Figure 1.

Rescue of telomerase activity in an mTR^−/− cell line with the human telomerase RNA. A plasmid with the hTR gene under a constitutive promoter, or with 5 kb of mouse genomic DNA that contained the mTR gene and upstream sequences (15), or an empty vector (Bluescript) were transfected into a mTR^−/− cell line (KO-3 at passage 23). Forty-eight hours after transfection, S-100 extracts were prepared and assayed for telomerase activity. As a control of the TRAP assay, telomerase activity was detected in wild-type (mTR^+/+) cells. All the extracts were pretreated (+) or not (−) with RNase before the telomerase assay. The protein concentration in the PCR step of the TRAP assay is given in μg/μl. The arrow indicates the position of the internal control (IC) for PCR efficiency.