Joint Center of Translational Precision Medicine, Guangzhou Institute of Pediatrics, Guangzhou Women and Children Medical Center, Guangzhou, China.
Joint Center of Translational Precision Medicine, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
J Virol. 2019 Mar 5;93(6). doi: 10.1128/JVI.02161-18. Print 2019 Mar 15.
Encapsidation of pregenomic RNA (pgRNA) is a crucial step in hepatitis B virus (HBV) replication. Binding by viral polymerase (Pol) to the epsilon stem-loop (ε) on the 5'-terminal region (TR) of pgRNA is required for pgRNA packaging. However, the detailed mechanism is not well understood. RNA-binding motif protein 24 (RBM24) inhibits core translation by binding to the 5'-TR of pgRNA. Here, we demonstrate that RBM24 is also involved in pgRNA packaging. RBM24 directly binds to the lower bulge of ε via RNA recognition submotifs (RNPs). RBM24 also interacts with Pol in an RNA-independent manner. The alanine-rich domain (ARD) of RBM24 and the reverse transcriptase (RT) domain of Pol are essential for binding between RBM24 and Pol. In addition, overexpression of RBM24 increases Pol-ε interaction, whereas RBM24 knockdown decreases the interaction. RBM24 was able to rescue binding between ε and mutant Pol lacking ε-binding activity, further showing that RBM24 mediates the interaction between Pol and ε by forming a Pol-RBM24-ε complex. Finally, RBM24 significantly promotes the packaging efficiency of pgRNA. In conclusion, RBM24 mediates Pol-ε interaction and formation of a Pol-RBM24-ε complex, which inhibits translation of pgRNA and results in pgRNA packing into capsids/virions for reverse transcription and DNA synthesis. Hepatitis B virus (HBV) is a ubiquitous human pathogen, and HBV infection is a major global health burden. Chronic HBV infection is associated with the development of liver diseases, including fulminant hepatitis, hepatic fibrosis, cirrhosis, and hepatocellular carcinoma. A currently approved vaccine can prevent HBV infection, and medications are able to reduce viral loads and prevent liver disease progression. However, current treatments rarely achieve a cure for chronic infection. Thus, it is important to gain insight into the mechanisms of HBV replication. In this study, we found that the host factor RBM24 is involved in pregenomic RNA (pgRNA) packaging and regulates HBV replication. These findings highlight a potential target for antiviral therapeutics of HBV infection.
包膜 pgRNA 是乙型肝炎病毒 (HBV) 复制的关键步骤。病毒聚合酶 (Pol) 与 pgRNA5'-末端区域 (TR) 上的ε茎环 (ε) 的结合是 pgRNA 包装所必需的。然而，其详细机制尚不清楚。RNA 结合基序蛋白 24（RBM24）通过与 pgRNA 的 5'-TR 结合来抑制核心翻译。在这里，我们证明 RBM24 也参与 pgRNA 包装。RBM24 通过 RNA 识别亚基（RNPs）直接结合到 ε 的下突环。RBM24 还以 RNA 非依赖性方式与 Pol 相互作用。RBM24 的富含丙氨酸结构域 (ARD) 和 Pol 的逆转录酶 (RT) 结构域对于 RBM24 和 Pol 之间的结合是必不可少的。此外，RBM24 的过表达增加了 Pol-ε 的相互作用，而 RBM24 的敲低则减少了相互作用。RBM24 能够挽救缺乏 ε 结合活性的突变 Pol 与 ε 之间的结合，进一步表明 RBM24 通过形成 Pol-RBM24-ε 复合物来介导 Pol 和 ε 之间的相互作用。最后，RBM24 显著提高了 pgRNA 的包装效率。总之，RBM24 介导 Pol-ε 相互作用并形成 Pol-RBM24-ε 复合物，抑制 pgRNA 的翻译，导致 pgRNA 包装到衣壳/病毒中进行逆转录和 DNA 合成。乙型肝炎病毒 (HBV) 是一种普遍存在的人类病原体，HBV 感染是全球主要的健康负担。慢性 HBV 感染与肝脏疾病的发展有关，包括暴发性肝炎、肝纤维化、肝硬化和肝细胞癌。目前批准的疫苗可以预防 HBV 感染，药物能够降低病毒载量并阻止肝病进展。然而，目前的治疗方法很少能治愈慢性感染。因此，深入了解 HBV 复制的机制非常重要。在这项研究中，我们发现宿主因子 RBM24 参与了前基因组 RNA（pgRNA）的包装，并调节了 HBV 的复制。这些发现突出了针对 HBV 感染的抗病毒治疗的潜在靶点。
