Glycidaldehyde is an industrial chemical which has been shown to be genotoxic in 
in vitro experiments and carcinogenic in rodent studies. It is a bifunctional 
alkylating agent capable of reacting with DNA to form exocyclic 
hydroxymethyl-substituted ethenobases. In this work, 
8-(hydroxymethyl)-3,N4-etheno-2'-deoxycytidine (8-HM-epsilondC), a potential 
nucleoside derivative of glycidaldehyde, was synthesized using phosphoramidite 
chemistry and site-specifically incorporated into a defined 25-mer 
oligodeoxynucleotide. The 8-HM-epsilonC adduct is structurally related to 
3,N4-ethenocytosine (epsilonC), a product of reaction with vinyl chloride or 
through lipid peroxidation. In Escherichia coli, epsilonC has been shown 
previously to be a primary substrate for the mismatch uracil-DNA glycosylase 
(Mug). In this study, we report that the same glycosylase also acts on 
8-HM-epsilonC in an oligonucleotide duplex. The enzyme binds to the 
8-HM-epsilonC-oligonucleotide to a similar extent as the 
epsilonC-oligonucleotide. The Mug excision activity toward 8-HM-epsilonC is 
approximately 2.5-fold lower than that toward the epsilonC substrate. Both 
activities can be stimulated up to approximately 2-fold higher by the addition 
of E. coli endonuclease IV. These two adducts, when mispaired with normal bases, 
were all excised from DNA by Mug with similar efficiencies. Structural studies 
using molecular simulations showed similar adjustment and hydrogen bonding 
pattern for both 8-HM-epsilonC*G and epsilonC*G pairs in oligomer duplexes. We 
believe that these findings may have biological and structural implications in 
defining the role of 8-HM-epsilonC in glycosylase recognition/repair.