Adenovirus 2 peptide IX gene is expressed only on replicated DNA molecules

Transcription of the adenovirus type 2 peptide IX (pIX) gene was examined in transient expression assays. When a nonreplicating plasmid DNA containing the pIX gene was introduced into HeLa cells by the DEAE-dextran method, no pIX gene transcript was detected. In contrast, efficient transcription was observed in the cells transfected with a replicating plasmid containing the pIX gene. Adenovirus early genes did not affect the level of transcription of the pIX gene on either a nonreplicating or a replicating plasmid. Inhibition of plasmid replication with cytosine arabinoside prevented transcription of the pIX gene. By quantitative analysis of the amount of the pIX gene and its transcript in transfected cells, it was concluded that active transcription of the pIX gene occurred only on DNA molecules replicated in the cell.