Formation of a fairly stable diazoate intermediate of 5-methyl-2'-deoxycytidine by HNO2 and NO, and its implication to a novel mutation mechanism in CpG site

NO-dependent modifications of nucleic acids

This review is devoted to chemical transformations of nucleic acids and their components under the action of nitrogen oxide metabolites. The deamination reaction of bases is discussed in the context of possible competing transformations of its intermediates (nitrosamines, diazonium cations, diazotates, triazenes, and diazoanhydrides) and mechanisms of crosslink formation with proteins and nucleic acids. The oxidation and nitration of bases by NO2 is considered together with the possibility of radical transfer to domains from the base stacks in DNA. Reduction of redox potentials of bases as a result of stacking interactions explains the possibility of their reactions within nucleic acids with the oxidants whose redox potential is insufficient for the effective reactions with mononucleotides. Modifications of nucleic acids with peroxynitrite derivatives are discussed in the context of the effect of the DNA primary structure and the modification products formed on the reactivity of single bases. The possibility of reduction of nitro groups within modified bases to amino derivatives and their subsequent diazotation is considered. The substitution of oxoguanine for nitroguanine residues may result; the reductive diazotation can lead to undamaged guanine. The intermediate modified bases, e.g., 8-aminoguanine and 8-diazoguanine, were shown to participate in noncanonical base pairing, including the formation of more stable bonds with two bases, which is characteristic of the DNA Z-form. A higher sensitivity of RNA in comparison with DNA to NO-dependent modifications (NODMs) is predicted on the basis of the contribution of medium microheterogeneity and the known mechanisms of nitrosylation and nitration. The possible biological consequences of nucleic acids NODMs are briefly considered. It is shown that the NODMs under the action of nitrogen oxide metabolites generated by macrophages and similar cells in inflammations or infections should lead to a sharp increase in the number of mutations in the case of RNA-containing viruses. As a result, the defense mechanisms of the host organism may contribute to the appearance of new, including more dangerous, variants of infecting viruses.

Design of highly efficient and selective transfer reaction of nitrosyl group to dc and d(M)C resulting in specific deamination

Nitric oxide (NO) is an important endogenous regulatory molecule, and S-nitrosothiols are believed to play a significant role in NO storage, transport, and delivery. Based on the ability to generate NO in vivo, S-nitrosothiols can be used as therapeutic drugs. In this study, we have developed an innovative method for sequence- and base-specific delivery of NO to a specific site of DNA followed by specific deamination.

Sequence- and base-specific delivery of nitric oxide to cytidine and 5-methylcytidine leading to efficient deamination

Nitric oxide (NO) is an important endogenous regulatory molecule, and S-nitrosothiols are believed to play a significant role in NO storage, transport, and delivery. On the basis of their ability to generate NO in vivo, S-nitrosothiols can be used as therapeutic drugs. In this study, we have developed an innovative method for sequence- and base-specific delivery of NO to a specific site of DNA followed by specific deamination. We designed a NO transfer reaction from S-nitroso thioguanine to an imino tautomer of cytosine. Nitrosation of the thioguanosine-containing ODN 1 was carried out with S-nitroso-N-acetylpenicillamine (SNAP) to produce ODN 2. An interstrand NO transfer reaction was performed using ODN 2 and its complementary ODN 3 having dC or dmC at the target site, and a rapid NO transfer reaction was observed. In contrast, a transfer reaction was not observed either with ODN 3 having dT, dA, or dG at the target site or with ODN 5-7 having dC at a nontarget site. In the analysis of deaminated products of the NO-transferred ODN 4, it was found that the transformation ratio from dmC to dT was as high as 42% together with the dmC-diazoate (13%). In conclusion, we have demonstrated the innovative method of sequence- and base-specific delivery of nitric oxide to cytidine and 5-methylcytidine. The selectivity and efficiency of NO transfer followed by deamination exhibited in this study are extremely high compared to those of the conventional methods.