The major DNA polymerase in a nuclear membrane complex that is capable of synthesizing viral DNA sequences in vitro has been purified about 900-fold from adenovirus 2-infected KB cells. The enzyme was characterized as belonging to the class of mammalian DNA polymerases (DNA polymerase-y) that can utilize poly(A)-oligo(dT) as template primer.

The infectivity of adenovirus type 2 DNA and a DNA-protein complex was studied in 293 cells, a human embryonic kidney cell line transformed by sheared adenovirus type 5 DNA, and in human KB cells. Adenovirus type 2 DNA was more infectious (up to about 40-fold) in 293 cells than in KB cells, whereas a DNA-protein complex (prepared by a rapid procedure) had about the same infectivity in both cell lines. These data may mean that a factor present in 293 cells (perhaps a viral-coded protein) enhances the infectivity of free viral DNA. The infectivity of DNA and the DNA-protein complex was increased up to fivefold by brief treatment of cell monolayers with 25% dimethyl sulfoxide after transfection. Under these conditions, (i) the infectivity of native adenovirus type 2 DNA ranged from 400 to 1,300 PFU/,ug of DNA in 293 cells and from about 9 to 14 PFU/,ug of DNA in KB cells, and (ii) the infectivity of the DNA-protein complex was 6 x 103 to 2 x 104 PFU/,ug in 293 cells and 1.4 x 104 to 1.6 x 104 PFU/,tg in KB cells.