Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia.
Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia.
J Virol. 2024 Apr 16;98(4):e0153823. doi: 10.1128/jvi.01538-23. Epub 2024 Mar 19.
Prior to nuclear export, the hepatitis B virus (HBV) pregenomic RNA may be spliced by the host cell spliceosome to form shorter RNA sequences known as splice variants. Due to deletions in the open reading frames, splice variants may encode novel fusion proteins. Although not essential for HBV replication, the role of splice variants and their novel fusion proteins largely remains unknown. Some splice variants and their encoded novel fusion proteins have been shown to impair or promote wild-type HBV replication and although splice variants Sp3 and Sp9 are two of the most common splice variants identified to date, their replication phenotype and their impact on wild-type HBV replication are unclear. Here, we utilize greater than genome-length Sp3 and Sp9 constructs to investigate their replication phenotype , and their impact on wild-type HBV replication. We show that Sp3 and Sp9 were incapable of autonomous replication, which was rescued by providing the polymerase and core proteins . Furthermore, we showed that Sp3 had no impact on wild-type HBV replication, whereas Sp9 strongly reduced wild-type HBV replication in co-transfection experiments. Knocking out Sp9 novel precore-surface and core-surface fusion protein partially restored replication, suggesting that these proteins contributed to suppression of wild-type HBV replication, providing further insights into factors regulating HBV replication .
The role of hepatitis B virus (HBV) splice variants in HBV replication and pathogenesis currently remains largely unknown. However, HBV splice variants have been associated with the development of hepatocellular carcinoma, suggesting a role in HBV pathogenesis. Several co-transfection studies have shown that different splice variants have varying impacts on wild-type HBV replication, perhaps contributing to viral persistence. Furthermore, all splice variants are predicted to produce novel fusion proteins. Sp1 hepatitis B splice protein contributes to liver disease progression and apoptosis; however, the function of other HBV splice variant novel fusion proteins remains largely unknown. We show that Sp9 markedly impairs HBV replication in a cell culture co-transfection model, mediated by expression of Sp9 novel fusion proteins. In contrast, Sp3 had no effect on wild-type HBV replication. Together, these studies provide further insights into viral factors contributing to regulation of HBV replication.
在核输出之前，乙型肝炎病毒 (HBV) 前基因组 RNA 可能被宿主细胞剪接体剪接，形成称为剪接变体的较短 RNA 序列。由于开放阅读框缺失，剪接变体可能编码新的融合蛋白。尽管剪接变体及其新融合蛋白对于 HBV 复制不是必需的，但它们的作用在很大程度上仍然未知。一些剪接变体及其编码的新融合蛋白已被证明会损害或促进野生型 HBV 复制，尽管剪接变体 Sp3 和 Sp9 是迄今为止鉴定出的最常见的剪接变体之一，但它们的复制表型及其对野生型 HBV 复制的影响尚不清楚。在这里，我们利用大于基因组长度的 Sp3 和 Sp9 构建体来研究它们的复制表型及其对野生型 HBV 复制的影响。我们表明 Sp3 和 Sp9 不能自主复制，提供聚合酶和核心蛋白可挽救该复制。此外，我们表明 Sp3 对野生型 HBV 复制没有影响，而 Sp9 在共转染实验中强烈降低野生型 HBV 复制。敲除 Sp9 新的前核心-表面和核心-表面融合蛋白部分恢复了复制，表明这些蛋白有助于抑制野生型 HBV 复制，进一步深入了解调节 HBV 复制的因素。
乙型肝炎病毒 (HBV) 剪接变体在 HBV 复制和发病机制中的作用目前在很大程度上仍然未知。然而，HBV 剪接变体与肝细胞癌的发展有关，这表明其在 HBV 发病机制中起作用。几项共转染研究表明，不同的剪接变体对野生型 HBV 复制的影响不同，这可能导致病毒持续存在。此外，所有剪接变体均预测会产生新的融合蛋白。Sp1 乙型肝炎剪接蛋白有助于肝病进展和细胞凋亡；然而，其他 HBV 剪接变体新融合蛋白的功能在很大程度上仍然未知。我们表明，Sp9 在细胞培养共转染模型中显著损害 HBV 复制，这是由 Sp9 新融合蛋白的表达介导的。相比之下，Sp3 对野生型 HBV 复制没有影响。总之，这些研究为调节 HBV 复制的病毒因素提供了进一步的见解。
