Key Laboratory for Experimental Teratology of Ministry of Education, Key Laboratory of Infection and Immunity of Shandong Province, and Department of Immunology, Shandong University School of Basic Medical Science, Jinan, Shandong, PR China; Department of Gastroenterology, Qilu Hospital of Shandong University, Jinan, Shandong, PR China.
Key Laboratory for Experimental Teratology of Ministry of Education, Key Laboratory of Infection and Immunity of Shandong Province, and Department of Immunology, Shandong University School of Basic Medical Science, Jinan, Shandong, PR China.
Antiviral Res. 2018 May;153:114-123. doi: 10.1016/j.antiviral.2018.03.008. Epub 2018 Mar 23.
Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA), the stable genomic form as the template for viral transcription, plays a crucial role in viral persistence which remains a major global health problem. While accumulating evidence suggests the involvement of transcription factors and epigenetic machinery in cccDNA transcription, the roles of host transcription factors which contribute to epigenetic modification of cccDNA remain largely unknown. Zinc finger and homeoboxes 2 (ZHX2) is abundantly expressed in adult hepatocytes, where it acts as a transcriptional repressor and tumor suppressor by directly inhibiting the promoter activities of target genes. However, whether ZHX2 influences HBV replication or is involved in cccDNA epigenetic regulation remain unknown. In this study, we investigated the role of ZHX2 in cccDNA transcription. Analysis of immunohistochemistry showed that ZHX2 nuclear expression negatively correlated with serum HBV DNA and HBeAg. Remarkably, ZHX2 significantly decreased HBV antigens expression, pregenomic RNA (pgRNA) and HBV core particle DNA production both in vitro and in mouse livers supporting HBV antigens expression and cccDNA transcription. Dual luciferase and cccDNA ChIP assays confirmed that ZHX2 could bind to cccDNA and transcriptionally inhibit HBV promoter activities. In addition, ZHX2 suppressed the expression of histone regulator genes, such as cccDNA bound p300/CBP, and led to epigenetic repression of cccDNA. These findings highlight the roles of a novel restriction factor, ZHX2, in modulating HBV replication via regulating HBV promoter activities and cccDNA modifications. This study furthers our understanding of HBV transcription from cccDNA and offers new insights on potential HBV therapy.
乙型肝炎病毒（HBV）共价闭合环状 DNA（cccDNA）作为病毒转录的模板，是病毒持续存在的稳定基因组形式，这仍然是一个全球性的健康问题。尽管越来越多的证据表明转录因子和表观遗传机制参与了 cccDNA 的转录，但宿主转录因子在 cccDNA 表观遗传修饰中的作用在很大程度上仍不清楚。锌指和同源盒 2（ZHX2）在成人肝细胞中大量表达，作为转录抑制剂和肿瘤抑制剂，通过直接抑制靶基因的启动子活性起作用。然而，ZHX2 是否影响 HBV 复制或参与 cccDNA 表观遗传调控仍不清楚。在这项研究中，我们研究了 ZHX2 在 cccDNA 转录中的作用。免疫组织化学分析表明，ZHX2 核表达与血清 HBV DNA 和 HBeAg 呈负相关。值得注意的是，ZHX2 显著降低了体外和小鼠肝脏中 HBV 抗原表达、前基因组 RNA（pgRNA）和 HBV 核心粒子 DNA 的产生，支持 HBV 抗原表达和 cccDNA 转录。双荧光素酶和 cccDNA ChIP 分析证实，ZHX2 可以与 cccDNA 结合并转录抑制 HBV 启动子活性。此外，ZHX2 抑制了组蛋白调节基因的表达，如 cccDNA 结合的 p300/CBP，并导致 cccDNA 的表观遗传抑制。这些发现强调了一种新型限制因子 ZHX2 通过调节 HBV 启动子活性和 cccDNA 修饰来调节 HBV 复制的作用。这项研究进一步加深了我们对 HBV 从 cccDNA 转录的理解，并为潜在的 HBV 治疗提供了新的见解。
