We report a crystal structure that shows an antibiotic that extracts a nucleobase from a DNA molecule 'caught in the act' after forming a covalent bond but before departing with the base. The structure of trioxacarcin A covalently bound to double-stranded d(AACCGGTT) was determined to 1.78 A resolution by MAD phasing employing brominated oligonucleotides. The DNA-drug complex has a unique struc...

Two DNA hexadecamers containing one central 5'-GC-3' base step have been examined by footprinting methodology in the presence and absence of actinomycin D. The results of these studies, coupled with imino proton NMR measurements indicate that the antitumor drug causes a change in DNA conformation at a distance from the actinomycin intercalation site in a molecule of sequence d[ATATATAGCTATATAT]...

Dihydrotanshinone I induced topoisomerase I-mediated DNA cleavage in vitro as strongly as camptothecin, but topoisomerase II-mediated DNA cleavage was not affected. In a DNA relaxation assay using calf thymus DNA topoisomerase I and supercoiled pBR322 plasmid DNA, dihydrotanshinone I reduced topoisomerase I-mediated DNA relaxation in a dose-dependent manner. Heat treatment (65°C) of the reactio...

DNA-mediated charge transport (CT) chemistry is sensitive to DNA structure and base pair stacking. In an electrochemical assay based upon DNA CT, DNA-modified electrode surfaces are used to examine the electrochemical reduction of methylene blue (MB), a small molecule that binds to the DNA film by intercalation. Here electrochemically we probe CT in the three primary conformations of double-str...

Ditercalinium is a synthetic anticancer drug that binds to DNA by bis-intercalation and activates DNA repair processes. In prokaryotes, noncovalent DNA-ditercalinium complexes are incorrectly recognized by the uvrABC repair system as covalent lesions on DNA. In eukaryotes, mitochondrial DNA is degraded by excess and futile DNA repair. Using x-ray crystallography, we have determined, to 1.7 A re...

The ETS family of transcription factors consists of a group of proteins that share a highly conserved 85 amino acid DNA-binding domain (DBD). This family recognizes a consensus sequence rich in purine bases with a central GGAA motif. A comparison of the published three-dimensional structures of the DBD/DNA complexes of ETS1 by NMR [Werner et al. (1995) Cell, 83, 761-771] and the related Pu.1 by...

The crystal structure of the ruthenium DNA 'light-switch' complex Λ-[Ru(TAP)2(11-Cl-dppz)](2+) (TAP=tetraazaphenanthrene, dppz=dipyrido[3,2-a':2',3'-c]phenazine) bound to the oligonucleotide duplex d(TCGGCGCCGA)2 is reported. The synthesis of the racemic ruthenium complex is described for the first time, and the racemate was used in this study. The crystal structure, at atomic resolution (1.0 Å...

Spectroscopic parameters for two novel ruthenium complexes on binding to nucleic acids of varying sequences and conformations have been determined. These complexes, Ru(bpy)2dppz2+ and Ru(phen)2dppz2+ (bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline; dppz = dipyrido[3,2:a-2',3':c]-phenazine) serve as "molecular light switches" for DNA, displaying no photoluminescence in aqueous solution but lu...

Human RAD52 promotes annealing of complementary single-stranded DNA (ssDNA). In-depth knowledge of RAD52-DNA interaction is required to understand how its activity is integrated in DNA repair processes. Here, we visualize individual fluorescent RAD52 complexes interacting with single DNA molecules. The interaction with ssDNA is rapid, static, and tight, where ssDNA appears to wrap around RAD52 ...

The interaction between isatin-β-thiosemicarbazone (IBT) and calf thymus DNA (CT-DNA) was investigated in physiological buffer (pH 7.4) using Neutral Red (NR) dye as a spectral probe by UV-Vis absorption and fluorescence spectroscopy, as well as viscosity measurements. The IBT is stabilized by intercalation in the DNA (K [IBT -DNA] = 1.03×10(5) M(-1)), and displaces the NR dye from the NR-DNA co...