title: Novel activity of Escherichia coli mismatch uracil-DNA glycosylase (Mug) excising 8-(hydroxymethyl)-3,N4-ethenocytosine, a potential product resulting from glycidaldehyde reaction.
abstract: 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.
authors.affiliation: Donner Laboratory, Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, USA. Bo_Hang@lbl.gov
authors.forename: Bo
authors.initials: B
authors.lastname: Hang
authors.forename: Gary
authors.initials: G
authors.lastname: Downing
authors.forename: Anton B
authors.initials: AB
authors.lastname: Guliaev
authors.forename: B
authors.initials: B
authors.lastname: Singer
mesh_terms: D000447:Aldehydes / Q000737:chemistry* / Q000378:metabolism; D000477:Alkylating Agents / Q000737:chemistry; D020137:Base Pair Mismatch; D002273:Carcinogens / Q000737:chemistry; D003596:Cytosine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D018736:DNA Adducts / Q000737:chemistry* / Q000378:metabolism; D004260:DNA Repair; D004277:DNA, Single-Stranded / Q000737:chemistry; D004852:Epoxy Compounds / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D008958:Models, Molecular; D009153:Mutagens / Q000737:chemistry; D009699:N-Glycosyl Hydrolases / Q000737:chemistry* / Q000378:metabolism; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry; D011485:Protein Binding; D044502:Thymine DNA Glycosylase
chemical_list: C018289:3,N(4)-ethenocytosine; C415024:8-(hydroxymethyl)-3,N(4)-ethenocytosine; D000447:Aldehydes; D000477:Alkylating Agents; D002273:Carcinogens; D018736:DNA Adducts; D004277:DNA, Single-Stranded; D004852:Epoxy Compounds; D009153:Mutagens; D009692:Nucleic Acid Heteroduplexes; D003596:Cytosine; D009699:N-Glycosyl Hydrolases; D044502:Thymine DNA Glycosylase; C113921:mismatch-specific thymine uracil-DNA glycosylase; C007871:glycinaldehyde