FIG. 1.

E4orf1 imposes a G₁ restriction on virus production directed by E1B-55K deletion mutant adenoviruses. Synchronously dividing cultures of HeLa cells were generated by mitotic detachment and HU treatment as described in Materials and Methods. Cells were infected at early G₁ (hatched bars) or early S phase (light bars) with the indicated viruses. (A) Infected cells were harvested after 32 h, and at least 100 infected cells from multiple samples were evaluated by transmission electron microscopy for the presence of progeny viral particles. The percentages of cells containing progeny viral particles from four (dl309 and dl1520) and two (dl1018) independent experiments are shown with the standard deviation indicated by error bars. (B) Synchronously dividing HeLa cells were generated and infected as in panel A with the viruses indicated in panel B. After 72 h, the yield of progeny virus was determined by plaque assay and is presented as the infectious virus per infected cell. Results from three independent experiments are represented as the mean with standard error of the mean. The status of the relevant viral gene is indicated below each bar.