Fig. 2.

Hypothesis: Damaged bases in DNA might promote mutagenic break repair by allowing DNA polymerase exchange. We show how Pol IV could make − 1 basepair deletions when oxidized guanine is correctly incorporated into DNA opposite template cytosine (Moore et al. 2017). a At a repair replisome, the replicative DNA polymerase Pol III incorporates 8-oxo-guanine (G=O) opposite template C (Moore et al. 2017). b Pol III does not extend from the 8-oxoG:C base pair efficiently (Yamada et al. 2012), causing the replisome to stall, and Pol III to leave the replisome active site (Markkanen et al. 2012). c DNA polymerase Pol IV acquires the replisome active site (Heltzel et al. 2012) and can extend from the 8-oxoG:C base pair (orange). d The active site of Pol IV can accommodate extrahelical bases, shown here as an extrahelical G in a run of five Gs (Kobayashi et al. 2002; Kokoska et al. 2002), which results in a − 1 bp deletion because GGGGG is replicated to CCCC. Pol zeta might play a similar role in yeast [reviewed by (Szwajczak et al. 2017)]. e Because Pol IV has low processivity, about 400 basepairs (Wagner et al. 2000), it leaves the replisome and Pol III resumes accurate replication (blue). Pol III is shown as a blue circle, Pol IV as an orange circle. Lines represent single DNA strands. Half arrows indicate 3′ DNA ends. Parental DNA is shown as black, new Pol III synthesis in blue and new Pol IV synthesis in orange