Forms a proteinaceous shell that encloses the viral DNA and compartmentalizes proteins and DNA during viral infection (PubMed:28813669, PubMed:28082593). This shell is the site of viral replication, with the proteins involved in DNA replication localized inside the compartment (PubMed:28813669, PubMed:28082593). Provides a surface for docking of capsids during packaging (PubMed:28082593). In infected host cells assembles as a nucleus-like structure in the host cytoplasm. Expressed very early after infection (PubMed:28082593). Encloses the DNA at 45 mpi (PubMed:28082593). Belongs to the Phikzvirus gp105 family.