[Changes in the spatial organization of DNA molecules induced by anthracycline antibiotics]

The optical properties of the mesophases modeling the condensed state of cell DNA molecules formed from the complexes of 7-anthracycline antibiotics with double-stranded low-molecular DNA and polynucleotides were studied. The parameters of the antibiotic binding to the DNA during formation of the mesophases (0.3 M NaCl, 150 mg/ml of polyethylene glycol) are presented. It was found that the CD mesophase spectrum formed from the complex of DNA-antibiotic was characterized by the presence of intensive negative bands in the region of absorption of the chromophores of both DNA and antibiotic. This is indicative of regular spiral organization of the DNA mesophase. Binding of the antibiotic to DNA and polynucleotides was accompanied by changing of the band negative mark (at definite levels of the DNA molecule filling with the antibiotic) in the CD mesophase spectrum to the positive one. It was shown that with respect to the mesophases formed from the complexes of DNA with iremycin and aclacinomycin A no changing in the band marks was observed. Consequently, antibiotics may be conditionally divided into 2 groups. The antibiotics of the first group induce changes in the spin direction of the DNA mesophase, while the antibiotics of the second group had no such effect. It was demonstrated that antibiotic binding with the AT-rich sequences induce more pronounced changes in the mesophase properties than that with the GC-rich sequences. Possible causes of the mark changing in the spin of the DNA mesophase during the DNA binding with antharcyclines are discussed. Biological significance of the phenomenon is still unclear.