Hepatitis B virus (HBV) is a partially double-stranded DNA virus that replicates by reverse transcription. We previously demonstrated that the host restriction factor-APOBEC3B (A3B) inhibited HBV replication which was dependent on its deaminase activity during reverse transcription. However, the host factors involved in the process of regulating the anti-HBV function of A3B are less known. In this research, to obtain a comprehensive understanding of the interaction networks of A3B, we conducted coimmunoprecipitation and mass spectrometry to identify A3B-interacting proteins in the presence of HBV. By this approach, we determined that DExD/H-box helicase 9 (DHX9) suppressed the anti-HBV effect of A3B, and this suppression was dependent on their interaction. Although DHX9 did not affect the deamination activity of A3B in vitro assay or the viral DNA editing of A3B in HepG2-NTCP cells that support HBV infection, it inhibited the binding of A3B with pgRNA. These data suggest that DHX9 can interact with A3B and attenuate the anti-HBV efficacy of A3B.Abbreviations: 3D-PCR: differential DNA denaturation PCR; APOBEC3: apolipoprotein B mRNA-editing catalytic polypeptide 3; cccDNA: covalently closed circular DNA; co-IP: coimmunoprecipitation; DDX: DExD-box RNA helicases; HBc: HBV core protein; HBV: hepatitis B virus; HepAD38: HepG2 cell line stably transfected with HBV DNA; HepG2-NTCP: HepG2 cell line stably transfected with Na+/taurocholate cotransporter polypeptide; Huh7: human hepatoma cell line; pgRNA: pregenomic RNA; PPI: protein-protein interactions; RC DNA: relaxed circular DNA.

中文翻译：

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DHX9与APOBEC3B相互作用并减弱APOBEC3B的抗HBV作用。

乙型肝炎病毒（HBV）是部分双链DNA病毒，可通过逆转录复制。我们先前证明了宿主限制因子-APOBEC3B（A3B）抑制了HBV复制，这取决于其在逆转录过程中的脱氨酶活性。但是，涉及调节A3B抗HBV功能过程中的宿主因素鲜为人知。在这项研究中，为了获得对A3B相互作用网络的全面了解，我们进行了共免疫沉淀和质谱分析，以鉴定在HBV存在下与A3B相互作用的蛋白。通过这种方法，我们确定DExD / H-box解旋酶9（DHX9）抑制了A3B的抗HBV效应，而这种抑制取决于它们的相互作用。尽管DHX9不会影响A3B的体外测定的脱氨活性或在支持HBV感染的HepG2-NTCP细胞中对A3B的病毒DNA编辑，但它会抑制A3B与pgRNA的结合。这些数据表明DHX9可以与A3B相互作用并减弱A3B的抗HBV效力。APOBEC3：载脂蛋白B mRNA编辑催化多肽3；cccDNA：共价闭合的环状DNA；co-IP：共免疫沉淀；DDX：DExD-box RNA解旋酶；HBc：HBV核心蛋白；HBV：乙型肝炎病毒；HepAD38：用HBV DNA稳定转染的HepG2细胞系；HepG2-NTCP：用Na + /牛磺胆酸盐共转运蛋白多肽稳定转染的HepG2细胞系；Huh7：人肝癌细胞系；pgRNA：基因组前RNA；PPI：蛋白质间相互作用；RC DNA：松弛的环状DNA。