Overexpression of catalytically inactive hTR mutants protects from hTERT-induced apoptosis. (A) Telomerase activity with hTR and hTERT cooverexpression. Error bars represent standard deviation of biological triplicates. (B) RNA levels with hTR and hTERT cooverexpression. Error bars represent standard deviation of PCR triplicates. (C) Live cell counts with hTR and hTERT cooverexpression. Error bars represent standard deviation of biological triplicates. (D) Caspase-3/7 activity measured by luminescence. Error bars represent standard deviation of biological triplicates. Significance assessed by unpaired Student t test. **P < .01; ***P < .001; ****P < .0001.