FIG. 2.

Primer extension by hTERT T-motif mutants. In vitro-reconstituted telomerase mutants were assayed for telomerase activity via direct primer extension as described in Materials and Methods. The numbers to the left of the gels (+4, +10, etc.) indicate the positions of products corresponding to the end of each round of template copying (expressed as the number of nucleotides added to the primer). Marker sizes (in nucleotides) are indicated to the right of the gels. The lighter exposure under each gel shows the unextended d(TTAGGG)₃ substrate primer (P) within each reaction, which served as a loading control (as it represented >95% of the recovered material). WT, wild type.