Plays an essential role in the viral genome replication. Participates, together with NSP2, in the formation of viral factories (viroplasms), which are large inclusions in the host cytoplasm where replication intermediates are assembled and viral RNA replication takes place. Orchestrates the recruitment of viroplasmic proteins such as capsid proteins to these factories. Participates in the selective exclusion of host proteins from stress granules (SG) and P bodies (PB). Participates also in the sequestration of these remodeled organelles in viral factories