Mutational Analysis of Hepatitis C Virus Core Protein

Abstract

Hepatitis C virus (HCV) is the main blood-borne non-A, non-B hepatitis virus which plays a major role in development of chronic hepatitis and hepatocellular carcinoma. Our laboratory previously demonstrated that the core protein (191 amino acids) of HCV exhibits the suppressive activity to the gene expression and replication of hepatitis B virus (HBV) and this suppression effect is modulated by phosphorylation. Previous results also indicated that N-terminal 122 amino acid fragment, but not the 101-amino-acid fragment, of the HCV core protein retained the same suppressive effect as the full-length core protein. Thus, it is likely that the region between amino acids 101 and 122 of the HCV core polypeptide is responsible for the suppressive activity of the HCV core protein. This 21-amino acid segment of the HCV core polypeptide contains six arginine residues. In this study, we investigated the role of these six arginines residues in the suppressive activity. Based on the mutational analysis, results suggested that mutation of Arg117 did not interfere with the Irans-suppressive activity of the HCV core protein and the role of Arg101 in the trans-suppressive activity of the core protein was involved in phosphorylation of Ser99 by protein kinase C. Arg104 mutants blocked HBV encapsidation but did not confer any effect on the suppression of the HBV gene expression. However, single mutation at Arg113, Arg114 Arg115 led to the loss of both effects. Taken together, results suggests that the effects of HCV core protein on the transcription of HBV gene and viral encapsidation can be decoupled. Additionally, this study also demonstrates that the role of phosphoiylation in the control of trans-suppressive activity of the HCV core protein could not be mimic by introducing the acidic residues.