Formation of 1,4-Dioxo-2-butene-Derived Adducts of 2‘-Deoxyadenosine and 2‘-Deoxycytidine in Oxidized DNA

Abstract

Oxidation of deoxyribose in DNA produces a variety of electrophilic residues that are capable of reacting with nucleobases to form adducts such as M 1 dG, the pyrimidopurinone adduct of dG. We now report that deoxyribose oxidation in DNA leads to the formation of oxadiazabicyclo(3.3.0) octaimine adducts of dC and dA. We previously demonstrated that these adducts arise in reactions of nucleosides and DNA with trans-1,4-dioxo-2-butene, the β-elimination product of the 2-phosphoryl-1,4-dioxobutane residue arising from 5′-oxidation of deoxyribose in DNA and with cis-1,4-dioxo-2-butene, a metabolite of furan. Treatment of DNA with enediyne antibiotics capable of oxidizing the 5′-position of deoxyribose (calicheamicin and neocarzinostatin) led to a concentration-dependent formation of oxadiazabicyclo(3.3.0)octaimine adducts of dC and dA, while the antibiotic bleomycin, which is capable of performing only 4-oxidation of deoxyribose, did not give rise to the adducts. The non-specific DNA oxidant, γ-radiation, also produced the adducts that represented ~0.1% of the 2-phosphoryl-1,4-dioxobutane residues formed during the irradiation. These results suggest that the oxadiazabicyclo(3.3.0)octaimine adducts of dC and dA could represent endogenous DNA lesions arising from oxidative stresses that also give rise to other DNA adducts.

Oxidation of the sugar moiety of DNA by ionizing radiation or bleomycin could induce the formation of a cluster DNA lesion

“…It could be also mentioned that the formation of an adduct between dGuo and phosphoglycolaldehyde has been reported (14). Dedon et al (15,16) have highlighted the formation of trans-1,4-dioxo-2-butene DNA adducts that could be generated during ␥-irradiation of DNA (17).…”

An Oxidized Abasic Lesion as an Intramolecular Source of DNA Adducts

“…Peterson and coworkers detected ~0.1% of dC ( 2 ) and dA ( 3 ) adducts arising from the oxidation of calf thymus DNA (~10 nM), which was oxidized by the antitumour antibiotics calicheamicin and esperamicin (100 μM) or γ radiation. [8] In their study, the yields were determined using a previously determined amount of DOB in DNA exposed to the same reaction conditions. They were unable to detect the dG adduct owing to its instability to the derivatization and analysis conditions.…”

“…[7] The trans isomer ( trans - 1 ), which also forms adducts with nucleotides in DNA, is released from 5′-(2-phosphoryl-1,4-dioxobutane) (DOB), an oxidized abasic lesion resulting from C5′-hydrogen-atom abstraction. [8,11] The DOB lesion is produced by several antitumour agents and by γ radiation. [11–14] This lesion is a potent irreversible inhibitor of DNA polymerase β, an enzyme that is a primary component of base excision repair that is overexpressed in many cancers.…”

“…[21] Although cis - and trans - 1 form exocyclic adducts with the three nucleosides containing exocyclic amines, the corresponding adduct with dG was unstable to the analytical conditions. [8,22] Consequently, only dA and dC adducts of trans -but-2-en-1,4-dial ( trans - 1 ) were detected in oxidatively damaged DNA. [8] We took advantage of our ability to chemically synthesize oligonucleotides containing DOB from a stable precursor ( 6 , Scheme 2) to enhance detection of but-2-en-1,4-dial ( 1 ) adducts of dA, dC, and dG ( 2 – 4 ) by using tritium labeling.…”

“…[8,22] Consequently, only dA and dC adducts of trans -but-2-en-1,4-dial ( trans - 1 ) were detected in oxidatively damaged DNA. [8] We took advantage of our ability to chemically synthesize oligonucleotides containing DOB from a stable precursor ( 6 , Scheme 2) to enhance detection of but-2-en-1,4-dial ( 1 ) adducts of dA, dC, and dG ( 2 – 4 ) by using tritium labeling. [20] …”