Alterations in early adenovirus transcription and mRNA abundance induced by translational inhibitors.

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At least six viral genes are activated early after adenovirus 2 infection of HeLa cells. In an effort to define more clearly the effects of protein synthesis inhibition on early viral gene expression, the rate of transcription and the cytoplasmic abundance of viral mRNA from each transcription unit were studied in infected cells treated with translational inhibitors added at different times during infection and at concentrations known to inhibit 95 to 99% of protein synthesis. Tritiated uridine-labeled nuclear and cytoplasmic viral RNA molecules synthesized in infected HeLa cells in both the presence and absence of inhibitors were analyzed and compared by hybridization using specific DNA probes. Translational inhibitors (25 micrograms/ml of cycloheximide or 10 microM anisomycin) added 30 min to 1 h after infection stimulated the over-accumulation of cytoplasmic viral mRNA from 3- to 20-fold, early regions E1A, E2, and E4 being affected most. This overproduction of viral mRNA was found to result from enhanced transcription of the respective early genes. Treatment of cells with 100 microM anisomycin 1 h prior to and during infection did not prevent the accumulation of early viral mRNA molecules; however, total cellular RNA synthesis was drastically inhibited in 100 microM anisomycin-treated cells. These results support the hypothesis that a cellular factor may function in the regulation of early viral gene expression at a transcriptional level.