Thermodynamic consequences of the hyperoxidized guanine lesion guanidinohydantoin in duplex DNA.
Guanidinohydantoin (Gh) is a hyperoxidized DNA lesion produced by oxidation of 8-oxo-7,8-dihydroguanine (8-oxoG). Previous work has shown that Gh is potently mutagenic in both in vitro and in vivo coding for G → T and G → C transversion mutations. In this work, analysis by circular dichroism shows that the Gh lesion does not significantly alter the global structure of a 15-mer duplex and that the DNA remains in the B-form. However, we find that Gh causes a large decrease in the thermal stability, decreasing the duplex melting temperature by ~17 °C relative to an unmodified duplex control. Using optical melting analysis and differential scanning calorimetry, the thermodynamic parameters describing duplex melting were also determined. We find that the Gh lesion causes a dramatic decrease in the enthalpic stability of the duplex. This enthalpic destabilization is somewhat tempered by entropic stabilization; yet, Gh results in an overall decrease in thermodynamic stability of the duplex relative to a control that lacks DNA damage, with a ΔΔG° of -7 kcal/mol. These results contribute to our understanding of the consequences of hyperoxidation of G and provide insight into how the thermal and thermodynamic destabilization caused by Gh may influence replication and/or repair of the lesion.
Department of Chemistry, Brown University, Providence, RI 02912, USA.
Craig J
CJ
Yennie
Sarah
S
Delaney
D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D004247:DNA / Q000138:chemical synthesis / Q000737:chemistry*; D006146:Guanidines / Q000737:chemistry*; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry; D006827:Hydantoins / Q000737:chemistry*; D010084:Oxidation-Reduction; D013816:Thermodynamics; D044366:Transition Temperature
D006146:Guanidines; D006827:Hydantoins; C467338:guanidinohydantoin; C024829:8-hydroxyguanine; D006147:Guanine; D004247:DNA