Thermodynamic Profiles and Nuclear Magnetic Resonance Studies of Oligonucleotide Duplexes Containing Single Diastereomeric Spiroiminodihydantoin Lesions

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• 作者：Irine Khutsishvili ; Na Zhang ; Luis A. Marky ; Conor Crean ; Dinshaw J. Patel ; Nicholas E. Geacintov ; Vladimir Shafirovich
• 刊名：Biochemistry
• 出版年：2013
• 出版时间：February 26, 2013
• 年：2013
• 卷：52
• 期：8
• 页码：1354-1363
• 全文大小：473K
• 年卷期：v.52,no.8(February 26, 2013)
• ISSN：1520-4995

文摘

The spiroiminodihydantoins (Sp) are highly mutagenic oxidation products of guanine and 8-oxo-7,8-dihydroguanine in DNA. The Sp lesions have recently been detected in the liver and colon of mice infected with Helicobacter hepaticus that induces inflammation and the development of liver and colon cancers in murine model systems [Mangerich, A., et al. (2012) Proc. Natl. Acad. Sci. U.S.A. 109, E1820鈥揈1829]. The impact of Sp lesions on the thermodynamic characteristics and the effects of the diastereomeric Sp-R and Sp-S lesions on the conformational features of double-stranded 11-mer oligonucleotide duplexes have been studied by a combination of microcalorimetric methods, analysis of DNA melting curves, and two-dimensional nuclear magnetic resonance methods. The nonplanar, propeller-like shapes of the Sp residues strongly diminish the extent of local base stacking interactions that destabilize the DNA duplexes characterized by unfavorable enthalpy contributions. Relative to that of an unmodified duplex, the thermally induced unfolding of the duplexes with centrally positioned Sp-R and Sp-S lesions into single strands is accompanied by a smaller release of cationic counterions (螖n_Na⁺ = 0.6 mol of Na⁺/mol of duplex) and water molecules (螖n_w = 17 mol of H₂O/mol of duplex). The unfolding parameters are similar for the Sp-R and Sp-S lesions, although their orientations in the duplexes are different. The structural disturbances radiate one base pair beyond the flanking C:G pair, although Watson鈥揅rick hydrogen bonding is maintained at all flanking base pairs. The observed relatively strong destabilization of B-form DNA by the physically small Sp lesions is expected to have a significant impact on the processing of these lesions in biological environments.