BRCA1/BARD1 ubiquitinates PCNA in unperturbed conditions to promote continuous DNA synthesis

Nat Commun. 2024 May 20;15(1):4292. doi: 10.1038/s41467-024-48427-6.

Abstract

Deficiencies in the BRCA1 tumor suppressor gene are the main cause of hereditary breast and ovarian cancer. BRCA1 is involved in the Homologous Recombination DNA repair pathway and, together with BARD1, forms a heterodimer with ubiquitin E3 activity. The relevance of the BRCA1/BARD1 ubiquitin E3 activity for tumor suppression and DNA repair remains controversial. Here, we observe that the BRCA1/BARD1 ubiquitin E3 activity is not required for Homologous Recombination or resistance to Olaparib. Using TULIP2 methodology, which enables the direct identification of E3-specific ubiquitination substrates, we identify substrates for BRCA1/BARD1. We find that PCNA is ubiquitinated by BRCA1/BARD1 in unperturbed conditions independently of RAD18. PCNA ubiquitination by BRCA1/BARD1 avoids the formation of ssDNA gaps during DNA replication and promotes continuous DNA synthesis. These results provide additional insight about the importance of BRCA1/BARD1 E3 activity in Homologous Recombination.

MeSH terms

  • BRCA1 Protein* / genetics
  • BRCA1 Protein* / metabolism
  • Cell Line, Tumor
  • DNA / metabolism
  • DNA Replication*
  • Female
  • HEK293 Cells
  • Homologous Recombination
  • Humans
  • Phthalazines* / pharmacology
  • Piperazines* / pharmacology
  • Proliferating Cell Nuclear Antigen* / metabolism
  • Tumor Suppressor Proteins* / genetics
  • Tumor Suppressor Proteins* / metabolism
  • Ubiquitin-Protein Ligases* / genetics
  • Ubiquitin-Protein Ligases* / metabolism
  • Ubiquitination*

Substances

  • BARD1 protein, human
  • BRCA1 protein, human
  • olaparib
  • PCNA protein, human