FIG. 8.

Coexpression of E4-17K and E4-16K does not prevent G₂ arrest but does inhibit cellular DNA replication. (A) SCC-12F cells were infected with rAds for 72 h, and cell cycle profiles were analyzed by fluorescence-activated cell sorting. (B) Western blot analysis of E4 expression in SCC-12F cells infected with the different rAd E4 proteins. Note that a small amount of E4-16K is generated in cells infected with AdE4-17K (34). (C) SCC-12F cells were infected with rAds and pulse-labeled with BrdU. Coexpression of E4-17K and E4-16K inhibited BrdU incorporation into cells with a DNA content of greater than 4N (>4N) and also induced a decrease in BrdU incorporation into proliferating diploid cells. (D) COS-1 epithelial cells were transfected with expression plasmids and pulse-labeled with BrdU. The percentage of BrdU cells with a >4N DNA content (a) and the percentage of BrdU-positive S phase cells (b) are shown. Note that coexpression of E4-17K and E4-16K induces a significant decrease in BrdU incorporation into both populations of cells. The asterisk indicates that the increase in BrdU-positive cells of >4N and the decrease in BrdU-positive S-phase cells were significant (99.9%).