AlkB Homologue 2–Mediated Repair of Ethenoadenine Lesions in Mammalian DNA
2008
Endogenous formation of the mutagenic
DNA adduct1, N 6 -ethenoadenine (eA) originates from lipid peroxidation. Elevated levels of eA in cancer-prone tissues suggest a role for this adduct in the development of some cancers. The
base excision repairpathway has been considered the principal repair system for eA lesions until recently, when it was shown that the Escherichia coli
AlkB
dioxygenasecould directly reverse the damage. We report here kinetic analysis of the recombinant human
AlkBhomologue 2 (hABH2), which is able to repair eA lesions in DNA. Furthermore, cation exchange chromatography of nuclear extracts from wild-type and mABH2 −/− mice indicates that mABH2 is the principal
dioxygenasefor eA repair in vivo . This is further substantiated by experiments showing that hABH2, but not hABH3, is able to complement the E. coli
alkBmutant with respect to its defective repair of etheno adducts. We conclude that ABH2 is active in the direct reversal of eA lesions, and that ABH2, together with the alkyl- N -adenine-
DNA glycosylase, which is the most effective enzyme for the repair of eA, comprise the cellular defense against eA lesions. [Cancer Res 2008;68(11):4142–9]
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