Identification of G-Quadruplex Inducers Usinga Simple, Inexpensiveand Rapid High Throughput Assay, and TheirInhibition of Human Telomerase

Maria Florencia Sassano, Alexander P Schlesinger , Michael B Jarstfer*
Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599

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© Sassano et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the UNC Chapel Hill, Eshelman School of Pharmacy, CB 7568,Chapel Hill, NC27599-7568, Tel; +1 919 966-6422; Fax +1 919 966-0204; E-mail:


Telomeres are protein and DNA complexes located atchromosome ends. Telomeric DNA is composed of a double stranded region of repetitive DNA followed by single-stranded 3' extension of aG-rich sequence. Single-stranded G-rich sequencescan fold into G-quadruplex structures,and molecules that stabilize G-quadruplexes are known to inhibit the enzyme telomerase and disrupt telomere maintenance. Because telomere maintenance is required for proliferation of cancer cells, G-quadruplex stabilizers have become attractive prospects for anticancer drug discovery.However, telomere-targeting G-quadruplex ligands have yet to enter the clinic owing in part to poor pharmacokinetics and target selectivity. Increasing the pharmacophore diversity of G-quadruplex and specifically telomeric-DNA targeting agents should assist in overcoming these shortcomings. In this work, we report the identification and validation ofligands that bind telomeric DNA and induce G-quadruplex formationusing the NCI Diversity Set I, providing validation of anextremely simple, rapid and high-throughput screen using FRET technology. Hits from the screen were validated by examining telomerase inhibition and G-quadruplex inductionusing CD spectroscopy and DNA polymerase stop assays. We show that two known DNA binding molecules, ellipticine derivativeNSC 176327 (apyridocarbazole) and NSC 305831 (an antiparasitic hetero-cyclediamidine referred to as furamidine and DB75),are selective induceG-quadruplex formation in the human telomeric sequence and bind telomeric DNA quadruplexes in the absence of stabilizing monovalent cations with molar ratios(molecule: DNA)of 4:1and 1.5:1, respectively.

Keywords: Ellipticine, furamidine, G-quadruplex, telomerase, telomere .