DNA repair network analysis reveals shielding as a key regulator of NEHJ and PARP inhibitor sensitivity

Rajat Gupta, Kumar Somyajit, Takeo Narita, Elina Maskey, Andre Stanlie, Magdalena Kremer, Dimitris Typas, Michael Lammers, Niels Mailand, Andre Nussenzweig, Jiri Lukas, Chunaram Choudhary

Research output: Contribution to journalJournal articleResearchpeer-review


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. Application of proximity-based quantitative proteomics allows the characterization of endogenous protein networks among major DNA damage repair factors and reveals the role of the protein complex shieldin in regulating NHEJ, antibody class switching, and sensitivity to PARP inhibitors.

Original languageEnglish
Issue number4
Pages (from-to)972-988.e23
Publication statusPublished - 3. May 2018


  • Adaptor Proteins, Signal Transducing
  • BRCA1 Protein/antagonists & inhibitors
  • Cell Cycle Proteins
  • Cell Line, Tumor
  • DNA Breaks, Double-Stranded
  • DNA End-Joining Repair/drug effects
  • DNA-Binding Proteins/antagonists & inhibitors
  • Humans
  • Immunoglobulin Class Switching/drug effects
  • Mad2 Proteins/antagonists & inhibitors
  • Mutagenesis, Site-Directed
  • Nuclear Proteins/genetics
  • Poly(ADP-ribose) Polymerase Inhibitors/pharmacology
  • RNA Interference
  • RNA, Small Interfering/metabolism
  • Telomere-Binding Proteins/antagonists & inhibitors
  • Trans-Activators/genetics
  • Tumor Suppressor p53-Binding Protein 1/antagonists & inhibitors
  • Ubiquitin-Protein Ligases/antagonists & inhibitors


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