Dual modes of interaction between XRCC4 and polynucleotide kinase/phosphatase: implications for nonhomologous end joining

J Biol Chem. 2010 Nov 26;285(48):37619-29. doi: 10.1074/jbc.M109.058719. Epub 2010 Sep 17.

Abstract

XRCC4 plays a crucial role in the nonhomologous end joining (NHEJ) pathway of DNA double-strand break repair acting as a scaffold protein that recruits other NHEJ proteins to double-strand breaks. Phosphorylation of XRCC4 by protein kinase CK2 promotes a high affinity interaction with the forkhead-associated domain of the end-processing enzyme polynucleotide kinase/phosphatase (PNKP). Here we reveal that unphosphorylated XRCC4 also interacts with PNKP through a lower affinity interaction site within the catalytic domain and that this interaction stimulates the turnover of PNKP. Unexpectedly, CK2-phosphorylated XRCC4 inhibited PNKP activity. Moreover, the XRCC4·DNA ligase IV complex also stimulated PNKP enzyme turnover, and this effect was independent of the phosphorylation of XRCC4 at threonine 233. Our results reveal that CK2-mediated phosphorylation of XRCC4 can have different effects on PNKP activity, with implications for the roles of XRCC4 and PNKP in NHEJ.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Casein Kinase II / genetics
  • Casein Kinase II / metabolism
  • DNA / genetics
  • DNA / metabolism
  • DNA Ligases / genetics
  • DNA Ligases / metabolism
  • DNA Repair Enzymes / genetics
  • DNA Repair Enzymes / metabolism*
  • DNA Repair*
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • HeLa Cells
  • Humans
  • Phosphorylation
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Protein Binding
  • Protein Structure, Tertiary

Substances

  • DNA-Binding Proteins
  • XRCC4 protein, human
  • DNA
  • PNKP protein, human
  • Phosphotransferases (Alcohol Group Acceptor)
  • Casein Kinase II
  • DNA Ligases
  • DNA Repair Enzymes