Figure 2.

Primer extension by hTERT C-motif mutants. (A) In vitro reconstituted telomerase mutants were assayed for telomerase activity via direct primer extension as described in Materials and Methods section. Lysate lane: extension reaction with control IVR containing RRL only. Unextended d(TTAGGG)₃ substrate primer (P) within each reaction served as loading control (as it represented >95% of the recovered material). Numbers on left (+4, +10, etc.) indicate the positions of products corresponding to the end of each round of template copying (expressed as number of nucleotides added to the primer). Marker sizes (in nucleotides) are indicated. A representative repeat + 3 (R + 3) product is indicated by arrowhead. (B) Schematic diagram of major synthesis products from primer extension reactions. Potential product alignments of R + 3 and repeat + 6 (R + 6) products with the template RNA are shown. Nucleotides added during each round of primer elongation are shown in lower case. hTR nucleotide positions are indicated next to template sequence.