Characterization of DNA polymerase β mutants with amino acid substitutions located in the C-terminal portion of the enzyme

We used quantitative complementation assays to characterize individual DNA polymerase β (Pol β) mutants for their ability to function in DNA replication and DNA repair. We also describe a screen for detecting imitator activity of DNA polymerase β mutants. By using these bioassays, together with DNA polymerase activity gels, we characterized 15 new DNA polymerase β mutants that display a wide spectrum of phenotypes. Most of these mutants are generally defective in their ability to synthesize DNA. However, two of our Pol β mutants show more complex phenotypes: they are able to function in DNA repair but unable to participate in DNA replication. One of our mutants displays imitator activity in vivo. Our work provides a model to study mutant mammalian enzymes in Escherichia coli with phenotypes that are otherwise difficult to assess.