Department of Biotechnology, Chonnam National University, Gwangju 500-757, Korea.
Curr Med Chem. 2014;21(8):1050-60. doi: 10.2174/09298673113206660306.
DEAD-box RNA helicase DDX3 is a well-known host factor that inhibits hepatitis B viral proliferation and boosts innate immune responses via TANK-binding kinase 1 (TBK1)/IKKε-mediated and/or interferon (IFN)-β promoter stimulator-1 (IPS-1)-mediated IFN-β induction. Previously, we demonstrated the anti-hepatitis B activity of Rg3 via stimulation of TRAF6/TAK1 degradation and inhibition of JNK/AP-1 signaling. To determine the effects of Rg3 on innate immunity, an IFN-β promoter assay was performed. Rg3 ameliorated IFN-β expression via upregulation of both the TBK1/IKKε pathway and DDX3 expression. In addition, Rg3 induced the phosphorylation of IRF3 and its translocation into nucleus, which is a key molecule to induction of IFN-β expression. To evaluate the molecular mechanism of Rg3 on DDX3 expression, the DDX3 promoter (-1406/+105) was subjected to luciferase assay and ChIP analysis. p53 phosphorylation resulted in upregulation of DDX3 expression, which enhanced DDX3 promoter transactivation activity. Transient transfection with wild-type p53 increased DDX3 promoter activity in Hep3B cells which have null mutant of p53, whereas knockdown p53 by si-p53 reduced DDX3 promoter activity in HepG2.2.15 and HepG2 cells, respectively. Rg3- mediated phosphorylation of p53 resulted in inhibition of Akt phosphorylation, which in turn reduced MDM2-mediated p53 degradation. An Akt inhibitor augmented DDX3 promoter activity and reduced the secretion of hepatitis B surface antigen. Our data indicate that Rg3 enhances innate immunity by inducing IFN-β expression through upregulation of DDX3 promoter activity via p53-mediated transactivation and activation of the TBK1/IKKε/IRF3 pathway.
DEAD 框 RNA 解旋酶 DDX3 是一种众所周知的宿主因子，通过 TANK 结合激酶 1 (TBK1)/IKKε 介导和/或干扰素 (IFN)-β 启动子刺激物-1 (IPS-1) 介导的 IFN-β 诱导，抑制乙型肝炎病毒的增殖并增强先天免疫反应。之前，我们通过刺激 TRAF6/TAK1 降解和抑制 JNK/AP-1 信号通路来证明 Rg3 的抗乙型肝炎活性。为了确定 Rg3 对先天免疫的影响，进行了 IFN-β 启动子测定。Rg3 通过上调 TBK1/IKKε 途径和 DDX3 表达来改善 IFN-β 的表达。此外，Rg3 诱导 IRF3 的磷酸化及其向核内易位，这是诱导 IFN-β 表达的关键分子。为了评估 Rg3 对 DDX3 表达的分子机制，进行了 DDX3 启动子 (-1406/+105) 的荧光素酶测定和 ChIP 分析。p53 磷酸化导致 DDX3 表达上调，从而增强 DDX3 启动子的转录激活活性。在具有 p53 缺失突变的 Hep3B 细胞中转染野生型 p53 可增加 DDX3 启动子活性，而用 si-p53 敲低 HepG2.2.15 和 HepG2 细胞中的 p53 可分别降低 DDX3 启动子活性。Rg3 介导的 p53 磷酸化导致 Akt 磷酸化的抑制，从而减少 MDM2 介导的 p53 降解。Akt 抑制剂增强了 DDX3 启动子活性并减少了乙型肝炎表面抗原的分泌。我们的数据表明，Rg3 通过诱导 DDX3 启动子活性的增加来增强先天免疫，从而通过 p53 介导的转录激活和 TBK1/IKKε/IRF3 途径的激活来诱导 IFN-β 的表达。
