(A) Telomerase activity is dependent upon E7. HFKs expressing the separate E6 and E7 genes were transfected with either the E6 and E7 siRNAs and quantified for telomerase activity as described. Both siRNAs decreased telomerase activity when transfected into recipient cells. Thus, E7 is required for full telomerase activity and its effect on the hTERT promoter is independent of E6. As shown previously in panel C, Myc siRNA also inhibited telomerase activity. (B) hTERT promoter activity is also dependent upon E7. An hTERT promoter reporter construct was transfected into the indicated cells together with siRNA for either E6, E7, or control siRNA. The value of the promoter activity with control siRNA was set to 100. hTERT promoter activity was reduced dramatically in both types of HFKs after treatment with either E6 or E7 specific siRNA. However, only the experiment with HFKs expressing the separate E6 and E7 genes conclusively demonstrates the specific requirement for E7 in maintaining full telomerase activity.