FIG 4.

Neither CHK1 nor PKA phosphorylates E6 in the absence of E6AP. HeLa cells were transfected with siRNAs against E6AP, E6/E7, and luciferase (Luci) as control. After 60 h, CHK1 (100 nM) (A) and PKA (15 μM) (B) inhibitors, and dimethyl sulfoxide (DMSO) as control, were added to the cells, followed by further incubation for 12 h. Cells were then harvested, and samples were analyzed using Western blotting with the antibodies against total E6, pE6, and E6AP; α-tubulin was used as a loading control. (C) HeLa cells were treated with PKA inhibitor (15 μM) for 15 h, followed by treatment with DMSO (as control) or H₂O₂ (500 μM) for 4 h. Western blots were probed using antibodies specific against total E6, pE6, and α-tubulin (loading control).