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Updated: Jan 28, 2026

Identifying the Effects of BRCA1 Mutations on Homologous Recombination using Cells that Express Endogenous Wild-type BRCA1
08:53

Identifying the Effects of BRCA1 Mutations on Homologous Recombination using Cells that Express Endogenous Wild-type BRCA1

Published on: February 17, 2011

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H4K20me0 recognition by BRCA1-BARD1 directs homologous recombination to sister chromatids

Kyosuke Nakamura1,2, Giulia Saredi1,3, Jordan R Becker4

  • 1Biotech Research and Innovation Centre, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.

Nature Cell Biology
|February 27, 2019
PubMed

Insights

The BRCA1-BARD1 complex monitors genome replication by reading histone marks, ensuring DNA double-strand breaks (DSBs) are repaired correctly via homologous recombination (HR) only when a sister chromatid is available.

Area of Science:

  • Molecular Biology
  • Cell Cycle Regulation
  • DNA Repair Mechanisms

Background:

  • Genotoxic DNA double-strand breaks (DSBs) pose a significant threat to genomic stability.
  • Homologous recombination (HR) is an error-free repair pathway for DSBs, but is restricted to S and G2 cell cycle phases.
  • Breast cancer type 1 susceptibility protein (BRCA1) promotes HR but its cell cycle-specific function is not fully understood.

Purpose of the Study:

  • To elucidate the mechanism limiting BRCA1 function to the S and G2 phases of the cell cycle.
  • To identify how DNA double-strand break repair pathway choice is regulated in a cell cycle-dependent manner.

Main Methods:

  • Investigated the role of histone modifications in recruiting BRCA1 to DSBs.
  • Utilized BARD1 ankyrin repeat domain mutations to assess H4K20me0 recognition.
  • Analyzed the impact of these mutations on DSB repair pathway choice and cell cycle progression.

Main Results:

  • BRCA1 recruitment to DSBs is dependent on the recognition of unmethylated histone H4 at lysine 20 (H4K20me0).
  • BARD1 acts as an H4K20me0 reader, linking BRCA1 function to post-replicative chromatin.
  • Disruption of BARD1-H4K20me0 interaction leads to impaired HR, increased 53BP1 accumulation, and loss of resistance to PARP inhibitors.

Conclusions:

  • BRCA1-BARD1 complex functions as a sensor of the replicative state of the genome.
  • This mechanism ensures that only DSBs occurring in the presence of a sister chromatid are channeled to HR.
  • This finding provides a critical link between cell cycle progression, DNA repair pathway selection, and genomic stability.

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