APLF (C2orf13) is a novel human protein involved in the cellular response to chromosomal DNA strand breaks

Mol Cell Biol. 2007 May;27(10):3793-803. doi: 10.1128/MCB.02269-06. Epub 2007 Mar 12.


Aprataxin and polynucleotide kinase (PNK) are DNA end processing factors that are recruited into the DNA single- and double-strand break repair machinery through phosphorylation-specific interactions with XRCC1 and XRCC4, respectively. These interactions are mediated through a divergent class of forkhead-associated (FHA) domain that binds to peptide sequences in XRCC1 and XRCC4 that are phosphorylated by casein kinase 2 (CK2). Here, we identify the product of the uncharacterized open reading frame C2orf13 as a novel member of this FHA domain family of proteins and we denote this protein APLF (aprataxin- and PNK-like factor). We show that APLF interacts with XRCC1 in vivo and in vitro in a manner that is stimulated by CK2. Yeast two-hybrid analyses suggest that APLF also interacts with the double-strand break repair proteins XRCC4 and XRCC5 (Ku86). We also show that endogenous and yellow fluorescent protein-tagged APLF accumulates at sites of H(2)O(2) or UVA laser-induced chromosomal DNA damage and that this is achieved through at least two mechanisms: one that requires the FHA domain-mediated interaction with XRCC1 and a second that is independent of XRCC1 but requires a novel type of zinc finger motif located at the C terminus of APLF. Finally, we demonstrate that APLF is phosphorylated in a DNA damage- and ATM-dependent manner and that the depletion of APLF from noncycling human SH-SY5Y neuroblastoma cells reduces rates of chromosomal DNA strand break repair following ionizing radiation. These data identify APLF as a novel component of the cellular response to DNA strand breaks in human cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Casein Kinase II / genetics
  • Casein Kinase II / metabolism
  • Cell Line, Tumor
  • Chromosomes / metabolism*
  • DNA Damage* / radiation effects
  • DNA Helicases / genetics
  • DNA Helicases / metabolism
  • DNA Repair
  • DNA-(Apurinic or Apyrimidinic Site) Lyase
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Forkhead Transcription Factors / genetics
  • Forkhead Transcription Factors / metabolism*
  • Humans
  • Ku Autoantigen
  • Molecular Sequence Data
  • Open Reading Frames*
  • Phosphoproteins / chemistry
  • Phosphoproteins / metabolism*
  • Poly-ADP-Ribose Binding Proteins
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae
  • Sequence Alignment
  • Two-Hybrid System Techniques
  • Ultraviolet Rays
  • X-ray Repair Cross Complementing Protein 1


  • DNA-Binding Proteins
  • Forkhead Transcription Factors
  • Phosphoproteins
  • Poly-ADP-Ribose Binding Proteins
  • Recombinant Fusion Proteins
  • X-ray Repair Cross Complementing Protein 1
  • XRCC1 protein, human
  • XRCC4 protein, human
  • Casein Kinase II
  • DNA Helicases
  • XRCC5 protein, human
  • Ku Autoantigen
  • APLF protein, human
  • DNA-(Apurinic or Apyrimidinic Site) Lyase