Department of Integrated Biological Science, The Graduate School, Pusan National Universitygrid.262229.f, Busan, Republic of Korea.
Department of Microbiology, College of Natural Science, Pusan National Universitygrid.262229.f, Busan, Republic of Korea.
Microbiol Spectr. 2022 Dec 21;10(6):e0143222. doi: 10.1128/spectrum.01432-22. Epub 2022 Nov 14.
Most clinical and experimental studies have suggested that hepatitis C virus (HCV) is dominant over hepatitis B virus (HBV) during coinfection, although the underlying mechanism remains unclear. In this study, we found that the HBV X protein (HBx) upregulates the levels of the HCV core protein to stimulate HCV replication during coinfection in human hepatoma cells. For this purpose, HBx upregulated both the protein levels and enzyme activities of cellular DNA methyltransferase 1 (DNMT1) and DNMT3b, and this subsequently reduced the expression levels of the E6-associated protein (E6AP), an E3 ligase of the HCV core protein, via DNA methylation. The ubiquitin-dependent proteasomal degradation of the HCV core protein was severely impaired in the presence of HBx, whereas this effect was not observed when was either ectopically expressed or restored by treatment with 5-aza-2'dC or DNMT1 knockdown. The effect of HBx on the HCV core protein was accurately reproduced in HBV/HCV coinfection systems, which were established by either monoinfection by HCV in Huh7D cells transfected with a 1.2-mer HBV replicon or coinfection by HBV and HCV in Huh7D-Na-taurocholate cotransporting polypeptide cells, providing evidence for the stimulation of HCV replication by HBx. The present study may provide insights into understanding HCV dominance during HBV/HCV coinfection in patients. Hepatitis B virus (HBV) and hepatitis C virus (HCV) are major human pathogens that cause a substantial proportion of liver diseases worldwide. As the two hepatotropic viruses have the same modes of transmission, coinfection is often observed, especially in areas and populations where HBV is endemic. High-risk populations include people who inject drugs. Both clinical and experimental studies have shown that HCV is more dominant than HBV during coinfection, but the underlying mechanism remains unclear. In this study, we show that HBV X protein (HBx) stimulates HCV replication by inhibiting the expression of E6-associated protein () via DNA methylation, thereby protecting the HCV core protein from proteasomal degradation, which can contribute to HCV dominance during HBV/HCV coinfection.
大多数临床和实验研究表明，在合并感染中，丙型肝炎病毒 (HCV) 比乙型肝炎病毒 (HBV) 更为优势，尽管其潜在机制尚不清楚。在本研究中，我们发现乙型肝炎病毒 X 蛋白 (HBx) 在人肝癌细胞合并感染时上调 HCV 核心蛋白的水平，从而刺激 HCV 复制。为此，HBx 上调了细胞 DNA 甲基转移酶 1 (DNMT1) 和 DNMT3b 的蛋白水平和酶活性，随后通过 DNA 甲基化降低了 HCV 核心蛋白的 E6 相关蛋白 ()，一种 HCV 核心蛋白的 E3 连接酶的表达水平。在存在 HBx 的情况下，HCV 核心蛋白的泛素依赖性蛋白酶体降解严重受损，而当过表达 或用 5-aza-2'dC 或 DNMT1 敲低处理恢复时，未观察到这种效应。在 HCV 在 Huh7D 细胞中转染 1.2mer HBV 复制子的单感染或 HBV 和 HCV 在 Huh7D-Na-牛磺胆酸钠协同转运多肽细胞中的合并感染建立的 HBV/HCV 合并感染系统中，HBx 对 HCV 核心蛋白的作用得到了准确再现，为 HBx 刺激 HCV 复制提供了证据。本研究可能为理解患者 HBV/HCV 合并感染中 HCV 优势提供了思路。乙型肝炎病毒 (HBV) 和丙型肝炎病毒 (HCV) 是主要的人类病原体，在全球范围内导致相当一部分肝病。由于这两种嗜肝病毒的传播方式相同，合并感染经常观察到，特别是在 HBV 流行的地区和人群中。高危人群包括吸毒者。临床和实验研究均表明，在合并感染中 HCV 比 HBV 更具优势，但潜在机制尚不清楚。在本研究中，我们表明 HBV X 蛋白 (HBx) 通过 DNA 甲基化抑制 E6 相关蛋白 () 的表达来刺激 HCV 复制，从而保护 HCV 核心蛋白免受蛋白酶体降解，这有助于 HBV/HCV 合并感染期间 HCV 的优势。
