The role of deoxyribonucleotide metabolism in 5-bromo-2'-deoxyuridine mutagenesis in mammalian cells.

The effects of deoxyribonucleoside triphosphate (dNTP) pool imbalance on the induction of mutations and sister-chromatid exchanges (SCEs) by 5-bromo-2'-deoxyuridine (BrdUrd) in mammalian cells is reviewed. The INC BrdUrd mutagenesis protocol involves the incorporation of BrdUrd into DNA under conditions of specific dNTP pool imbalance, while the REP BrdUrd mutagenesis protocol involves the replication of 5-bromouracil (BrUra)-substituted DNA in the presence of specific (but different) dNTP pool imbalance. Biochemical and genetic analyses of both the INC and REP mutagenesis protocols provided evidence that (1) INC mutagenesis resulted from errors of incorporation due to the mispairing of BrdUTP with a guanine residue in replicating DNA leading to GC to AT transitions and (2) REP mutagenesis resulted from errors of replication due to the mispairing of dGTP with a BrUra residue in replicating DNA leading to AT to GC transitions. Further analyses involving different cell lines has led to an hypothesis describing the role of mismatch repair in the induction of mutations and SCEs.