Actions of aprataxin in multiple DNA repair pathways.
Mutations in the Aptx gene lead to a neurological disorder known as ataxia oculomotor apraxia-1. The product of Aptx is Aprataxin (Aptx), a DNA-binding protein that resolves abortive DNA ligation intermediates. Aprataxin catalyzes the nucleophilic release of adenylate groups covalently linked to 5' phosphate termini, resulting in termini that can again serve as substrates for DNA ligases. Here we show that Aprataxin acts preferentially on adenylated nicks and double-strand breaks rather than on single-stranded DNA. Moreover, we show that whereas the catalytic activity of Aptx resides within the HIT domain, the C-terminal zinc finger domain provides stabilizing contacts that lock the enzyme onto its high affinity AMP-DNA target site. Both domains are therefore required for efficient AMP-DNA hydrolase activity. Additionally, we find a role for Aprataxin in base excision repair, specifically in the removal of adenylates that arise from abortive ligation reactions that take place at incised abasic sites in DNA. We suggest that Aprataxin may have a general proofreading function in DNA repair, removing DNA adenylates as they arise during single-strand break repair, double-strand break repair, and in base excision repair.
Rass
Ulrich
U
Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, United Kingdom.
Ahel
Ivan
I
Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, United Kingdom.
West
Stephen C
SC
Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, United Kingdom. Electronic address: stephen.west@cancer.org.uk.
D000249:Adenosine Monophosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D013379:Substrate Specificity / Q000235:genetics
C438188:APTX protein, human; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D000249:Adenosine Monophosphate