Adenovirus-associated virus multiplication. VII. Helper requirement for viral deoxyribonucleic acid and ribonucleic acid synthesis.

The adsorption of adenovirus-associated virus (AAV) type 2 by KB cells and the subsequent penetration of the AAV genome to the cell nucleus was measured with and without helper adenovirus type 2 (Ad2). It was found that the helper virus did not enhance either process. On the other hand, a synthesis of AAV deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) was not detected by nucleic acid hybridization after KB cells were infected with AAV type 2 alone, whereas both AAV DNA and RNA synthesis were readily detected when cells were additionally infected with Ad2 or herpes simplex virus type 1, a partial helper of AAV replication. AAV RNA synthesis was initially observed 10 to 11 hr after simultaneous infection with Ad2, but the interval between AAV infection and AAV transcription could be reduced to 4 to 5 hr when cells were first infected with Ad2 for 10 hr. It was estimated that AAV DNA synthesis accounted for 3% of the total DNA in cells after a simultaneous infection with Ad2. These findings, together with the previous observation that adenovirus provides a helper function(s) after AAV uncoating, suggest that AAV are defective only subsequent to the uncoating process, and that helper viruses may provide a factor(s) needed for initiating synthesis of AAV DNA, RNA, or both.