Complexes of G-Quadruplex DNA with Drug Like Molecules

Structural information on the complexes of drug like molecules with quadruplex DNAs can aid the development of therapeutics and research tools that selectively target specific quadruplex DNAs. Screening can identify candidate molecules that require additional evaluation. An enhanced hydroxyl radical cleavage protocol is demonstrated that can efficiently provide structural information on the complexes of the candidate molecules with quadruplex DNA. NMR methods have been used to offer additional structural information about the complexes as well as validate the results of the hydroxyl radical approach. This multi-step protocol has been demonstrated on complexes of the quadruplex formed by the thrombin binding aptamer (TBA) and promoter region of c-kit. The hydroxyl radical results indicate that NSC 176319, Cain's quinolinium that was found by screening, exhibits selective binding to the two TT loops. The NMR results are consistent with selective disruption of the hydrogen bonding between T4 and T13 as well as unstacking of these residues from the bottom quartet. The preliminary result indicates that the NSC 176319 also binds to the loops of the quadruplex formed by the promoter region of c-kit. NSC 176319 is used as a hit and the structurally similar molecules are being screened to find other candidate molecules. Thus, the combination of screening, hydroxyl radical footprinting and NMR can find new molecules that selectively bind to quadruplex DNAs as well as provide structural information about their complexes.