FIG. 5.

Effect of the hTR template sequence on primer extension by hTERT T-motif mutants. (A) Wild-type and T-motif mutant hTERT proteins were reconstituted in the presence of wild-type and template mutant MH3 hTR RNA (12) shown. (B) Primer extension reactions were carried out under competitor challenge conditions as detailed in Materials and Methods. Postchase aliquots were taken at 3 min and analyzed via PAGE (4% gel). The prechased lane shows a 3-min extension reaction where excess competitor primer was added before IVR wild-type telomerase was added. Marker sizes (in nucleotides) are indicated to the left of the gel.