Chemical stability of oligonucleotides containing the acetylated and deacetylated adducts of the carcinogen N-2-acetylaminofluorene

Synthesis and characterization of oligodeoxynucleotides containing the major DNA adducts formed by 1,6- and 1,8-dinitropyrene

[reaction: see text] An efficient method for the synthesis of oligonucleotides containing a site-specific DNA adduct formed by the carcinogens 1,6- and 1, 8-dinitropyrene has been developed. Palladium-catalyzed amination provided a straightforward route for the synthesis of aminonitropyrenes which, following separation, were reduced to the nitrosonitropyrenes. The N-hydroxyaminonitropyrene, generated in situ from each nitrosonitropyrene, was used successfully to introduce the dinitropyrene-derived DNA adduct at a defined site in an oligonucleotide.

Genetic toxicity of 2-acetylaminofluorene, 2-aminofluorene and some of their metabolites and model metabolites

2-Acetylaminofluorene and 2-aminofluorene are among the most intensively studied of all chemical mutagens and carcinogens. Fundamental research findings concerning the metabolism of 2-acetylaminofluorene to electrophilic derivatives, the interaction of these derivatives with DNA, and the carcinogenic and mutagenic responses that are associated with the resulting DNA damage have formed the foundation upon which much of genetic toxicity testing is based. The parent compounds and their proximate and ultimate mutagenic and carcinogenic derivatives have been evaluated in a variety of prokaryotic and eukaryotic assays for mutagenesis and DNA damage. The reactive derivatives are active in virtually all systems, while 2-acetylaminofluorene and 2-aminofluorene are active in most systems that provide adequate metabolic activation. Knowledge of the structures of the DNA adducts formed by 2-acetylaminofluorene and 2-aminofluorene, the effects of the adducts on DNA conformation and synthesis, adduct distribution in tissues, cells and DNA, and adduct repair have been used to develop hypotheses to understand the genotoxic and carcinogenic effects of these compounds. Molecular analysis of mutations produced in cell-free, bacterial, in vitro mammalian, and intact animal systems have recently been used to extend these hypotheses.

Solid-phase synthesis of oligonucleotides containing site-specific N-(2'-deoxyguanosin-8-yl)-2-(acetylamino)fluorene adducts using 9-fluorenylmethoxycarbonyl as the base-protecting group

Eight oligodeoxyribonucleotides containing a site-specific N-(2'-deoxyguanosin-8-yl)-2-(acetyl-amino)fluorene (dG-C8-AAF) adduct were prepared successfully by solid-phase DNA synthesis using the 2-cyanoethyl N,N-diisopropylphosphoramidites of dA, dC, dG, dT, and dG-C8-AAF, with 9-fluorenyl-methoxycarbonyl (Fmoc) as the base-protecting group. The oligonucleotides were deprotected and released from the support by 1:9 piperidine/MeOH at room temperature for 22-36 h or by 1:1 diisopropylamine in MeOH at 55 degrees C for 15 h, purified by HPLC, and fully characterized. About 6 mg of HPLC-purified d[GTGGCG(C8-AAF)CCAAGT] and 7 mg of d[GTGATG(C8-AAF)ATAAGT] were obtained from the 10-mumol-scale synthesis, and their 1D 1H NMR spectra were consistent with the presence of a dG-C8-AAF adduct. The dG-C8-AAF oligonucleotides were also deacetylated to afford the corresponding dG-C8-AF oligonucleotides. d[GTGGCG(C8-AAF)CCAAGT] formed stable 1:1 duplexes with both the fully complementary 12-mer and a GC-deleted (across the adduct) 10-mer complement, and identical melting temperatures were observed for both duplexes. The multidimensional NMR study of these duplexes is presently under investigation.

The DNA bending by acetylaminofluorene residues and by apurinic sites

We have studied the distortions induced in double-stranded oligonucleotides by covalently bound acetylaminofluorene residues and by apurinic sites. Within the acetylaminofluorene-modified oligonucleotide three base-pairs are unpaired as detected by the chemical probes chloroacetaldehyde and osmium tetroxide. These two probes reveal that the bases adjacent to the apurinic site are paired. In both the modified double-stranded oligonucleotides, the backbone on the 5' side of the modification is more reactive with 1,10-phenanthroline copper than the backbone on the 3' side. On polyacrylamide gels, the ligated multimers of acetylaminofluorene or apurinic site-modified oligonucleotides migrate slower than the multimers of the unmodified oligonucleotides. It is suggested that the acetylaminofluorene-modified guanine residues and the apurinic sites behave more as hinge joints than as the centres of directed bends.