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  • Title: 3'-phosphodiesterase and 3'-->5' exonuclease activities of yeast Apn2 protein and requirement of these activities for repair of oxidative DNA damage.
    Author: Unk I, Haracska L, Prakash S, Prakash L.
    Journal: Mol Cell Biol; 2001 Mar; 21(5):1656-61. PubMed ID: 11238902.
    Abstract:
    In Saccharomyces cerevisiae, the AP endonucleases encoded by the APN1 and APN2 genes provide alternate pathways for the removal of abasic sites. Oxidative DNA-damaging agents, such as H(2)O(2), produce DNA strand breaks which contain 3'-phosphate or 3'-phosphoglycolate termini. Such 3' termini are inhibitory to synthesis by DNA polymerases. Here, we show that purified yeast Apn2 protein contains 3'-phosphodiesterase and 3'-->5' exonuclease activities, and mutation of the active-site residue Glu59 to Ala in Apn2 inactivates both these activities. Consistent with these biochemical observations, genetic studies indicate the involvement of APN2 in the repair of H(2)O(2)-induced DNA damage in a pathway alternate to APN1, and the Ala59 mutation inactivates this function of Apn2. From these results, we conclude that the ability of Apn2 to remove 3'-end groups from DNA is paramount for the repair of strand breaks arising from the reaction of DNA with reactive oxygen species.
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