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Updated: Dec 5, 2025
Utilizing Murine Inducible Telomerase Alleles in the Studies of Tissue Degeneration/Regeneration and Cancer
Published on: April 13, 2015
Mechanisms of telomerase inhibition by oxidized and therapeutic dNTPs
Samantha L Sanford1, Griffin A Welfer2, Bret D Freudenthal2
1Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health and UPMC Hillman Cancer Center, Pittsburgh, PA, USA.
Abstract:
Telomerase is a specialized reverse transcriptase that adds GGTTAG repeats to chromosome ends and is upregulated in most human cancers to enable limitless proliferation. Here, we uncover two distinct mechanisms by which naturally occurring oxidized dNTPs and therapeutic dNTPs inhibit telomerase-mediated telomere elongation. We conduct a series of direct telomerase extension assays in the presence of modified dNTPs on various telomeric substrates. We provide direct evidence that telomerase can add the nucleotide reverse transcriptase inhibitors ddITP and AZT-TP to the telomeric end, causing chain termination. In contrast, telomerase continues elongation after inserting oxidized 2-OH-dATP or therapeutic 6-thio-dGTP, but insertion disrupts translocation and inhibits further repeat addition. Kinetics reveal that telomerase poorly selects against 6-thio-dGTP, inserting with similar catalytic efficiency as dGTP. Furthermore, telomerase processivity factor POT1-TPP1 fails to restore processive elongation in the presence of inhibitory dNTPs. These findings reveal mechanisms for targeting telomerase with modified dNTPs in cancer therapy.
Insights
Modified nucleotides inhibit telomerase by causing chain termination or disrupting translocation. These findings reveal new strategies for targeting telomere elongation in cancer therapy.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Telomerase is a key enzyme in cancer, enabling unlimited cell proliferation by maintaining telomere length.
- Understanding telomerase inhibition is crucial for developing effective cancer therapies.
Purpose of the Study:
- To investigate how oxidized and therapeutic modified deoxynucleotides (dNTPs) inhibit telomerase activity.
- To elucidate the distinct mechanisms of inhibition by various modified dNTPs.
Main Methods:
- Direct telomerase extension assays using modified dNTPs and telomeric substrates.
- Kinetic analysis of telomerase activity and processivity.
Main Results:
- Telomerase can incorporate chain-terminating inhibitors like ddITP and AZT-TP.
- Oxidized 2-OH-dATP and 6-thio-dGTP are incorporated but disrupt telomere elongation translocation.
- Telomerase poorly discriminates against 6-thio-dGTP, inserting it similarly to dGTP.
- The POT1-TPP1 complex does not restore processivity with inhibitory dNTPs.
Conclusions:
- Modified dNTPs inhibit telomerase through distinct mechanisms, including chain termination and translocation disruption.
- These findings offer insights into targeting telomerase for cancer treatment using modified dNTPs.
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