Photoinduced deoxyribose C2′ oxidation in DNA. Alkali-dependent cleavage of erythrose-containing sites via a retroaldol reaction

Article abstract of DOI:10.1021/ja00064a004

Photoreactions of various 5-iodouracil- (¹U)-containing oligonucleotides have been investigated. It was found that d(GCA¹UGC)₂ undergoes a competitive Cl′ and C2′ oxidation at the 5′ side of the ¹U residue to give deoxyribonolactone-containing hexamer 1 and erythrose-containing hexamer 2, respectively. Upon heating under alkaline conditions, erythrose-containing hexamer 2 was shown to undergo a remarkably facile retroaldol reaction to give two fragments, both having phosphoroglycoaldehyde termini in high yields. On the basis of the chemical reactivity of 2, a new specific method for detection of the erythrose-containing sites resulting from deoxyribose C2′ oxidation in DNA was devised. Erythrose-containing sites were prepared by photoirradiation of duplex ¹U-containing 13 mer 5′-d(CG¹UGT'UTA¹UAC ¹UG)-3′/5′-d(CAGTATAAACACG)-3′. After photoirradiation, the reaction mixture was treated with hot alkali and NaBH₄ and then subjected to enzymatic digestion. HPLC analysis of the digested mixture revealed the formation of modified mononucleotides 25-28, allowing the quantification of the erythrose-containing sites being produced at the 5′ side of all four ¹U residues of the 13 mer. These results indicate that this method can be used for the detection and quantification of erythrose-containing sites resulting from deoxyribose C2′ oxidation in DNA.