Fig. 6.

MutT mutator phenotype: a multi-polymerase affair. Pol III HE (oval) incorporates 8-oxo-dGTP (G*) opposite template A during the chromosomal replication. We suggest that while pol III accounts for nearly all 8-oxo-dGTP incorporation opposite template A, it only extends ≍ 30% of them, the remaining 70% being extended by the combined action of pol I, pol II, pol IV or pol V (based on data from Fig. 1). We also speculate that the roles of the auxiliary pols might be redundant because the mutation frequency was significantly reduced only when three or four auxiliary pols are deleted (Fig. 1). Following a short patch (a thick line) of DNA synthesis by the auxiliary pols, pol III HE will resume chromosomal replication.