Chemistry of DNA damage

The hydroxyl radical OH represents one of the most dangerous species that alter biomolecules and are involved in biological damages and ageing. This reactivity can cause changes of the four nucleotide units adenosine, guanosine, thymine and cytosine. The EU-funded 'Formation and roles of the 5',8-cyclo-2'-deoxyguanosine lesion' (CYCLOGUO) project specifically addressed the DNA lesions known as tandem damage of the purine bases 2'-deoxyadenosine and 2'-deoxyguanosine.

Project partners focused on chemical studies of the 5',8-cyclopurine lesions (5',8-cPus), solving problems in the synthesis of the four diastereomeric structures. The availability of the four lesions is necessary in order to conduct subsequent studies on their structural, functional and biological properties. The incorporation of these modified phosphoroamidite analogues in oligonucleotide sequences can simulate the lesions occurring on the DNA strands. This biomimetic study is necessary for understanding of the potential consequences in vivo.

The CYCLOGUO project dealt with the synthesis of the 5',8-cPus and their phosphoramidites derived from 2'-deoxyguanosine, and developed a synthetic protocol for the 5',8-cyclo-dGuo lesions. The new methodology was completed with the synthesis of 5',8-cyclo-dGuo phosphoramidites. The two adenine 5',8-cPu phosphoramidites were also synthesised and each lesion incorporated into oligonucleotides strands according to the DNA solid-phase synthesis technique.

Additionally, the 5',8-cPus compounds have been developed as DNA oxidative stress biomarkers for comparison with currently used 8-oxo-7,8-dihydro-2'-deoxyguanosine. Researchers synthesised the isotopic-enriched 15N equivalents of the four 5',8-cPus for the evaluation of DNA samples based on the stable isotope dilution tandem mass spectrometry technique.

CYCLOGUO studied the chemical biology of DNA damage and repair. This topic has significant medical application, since the alteration of DNA and impairment of the repair systems lead to mutations and diseases.