Fig. 6. Production of catalytically inactive mTERT does not protect ES cells from apoptosis. (A) Expression of a gene encoding catalytically inactive mTERT was determined by RT-PCR in vector-transfected and inactive-mTERT-producing ES cells. 3 µg RNA was extracted from undifferentiated ES cells and reverse transcribed into cDNA for PCR. (B) Telomerase activity of vector-transfected and inactive-mTERT-producing ES cells was determined by a TRAP assay. Decreasing amounts of protein (50 ng and 5 ng) were used in the assay. (C) The indicated undifferentiated ES cells were treated with various doses of doxorubicin for 12 hours, and cell death was determined by PI exclusion. Data represent means±s.d. from one of the three independent experiments in duplicate.