1,N2-ethenoguanine, a mutagenic DNA adduct, is a primary substrate of Escherichia coli mismatch-specific uracil-DNA glycosylase and human alkylpurine-DNA-N-glycosylase

Rhoderick Elder, Murat Saparbaev, Sophie Langouët, Cyril V. Privezentzev, F. Peter Guengerich, Hongliang Cai, Rhoderick H. Elder, Jacques Laval

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The promutagenic and genotoxic exocyclic DNA adduct 1,N2-ethenoguanine (1,N2-εG) is a major product formed in DNA exposed to lipid peroxidation-derived aldehydes in vitro. Here, we report that two structurally unrelated proteins, the Escherichia coli mismatch-specific uracil-DNA glycosylase (MUG) and the human alkylpurine-DNA-N-glycosylase (ANPG), can release 1,N2-εG from defined oligonucleotides containing a single modified base. A comparison of the kinetic constants of the reaction indicates that the MUG protein removes the 1,N2-εG lesion more efficiently (kcat/Km 0.95 × 10-3 min-1 nM-1) than the ANPG protein (kcat/Km = 0.1 × 10-3 nM-1). Additionally, while the non-conserved, N-terminal 73 amino acids of the ANPG protein are not required for activity on 1,N6-ethenoadenine, hypoxanthine, or N-methylpurines, we show that they are essential for 1,N2-εG-DNA glycosylase activity. Both the MUG and ANPG proteins preferentially excise 1,N2-εG when it is opposite dC; however, unlike MUG, ANPG is unable to excise 1,N2-εG when it is opposite dG. Using cell-free extracts from genetically modified E. coli and murine embryonic fibroblasts lacking MUG and mANPG activity, respectively, we show that the incision of the 1,N2-εG-containing duplex oligonucleotide has an absolute requirement for MUG or ANPG. Taken together these observations suggest a possible role for these proteins in counteracting the genotoxic effects of 1,N2-εG residues in vivo.
    Original languageEnglish
    Pages (from-to)26987-26993
    Number of pages6
    JournalJournal of Biological Chemistry
    Volume277
    Issue number30
    DOIs
    Publication statusPublished - 26 Jul 2002

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