Apurinic endonuclease activity from wild-type and repair-deficient mei-9 Drosophila ovaries

An endonuclease which acts on apurinic (AP) sites in DNA was partially purified from Drosophila ovaries. The enzyme present in the female germ line has a molecular weight of 63,000 daltons, is Mg++ dependent, and produces a site upon cleaving depurinated DNA that supports DNA repair synthesis. Although the same characteristics are shared by the enzyme present in the excision-deficient mutant mei-9, specific activity for the AP endonuclease is reduced 98% when compared with that found for its wild-type counterpart. Moreover, cross-reactivity toward an antibody that recognizes the wild-type AP endonuclease protein is reduced roughly 90% for partially purified preparations from mei-9. Mixing experiments between extracts of mei-9 and wild type suggest that the mei-9 structural gene somehow alters or influences the levels of the AP endonuclease protein, but in view of the complex phenotype of this mutant the endonuclease is probably not the product of the gene itself.