The DNA sequence effect is an important structural factor for determining the extent and nature of lesion-induced mutational and repair outcomes. We recently completed conformational mapping of all 16-possible DNA duplexes (CTTCTNG*NCCTC: N= A, G, C, T; G*=lesion) containing dG-C8-ABP and dG-C8-AF lesions derived from the human bladder carcinogen 4-aminobiphenyl and the animal carcinogen aminofluorene, respectively. Several sequences were identified that could act as potential mutational and repair hot spots. The planar AF lesions exhibit a sequence-dependent mixture of S- and B-conformations, whereas the nonplanar ABP adducts exist primarily in the B- conformation. These results suggest an energetic penalty associated with the intercalation of ABP relative to the planar AF. Specifically, ABP exclusively favors B in the TG1G2*T sequence, whereas in the G1*G2T context it favors a 67:33% mixture of B:S. This striking DNA sequence effect represents a direct flanking sequence effect (e.g., GG*T vs. TG*G). Similar trends were observed with AF-modified duplexes in the same sequence contexts. We obtained dynamic 19F NMR spectra for two 16-mer modified templates during primer elongation via a simulated translesion synthesis: G1*G2T [d(5'-CTTCTG*GTCCTCATTC-3')] and G1G2*T [d(5'-CTTCTGG*TCCTCATTC-3')](G*=fluorine-tagged FABP or FAF). It was found that the arylamine-induced S/B-conformational heterogeneity and the associated thermodynamics were sensitive to the flanking sequence context surrounding the lesion. The lesion stacking is favored in the G1*G2T sequence compared to the G1G2*T counterpart and this stacking argument was supported by thermodynamics, binding, and primer extension data. The results will be discussed in terms of how the mutagenic ABP and AF could exhibit sequence-dependent conformational heterogeneity during translesion synthesis, leading to complex mutagenic outcomes.

Sequence effects on translesion synthesis of an aminobiphenyl-DNA adduct: Conformational, thermodynamic, and binding studies

250th National Meeting (2015)

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