Kaposi's sarcoma-associated herpesvirus K-bZIP is a coregulator of K-Rta: Physical association and promoter-dependent transcriptional repression
Kaposi's sarcoma-associated herpesvirus K-bZIP is a coregulator of K-Rta: Physical association and promoter-dependent transcriptional repression
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DOI：
10.1128/jvi.77.2.1441-1451.2003
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发表时间：
2003-01-01
影响因子：
5.4
通讯作者：
Kung, HJ
中科院分区：
文献类型：
--
作者：
Izumiya, Y;Lin, SF;Kung, HJ
卡波西肉瘤相关疱疹病毒（KSHV）是一种人类γ疱疹病毒，与卡波西肉瘤和B细胞肿瘤的发病机制有关。KSHV的基因组结构与EB病毒（EBV）相似。EBV编码两种转录因子Rta和Zta，它们在复制和从潜伏期再激活期间功能性地相互作用以反式激活EBV基因。KSHV编码碱性亮氨酸拉链蛋白（K-bZIP），EBV Zta的同源物，和K-Rta，EBV Rta的同源物。EBV Rta和Zta是强转录反式激活因子。尽管有充分的证据表明K-Rta是一种有效的反式激活因子，但K-bZIP作为转录因子的作用还不清楚。在这项研究中，我们报告，K-bZIP调节K-Rta功能。我们表明，K-bZIP直接与K-Rta在体内和体外相互作用。这种结合是特异性的，需要K-bZIP的碱性结构域（氨基酸122至189）和K-Rta的特异性区域（氨基酸499至550），并且可以用用十四烷酰基佛波醇乙酸酯处理的BCBL-1细胞中内源表达的K-bZIP和K-Rta检测。通过观察K-bZIP以剂量依赖性方式抑制K-Rta对ORF 57启动子的反式激活，揭示了这种关联的功能相关性。缺乏相互作用结构域的K-bZIP不能抑制K-Rta介导的反式激活;这一发现证明了抑制的特异性。有趣的是，对于K-Rta的另一个靶点多聚腺苷酸化核（PAN）RNA的启动子，没有观察到这种抑制;因此，抑制是启动子依赖性的。最后，我们提供的证据表明，K-BZIP的K-Rta的调制也发生在体内的病毒基因组在BCBL-1细胞中的再激活过程中。当K-bZIP在BCBL-1细胞中过表达时，ORF 57而不是PAN RNA的表达水平被抑制。这些数据支持K-bZIP的功能之一是调节转录反式激活因子K-Rta的活性的模型。
Kaposi's sarcoma-associated herpesvirus (KSHV) is a human gammaherpesvirus that has been implicated in the pathogenesis of Kaposi's sarcoma and B-cell neoplasms. The genomic organization of KSHV is similar to that of Epstein-Barr virus (EBV). EBV encodes two transcriptional factors, Rta and Zta, which functionally interact to transactivate EBV genes during replication and reactivation from latency. KSHV encodes a basic leucine zipper protein (K-bZIP), a homologue of EBV Zta, and K-Rta, the homologue of EBV Rta. EBV Rta and Zta are strong transcriptional transactivators. Although there is ample evidence that K-Rta is a potent transactivator, the role of K-bZIP as a transcriptional factor is much less clear. In this study, we report that K-bZIP modulates K-Rta function. We show that K-bZIP directly interacts with K-Rta in vivo and in vitro. This association is specific, requiring the basic domain (amino acids 122 to 189) of K-bZIP and a specific region (amino acids 499 to 550) of K-Rta, and can be detected with K-bZIP and K-Rta endogenously expressed in BCBL-1 cells treated with tetradecanoyl phorbol acetate. The functional relevance of this association was revealed by the observation that K-bZIP represses the transactivation of the ORF57 promoter by K-Rta in a dose-dependent manner. K-bZIP lacking the interaction domain fails to repress K-Rta-mediated transactivation; this finding attests to the specificity of the repression. Interestingly, this repression is not observed for the promoter of polyadenylated nuclear (PAN) RNA, another target of K-Rta; thus, repression is promoter dependent. Finally, we provide evidence that the modulation of K-Rta by K-bZIP also occurs in vivo during reactivation of the viral genome in BCBL-1 cells. When K-bZIP is overexpressed in BCBL-1 cells, the level of expression of ORF57 but not PAN RNA is repressed. These data support the model that one function of K-bZIP is to modulate the activity of the transcriptional transactivator K-Rta.