What effect is expected from a mutation in this gene?

The epsilon subunit of DNA polymerase III catalyzes the 3' to 5' proofreading exonuclease activity of the holoenzyme. This activity is required to prevent spontaneous mutations and may play a role in preventing UV mutagenesis and lesion bypass synthesis as well. The epsilon subunit suppresses both misincorporation of dCMP and transversion mutations.

Episilon is required for speed and processivity of DNA polymerase III function. In the presence of polymerase III alpha subunit, epsilon activity increases ten- to eighty-fold, and its affinity for the 3'-hydroxy terminus of DNA increases substantially. Single-stranded DNA binding protein inhibits epsilon activity during replication.