A number of DNA minor groove-binding ligands (MGBLs) are known to exhibit antitumor and antimicrobial activities. We show that DNA topoisomerase (Topo) I may be a pharmacological target of MGBLs. In the presence of calf thymus Topo I, MGBLs induced limited but highly specific single-strand DNA breaks. The 3' ends of the broken DNA strands are covalently linked to Topo I polypeptides. Proteinlinked DNA breaks are readily reversed by a brief heating to 65°C or the addition of 0.5 M NaCl. These results suggest that MGBLs, like camptothecin, abort Topo I reactions by trapping reversible deavable complexes. The sites of cleavage induced by MGBLs are distinctly different from those induced by camptothecin. Two of the major cleavage sites have been sequenced and shown to be highly A+T-rich, suggesting the possible involvement of a Topo I-drug-DNA ternary complex at the sites of deavage. Different MGBLs also exhibit varying effciency in inducing Topo I-cleavable complexes, and the order of efficiency is as follows: Hoechst 33342 and 33258 >> distamycin A > berenil > netropsin. The lack of correlation between DNA binding and cleavage efficiency suggests that, in addition to binding to the minor grooves ofDNA, MGBLs must also interact with Topo I in trapping Topo I-cleavable complexes.Many DNA-binding (5, 6). Their modes of interaction with DNA have been studied extensively (reviewed in refs. 7 and 8). Some of the most commonly studied minor groove-binding compounds, such as distamycin A, netropsin, and the bisbenzimidazole dyes (Hoechst dyes) [e.g., 2'-(4-ethoxyphenyl)-5-(4-methyl-1-piperazinyl)-2,5'-bi-lH-benzimidazole trihydrochloride trihydrate (Hoechst 33342) and 2'-(4-hydroxyphenyl)-5-(4-methyl-1-piperizinyl)-2,5'-bi-lH-benzimidazole trihydrochloride pentahydrate (Hoechst 33258)] are known to bind to the minor groove of DNA with A+T specificity and to cause widening of the minor grooves (7, 8). Despite extensive investigation into the DNA-binding mode of these compounds, the cellular targets of these compounds other than DNA have not been identified.Most DNA minor groove-binding ligands (MGBLs) are positively charged (see Fig. 1 MATERUILS AND METHODS Materials. Hoechst 33342 and 33258, DAPI (4',6-diamidino-2-phenylindole), berenil, and distamycin A were purchased from Sigma; netropsin was from Boehringer Mannheim. All compounds were dissolved in 10 mM dimethyl sulfoxide and kept frozen in aliquots at -20°C. DNA Topos I and II were purified from calf thymus glands by using published procedures (14, 15). YEpG is a derivative of YEP24, which has the regulated yeast GALI promoter inserted between the BamHI and Sal I sites ofthe tetracyclineresistance gene (16). The Sequenase kit was purchased from United States Biochemical.DNA Topos I and H Cleavage Assays. DNA Topos I and II cleavage assays were done as described (17, 18). The procedure for end-labeling ofplasmid DNA has been described (19). Mapping and Sequencing the Cleavage Sites. The mapping of cleavage sites induced by Hoechst 33342 and 33258 was done ...

No abstract

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

No abstract

Anthracenedione derivatives are widely used structures to target DNA in chemotherapy. One of the major problem related to their use is their lack of sequence selectivity along the genome. With the aim of favoring recognition of selected DNA sequences, we synthesized four novel aminoacyl derivatives. Two side chains carrying aminoacid residues different for charge and chirality have been introduced at positions 1 and 4 of 5,8-dihydroxyanthracene-9,10-dione. An aminoethylamino spacer was inserted between the planar ring system and the selected aminoacid residues. Investigations in DNA binding properties of these new derivatives showed a large modulation of the drugs affinities for the nucleic acid depending upon the charge of the aminoacid used but irrespective of its chirality. However, as shown by topoisomerase II poisoning, prominent DNA-binding properties did not grant superior topoisomerase inhibition due mainly to template effect. In turn, aminoacid chirality plays a critical role in the in vitro cytotoxicity, L enantiomers being much more effective than D enantiomers. These findings suggest that conjugation of the anthracenedione moiety to aminoacids/peptides can be a valuable tool to selectively target cancer cells.