DNA BASE SEQUENCE EFFECTS IN CHEMICAL CARCINOGENESIS

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DESCRIPTION: The major hypothesis to be tested in this application is that the conformational and functional properties of site-specifically modified DNA sequences with single, stereochemical defined benzopyrene diolepoxide (BPDE)-deoxyguanosine, BPDE-deoxyadenosine, and deoxyadenosine adducts derived from the fjord region anti-benzo(c)phenathrene-3,4-diol-1,2-epoxide, depend on the bases flanking the lesions. This hypothesis will be tested by 1) determining the effects of base sequence on the conformational characteristics of structurally and stereochemical defined adducts, 2) investigating the structural characteristics that are critical to the interactions with and excision of these lesions, positioned in different base sequence contexts, by nucleotide excision repair enzymes in vitro, and 3) investigating the effects of base sequence on the mutation prone processing of these adducts by DNA polymerases in vitro. A number of DNA adduct structures have already been established by NMR methods, thus providing a fertile basis for understanding structure biological activity relationships. These structurally characterized adducts will be selected for study, followed by studies of guanine-rich sequences that are known to be mutation hot spots in vivo, and by a systematic examination of the effects of the two bases flanking the lesions. The effects of base sequence on adduct induced bends and flexible hinge joints, direction of bending, and helix unwinding, will be examined using gel electrophoresis techniques. The principal investigator hypothesizes that base sequences leading to flexibility can affect the multiplicity of adduct conformations that can be assumed by the polycyclic residues at primer/template junctions in DNA replication enzyme complexes in vitro, thus influencing the mutagenic specificities of the adducts.