Functional analysis of a transrepressor domain in the hepatitis C virus core protein

Hepatitis C virus (HCV) is one of the major causative agents of chronic liver disease with the potential for development of hepatocellular carcinoma. The putative core protein of the virus has many intriguing properties, including transcriptional regulation of cellular and unrelated viral promoters. To further characterize the transregulatory function, a number of chimeric constructs were made by fusion of the core gene to the DNA binding domain of the yeast transactivator factor GAL4. The fusion protein exhibited a repressor activity on the herpes simplex virus thymidine kinase promoter via the upstream GAL4 DNA binding sites. A structure /function analysis of HCV core mutants in the context of the GAL4 DNA binding domain revealed that the transcriptional repressor activity was located near the N-terminus (amino acids 26–85). Transcription was strongly inhibited upon transfer of this repressor domain to a heterologous activation domain, (3CGln) of Epstein Barr virus transcription factor EBNA3C. Results from this study suggest that the HCV core protein contains an overall repressor activity, and that the repressor domain is located near the N-terminus.