Requirement of DNA polymerase activity of yeast Rad30 protein for its biological function

The RAD30 gene of Saccharomyces cerevisiae encodes a DNA polymerase, Polη. The Rad30 protein shares homology with the yeast Rev1 and the Escherichia coli DinB and UmuC proteins. Although these proteins contain several highly conserved motifs, only Rad30 has been shown to possess a DNA polymerase activity. To determine whether the DNA polymerase activity of Rad30 was essential for its biological function, we made a mutation in the highly conserved SIDE sequence in Rad30, in which the aspartate and glutamate residues have each been changed to alanine. The mutant Rad30 protein lacks the DNA polymerase activity, and the mutant gene does not complement the rad30Δ mutation. These findings indicate that DNA polymerase activity is indispensable for the biological function of RAD30.