Deciphering molecular aspects of interaction between anticancer drug mitoxantrone and tRNA

Mitoxantrone (1,4-dihydroxy-5,8-bis[[2-[(2-hydroxyethyl)amino]ethyl]amino]-9,10-anthracenedione) is a synthetically designed antineoplastic agent and structurally similar to classical anthracyclines. It is widely used as a potent chemotherapeutic component against various kinds of cancer and possesses lesser cardio-toxic effects with respect to naturally occurring anthracyclines. In the present study, we have investigated the binding features of mitoxantrone–tRNA complexation at physiological pH using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, circular dichroism (CD) spectroscopy, isothermal titration calorimetry, and UV–visible absorption spectroscopic techniques. FTIR analysis reveals that mitoxantrone interacts mainly with heterocyclic base residues of tRNA along with slight external binding with phosphate–sugar backbone. In particular, mitoxantrone binds at uracil (C=O) and adenine (C=N) sites of biomolecule (tRNA). CD spectroscopic results suggest that there is no major conformational transition in native A-form of tRNA upon mitoxantrone–tRNA adductation except an intensification in the secondary structure of tRNA is evident. The association constant calculated for mitoxantrone–tRNA association is found to be 1.27?×?10⁵ M^?1 indicating moderate to strong binding affinity of drug with tRNA. Thermodynamically, mitoxantrone–tRNA interaction is an enthalpy-driven exothermic reaction. Investigation into drug–tRNA interaction can play an essential role in the rational development of RNA targeting chemotherapeutic agents, which also delineate the structural–functional relationship between drug and its target at molecular level.