Interaction of adriamycin with a regulatory element of hmgb1: spectroscopic and calorimetric approach

Abstract

HMGB1 is a non-histone nuclear protein which plays important role in transcription, variable, diverse and joining (VDJ) recombination, chromatin remodeling, and DNA repair, etc. and its over expression is directly correlated with various human malignancies and inflammatory diseases. Because of the clear association between HMGB1 and cancer, we studied the binding of adriamycin (ADM), a well-known anticancer drug with the promoter region (−165 to −183) of hmgb1 by using a variety of spectroscopic, calorimetric techniques, and in-silico molecular modeling. Changes in UV and CD spectral characteristics (intensity and wavelength) of ADM and DNA associated with an induced peak (300 nm) in CD spectrum of DNA and a high binding constant of 2.0 × 105 M−1 suggest a strong and stable complex formation between DNA and ADM. Scatchard analysis of spectroscopic data indicate that ADM binds to DNA in a non-cooperative nature. Further the quenching of fluorescence emission of ADM and isothermal titration calorimetry of ADM in presence of DNA points out to the intercalative mode of ADM binding to DNA which is enthalpically driven with additional small entropic contribution. Results from molecular modeling, Isothermal titration calorimetry, and Fourier transform infrared spectroscopy reveal that ADM has no marked preference between AT vs. GC base pair in binding to DNA. Therefore, hmgb1 can be considered as a novel potential chemotherapeutic target in treating cancers associated with HMGB1 upregulation.