title: Xrcc4 physically links DNA end processing by polynucleotide kinase to DNA ligation by DNA ligase IV.
abstract: Nonhomologous end joining (NHEJ) is the major DNA double-strand break (DSB) repair pathway in mammalian cells. A critical step in this process is DNA ligation, involving the Xrcc4-DNA ligase IV complex. DNA end processing is often a prerequisite for ligation, but the coordination of these events is poorly understood. We show that polynucleotide kinase (PNK), with its ability to process ionizing radiation-induced 5'-OH and 3'-phosphate DNA termini, functions in NHEJ via an FHA-dependent interaction with CK2-phosphorylated Xrcc4. Analysis of the PNK FHA-Xrcc4 interaction revealed that the PNK FHA domain binds phosphopeptides with a unique selectivity among FHA domains. Disruption of the Xrcc4-PNK interaction in vivo is associated with increased radiosensitivity and slower repair kinetics of DSBs, in conjunction with a diminished efficiency of DNA end joining in vitro. Therefore, these results suggest a new role for Xrcc4 in the coordination of DNA end processing with DNA ligation.
authors.affiliation: Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Christine Anne
authors.initials: CA
authors.lastname: Koch
authors.forename: Roger
authors.initials: R
authors.lastname: Agyei
authors.forename: Sarah
authors.initials: S
authors.lastname: Galicia
authors.forename: Pavel
authors.initials: P
authors.lastname: Metalnikov
authors.forename: Paul
authors.initials: P
authors.lastname: O'Donnell
authors.forename: Andrei
authors.initials: A
authors.lastname: Starostine
authors.forename: Michael
authors.initials: M
authors.lastname: Weinfeld
authors.forename: Daniel
authors.initials: D
authors.lastname: Durocher
mesh_terms: D000818:Animals; D016466:CHO Cells / Q000378:metabolism; D006224:Cricetinae; D004247:DNA / Q000378:metabolism*; D004249:DNA Damage; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism*; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000378:metabolism; D010748:Phosphopeptides / Q000378:metabolism; D010766:Phosphorylation; D011116:Polynucleotide 5'-Hydroxyl-Kinase / Q000378:metabolism*; D011839:Radiation, Ionizing; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C000607891:DNL4 protein, S cerevisiae; C000607893:LIG4 protein, human; D010748:Phosphopeptides; D029701:Saccharomyces cerevisiae Proteins; C101467:XRCC4 protein, human; D004247:DNA; D011116:Polynucleotide 5'-Hydroxyl-Kinase; D011088:DNA Ligases; D000072481:DNA Ligase ATP