Selective targeting of G-quadruplex using furan-based cyclic homooligopeptides: effect on c-MYC expression.
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.
Agarwal
Tani
T
Proteomics and Structural Biology Unit, Institute of Genomics and Integrative Biology, CSIR, Mall Road, New Delhi 110 007, India.
Roy
Saumya
S
Chakraborty
Tushar Kanti
TK
Maiti
Souvik
S
D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D005663:Furans; D054856:G-Quadruplexes; D006801:Humans; D008024:Ligands; D020349:Surface Plasmon Resonance
D005663:Furans; D008024:Ligands; D004247:DNA; C039281:furan