FIG. 1.

Expression of NS induces apoptosis in HeLa cells. (A) Confluent cultures of HeLa cells expressing pUHD 10-3 containing the NS gene from A/Ty/Ont/66 were washed two times with PBS and then incubated for 5, 24, or 48 h in medium with (+) or without (−) anhydrotetracycline. Cell monolayers were lysed, and 5 mg of total protein was loaded per lane under reducing conditions and resolved by SDS-PAGE. After being transferred to nitrocellulose, proteins were probed for NS with a mouse monoclonal antibody against NS. Bands were detected by enhanced chemiluminescence as instructed by the manufacturer. The arrow indicates the location of NS1. Molecular size markers are indicated on the left. MDCK cells infected with A/Ty/Ont/66 at an MOI of 0.5 for 24 h served as a positive control (virus lane). (B) Confluent cultures of HeLa cells in 25-cm² flasks expressing pUHD 10-3 containing the NS gene from A/Ty/Ont/66 were washed two times with PBS and then incubated for 8 or 24 h in medium containing anhydrotetracycline (+) or anhydrotetracycline-free medium (−) containing 1% FBS at 37°C in 5% CO₂. DNA was collected and analyzed for DNA fragmentation by agarose gel analysis.