Fig. 4.

The multiplication cycle of the calicivirus. The replication of the calicivirus can be schematically subdivided into eleven steps. After attachment of the protein core to the cellular receptor, the virion is internalized in the cell (step 1). Uncoating of the viral genome (step 2) is followed by translation of the polyprotein precursor (step 3) and a co-translational processing releasing the non-structural proteins (step 4). Those proteins assemble in a replication complex (step 5) that synthesizes the antigenomic RNA (step 6), being itself used as a template for synthesis of the genomic RNA (step 7). The newly synthesized genomic RNA is translated as a polyprotein precursor (step 3) or being used for packaging in the assembled viral protein core (step 10). The antigenomic RNA is also the template for synthesis of subgenomic RNA (step 8). In noroviruses, vesiviruses and possibly recoviruses, the subgenomic RNA is translated as structural proteins, VP1 and VP2 (step 9). In sapoviruses, lagoviruses and possibly beco/naboviruses, the VP1 is released from the polyprotein precursor after processing by the viral protease. At a still not defined time in the multiplication cycle, assembly of the structural proteins as well as packaging of the genomic RNA occurs (step 10), followed by release of the mature virion from the cell (step 11).