Adenoviral protein VII packages intracellular viral DNA throughout the early phase of infection.

The proteins associated with parental, adenoviral DNA in productively-infected HeLa cells have been examined both directly and indirectly. HeLa cells infected with 32P-labelled Ad2 were irradiated with u.v. light at various points in the infectious cycle. Following degradation of the DNA, nuclear proteins carrying cross-linked nucleotides, or oligonucleotides, were distinguished from virion phosphoproteins by the resistance of their 32P radioactivity to 1 M NaOH. The major core protein of the virion, protein VII, was found to be associated with viral DNA throughout infection, even when cells were infected at a multiplicity of 0.14. Micrococcal nuclease digestion of intranuclear viral DNA 4 h after infection liberated two nucleoprotein particles containing viral DNA, neither of which co-migrated with HeLa cell mononucleosomes. These results indicate that core protein VII remains associated with parental adenoviral DNA during productive infections. The observation that protein VII can be cross-linked to DNA in cells infected at very low multiplicity, together with the results of a comparison of proteins cross-linkable to viral DNA in cells infected by wild-type virus and a non-infectious mutant containing the precursor to protein VII, suggest that nucleoproteins comprising viral DNA and protein VII must be the templates for expression of pre-early and early viral genes.