Aprataxin, poly-ADP ribose polymerase 1 (PARP-1) and apurinic endonuclease 1 (APE1) function together to protect the genome against oxidative damage

Aprataxin, defective in the neurodegenerative disorder ataxia oculomotor apraxia type 1 (AOA1), is a DNA repair protein that processes the product of abortive ligations, 5' adenylated DNA. In addition to its interaction with the single-strand break repair protein XRCC1, aprataxin also interacts with poly-ADP ribose polymerase 1 (PARP-1), a key player in the detection of DNA single-strand breaks. Here, we reveal reduced expression of PARP-1, apurinic endonuclease 1 (APE1) and OGG1 in AOA1 cells and demonstrate a requirement for PARP-1 in the recruitment of aprataxin to sites of DNA breaks. While inhibition of PARP activity did not affect aprataxin activity in vitro, it retarded its recruitment to sites of DNA damage in vivo. We also demonstrate the presence of elevated levels of oxidative DNA damage in AOA1 cells coupled with reduced base excision and gap filling repair efficiencies indicative of a synergy between aprataxin, PARP-1, APE-1 and OGG1 in the DNA damage response. These data support both direct and indirect modulating functions for aprataxin on base excision repair.