Targeting Telomerase via Its Key RNA/DNA Heteroduplex

Telomerase is a promising “universal” anticancer target. It has been demonstrated that inhibition of telomerase leads to mortalization and death of previously immortal cell lines. We are interested in targeting telomerase by binding to the RNA/DNA duplex that forms during its catalytic cycle. The RNA strand of this duplex is a component of telomerase and acts as a template to direct the synthesis of the single-stranded DNA telomere. We have hypothesized that molecules that bind to this duplex will inhibit the enzyme by either preventing strand dissociation or by sufficiently distorting the substrate, thereby causing a misalignment of key catalytic residues. To test this hypothesis we have examined the activity of telomerase in the presence of a range of intercalating molecules, known for their broad duplex binding properties. Of the nine compounds we examined, four show promising lead activity in the low micromolar range. A kinetic analysis of the telomeric products suggests that these compounds do not act by stabilizing G-quartets, thereby supporting the telomeric RNA/DNA heteroduplex as the site of action. We anticipate using these lead compounds as the basis for combinatorial variation to increase the affinity and specificity for the target telomerase.