In vitro encapsidation of plasmid DNA into human adenovirus empty capsids

Plasmid DNA, added to extracts of human adenovirus type 3-infected HeLa cells, binds to empty viral capsids and can be purified using cesium density gradient centrifugation. The fraction of DNA bound depends on the amount of DNA added to the extract, and the capsid partially protects the bound DNA from digestion by DNase I. This capsid binding of plasmid DNA does not require the presence of the adenovirus DNA packaging sequence. However, the presence of the adenovirus packaging sequence in the plasmid results in better protection of the bound plasmid molecule from cellular nucleases.