Activity of DNA ligase IV stimulated by complex formation with XRCC4 protein in mammalian cells

Nature. 1997 Jul 31;388(6641):492-5. doi: 10.1038/41358.


Mutation of the XRCC4 gene in mammalian cells prevents the formation of the signal and coding joints in the V(D)J recombination reaction, which is necessary for production of a functional immunoglobulin gene, and renders the cells highly sensitive to ionizing radiation. However, XRCC4 shares no sequence homology with other proteins, nor does it have a biochemical activity to indicate what its function might be. Here we show that DNA ligase IV co-immunoprecipitates with XRCC4 and that these two proteins specifically interact with one another in a yeast two-hybrid system. Ligation of DNA double-strand breaks in a cell-free system by DNA ligase IV is increased fivefold by purified XRCC4 and seven- to eightfold when XRCC4 is co-expressed with DNA ligase IV. We conclude that the biological consequences of mutating XRCC4 are primarily due to the loss of its stimulatory effect on DNA ligase IV: the function of the XRCC4-DNA ligase IV complex may be to carry out the final steps of V(D)J recombination and joining of DNA ends.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • Cloning, Molecular
  • Cricetinae
  • DNA / metabolism
  • DNA Ligase ATP
  • DNA Ligases / genetics
  • DNA Ligases / metabolism*
  • DNA-Binding Proteins / metabolism*
  • Enzyme Activation
  • Humans
  • Mammals
  • Mutation
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Recombination, Genetic
  • Transfection


  • DNA-Binding Proteins
  • LIG4 protein, human
  • Recombinant Fusion Proteins
  • XRCC4 protein, human
  • DNA
  • DNA Ligases
  • DNA Ligase ATP