title: Activity of DNA ligase IV stimulated by complex formation with XRCC4 protein in mammalian cells.
abstract: 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.
authors.affiliation: Washington University School of Medicine, Division of Molecular Oncology, Department of Pathology, St Louis, Missouri 63110, USA.
authors.forename: U
authors.initials: U
authors.lastname: Grawunder
authors.forename: M
authors.initials: M
authors.lastname: Wilm
authors.forename: X
authors.initials: X
authors.lastname: Wu
authors.forename: P
authors.initials: P
authors.lastname: Kulesza
authors.forename: T E
authors.initials: TE
authors.lastname: Wilson
authors.forename: M
authors.initials: M
authors.lastname: Mann
authors.forename: M R
authors.initials: MR
authors.lastname: Lieber
mesh_terms: D000818:Animals; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D004247:DNA / Q000378:metabolism; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D008322:Mammals; D009154:Mutation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; C000607893:LIG4 protein, human; D011993:Recombinant Fusion Proteins; C101467:XRCC4 protein, human; D004247:DNA; D011088:DNA Ligases; D000072481:DNA Ligase ATP