Physical and functional interaction between HCV core protein and the different p73 isoforms.

Hepatitis C virus (HCV) core protein is a structural viral protein that packages the viral genomic RNA. In addition to this function, HCV core also modulates a number of cellular regulatory functions. In fact, HCV core protein has been found to modulate the expression of the cyclin-dependent inhibitor p21(WAF1/CIP1) and to promote both apoptosis and cell proliferation through its physical interaction with p53. Here, we studied the ability of HCV core to bind the p53-related p73 protein, its isoforms and its deletion mutants. We found that HCV core co-immunoprecipitated with p73 in HepG2 and SAOS-2 cells. Deletion mutational analysis of p73 indicates that the domain involved in HCV core binding is located between amino-acid residues 321-353. We also demonstrate that p73/core interaction results in the nuclear translocation of HCV core protein either in the presence of the p73 alpha or p73 beta tumor-suppressor proteins. In addition, the interaction with HCV core protein prevents p73 alpha, but not p73 beta dependent cell growth arrest in a p53-dependent manner. Our findings demonstrate that HCV core protein may directly influence the various p73 functions, thus playing a role in HCV pathogenesis.