DNA Repair Network Analysis Reveals Shieldin as a Key Regulator of NHEJ and PARP Inhibitor Sensitivity

  • Cell. 2018 May 3;173(4):972-988.e23. doi: 10.1016/j.cell.2018.03.050.
Rajat Gupta  1 ,  Kumar Somyajit  2 ,  Takeo Narita  1 ,  Elina Maskey  1 ,  Andre Stanlie  3 ,  Magdalena Kremer  4 ,  Dimitris Typas  2 ,  Michael Lammers  5 ,  Niels Mailand  2 ,  Andre Nussenzweig  3 ,  Jiri Lukas  2 ,  Chunaram Choudhary  6
Affiliations
  • 1. Proteomics Program, the Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
  • 2. Protein Signaling Program, the Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
  • 3. Laboratory of Genome Integrity, NIH, Bethesda, MD 20892, USA.
  • 4. Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Joseph-Stelzmann-Str. 26, University of Cologne, 50931 Cologne, Germany.
  • 5. Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Joseph-Stelzmann-Str. 26, University of Cologne, 50931 Cologne, Germany; Institute for Biochemistry, Synthetic and Structural Biochemistry, Felix-Hausdorff-Str. 4, University of Greifswald, 17487 Greifswald, Germany.
  • 6. Proteomics Program, the Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark; Center for Chromosome Stability (CCS), Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark. Electronic address: [email protected].
PMID: 29656893 DOI: 10.1016/j.cell.2018.03.050
Abstract

Repair of damaged DNA is essential for maintaining genome integrity and for preventing genome-instability-associated diseases, such as Cancer. By combining proximity labeling with quantitative mass spectrometry, we generated high-resolution interaction neighborhood maps of the endogenously expressed DNA repair factors 53BP1, BRCA1, and MDC1. Our spatially resolved interaction maps reveal rich network intricacies, identify shared and bait-specific interaction modules, and implicate previously concealed regulators in this process. We identified a novel vertebrate-specific protein complex, shieldin, comprising REV7 plus three previously uncharacterized proteins, RINN1 (CTC-534A2.2), RINN2 (FAM35A), and RINN3 (C20ORF196). Recruitment of shieldin to DSBs, via the ATM-RNF8-RNF168-53BP1-RIF1 axis, promotes NHEJ-dependent repair of intrachromosomal breaks, immunoglobulin class-switch recombination (CSR), and fusion of unprotected telomeres. Shieldin functions as a downstream effector of 53BP1-RIF1 in restraining DNA end resection and in sensitizing BRCA1-deficient cells to PARP inhibitors. These findings have implications for understanding cancer-associated PARPi resistance and the evolution of antibody CSR in higher vertebrates.

Keywords
53BP1; BRCA1; DNA damage repair; NHEJ; PARP inhibitors; antibody class-switch recombination; proteomics; proximity labeling; shieldin; telomere maintenance.