HUMAN RPB5, A SUBUNIT SHARED BY EUKARYOTIC NUCLEAR-RNA POLYMERASES, BINDS HUMAN HEPATITIS-B VIRUS X-PROTEIN AND MAY PLAY A ROLE IN X-TRANSACTIVATION
HUMAN RPB5, A SUBUNIT SHARED BY EUKARYOTIC NUCLEAR-RNA POLYMERASES, BINDS HUMAN HEPATITIS-B VIRUS X-PROTEIN AND MAY PLAY A ROLE IN X-TRANSACTIVATION
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DOI：
10.1002/j.1460-2075.1995.tb06984.x
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发表时间：
1995-01-03
期刊：
影响因子：
11.4
通讯作者：
MURAKAMI, S
中科院分区：
文献类型：
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作者：
CHEONG, JH;YI, MK;MURAKAMI, S
人乙型肝炎病毒的X基因编码多肽HBx，该多肽通过存在于RNA聚合酶I、II和III启动子中的多种顺式作用增强子元件来交换病毒和宿主基因。为了更好地理解X转激活的机制，我们克隆了结合HBx的蛋白质的cdna。在这里，我们证明了其中一个cDNA是人类RPB5的全长cDNA， RPB5是RNA聚合酶共享的一个亚基。HBx转激活结构域和人类RPB5的中心区域对于两种蛋白的特异性结合是必需的，如下所示：(i)使用融合蛋白的缺失突变体进行体外实验；（ii）通过对转染HepG2细胞的非融合蛋白进行共免疫沉淀来检测相关蛋白的体内试验。在HBx转染的细胞中，过表达的HBx似乎与内源性人RPB5的组装形式有关，因为内源性RPB5与HBx共同免疫沉淀。人RPB5的HBx结合区本身刺激了几个具有x响应元件的不同报告基因的氯霉素乙酰转移酶活性。我们的研究结果支持了HBx和人类RPB5的相互作用可以促进HBx的转激活，并且人类RPB5具有一个可以与转录调控因子交流的结构域的观点。
The X gene of human hepatitis B virus encodes the polypeptide HBx which transactivates viral and host genes through a variety of cis-acting enhancer elements present in RNA polymerases I, II and III promoters. To better understand the mechanism of X transactivation, we cloned cDNAs of proteins that bind HBx. Here we demonstrate that one of these cDNAs is a full-length cDNA of human RPB5, a subunit shared by RNA polymerases. The HBx transactivation domain and the central region of human RPB5 were necessary for the specific binding of the two proteins as shown by: (i) in vitro assays using deletion mutants of fusion proteins; (ii) in vivo assays which detect associated proteins by co-immunoprecipitation of the non-fused proteins from transfected HepG2 cells. Over-expressed HBx seemed to associate with assembled forms of endogenous human RPB5 in HBx-transfected cells, since the endogenous RPB5 co-immunoprecipitated with HBx. The HBx binding region of human RPB5 by itself stimulated chloramphenicol acetyltransferase activities from several different reporters having X-responsive element(s). Our results support the idea that the interaction of HBx and human RPB5 can facilitate HBx transactivation and that human RPB5 has a domain which can communicate with transcriptional regulators.