CtIP tetramer assembly is required for DNA-end resection and repair

Nat Struct Mol Biol. 2015 Feb;22(2):150-157. doi: 10.1038/nsmb.2937. Epub 2015 Jan 5.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carrier Proteins / chemistry*
  • Carrier Proteins / metabolism*
  • Crystallography, X-Ray
  • DNA Breaks, Double-Stranded
  • DNA Repair / physiology
  • Endodeoxyribonucleases
  • Humans
  • Nuclear Proteins / chemistry*
  • Nuclear Proteins / metabolism*
  • Protein Multimerization / physiology*

Substances

  • Carrier Proteins
  • Nuclear Proteins
  • Endodeoxyribonucleases
  • RBBP8 protein, human

Associated data

  • PDB/4D2H