title: CtIP tetramer assembly is required for DNA-end resection and repair.
abstract: Mammalian CtIP protein has major roles in DNA double-strand break (DSB) repair. Although it is well established that CtIP promotes DNA-end resection in preparation for homology-dependent DSB repair, the molecular basis for this function has remained unknown. Here we show by biophysical and X-ray crystallographic analyses that the N-terminal domain of human CtIP exists as a stable homotetramer. Tetramerization results from interlocking interactions between the N-terminal extensions of CtIP's coiled-coil region, which lead to a 'dimer-of-dimers' architecture. Through interrogation of the CtIP structure, we identify a point mutation that abolishes tetramerization of the N-terminal domain while preserving dimerization in vitro. Notably, we establish that this mutation abrogates CtIP oligomer assembly in cells, thus leading to strong defects in DNA-end resection and gene conversion. These findings indicate that the CtIP tetramer architecture described here is essential for effective DSB repair by homologous recombination.
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, UK.
authors.forename: Owen R
authors.initials: OR
authors.lastname: Davies
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, UK.|The Gurdon Institute, University of Cambridge, Cambridge, UK.|The Wellcome Trust Sanger Institute, Hinxton, UK.
authors.forename: Josep V
authors.initials: JV
authors.lastname: Forment
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, UK.
authors.forename: Meidai
authors.initials: M
authors.lastname: Sun
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, UK.|The Gurdon Institute, University of Cambridge, Cambridge, UK.
authors.forename: Rimma
authors.initials: R
authors.lastname: Belotserkovskaya
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, UK.|The Gurdon Institute, University of Cambridge, Cambridge, UK.
authors.forename: Julia
authors.initials: J
authors.lastname: Coates
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, UK.|The Gurdon Institute, University of Cambridge, Cambridge, UK.
authors.forename: Yaron
authors.initials: Y
authors.lastname: Galanty
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, UK.|The Gurdon Institute, University of Cambridge, Cambridge, UK.
authors.forename: Mukerrem
authors.initials: M
authors.lastname: Demir
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, UK.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Morton
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, UK.
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Rzechorzek
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, UK.|The Gurdon Institute, University of Cambridge, Cambridge, UK.|The Wellcome Trust Sanger Institute, Hinxton, UK.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Jackson
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, UK.
authors.forename: Luca
authors.initials: L
authors.lastname: Pellegrini
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000502:physiology; D004706:Endodeoxyribonucleases; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism*; D055503:Protein Multimerization / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D009687:Nuclear Proteins; D004706:Endodeoxyribonucleases; C410741:RBBP8 protein, human