NMR based structure reveals groove binding of mitoxantrone to two sites of [d-(TTAGGGT)]4 having human telomeric DNA sequence leading to thermal stabilization of G-quadruplex

• Published in: International journal of biological macromolecules Vol. 111; pp. 326 - 341
• Main Authors: Tripathi, Sweta, Barthwal, Ritu
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.2018
• Subjects: Anti-cancer drug mitoxantrone; External binding; Nuclear Magnetic Resonance; Restrained Molecular Dynamics; Telomeric G-quadruplex DNA; Thermal stabilization; External binding; Anti-cancer drug mitoxantrone; Nuclear Magnetic Resonance; Thermal stabilization; Restrained Molecular Dynamics; Telomeric G-quadruplex DNA
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2017.12.134

Interaction of mitoxantrone (MTX) with G-quadruplex, leading to inhibition of telomerase enzyme and anticancer action, is not understood. Titrations of MTX with [d-(TTAGGGT)]4, comprising human telomere single repeat sequence, have been monitored by fluorescence and 1H/31P NMR spectroscopy. Binding induces chemical shift changes in GNH (~0.3ppm), T2/T7/A3 base protons and sequence specific shifts in 31P resonances. Absence of large downfield shifts in 31P signals and presence of all sequential NOEs show that classical intercalation of drug between base quartets does not occur. The upfield shift (~0.53ppm) in 2/3H, 1/4OH and minor shift in 6/7H aromatic protons of MTX in complex rule out end stacking as a possible mode of interaction. The 26 short inter molecular contacts of 1/4OH, 11NH, 6/7H and 12CH2 protons of MTX with T1, T2, G6, G7 protons in the structure of complex obtained by restrained Molecular Dynamics simulations show binding at grooves accompanied by 4 hydrogen bonds and partial stacking of MTX with base pairs. Interaction causes thermal stabilization, ΔTm=35°C, which may be attributed to telomerase inhibition. The present study is the first report on solution structure of mitoxantrone-[d-(TTAGGGT)]4 complex and is significant for structure based designing of anthraquinone derivatives as future drugs. [Display omitted] •Phosphorus-31 NMR spectra show sequence specificity on binding of mitoxantrone.•26 short intermolecular contacts between MTX and [d-(TTAGGGT)]4 observed•Mitoxantrone binds at grooves forming 4 hydrogen bonds with no opening of base pairs.•First NMR based solution structure of 2:1 mitoxantrone-[d-(TTAGGGT)]4 complex•Mitoxantrone binding leads to thermal stabilization of guanine quartets by 35°C.