Fig. 4.

Differentiation-dependent viral genome amplification requires caspase activation. (A) HPV-31-positive CIN612 cells were treated with DMSO alone as a vehicle control, 20 μM the general caspase inhibitor Z-VAD-FMK (Upper), or 20 μM the caspase-3 inhibitor Z-DMQD-FMK (Lower) and grown in high-calcium medium for the indicated times. DNA was harvested from both control and treated cells and examined by Southern blot analysis by using the HPV genome as a probe. (B) Expression of keratin 10 (K10) in differentiating CIN612 cells. CIN612 cells were treated with DMSO as a vehicle control or 15 or 20 μM the general caspase inhibitor Z-VAD-FMK and were grown in high-calcium medium for 48 and 96 h. Lysates were analyzed by immunoblotting by using an antibody specific for K10. Experiments were repeated a minimum of three times with similar results.