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  • Title: Selective targeting of G-quadruplex using furan-based cyclic homooligopeptides: effect on c-MYC expression.
    Author: Agarwal T, Roy S, Chakraborty TK, Maiti S.
    Journal: Biochemistry; 2010 Sep 28; 49(38):8388-97. PubMed ID: 20712380.
    Abstract:
    Quadruplex-specific molecules can serve as suitable drugs in cancer therapy. We have synthesized a pair of furan-based cyclic homooligopeptides, ligand 1 and ligand 2, to specifically target G-quadruplexes. We have shown by CD spectroscopy and UV melting that these ligands can effectively induce G-quadruplex structures in the G-rich 22-mer c-MYC DNA sequence and further stabilize the structure. Equilibrium binding constants measured by isothermal titration calorimeter methods indicate a high affinity of the ligands for the quadruplex structures (K ∼ 10(7) M(-1)) and no affinity for the duplex DNA, demonstrating that these ligands are selective for G-quadruplex structures. Surface plasmon resonance was also used to compute the binding while fluorescence resonance energy transfer-based assay was additionally used to confirm the selectivity. Moreover, using real time PCR we observed up to 90% downregulation of c-MYC transcripts after 24 h of ligand treatment in HeLa cells. Using a luciferase assay we show the downregulation of the protein levels. Fluorescent-assisted cell sorter-based cell cycle analysis showed a prominent arrest of cells in the sub-G1 stage upon treatment of ligands that leads toward apoptosis. Altogether, these experiments support the hypothesis that the present molecules are effective in specifically binding and stabilizing quadruplexes and provide a suitable scaffold to develop into a quadruplex-targeting therapeutic agent.
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