Studies of sequence-specific DNA binding, DNA cleavage, and topoisomerase I inhibition by the dimeric chromomycin A3 complexed with Fe(II).
Chromomycin A3 (Chro) has been evidenced to exhibit much higher binding affinity toward Fe(II) by forming a highly stable 2:1 drug/metal complex, compared to its structural analogue, mithramycin (Mith). Different properties of the [(Chro)2-Fe(II)] complex acting on DNA, such as sequence specificity, DNA cleavage, and topoisomerase I (TopI) inhibition were studied. Kinetic analyses of surface plasmon resonance showed that the affinity of the [(Chro)2-Fe(II)] complex upon binding to hairpin DNA duplexes containing various tetranucleotide sequences follows the order: GGCC > CGCG > CCGG approximately GCGC > AGCT > ACGT > TGCA > TCGA. According to circular dichroism (CD) studies, most hairpin DNA duplexes appeared to retain their B-type conformations in the presence of the [(Chro)2-Fe(II)] complex, except the duplex containing the GGCC sequence, which exhibited the features of both A- and B-type DNA. In DNA-cleavage assays, the [(Chro) 2-Fe(II)] complex was shown to cause single-stranded cleavage of plasmid DNA because of a Fenton-type reaction. DNA cleavage activity of the [(Chro) 2-Fe(II)] complex was increased at low pH. Moreover, the complex was capable of inhibiting TopI activity. The [(Chro)2-Fe(II)] complex exhibited higher cytotoxicity than the [(Mith) 2-Fe(II)] complex in several cancer cell lines, most likely owing to its more stable dimeric structure and higher DNA-binding affinity. Our results provide significant evidence that the [(Chro)2-Fe(II)] complex could be promising in terms of its biological applications in the future.
Hou
Ming-Hon
MH
Biotechnology Center, National Chung Hsing UniVersity, Taichung, 402 Taiwan. mhho@dragon.nchu.edu.tw
Lu
Wen-Je
WJ
Lin
Hsin-Ying
HY
Yuann
Jeu-Ming P
JM
D001483:Base Sequence; D045744:Cell Line, Tumor; D014128:Chromomycin A3 / Q000737:chemistry* / Q000494:pharmacology*; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D019281:Dimerization; D006801:Humans; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D010957:Plasmids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D020349:Surface Plasmon Resonance; D059004:Topoisomerase I Inhibitors
D059004:Topoisomerase I Inhibitors; D004247:DNA; D014128:Chromomycin A3; D007501:Iron; D004264:DNA Topoisomerases, Type I