Molecular Mechanisms of ZAP/ISG20 mediated HBV RNA Decay

描述（由申请人提供）：干扰素是一种批准用于慢性B型肝炎的药物。在筛选干扰素刺激基因（ISG）对HBV复制的潜在抗病毒活性时，我们鉴定了两种宿主蛋白，特别是锌指抗病毒蛋白（ZAP）和ISG 20，它们主要通过下调病毒RNA的转录后水平来抑制HBV复制。我们的数据还表明，ZAP和ISG 20都与HBV RNA发生物理相互作用;虽然ZAP介导的HBV RNA降解需要四个CCCH型锌指基序的完整性，但ISG 20对HBV RNA的还原取决于其核糖核酸酶活性。有趣的是，ISG 20的酶失活形式通过与病毒前基因组（pg）RNA相互作用并随后干扰pgRNA的糖苷化而保留了针对HBV复制的抗病毒活性。此外，ZAP和ISG 20在肝细胞中均以基础水平表达，并且可以在干扰素刺激后进一步诱导，表明它们在HBV的宿主限制中的潜在作用。在这里，我们建议进一步阐明ZAP/ISG 20介导的HBV RNA衰变的分子机制。拟议的目标包括：（1）将鉴定负责ZAP和ISG 20介导的RNA降解的HBV RNA的序列元件;（2）将确定ZAP和ISG 20在先天免疫引发的抗HBV应答中的生理作用;（3）通过蛋白质组学方法鉴定ZAP和ISG 20介导的HBV RNA降解中的辅因子，（4）ZAP和ISG 20可能靶向的宿主RNA分子（包括mRNA和miRNA）的鉴定。阐明ZAP和ISG 20介导的复杂细胞抗病毒反应的分子机制将阐明病毒发病过程中的细胞生物学和病毒-宿主相互作用，并可能导致病毒感染。 开发利用宿主分子控制病毒感染的新疗法。

DESCRIPTION (provided by applicant): Interferon- ¿ is an approved medication for chronic hepatitis B. In the screening of interferon stimulated genes (ISG) for their potential antiviral activity against HBV replication, we identified two host proteins, specifically zinc finger antivirl protein (ZAP) and ISG20, which inhibit HBV replication primarily through posttranscriptional downregulation of viral RNA. Our data also demonstrated that both ZAP and ISG20 physically interact with HBV RNA; while the integrity of the four CCCH-type zinc finger motifs is required for ZAP-mediated HBV RNA degradation, the reduction of HBV RNA by ISG20 depends on its ribonuclease activity. Interestingly, the enzymatically inactive form of ISG20 retains antiviral activity against HBV replication by interacting with viral pregenomic (pg) RNA and subsequently interfering with pgRNA encapsidation. In addition, both ZAP and ISG20 are expressed at basal levels in hepatocytes, and can be further induced upon interferon stimulation, indicating their potential roles in host restriction of HBV. Here we propose to further elucidate the molecular mechanisms of ZAP/ISG20-mediated HBV RNA decay. The proposed Aims include: (1) The sequence element(s) of HBV RNA responsible for ZAP- and ISG20-mediated RNA degradation will be identified; (2) the physiologic role of ZAP and ISG20 in innate immunity-elicited anti-HBV responses will be determined; (3) co- factor(s) in ZAP- and ISG20-mediated HBV RNA decay will be identified through a proteomic approach, and the potential cooperative role between ZAP and ISG20 will also be investigated; (4) identification of the potential host RNA molecules targeted by ZAP and ISG20, including mRNA and miRNA. Elucidation of the molecular mechanisms of the intricate cellular antiviral response mediated by ZAP and ISG20 will shed light on cell biology and virus-host interaction during viral pathogenesis, and potentially lead to the development of novel therapeutics that exploit host molecules to control viral infection.