State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.
Guangdong Key Laboratory of Virology, Institute of Medical Microbiology, Jinan University, Guangzhou, China.
J Virol. 2020 May 18;94(11). doi: 10.1128/JVI.01800-19.
Hepatitis B virus (HBV) chronically infects approximately 350 million people worldwide, and 600,000 deaths are caused by HBV-related hepatic failure, liver cirrhosis, and hepatocellular carcinoma annually. It is important to reveal the mechanism underlying the regulation of HBV replication. This study demonstrated that osteopetrosis-associated transmembrane protein 1 (Ostm1) plays an inhibitory role in HBV replication. Ostm1 represses the levels of HBeAg and HBsAg proteins, HBV 3.5-kb and 2.4/2.1-kb RNAs, and core-associated DNA in HepG2, Huh7, and NTCP-HepG2 cells. Notably, Ostm1 has no direct effect on the activity of HBV promoters or the transcription of HBV RNAs; instead, Ostm1 binds to HBV RNA to facilitate RNA decay. Detailed studies further demonstrated that Ostm1 binds to and recruits the RNA exosome complex to promote the degradation of HBV RNAs, and knockdown of the RNA exosome component exonuclease 3 (Exosc3) leads to the elimination of Ostm1-mediated repression of HBV replication. Mutant analyses revealed that the N-terminal domain, the transmembrane domain, and the C-terminal domain are responsible for the repression of HBV replication, and the C-terminal domain is required for interaction with the RNA exosome complex. Moreover, Ostm1 production is not regulated by interferon-α (IFN-α) or IFN-γ, and the expression of IFN signaling components is not affected by Ostm1, suggesting that Ostm1 anti-HBV activity is independent of the IFN signaling pathway. In conclusion, this study revealed a distinct mechanism underlying the repression of HBV replication, in which Ostm1 binds to HBV RNA and recruits RNA exosomes to degrade viral RNA, thereby restricting HBV replication. Hepatitis B virus (HBV) is a human pathogen infecting the liver to cause a variety of diseases ranging from acute hepatitis to advanced liver diseases, fulminate hepatitis, liver cirrhosis, and hepatocellular carcinoma, thereby causing a major health problem worldwide. In this study, we demonstrated that Ostm1 plays an inhibitory role in HBV protein production, RNA expression, and DNA replication. However, Ostm1 has no effect on the activities of the four HBV promoters; instead, it binds to HBV RNA and recruits RNA exosomes to promote HBV RNA degradation. We further demonstrated that the anti-HBV activity of Ostm1 is independent of the interferon signaling pathway. In conclusion, this study reveals a distinct mechanism underlying the repression of HBV replication and suggests that Ostm1 is a potential therapeutic agent for HBV infection.
乙型肝炎病毒（HBV）在全球范围内慢性感染约 3.5 亿人，每年有 60 万人死于 HBV 相关肝衰竭、肝硬化和肝细胞癌。揭示 HBV 复制调控的机制非常重要。本研究表明，骨硬化蛋白相关跨膜蛋白 1（Ostm1）在 HBV 复制中发挥抑制作用。Ostm1 抑制 HBeAg 和 HBsAg 蛋白、HBV 3.5-kb 和 2.4/2.1-kb RNA 以及 HepG2、Huh7 和 NTCP-HepG2 细胞中核心相关 DNA 的水平。值得注意的是，Ostm1 对 HBV 启动子的活性或 HBV RNA 的转录没有直接影响；相反，Ostm1 结合 HBV RNA 以促进 RNA 降解。详细研究进一步表明，Ostm1 结合并募集 RNA 外切体复合物以促进 HBV RNA 的降解，并且 RNA 外切体成分外切酶 3（Exosc3）的敲低导致 Ostm1 介导的 HBV 复制抑制的消除。突变分析表明，N 端结构域、跨膜结构域和 C 端结构域负责抑制 HBV 复制，并且 C 端结构域是与 RNA 外切体复合物相互作用所必需的。此外，Ostm1 的产生不受干扰素-α（IFN-α）或 IFN-γ的调节，IFN 信号成分的表达不受 Ostm1 影响，这表明 Ostm1 的抗 HBV 活性不依赖于 IFN 信号通路。总之，本研究揭示了抑制 HBV 复制的一种独特机制，其中 Ostm1 结合 HBV RNA 并募集 RNA 外切体降解病毒 RNA，从而限制 HBV 复制。乙型肝炎病毒（HBV）是一种感染肝脏的人类病原体，可引起从急性肝炎到晚期肝病、暴发性肝炎、肝硬化和肝细胞癌等多种疾病，从而成为全球主要的健康问题。在这项研究中，我们证明 Ostm1 在 HBV 蛋白产生、RNA 表达和 DNA 复制中发挥抑制作用。然而，Ostm1 对四个 HBV 启动子的活性没有影响；相反，它结合 HBV RNA 并募集 RNA 外切体以促进 HBV RNA 降解。我们进一步证明，Ostm1 的抗 HBV 活性不依赖于干扰素信号通路。总之，本研究揭示了抑制 HBV 复制的一种独特机制，并表明 Ostm1 是治疗 HBV 感染的潜在治疗剂。
