Proteolytic activity of hepatitis A virus 3C protein

Although the genome organization and overall structure of hepatitis A virus are similar to those of other picornaviruses, nothing is known about the protein-processing pathways used by this virus to generate its capsid and nonstructural proteins from the polyprotein precursor. RNA transcripts of cloned hepatitis A virus cDNAs representing parts of the P2 and P3 regions of the genome were translated in rabbit reticulocyte lysates in vitro, and the translation products were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis before and after immunoprecipitation with specific antisera. Pulse-chase experiments demonstrated rapid cleavage at the P2-P3 junction, followed by further but incomplete processing at the 3C-3D junction. Mutation of the 3C coding sequence eliminated all cleavages. Efforts to demonstrate intermolecular cutting of the P2-P3 cleavage site by active 3C or 3CD sequences were unsuccessful; thus, it is likely that this cleavage occurs by intramolecular reaction, in cis.