title: Tetramerization and DNA ligase IV interaction of the DNA double-strand break repair protein XRCC4 are mutually exclusive.
abstract: The XRCC4 protein is of critical importance for the repair of broken chromosomal DNA by non-homologous end joining (NHEJ). The absence of XRCC4 abolishes chromosomal NHEJ almost completely. One reason for this severe phenotype is that XRCC4 binds and modulates the stability and activity of the NHEJ-specific ligase, DNA ligase IV. XRCC4 in solution is in equilibrium between the dimeric and tetrameric forms. Previous structural studies have shown that the interface between dimers is located in the same region as that implicated in DNA ligase IV interaction. With the use of equilibrium sedimentation analysis, we show here that only the XRCC4 dimer can associate with DNA ligase IV, forming a monodisperse complex of 2:1 stoichiometry in solution. In addition, physical analysis of XRCC4/DNA ligase IV complex formation, combined with mutational analysis of XRCC4, indicates that tetramerization and DNA ligase IV binding are mutually exclusive. We propose that the putative function of the XRCC4 tetramer is distinct from its DNA ligase IV-associated function.
authors: Department of Cell Biology and Genetics, Erasmus Medical Center, P.O. Box 1738, 3000 DR, Rotterdam, The Netherlands.
authors: Mauro
authors: M
authors: Modesti
authors: Murray S
authors: MS
authors: Junop
authors: Rodolfo
authors: R
authors: Ghirlando
authors: Mandy
authors: M
authors: van de Rakt
authors: Martin
authors: M
authors: Gellert
authors: Wei
authors: W
authors: Yang
authors: Roland
authors: R
authors: Kanaar
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004247:DNA / Q000378:metabolism*; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism*; D004260:DNA Repair / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015321:Gene Rearrangement / Q000235:genetics; D006801:Humans; D009154:Mutation; D011839:Radiation, Ionizing
chemical_list: D004268:DNA-Binding Proteins; C000607893:LIG4 protein, human; C101467:XRCC4 protein, human; D004247:DNA; D011088:DNA Ligases; D000072481:DNA Ligase ATP