1,N2-Etheno-2鈥?deoxyguanosine Adopts the syn Conformation about the Glycosyl Bond When Mismatched with Deoxyadenosine

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• 作者：Ganesh Shanmugam ; Ivan D. Kozekov ; F. Peter Guengerich ; Carmelo J. Rizzo ; Michael P. Stone
• 刊名：Chemical Research in Toxicology
• 出版年：2011
• 出版时间：July 18, 2011
• 年：2011
• 卷：24
• 期：7
• 页码：1071-1079
• 全文大小：961K
• 年卷期：v.24,no.7(July 18, 2011)
• ISSN：1520-5010

文摘

The oligodeoxynucleotide 5鈥?CGCATXGAATCC-3鈥猜?鈥?GGATTCAATGCG-3鈥?containing 1,N²-etheno-2鈥?deoxyguanosine (1,N²-蔚dG) opposite deoxyadenosine (named the 1,N²-蔚dG路dA duplex) models the mismatched adenine product associated with error-prone bypass of 1,N²-蔚dG by the Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4) and by Escherichia coli polymerases pol I exo^鈥?/i> and pol II exo^鈥?/i>. At pH 5.2, the T_m of this duplex was increased by 3 掳C as compared to the duplex in which the 1,N²-蔚dG lesion is opposite dC, and it was increased by 2 掳C compared to the duplex in which guanine is opposite dA (the dG路dA duplex). A strong NOE between the 1,N²-蔚dG imidazole proton and the anomeric proton of the attached deoxyribose, accompanied by strong NOEs to the minor groove A²⁰ H2 proton and the mismatched A¹⁹ H2 proton from the complementary strand, establish that 1,N²-蔚dG rotated about the glycosyl bond from the anti to the syn conformation. The etheno moiety was placed into the major groove. This resulted in NOEs between the etheno protons and T⁵ CH₃. A strong NOE between A²⁰ H2 and A¹⁹ H2 protons established that A¹⁹, opposite to 1,N²-蔚dG, adopted the anti conformation and was directed toward the helix. The downfield shifts of the A¹⁹ amino protons suggested protonation of dA. Thus, the protonated 1,N²-蔚dG路dA base pair was stabilized by hydrogen bonds between 1,N²-蔚dG N1 and A¹⁹ N1H⁺ and between 1,N²-蔚dG O⁹ and A¹⁹N⁶H. The broad imino proton resonances for the 5鈥? and 3鈥?flanking bases suggested that both neighboring base pairs were perturbed. The increased stability of the 1,N²-蔚dG路dA base pair, compared to that of the 1,N²-蔚dG路dC base pair, correlated with the mismatch adenine product observed during the bypass of 1,N²-蔚dG by the Dpo4 polymerase, suggesting that stabilization of this mismatch may be significant with regard to the biological processing of 1,N²-蔚dG.