6-thio-2-deoxyguanosine inhibits telomere elongation by inducing a non-productive stalled telomerase complex

Sanford, S. L.; Badstubner, M.; Gerber, M.; Mannherz, W.; Lampl, N.; Dannenberg, R.; Hinchie, A.; Schaich, M. K.; Myong, S.; Hedglin, M.; Agarwal, S.; Alder, J. K.; Stone, M.; Opresko, P. L.

doi:10.1101/2025.02.05.636339

bioRxiv · 10.1101/2025.02.05.636339

6-thio-2-deoxyguanosine inhibits telomere elongation by inducing a non-productive stalled telomerase complex

Sanford, S. L.·Badstubner, M.·Gerber, M.·Mannherz, W.·Lampl, N.·Dannenberg, R.·Hinchie, A.·Schaich, M. K.·Myong, S.·Hedglin, M.·Agarwal, S.·Alder, J. K.·Stone, M.·Opresko, P. L.

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Abstract

Most cancers upregulate the telomere lengthening enzyme telomerase to achieve unlimited cell division. How chemotherapeutic nucleoside 6-thio-2-deoxyguanosine (6-thio-dG) targets telomerase to inhibit telomere maintenance in cancer cells and tumors was unclear. Here, we demonstrate that telomerase insertion of 6-thio-dGTP prevents synthesis of additional telomeric repeats but does not disrupt telomerase binding to telomeres. Specifically, 6-thio-dG inhibits telomere extension after telomerase translocates along its product DNA to reposition the template, inducing a non-productive complex rather than enzyme dissociation. Furthermore, we provide direct evidence that 6-thio-dG treatment inhibits telomere synthesis by telomerase in cancer cells. In agreement, telomerase-expressing cancer cells harboring critically short telomeres are more sensitive to 6-thio-dG and show a greater induction of telomere losses compared to cancer cells with long telomere reserves. Our studies reveal that telomere length and telomerase status determine 6-thio-dG sensitivity and uncover the molecular mechanism by which 6-thio-dG selectively inhibits telomerase synthesis of telomeric DNA.

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Sanford, S. L., Badstubner, M., Gerber, M., Mannherz, W., Lampl, N., Dannenberg, R., Hinchie, A., Schaich, M. K., Myong, S., Hedglin, M., Agarwal, S., Alder, J. K., Stone, M., Opresko, P. L.. 2025-02-08. 6-thio-2-deoxyguanosine inhibits telomere elongation by inducing a non-productive stalled telomerase complex. https://doi.org/10.1101/2025.02.05.636339

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