Intracellular organization of herpes simplex virus type 1 DNA assayed by staphylococcal nuclease sensitivity

The nucleoprotein organization of herpes simplex virus type 1 (HSV-1) DNA during productive infection was analyzed using staphylococcal nuclease. Both prior to and during the genome replication phase of infection, digestion of nuclei revealed two readily discernible forms of viral DNA, resistant and sensitive. The identity of these forms was established by the use of a variety of assays, including velocity sedimentation, nucleic acid hybridization and restriction endonuclease digestion and by employing temperature sensitive (ts) mutants impaired in either DNA replication or encapsidation of progeny DNA. Thus, nuclease resistant DNA was derived from encapsidated unit length genomes while sensitive DNA represented digestion products of replicating viral genomes. Importantly, no evidence was obtained for the arrangement of either parental or progeny viral DNA in nucleosomes. These findings are discussed with regard to the nucleoprotein structure of replicating viral DNA.