Function and Mechanism of Hepatitis C Virus Non‐structural Protein 3 (HCV NS3) Unfolding of Viral G‐quadruplex RNA Structures

Abstract

Hepatitis C virus (HCV) is the major cause of chronic liver disease and hepatocellular carcinoma. It is currently estimated that over 71 million people in the world are chronically infected with HCV. The current HCV drugs are extremely expensive, and thus they are not available for the majority of patients infected with the virus. Moreover, due to high rate of mutation of the HCV genome, it is likely that the virus develops resistance to these drugs. Therefore, it is important to develop a cost‐effective anti‐viral compound that targets conserved regions within the HCV genome and prevent replication of various HCV genotypes and subtypes.The HCV genome encodes for ten different viral proteins, one of which is Non‐structural protein 3 (NS3). NS3 has both protease and helicase domain. The helicase domain of NS3 is essential for viral replication. However, its mechanism of action is not well understood. Previous works have shown the presence of conserved guanine‐rich consensus sequences within the HCV genome. These guanine rich sequences form G‐quadruplex (G4) secondary structures through Hoogesteen hydrogen bonding. It has been reported that both replication and translation of HCV genome could be inhibited by the formation of G4 structures. However, it is still unknown how these HCV G4RNA structures are regulated. We hypothesized that the Helicase domain of NS3 facilitates HCV replication by unfolding conserved G4 structures within the HCV genome.To investigate whether NS3 helicase resolves HCV G4RNA structures, we purchased synthetic HCV guanine rich RNA sequences and performed circular dichroism spectroscopy to confirm G4 formation. In addition, fluorescence anisotropy NS3 binding and trap unfolding assays were conducted. We showed that NS3 binds and resolves HCV G4RNA structure in an ATP dependent manner. Understanding the mechanism by which NS3 resolves HCV G4RNA might allow us to find processes and factors that could be targeted to prevent HCV replication in a host cell.Support or Funding InformationThis work is supported by MIRA grant R35GM122601This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.