HCV is classified into the genus Hepacivirus of the family Flaviviridae. Like all the members of the family, HCV is an enveloped, single-stranded, positive-sense RNA virus. Its genome (about 9600 nt) is flanked at both termini by conserved, highly structured non-translated regions (NTRs) and encodes a polyprotein precursor (about 3000 aa), which is proteolytically processed by host and viral proteases to produce the structural (core, E1, E2 and p7) and non-structural (NS2, NS3, NS4A, NS4B, NS5A and NS5B) proteins of the virus. Recently, an additional protein has been identified, whose function remains unknown. NS5A is a ~56 kDa pleiotropic protein with key roles in both viral RNA replication and modulation of the physiology of the host cell. It's exact role is not currently known (2008).
