Structural Studies of N6-(Deoxy-D-Erythro-Pentofuranosyl)-2,6-Diamino-3,4-Dihydro-4-Oxo-5-N-Methylformamido-Pyrimidine and 8-(Deoxyguanosin-N2-yl)-1-Aminopyrene

Abstract

N6-(Deoxy-D-Erythro-Pentofuranosyl)-2,6-Diamino-3,4-Dihydro-4-Oxo-5-N-Methylformamido-Pyrimidine (MeFapy-dG) is a deoxyribonucleic acid lesion that has been hypothesized to be induced by methylating chemotherapeutic agents. MeFapy-dG is known to block DNA replication, ultimately leading to a diverse mutagenic profile dependent on the sequence context. 8-(Deoxyguanosin-N2-yl)-1-Aminopyrene (N2-AP-dG) is a bulky DNA adduct that is a product of 1-nitropyrene (1-NP) nitroreduction. 1-NP is a prevalent chemical carcinogen found in diesel exhaust, coal fly ash, and other environmental pollutants. Previous research demonstrated that N2-AP-dG stalls replication with Dpo4 with the potential to induce various mutations. Both MeFapy-dG and N2-AP-dG were studied in the structural context using Nuclear Magnetic Resonance Spectroscopy (NMR). In the case of MeFapy-dG, important cross-peaks were located in the NMR spectra providing structural evidence of the ?- and ?-anomers, indicating that both populations were present in solution. Furthermore, the N2-AP-dG unmodified duplex was characterized, demonstrating that the unmodified sequence context adopted normal B-type DNA. The modified N2-AP-dG NMR spectra provided evidence that the adduct was oriented in the minor groove of the DNA duplex, pointing in the 3’ direction of the modified strand, with minimal perturbation of the global DNA structure.