Division of Infectious Diseases and Global Public Health, Department of Medicine, University of California San Diego, La Jolla, CA 92093.
Division of Infectious Diseases and Global Public Health, Department of Medicine, University of California San Diego, La Jolla, CA 92093
Proc Natl Acad Sci U S A. 2021 Jan 19;118(3). doi: 10.1073/pnas.2019455118.
Chronic hepatitis B virus (HBV) infections are one of the leading causes of cirrhosis and hepatocellular carcinoma. N6-methyladenosine (mA) modification of cellular and viral RNAs is the most prevalent internal modification that occurs cotranscriptionally. Previously, we reported the dual functional role of mA modification of HBV transcripts in the viral life cycle. Here, we show that viral HBV X (HBx) protein is responsible for the mA modifications of viral transcripts. HBV genomes defective in HBx failed to induce mA modifications of HBV RNAs during infection/transfection, while ectopic expression of HBx restores mA modifications of the viral RNAs but not the mutant HBx carrying the nuclear export signal. Using chromatin immunoprecipitation assays, we provide evidence that HBx and mA methyltransferase complexes are localized on the HBV minichromosome to achieve cotranscriptional mA modification of viral RNAs. HBx interacts with METTL3 and 14 to carry out methylation activity and also modestly stimulates their nuclear import. This role of HBx in mediating mA modification also extends to host phosphatase and tensin homolog (PTEN) mRNA. This study provides insight into how a viral protein recruits RNA methylation machinery to mA-modify RNAs.
慢性乙型肝炎病毒 (HBV) 感染是肝硬化和肝细胞癌的主要原因之一。N6-甲基腺苷 (mA) 修饰细胞和病毒 RNA 是最常见的转录共发生的内部修饰。此前，我们报道了 HBV 转录本中 mA 修饰在病毒生命周期中的双重功能作用。在这里，我们表明病毒 HBV X (HBx) 蛋白负责病毒转录本的 mA 修饰。在感染/转染过程中，缺失 HBx 的 HBV 基因组不能诱导 HBV RNA 的 mA 修饰，而 HBx 的异位表达则恢复了病毒 RNA 的 mA 修饰，但不能恢复携带核输出信号的突变 HBx。通过染色质免疫沉淀分析，我们提供了证据表明 HBx 和 mA 甲基转移酶复合物定位于 HBV 微染色体上，以实现病毒 RNA 的转录共 mA 修饰。HBx 与 METTL3 和 14 相互作用以进行甲基化活性，并且适度地刺激它们的核输入。HBx 在介导 mA 修饰中的这种作用也扩展到宿主磷酸酶和张力蛋白同源物 (PTEN) mRNA。本研究深入了解了一种病毒蛋白如何招募 RNA 甲基化机制来 mA 修饰 RNA。
