title: Mutagenic spectra arising from replication bypass of the 2,6-diamino-4-hydroxy-N(5)-methyl formamidopyrimidine adduct in primate cells.
abstract: DNA exposures to electrophilic methylating agents that are commonly used during chemotherapeutic treatments cause diverse chemical modifications of nucleobases, with reaction at N7-dG being the most abundant. Although this base modification frequently results in destabilization of the glycosyl bond and spontaneous depurination, the adduct can react with hydroxide ion to yield a stable, ring-opened MeFapy-dG, and this lesion has been reported to persist in animal tissues. Results from prior in vitro replication bypass investigations of the MeFapy-dG adduct had revealed complex spectra of replication errors that differed depending on the identity of DNA polymerase and the local sequence context. In this study, a series of nine site-specifically modified MeFapy-dG-containing oligodeoxynucleotides were engineered into a shuttle vector and subjected to replication in primate cells. In all nine sequence contexts examined, MeFapy-dG was shown to be associated with a strong mutator phenotype, predominantly causing base substitutions, with G to T transversions being most common. Single and dinucleotide deletions were also found in a subset of the sequence contexts. Interestingly, single-nucleotide deletions occurred at not only the adducted site, but also one nucleotide downstream of the adduct. Standard models for primer-template misalignment could account for some but not all mutations observed. These data demonstrate that in addition to mutagenesis predicted from replication of DNAs containing O(6)-Me-dG and O(4)-Me-dT, the MeFapy-dG adduct likely contributes to mutagenic events following chemotherapeutic treatments.
authors.affiliation: Center for Research on Occupational and Environmental Toxicology and §Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon 97239, United States.
authors.forename: Lauriel F
authors.initials: LF
authors.lastname: Earley
authors.forename: Irina G
authors.initials: IG
authors.lastname: Minko
authors.forename: Plamen P
authors.initials: PP
authors.lastname: Christov
authors.forename: Carmelo J
authors.initials: CJ
authors.lastname: Rizzo
authors.forename: R Stephen
authors.initials: RS
authors.lastname: Lloyd
mesh_terms: D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D018736:DNA Adducts / Q000737:chemistry / Q000187:drug effects* / Q000235:genetics*; D004261:DNA Replication / Q000187:drug effects / Q000235:genetics*; D016296:Mutagenesis / Q000187:drug effects / Q000235:genetics*; D009152:Mutagenicity Tests; D011743:Pyrimidines / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D018736:DNA Adducts; D011743:Pyrimidines; C037301:N(5)-methyl-N(5)-formyl-2,5,6-triamino-4-hydroxypyrimidine