title: APE2 is required for ATR-Chk1 checkpoint activation in response to oxidative stress.
abstract: The base excision repair pathway is largely responsible for the repair of oxidative stress-induced DNA damage. However, it remains unclear how the DNA damage checkpoint is activated by oxidative stress at the molecular level. Here, we provide evidence showing that hydrogen peroxide (H2O2) triggers checkpoint kinase 1 (Chk1) phosphorylation in an ATR [ataxia-telangiectasia mutated (ATM) and Rad3-related]-dependent but ATM-independent manner in Xenopus egg extracts. A base excision repair protein, Apurinic/apyrimidinic (AP) endonuclease 2 (APE2, APN2, or APEX2), is required for the generation of replication protein A (RPA)-bound single-stranded DNA, the recruitment of a checkpoint protein complex [ATR, ATR-interacting protein (ATRIP), and Rad9] to damage sites, and H2O2-induced Chk1 phosphorylation. A conserved proliferating cell nuclear antigen interaction protein box of APE2 is important for the recruitment of APE2 to H2O2-damaged chromatin. APE2 3'-phosphodiesterase and 3'-5' exonuclease activity is essential for single-stranded DNA generation in the 3'-5' direction from single-stranded breaks, referred to as single-stranded break end resection. In addition, APE2 associates with Chk1, and a serine residue (S86) in the Chk1-binding motif of APE2 is essential for Chk1 phosphorylation, indicating a Claspin-like but distinct role for APE2 in ATR-Chk1 signaling. Our data indicate that APE2 plays a vital and previously unexpected role in ATR-Chk1 checkpoint signaling in response to oxidative stress. Thus, our findings shed light on a distinct mechanism of how an ATR-Chk1-dependent DNA damage checkpoint is mediated by APE2 in the oxidative stress response.
authors.affiliation: Department of Biology, University of North Carolina at Charlotte, Charlotte, NC 28223, USA.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Willis
authors.forename: Yogin
authors.initials: Y
authors.lastname: Patel
authors.forename: Barry L
authors.initials: BL
authors.lastname: Lentz
authors.forename: Shan
authors.initials: S
authors.lastname: Yan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002474:Cell-Free System; D000071877:Checkpoint Kinase 1; D004249:DNA Damage; D004260:DNA Repair; D004277:DNA, Single-Stranded / Q000378:metabolism; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006861:Hydrogen Peroxide / Q000633:toxicity; D008969:Molecular Sequence Data; D010063:Ovum / Q000378:metabolism; D018384:Oxidative Stress; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D018797:Cell Cycle Proteins; D004277:DNA, Single-Stranded; D011994:Recombinant Proteins; D029867:Xenopus Proteins; D006861:Hydrogen Peroxide; D011494:Protein Kinases; C576898:Atr protein, Xenopus; D064007:Ataxia Telangiectasia Mutated Proteins; D000071877:Checkpoint Kinase 1; C000605875:Chek1 protein, Xenopus; D017346:Protein Serine-Threonine Kinases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase