Figure 5.

Cleavage of telomeric substrates by human telomerase may proceed by an exonucleolytic mechanism. DNA primer extension assays were performed with the indicated oligonucleotides. The 3′-end radiolabeled 5′-biotinylated primers, (T₂AG₃)₃ and (T₂AG₃)₄, migrate, respectively, as 19 and 25mers at the positions indicated by the arrows. Numbers represent the lengths of the elongation products. The asterisks indicate the positions of the phosphorothioate modifications within the primers.