Catalytic and noncatalytic roles of the CtIP endonuclease in double-strand break end resection

Mol Cell. 2014 Jun 19;54(6):1022-33. doi: 10.1016/j.molcel.2014.04.011. Epub 2014 May 15.

Abstract

The carboxy-terminal binding protein (CtBP)-interacting protein (CtIP) is known to function in 5' strand resection during homologous recombination, similar to the budding yeast Sae2 protein, but its role in this process is unclear. Here, we characterize recombinant human CtIP and find that it exhibits 5' flap endonuclease activity on branched DNA structures, independent of the MRN complex. Phosphorylation of CtIP at known damage-dependent sites and other sites is essential for its catalytic activity, although the S327 and T847 phosphorylation sites are dispensable. A catalytic mutant of CtIP that is deficient in endonuclease activity exhibits wild-type levels of homologous recombination at restriction enzyme-generated breaks but is deficient in processing topoisomerase adducts and radiation-induced breaks in human cells, suggesting that the nuclease activity of CtIP is specifically required for the removal of DNA adducts at sites of DNA breaks.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Binding Sites / genetics
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Catalysis
  • Cell Line
  • Cell Survival / genetics
  • DNA / genetics
  • DNA Breaks, Double-Stranded*
  • DNA End-Joining Repair / genetics*
  • DNA-Binding Proteins / genetics
  • Endonucleases / genetics
  • Endonucleases / metabolism*
  • Humans
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Phosphorylation / genetics
  • Protein Processing, Post-Translational / genetics
  • Radiation, Ionizing
  • Recombination, Genetic
  • Recombinational DNA Repair / genetics*

Substances

  • Carrier Proteins
  • DNA-Binding Proteins
  • Nuclear Proteins
  • DNA
  • Endonucleases
  • RBBP8 protein, human