Hepatitis B virus X protein stimulates viral genome replication via a DDB1-dependent pathway distinct from that leading to cell death
Hepatitis B virus X protein stimulates viral genome replication via a DDB1-dependent pathway distinct from that leading to cell death
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DOI：
10.1128/jvi.79.7.4238-4245.2005
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发表时间：
2005-04-01
影响因子：
5.4
通讯作者：
Strubin, M
中科院分区：
文献类型：
--
作者：
Leupin, O;Bontron, S;Strubin, M
乙肝病毒X蛋白(HBx)是病毒感染所必需的，并与慢性感染相关的肝癌的发生有关。HBX可以与多种细胞蛋白相互作用，在细胞培养中表现出多种活性，其中之一是干扰细胞活力和刺激乙肝病毒复制的能力。以前的工作表明，HBx通过与DDB1结合来影响细胞活力，DDB1是一种高度保守的蛋白质，参与DNA修复和细胞周期调节。我们现在表明，HBx也需要与DDB1相互作用来刺激乙肝病毒基因组复制。因此，当以反式形式提供HBx缺陷的乙肝病毒基因组时，检测到DDB1结合的HBx点突变不能补充HBx缺陷的乙肝病毒基因组的低水平复制，而当直接与DDB1融合时，这样的突变体恢复活性。此外，RNA干扰导致的DDB1缺失特别影响了野生型乙肝病毒的复制，这表明从病毒基因组产生的HBx也以DDB1依赖的方式发挥功能。我们还表明，与DDB1相关的HBx作用于细胞核，主要通过提高病毒mRNA水平来刺激乙肝病毒复制，无论蛋白质是从乙肝病毒基因组本身表达还是以反式供应。有趣的是，虽然HBx在HepG2和Huh-7肝癌细胞系中都能诱导细胞死亡，但它只在HepG2细胞中增强了乙肝病毒的复制，这表明这两种活性涉及不同的DDB1依赖途径。
The hepatitis B virus (HBV) X protein (HBx) is essential for virus infection and has been implicated in the development of liver cancer associated with chronic infection. HBx can interact with a number of cellular proteins, and in cell culture, it exhibits pleiotropic activities, among which is its ability to interfere with cell viability and stimulate HBV replication. Previous work has demonstrated that HBx affects cell viability by a mechanism that requires its binding to DDB1, a highly conserved protein implicated in DNA repair and cell cycle regulation. We now show that an interaction with DDB1 is also needed for HBx to stimulate HBV genome replication. Thus, HBx point mutants detective for DDB1 binding fail to complement the low level of replication of an HBx-deficient HBV genome when provided in trans, and one such mutant regains activity when directly fused to DDB1. Furthermore, DDB1 depletion by RNA interference specifically compromises replication of wild-type HBV, indicating that HBx produced from the viral genome also functions in a DDB1-dependent fashion. We also show that HBx in association with DDB1 acts in the nucleus and stimulates HBV replication mainly by enhancing viral mRNA levels, regardless of whether the protein is expressed from the HBV genome itself or supplied in trans. Interestingly, whereas HBx induces cell death in both HepG2 and Huh-7 hepatoma cell lines, it enhances HBV replication only in HepG2 cells, suggesting that the two activities involve distinct DDB1-dependent pathways.