Responsible for cleavages of polyprotein P2A and replicase polyprotein P2AB. Covalently attached to the 5' extremity of the genomic and subgenomic RNAs. It may serve as a primer for the replicase. Replicates the viral genome. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) The polyprotein is proteolytically cleaved into several chains by the viral protease. Produced by -1 ribosomal frameshifting at the 2A-2B genes boundary.