Anatomy of Herpes Simplex Virus DNA XII. Accumulation of Head-to-Tail Concatemers in Nuclei of Infected Cells and Their Role in the Generation of the Four Isomeric Arrangements of Viral DNA

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Abstract
Herpes simplex virus DNA extracted from virions accumulating in the cytoplasm of infected cells consists of 4 populations of linear molecules differing in the orientation of the covalently linked large (L) and small (S) components relative to each other. Together, these 4 isomeric arrangements of viral DNA display 4 different termini and 4 different L-S component junctions. Restriction endonucleases [BglII, BglIII, HsuI, EcoRI and HpaI] were used to analyze the newly replicated viral DNA shortly after the onset of viral DNA synthesis, the progeny DNA accumulating in the nuclei late in infection and rapidly sedimenting DNA present in nuclei of infected [African green monkey kidney Vero] cells at 8 h after infection. In each instance the nuclear viral DNA contained a decreased concentration of all 4 terminal fragments and an increase in the concentration of fragments spanning the junction of L and S components relative to the concentration of other DNA fragments. Thus the viral DNA accumulating in the nuclei consists of head-to-tail concatemers arising from the replication of DNA by a rolling-circle mechanism. A model is presented for generation of all 4 isomeric arrangements of herpes simplex virus DNA from 1 arrangement based on excision and repair of unit length DNA from head-to-tail concatemers and known features of the sequence arrangement of viral DNA.