The preformed procapsids are made in the nucleus proximal to DNA replication compartments. Encapsidation of unit-length viral DNA genomes depends on a terminase complex interacting with a specialized PORT penton. Terminase machinery recognizes free genomic ends and threads a single genome length of DNA through the PORT channel into each capsid. This process begins and ends at pac elements within terminal repeated a sequences, proceeding in a directional manner (S component first) on concatemeric DNA. A 129-bp region contains both cis-acting pac elements (pac1 and pac2) and is sufficient to direct cleavage and packaging leaving single-base 3 ́ extensions at both genomic ends.
Once the capsid has aquired the genome, it is designated a C capsid. Three capsid forms accumulate in the nucleus of herpesvirus-infected cells: A capsids that lack both scaffold and packaged viral DNA, B capsids that contain scaffold but lack viral DNA, and C capsids, contains viral DNA in place of scaffold and probably represents nucleocapsids in the process of maturation.