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RNF4-dependent hybrid SUMO-ubiquitin chains are signals for RAP80 and thereby mediate the recruitment of BRCA1 to sites of DNA damage.

The DNA repair function of the breast cancer susceptibility protein BRCA1 depends in part on its interaction with RAP80, which targets BRCA1 to DNA double-strand breaks (DSBs) through recognition of K63-linked polyubiquitin chains. The localization of BRCA1 to DSBs also requires sumoylation. We demonstrated that, in addition to having ubiquitin-interacting motifs, RAP80 also contains a SUMO-interacting motif (SIM) that is critical for recruitment to DSBs. In combination with the ubiquitin-binding activity of RAP80, this SIM enabled RAP80 to bind with nanomolar affinity to hybrid chains consisting of ubiquitin conjugated to SUMO. Furthermore, RNF4, a SUMO-targeted ubiquitin E3 ligase that synthesizes hybrid SUMO-ubiquitin chains, localized to DSBs and was critical for the recruitment of RAP80 and BRCA1 to sites of DNA damage. Our findings, therefore, connect ubiquitin- and SUMO-dependent DSB recognition, revealing that RNF4-synthesized hybrid SUMO-ubiquitin chains are recognized by RAP80 to promote BRCA1 recruitment and DNA repair.

Pubmed ID: 23211528


  • Guzzo CM
  • Berndsen CE
  • Zhu J
  • Gupta V
  • Datta A
  • Greenberg RA
  • Wolberger C
  • Matunis MJ


Science signaling

Publication Data

December 4, 2012

Associated Grants

  • Agency: NIGMS NIH HHS, Id: R01 GM060980
  • Agency: NIGMS NIH HHS, Id: U54 GM103520

Mesh Terms

  • Amino Acid Motifs
  • BRCA1 Protein
  • Carrier Proteins
  • Cell Line, Tumor
  • DNA Breaks, Double-Stranded
  • DNA Repair
  • Humans
  • Nuclear Proteins
  • SUMO-1 Protein
  • Sumoylation
  • Transcription Factors
  • Ubiquitin-Protein Ligases
  • Ubiquitins