| Abstract
| - We have investigated the miscoding properties of the exocyclic DNAadduct, 3,N4-etheno-2‘-deoxycytidine (εdC), using an experimental system designed todetect and quantify base substitutionsand deletions generated by primer extension in reactions catalyzed byDNA polymerases α, β, and δ.Oligodeoxynucleotides modified site-specifically with εdC wereused as DNA templates for this study.Pol α catalyzed incorporation of dTMP and dAMP opposite εdC,accompanied by lesser amounts ofdCMP and dGMP and some two-base deletions. Pol β promotedincorporation of dCMP and dAMP,along with small amounts of one-base and two-base deletions. Polδ catalyzed incorporation of dTMPand lesser amounts of dAMP and dGMP. The frequency of nucleotideinsertion opposite εdC and ofchain extension from the 3‘-primer terminus in reactions catalyzed bypol α and pol β was established bysteady-state kinetic analysis. Results of this study wereconsistent with those obtained in primer extensionexperiments. The miscoding properties of εdC determined invitro are consistent with observations ofεdC→A transversions and εdC→T transitions in site-specificmutagenesis experiments in mammaliancells (Moriya et al. (1994) Proc. Natl. Acad. Sci.U.S.A.91, 11899). We conclude from this studythatDNA polymerases may differ significantly in their miscoding potentialand that in vitro analysis can beused to predict mutagenic specificity of exocyclic DNA adducts inmammalian cells.
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