Excision Repair of Gamma-ray-induced Alkali-stable DNA Lesions with the Help of γ-endonuclease from Micrococcus Luteus

Summary

γ-Endonuclease Y, an enzyme that hydrolyses phosphodiester bonds at alkalistable lesions in γ-irradiated (N₂, tris buffer) DNA, has been partially purified from Micrococcus luteus. The enzyme has a molecular weight of about 19 000, induces single-strand breaks with 3′OH-5′PO₄ termini and contains endonuclease activity towards DNA treated with 7-bromomethylbenz(a)anthracene. γ-Endonuclease Y induces breaks in OsO₄-treated poly(dA—dT) and apparently is specific towards γ-ray-induced base lesions of the t′ type. The complete excision repair of γ-endonuclease Y substrate sites has been performed in vitro by γ-endonuclease Y, DNA polymerase and ligase.