Strong structural effect of the position of a single acetylaminofluorene adduct within a mutation hot spot.

摘要: The NarI restriction enzyme recognition site, G1G2CG3CC, has been identified as a hotspot for -2 frameshift mutations induced by N-2-acetylaminofluorene (AAF) on the basis of forward mutation assay in plasmid pBR322 bacterium Escherichia coli. AAF binds primarily to C-8 position guanine residues, and three guanines site are similarly reactive. Despite this similar chemical reactivity, only binding G3 residue causes mutations. To study mechanisms underlying specificity mutagenic processing further, we monitored structural changes single adduct within means CD spectroscopy thermal denaturation. sequence was studied part 12-mer ACCGGCGCCACA. purification characterization isomers having covalently bound one 12 mer described. analysis melting profiles duplexes formed when these annealed with oligonucleotide complementary shows same destabilizing effect DNA helices. It is also shown, from spectra, that modification G1 or G2 does not induce major helical structure DNA. On other hand, induces change signal suggests formation local left handed duplex. These results show polymorphic nature vicinity an adduct.