下游裂解期基因的表达，并对病毒粒子的产生有抑制作用。
该研究得到国家973计划、国家自然科学基金、中国科学院“百人计划”和上海浦江人才计划科研开发（A类）的资助。（生物谷Bioon.com）
生物谷推荐原文出处：
PLoS ONE 6(1): e16224. doi:10.1371/journal.pone.0016224
miR-K12-7-5p Encoded by Kaposi's Sarcoma-Associated Herpesvirus Stabilizes the Latent State by Targeting Viral ORF50/RTA
Xianzhi Lin1, Deguang Liang1, Zhiheng He1, Qiang Deng1, Erle S. Robertson2, Ke Lan1*
1 Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People's Republic of China, 2 Department of Microbiology and the Abramson Comprehensive Cancer Center, University of Pennsylvania Medical School, Philadelphia, Pennsylvania, United States of America
Abstract
Seventeen miRNAs encoded by Kaposi's sarcoma-associated herpesvirus (KSHV) have been identified and their functions have begun to be characterized. Among these miRNAs, we report here that miR-K12-7 directly targets the replication and transcription activator (RTA) encoded by open reading frame 50. We found that miR-K12-7 targeted the RTA 3′ untranslated region (RTA3′UTR) in a seed sequence-dependent manner. miR-K12-7-5p derived from miR-K12-7 mediates the inhibition of RTA expression, and the mutation of the seed match site totally abrogated the inhibitory effect of miR-K12-7 on RTA3′UTR. The inhibition of RTA expression by miR-K12-7 was further confirmed in the latently KSHV-infected 293/Bac36 cell line through transient transfection of miR-K12-7 expression plasmid or specific inhibitor of miR-K12-7-5p, respectively. The transient transfection of miR-K12-7 into 293/Bac36 cells reduced RTA expression and the expression of the downstream early genes regulated by RTA, and also the production of progeny virus was significantly reduced after treatment with chemical inducers. Our study revealed that another miRNA, miR-K12-7-5p, targets the viral immediate early gene RTA and that this miRNA contributes to the maintenance of viral latency.
