Laboratory of Biochemistry and Molecular Virology, Department of Molecular Biology and Genetics, Democritus University of Thrace, Alexandroupolis, Greece.
Laboratory of Molecular Virology, Hellenic Pasteur Institute, Athens, Greece.
J Virol. 2018 Apr 13;92(9). doi: 10.1128/JVI.02036-17. Print 2018 May 1.
Viruses often encompass overlapping reading frames and unconventional translation mechanisms in order to maximize the output from a minimum genome and to orchestrate their timely gene expression. Hepatitis C virus (HCV) possesses such an unconventional open reading frame (ORF) within the core-coding region, encoding an additional protein, initially designated ARFP, F, or core+1. Two predominant isoforms of core+1/ARFP have been reported, core+1/L, initiating from codon 26, and core+1/S, initiating from codons 85/87 of the polyprotein coding region. The biological significance of core+1/ARFP expression remains elusive. The aim of the present study was to gain insight into the functional and pathological properties of core+1/ARFP through its interaction with the host cell, combining and approaches. Our data provide strong evidence that the core+1/ARFP of HCV-1a stimulates cell proliferation in Huh7-based cell lines expressing either core+1/S or core+1/L isoforms and in transgenic liver disease mouse models expressing core+1/S protein in a liver-specific manner. Both isoforms of core+1/ARFP increase the levels of cyclin D1 and phosphorylated Rb, thus promoting the cell cycle. In addition, core+1/S was found to enhance liver regeneration and oncogenesis in transgenic mice. The induction of the cell cycle together with increased mRNA levels of cell proliferation-related oncogenes in cells expressing the core+1/ARFP proteins argue for an oncogenic potential of these proteins and an important role in HCV-associated pathogenesis. This study sheds light on the biological importance of a unique HCV protein. We show here that core+1/ARFP of HCV-1a interacts with the host machinery, leading to acceleration of the cell cycle and enhancement of liver carcinogenesis. This pathological mechanism(s) may complement the action of other viral proteins with oncogenic properties, leading to the development of hepatocellular carcinoma. In addition, given that immunological responses to core+1/ARFP have been correlated with liver disease severity in chronic HCV patients, we expect that the present work will assist in clarifying the pathophysiological relevance of this protein as a biomarker of disease progression.
病毒经常通过重叠的阅读框和非常规的翻译机制来最大限度地从最小基因组中输出，并协调其适时的基因表达。丙型肝炎病毒 (HCV) 在核心编码区具有这样一个非常规的开放阅读框 (ORF)，编码一个额外的蛋白质，最初被指定为 ARFP、F 或核心+1。已经报道了两种主要的核心+1/ARFP 同工型，核心+1/L 从密码子 26 起始，核心+1/S 从多蛋白编码区的密码子 85/87 起始。核心+1/ARFP 表达的生物学意义仍然难以捉摸。本研究的目的是通过其与宿主细胞的相互作用，结合和方法，深入了解核心+1/ARFP 的功能和病理特性。我们的数据提供了强有力的证据，表明 HCV-1a 的核心+1/ARFP 刺激在表达核心+1/S 或核心+1/L 同工型的基于 Huh7 的细胞系中的细胞增殖，并在以肝特异性方式表达核心+1/S 蛋白的转基因肝病小鼠模型中。两种核心+1/ARFP 同工型均增加了细胞周期蛋白 D1 和磷酸化 Rb 的水平，从而促进了细胞周期。此外，发现核心+1/S 可增强转基因小鼠的肝再生和肿瘤发生。在表达核心+1/ARFP 蛋白的细胞中，细胞周期的诱导以及与细胞增殖相关的癌基因的 mRNA 水平增加，表明这些蛋白具有致癌潜能，并在 HCV 相关发病机制中发挥重要作用。本研究阐明了一种独特的 HCV 蛋白的生物学重要性。我们在这里表明，HCV-1a 的核心+1/ARFP 与宿主机制相互作用，导致细胞周期加速和肝肿瘤发生增强。这种病理机制可能与具有致癌特性的其他病毒蛋白的作用互补，导致肝细胞癌的发生。此外，鉴于针对核心+1/ARFP 的免疫反应与慢性 HCV 患者的肝病严重程度相关，我们预计本工作将有助于阐明该蛋白作为疾病进展的生物标志物的病理生理学相关性。
