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

We used quantitative complementation assays to characterize individual DNA polymerase beta (Pol beta) mutants for their ability to function in DNA replication and DNA repair. We also describe a screen for detecting mutator activity of DNA polymerase beta mutants. By using these bioassays, together with DNA polymerase activity gels, we characterized 15 new DNA polymerase beta 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 beta 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 mutator activity in vivo. Our work provides a model to study mutant mammalian enzymes in Escherichia coli with phenotypes that are otherwise difficult to assess.