Comparison of human and monkey cells for the ability to attenuate transcripts that begin at the adenovirus major late promoter.

Late transcription from the adenovirus major late promoter can terminate prematurely at a site 182 to 188 nucleotides downstream. Experiments have been designed, with run-on transcription in nuclei in vitro or riboprobe protection of RNA obtained both in vivo and in vitro, that demonstrate that the ratio of attenuator RNA to readthrough RNA is greater in monkey cells (CV-1) than in human cells (HeLa). This may explain, in part, why the human adenoviruses replicate more poorly in CV-1 cells than in HeLa cells. A mutant adenovirus that replicates better than wild-type virus in monkey cells produces less of the attenuator RNA than wild-type adenovirus does in monkey cells. Monkey cell extracts have been shown to contain a factor that, when added to human cell extracts transcribing adenovirus DNA in vitro, increases the production of attenuator RNA in these reactions. These observations help to explain a portion of the block to the production of infectious adenoviruses in monkey cells.