Drosophila DNA polymerase delta. Purification and characterization.

A DNA polymerase with properties similar to mammalian polymerase delta has been isolated to near homogeneity from early embryos of Drosophila melanogaster. A combination of exclusion chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicates that this enzyme has a total molecular mass of 185 kDa and is composed of 138- and 47-kDa polypeptides. Its isoelectric point is 6.8. This polymerase activity is strongly inhibited by N-ethylmaleimide, aphidicolin, and high KCl concentration but is relatively insensitive to 2',3'-dideoxythymidine 5'-triphosphate. There was no reaction in an immunological test using monoclonal antibody against Drosophila DNA polymerase alpha. In a final purification step, this polymerase activity was accompanied by 3'-->5'-exonuclease activity as expected proof-reading activity. This polymerase activity is remarkably stimulated by mouse proliferating cell nuclear antigen, which is structurally and immunologically very similar to a Drosophila counterpart. These properties clearly indicate this enzyme belongs to the category of DNA polymerase delta.