cIAP2通過加快泛素蛋白酶體介導的聚合酶降解抑制乙肝病毒復制

J Virol 2011 Nov;85 (21): 11457-67. [IF:5.189]
Inhibition of hepatitis B virus replication by cIAP2 involves accelerating the ubiquitin-proteasome-mediated destruction of polymerase.
Wang Z , Ni J , Li J , Shi B , Xu Y , Yuan Z .
Key Laboratory of Medical Molecular Virology, Shanghai Medical College, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China.
復旦大學上海醫學院，復旦大學醫學分子病毒學重點實驗室

Abstract
Cellular inhibitor of apoptosis protein 2 (cIAP2) is a potent suppressor of apoptotic cell death. We have shown previously that cIAP2 is involved in the tumor necrosis factor alpha (TNF-α)-induced anti-hepatitis B virus (HBV) response; however, the mechanism for this antiviral effect remains unclear. In the present study, we demonstrate that cIAP2 can significantly reduce the levels of HBV DNA replication intermediates but not the total viral RNA or core protein levels. Domain-mapping analysis revealed that the carboxy-terminal domains of cIAP2 were indispensable for this anti-HBV ability and that an E3 ligase-deficient mutant of cIAP2 (termed cIAP2*) completely lost its antiviral activity. We further identified HBV polymerase as the target of cIAP2. Overexpression of cIAP2 but not cIAP2* reduced polymerase protein levels, while cIAP2 knockdown increased polymerase expression. In addition, we observed that cIAP2 promoted the degradation of the viral polymerase through a proteasome-dependent pathway. Further experiments demonstrated that cIAP2 can bind to polymerase and promote its polyubiquitylation. Finally, we found that cIAP2 downregulated the encapsidation of HBV pregenomic RNA. Taken together, these data reveal a novel mechanism for the inhibition of HBV replication by cIAP2 via acceleration of the ubiquitin-proteasome-mediated decay of polymerase and reduction of the encapsidation of HBV pregenomic RNA, making this mechanism a novel strategy for HBV therapy.

摘要
細胞抑制劑-凋亡蛋白2(cIAP2)是一種有效的凋亡細胞凋亡抑制劑。我們之前已經研究揭示cIAP2與腫瘤壞死因子α(TNF-α)誘導的抗乙肝病毒(HBV)反應有關；然而，對于這種抗病毒的機制依然不是很清楚。在此項研究中，我們發現cIAP2可以顯著降低HBV DNA復制的中間體水平，而不是降低整個病毒RNA或者核心蛋白水平。結構域圖譜分析顯示cIAP2的羧基端區域對于抗乙肝病毒是必不可少的，而cIAP2的突變體-E3連接酶缺陷(命名為cIAP2*)則完全失去抗病毒能力。我們進一步證實cIAP2的靶點為HBV聚合酶。過表達cIAP2而非cIAP2*會降低聚合酶蛋白水平，而cIAP2敲除則會增加聚合酶的表達。此外我們發現cIAP2通過蛋白酶體依賴途徑促進病毒聚合酶的降解。進一步的實驗揭示cIAP2能結合聚合酶并促進聚合酶的泛素化。最后，我們還發現cIAP2下調HBV前基因組RNA的衣殼化。綜合起來，這些數據揭示一種新的抑制HBV復制的機制，那就是通過cIAP2加快泛素蛋白酶體介導的聚合酶降解和減少HBV前基因組RNA的衣殼化，這也使得該種機制成為HBV治療的一種新的策略。