Molecular structure of an anticancer drug-DNA complex: daunomycin plus d(CpGpTpApCpG)

The structure of the crystalline daunomycin-d(CpGpTpApCpG) complex has been solved by x-ray diffraction analysis. The DNA forms a six-base-pair right-handed double helix with two daunomycin molecules intercalated in the d(CpG) sequences. The daunomycin aglycone chromophore is oriented at right angles to the long dimension of the DNA base pairs and the cyclohexene ring rests in the minor groove. Substituents on this ring have hydrogen bonding interactions to the base pairs above and below the intercalation site. These appear to be specific for anthracycline antibiotics. The amino sugar lies in the minor groove of the double helix without bonding to the DNA. The DNA double helix is distorted in a novel manner in accommodating the drug.