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Published on: September 19, 2017
Disruptions of G-quadruplex structures with a dianionic CuIICuII4 12-metallacrown-4
Agata Głuszyńska1, Curtis M Zaleski2, Elizabeth Manickas2
1Department of Analytical Chemistry, Adam Mickiewicz University, Uniwersytetu Poznańskiego St. 8, 61-614, Poznań, Poland.
None:
In this work, we describe the properties of a dianionic CuIICuII4 12-metallacrown-4 (MC) that can disrupt the structures of five different G-quadruplexes DNA (G4 DNA), derived from sequence motifs of human telomeres (22HT/Na and 22HT/K) as well as various human proto-oncogenes (c-MYC, c-KIT1 and Bcl-2). The interactions of the MC with G-quadruplexes were investigated by UV-Vis spectrophotometry, fluorescence, and CD spectroscopy. In CD titration experiments, distortions of CD signals exceeding 60 % were observed, with the highest distortions above 90 % observed for the G4 parallel structures of c-MYC and c-KIT1. The fluorescent G4-FID assay allowed the determination of the binding affinity of the CuIICuII4 12-MC-4 (KMC) to the different G4 structures. The G4 DNA structures with telomeric sequences 22HT/Na and 22HT/K displayed the greatest binding affinities, 3.1 and 6.2 × 105 M-1, respectively, with almost 100 % displacement of the fluorescent indicator in both cases. The KMC binding constants were arranged in the following order: G4 22HT/K (hybrid) > G4 22HT/Na (antiparallel) > G4 Bcl-2 (hybrid) > G4 c-KIT1 (parallel) > G4 c-MYC (parallel). In addition, a DNA melting analysis indicated that the interaction between the G4 DNA structures and the CuIICuII4 12-MC-4 are enthalpically favorable. The greatest destabilizing effect was observed for the MC/G4 c-MYC interaction as the Gibbs free energy (ΔG) changed from -7.4 to -2.2 kcal mol-1 at 0 equiv. and 3 equiv. of MC, respectively. This result compliments the CD titration results which indicated that the G4 c-MYC structure was disrupted to the greatest extent.
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