TOPBP1 regulates RAD51 phosphorylation and chromatin loading and determines PARP inhibitor sensitivity

J Cell Biol. 2016 Feb 1;212(3):281-8. doi: 10.1083/jcb.201507042. Epub 2016 Jan 25.

Abstract

Topoisomerase IIβ-binding protein 1 (TOPBP1) participates in DNA replication and DNA damage response; however, its role in DNA repair and relevance for human cancer remain unclear. Here, through an unbiased small interfering RNA screen, we identified and validated TOPBP1 as a novel determinant whose loss sensitized human cells to olaparib, an inhibitor of poly(ADP-ribose) polymerase. We show that TOPBP1 acts in homologous recombination (HR) repair, impacts olaparib response, and exhibits aberrant patterns in subsets of human ovarian carcinomas. TOPBP1 depletion abrogated RAD51 loading to chromatin and formation of RAD51 foci, but without affecting the upstream HR steps of DNA end resection and RPA loading. Furthermore, TOPBP1 BRCT domains 7/8 are essential for RAD51 foci formation. Mechanistically, TOPBP1 physically binds PLK1 and promotes PLK1 kinase-mediated phosphorylation of RAD51 at serine 14, a modification required for RAD51 recruitment to chromatin. Overall, our results provide mechanistic insights into TOPBP1's role in HR, with potential clinical implications for cancer treatment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Cycle Proteins / metabolism
  • Chromatin / metabolism*
  • Chromatin Assembly and Disassembly*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Dose-Response Relationship, Drug
  • Female
  • HEK293 Cells
  • HeLa Cells
  • Homologous Recombination*
  • Humans
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Ovarian Neoplasms / drug therapy*
  • Ovarian Neoplasms / enzymology
  • Ovarian Neoplasms / genetics
  • Ovarian Neoplasms / pathology
  • Phosphorylation
  • Phthalazines / pharmacology*
  • Piperazines / pharmacology*
  • Poly(ADP-ribose) Polymerase Inhibitors / pharmacology*
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein-Serine-Threonine Kinases / metabolism
  • Proto-Oncogene Proteins / metabolism
  • RNA Interference
  • Rad51 Recombinase / genetics
  • Rad51 Recombinase / metabolism*
  • Signal Transduction / drug effects
  • Time Factors
  • Transfection

Substances

  • Carrier Proteins
  • Cell Cycle Proteins
  • Chromatin
  • DNA-Binding Proteins
  • Nuclear Proteins
  • Phthalazines
  • Piperazines
  • Poly(ADP-ribose) Polymerase Inhibitors
  • Proto-Oncogene Proteins
  • TOPBP1 protein, human
  • Protein-Serine-Threonine Kinases
  • polo-like kinase 1
  • RAD51 protein, human
  • Rad51 Recombinase
  • olaparib