Department of Pathology, Saint Louis Universitygrid.262962.b, Saint Louis, Missouri, USA.
Department of Pharmacology and Physiology, Saint Louis Universitygrid.262962.b, Saint Louis, Missouri, USA.
J Virol. 2021 Aug 10;95(17):e0095221. doi: 10.1128/JVI.00952-21.
Hepatitis C virus (HCV) regulates many cellular genes in modulating the host immune system for benefit of viral replication and long-term persistence in a host for chronic infection. Long noncoding RNAs (lncRNAs) play an important role in the regulation of many important cellular processes, including immune responses. We recently reported that HCV infection downregulates lncRNA Linc-Pint (long intergenic non-protein-coding RNA p53-induced transcript) expression, although the mechanism of repression and functional consequences are not well understood. In this study, we demonstrate that HCV infection of hepatocytes transcriptionally reduces Linc-Pint expression through CCAAT/enhancer binding protein β (C/EBP-β). Subsequently, we observed that the overexpression of Linc-Pint significantly upregulates interferon alpha (IFN-α) and IFN-β expression in HCV-replicating hepatocytes. Using unbiased proteomics, we identified that Linc-Pint associates with DDX24, which enables RIP1 to interact with IFN-regulatory factor 7 (IRF7) of the IFN signaling pathway. We furthermore observed that IFN-α14 promoter activity was enhanced in the presence of Linc-Pint. Together, these results demonstrated that Linc-Pint acts as a positive regulator of host innate immune responses, especially IFN signaling. HCV-mediated downregulation of Linc-Pint expression appears to be one of the mechanisms by which HCV may evade innate immunity for long-term persistence and chronicity. The mechanism by which lncRNA regulates the host immune response during HCV infection is poorly understood. We observed that Linc-Pint was transcriptionally downregulated by HCV. Using a chromatin immunoprecipitation (ChIP) assay, we showed inhibition of transcription factor C/EBP-β binding to the Linc-Pint promoter in the presence of HCV infection. We further identified that Linc-Pint associates with DDX24 for immunomodulatory function. The overexpression of Linc-Pint reduces DDX24 expression, which in turn results in the disruption of DDX24-RIP1 complex formation and the activation of IRF7. The induction of IFN-α14 promoter activity in the presence of Linc-Pint further confirms our observation. Together, our results suggest that Linc-Pint acts as a positive regulator of host innate immune responses. Downregulation of Linc-Pint expression by HCV helps in escaping the innate immune system for the development of chronicity.
丙型肝炎病毒 (HCV) 通过调节宿主免疫系统，有利于病毒复制和长期在宿主体内持续存在，从而感染慢性。长非编码 RNA (lncRNA) 在调节许多重要的细胞过程中发挥重要作用，包括免疫反应。我们最近报道，HCV 感染下调 lncRNA Linc-Pint（长基因间非蛋白编码 RNA p53 诱导转录物）的表达，尽管抑制的机制和功能后果尚不清楚。在这项研究中，我们证明 HCV 感染通过 CCAAT/增强子结合蛋白 β (C/EBP-β) 转录降低 Linc-Pint 的表达。随后，我们观察到在 HCV 复制的肝细胞中，Linc-Pint 的过表达显著上调干扰素 α (IFN-α) 和 IFN-β 的表达。使用无偏 proteomics，我们发现 Linc-Pint 与 DDX24 结合，从而使 RIP1 与 IFN 信号通路中的干扰素调节因子 7 (IRF7) 相互作用。我们还观察到在 Linc-Pint 存在的情况下，IFN-α14 启动子活性增强。总之，这些结果表明 Linc-Pint 作为宿主先天免疫反应的正调节剂发挥作用，特别是 IFN 信号。HCV 介导的 Linc-Pint 表达下调似乎是 HCV 逃避先天免疫以长期持续和慢性存在的机制之一。 HCV 感染期间 lncRNA 调节宿主免疫反应的机制尚不清楚。我们观察到 HCV 转录下调 Linc-Pint。使用染色质免疫沉淀 (ChIP) 测定，我们表明在 HCV 感染存在的情况下，转录因子 C/EBP-β 对 Linc-Pint 启动子的结合被抑制。我们进一步发现 Linc-Pint 与 DDX24 结合用于免疫调节功能。Linc-Pint 的过表达降低 DDX24 的表达，这反过来又导致 DDX24-RIP1 复合物形成的破坏和 IRF7 的激活。在 Linc-Pint 存在的情况下，IFN-α14 启动子活性的诱导进一步证实了我们的观察结果。总之，我们的结果表明 Linc-Pint 作为宿主先天免疫反应的正调节剂发挥作用。HCV 下调 Linc-Pint 的表达有助于逃避先天免疫系统的作用，从而导致慢性发生。
