Integration of the Deoxyribonucleic Acid of Adenovirus Type 12 into the Deoxyribonucleic Acid of Baby Hamster Kidney Cells

Abstract

In a previous report, evidence was presented that the deoxyribonucleic acid (DNA) of adenovirus type 12 (Ad12) is integrated by covalent linkage into the DNA of baby hamster kidney cells (BHK-21 cells). These studies have been extended. The DNA of Ad12 and that of BHK-21 cells grown in medium containing 5-bromodeoxyuridine could be separated by equilibrium centrifugation in alkaline CsCl density gradients. BHK-21 cells were infected with 3 H-labeled Ad12, and the total intracellular DNA was analyzed at various times after infection in alkaline CsCl density gradients. The 3 H label in the position of cellular DNA hybridized predominantly with viral DNA and to a lesser extent also with cellular DNA. Replication of viral DNA could not be detected in BHK-21 cells. The appearance of viral 3 H label in the density stratum of cellular DNA was not significantly affected when DNA synthesis in Ad12-infected BHK-21 cells was inhibited >96% by cytosine arabinoside. These findings provided additional evidence for integration of Ad12 DNA into the DNA of BHK-21 cells. It could be calculated that 5 to 55 Ad12 DNA equivalents per cell are integrated. Replication of viral or cellular DNA was not required for integration. Inhibition of protein or ribonucleic acid synthesis interfered with integration only slightly.