Analysis of hepatitis C virus core protein interaction domains.

Hepatitis C virus (HCV) core protein forms the internal viral coat that encapsidates the genomic RNA and is enveloped in a host cell-derived lipid membrane. As the single capsid protein, core should be capable of multimerization but attempts to produce virus-like particles following expression of HCV structural proteins have not been successful. In this study, we have analysed the interaction capacity of full-length and truncated HCV core using the yeast two-hybrid system. Full-length core containing or lacking the translocation signal for the E1 glycoprotein did not interact with full-length or truncated core proteins. Truncation to the N-terminal 122 aa revealed an interaction domain which was mapped to the tryptophan-rich sequence from aa 82-102 and was termed the main homotypic interaction domain. The C-terminal hydrophobic fragment of core (aa 122-172) was incapable of interacting with itself but interacted with the main homotypic interaction domain in trans (the weak heterotypic interaction domain). Core proteins truncated at their N and C termini (aa 46-102) were trans-activating when fused to the DNA-binding domain of GAL4. Based on our results, we suggest that the C-terminal segment may interact in cis with the main homotypic interaction domain and thereby prevent multimerization. Core-core interaction was also observed for in vitro-translated proteins bound to truncated immobilized core 102. However, interaction was less specific in this system suggesting that protein interaction and possibly conformational alteration of core may be dependent on the experimental system.