Influence of the Oxidatively Damaged Adduct 8-Oxodeoxyguanosine on the Conformation, Energetics, and Thermodynamic Stability of a DNA Duplex

Abstract

As part of an overall program to characterize the impact of mutagenic lesions on the physiochemical properties of DNA, we report here the results of a comparative spectroscopic and calorimetric study on a family of DNA duplexes both with and without the oxidative lesion 2'-deoxy-7-hydro-8-oxoguanosine (8-oxodG). Specifically, we have studied a family of eight 13-mer duplexes of the form [5'-GCGTAC[G* or G]CATGCG-3'].[3'-CGCATG[C, A, T, or G]GTACGC-5'] in which G* is the 8-oxodG lesion. These eight duplexes, which we designate by the identity of the variable central base pair (e.g., G*C), reflect two subsets: four duplexes in which the modified guanine base is positioned opposite each of the four possible canonical residues (G*C, G*A, G*G, G*T) and the corresponding four "control" duplexes in which the guanine is not modified (GC, GA, GG, GT). The data derived from our spectroscopic and calorimetric measurements on these eight duplexes allow us to evaluate the influence of the 8-oxodG lesion, as well as the base opposite the lesion, on the conformation, the thermal and thermodynamic stability, and the melting thermodynamics of the host DNA duplex. We find that modification of dG to 8-oxodG (G*) does not change the global DNA duplex conformation as judged by circular dichroism spectra. Despite this structural similarity, our data reveal that the dG to dG* modification does influence duplex thermal and thermodynamic properties, some of which depend on the base opposite the lesion. Thus, apparent structural identity does not mean that two duplexes necessarily will exhibit equivalent thermal and/or thermodynamic properties. In general, we find that the thermodynamic effects induced by the lesion (e.g., GC vs G*C) or by mismatched base pairs (e.g., GC vs GG) can result in relatively large changes in enthalpy which are partially or wholly compensated entropically to produce relatively modest changes in free energy. Our data also suggest that the biologically observed differential recognition of 8-oxodG duplexes and the preferential nucleotide insertion opposite 8-oxodG residues cannot be rationalized simply in terms of large thermodynamic differences.

Synthesis and Thermodynamic Studies of Oligodeoxyribonucleotides Containing Tandem Lesions of Thymidine Glycol and 8-Oxo-2‘-deoxyguanosine

“…These results are consistent with previous thermodynamic results as well as NMR and X-ray crystal structure studies (50)(51)(52), which showed that 8-oxodG can form base pairs with both dC and dA, depending on whether the damaged nucleoside adopts an anti or syn configuration about the glycosidic bond (50,51).…”

Analytics of oxidative stress markers in the early diagnosis of oxygen DNA damage

“…It is believed that the presence of 8-hydroxy-2'-deoxyguanosine in urine reflects DNA repair processes taking place in the body. 31,32,35 Correlations between the amount of 8-OHdG in urine with the amount in tissues in different pathogenic processes are still being investigated. Undoubtedly, the greatest interest is in the correlation between the amount of 8-hydroxy-2'-deoxyguanosine and cancer, which can be explained by the mutagenic properties of 8-OHdG -namely, its ability to disrupt pairing rules in DNA transversion.…”

Dynamic two-stage mechanism of versatile DNA damage recognition by xeroderma pigmentosum group C protein

“…The general affinity for destabilized DNA sites may facilitate other excision repair processes, as XPC has been shown to interact with 3-methyladenine DNA glycosylase [49], thymine DNA glycosylase [50] and 8-oxoguanine DNA glycosylase [6]. It is relevant to note that even a subtle 8-oxoguanine lesion perturbs the thermodynamic stability of the duplex [51]. Accordingly, the XPC complex may provide a molecular platform not only for the loading of GGR players onto damaged DNA, but also for the recruitment of a battery of enzymes involved in base excision or other repair pathways.…”