The Bloom syndrome complex senses RPA-coated single-stranded DNA to restart stalled replication forks

Nat Commun. 2021 Jan 26;12(1):585. doi: 10.1038/s41467-020-20818-5.


The Bloom syndrome helicase BLM interacts with topoisomerase IIIα (TOP3A), RMI1 and RMI2 to form the BTR complex, which dissolves double Holliday junctions to produce non-crossover homologous recombination (HR) products. BLM also promotes DNA-end resection, restart of stalled replication forks, and processing of ultra-fine DNA bridges in mitosis. How these activities of the BTR complex are regulated in cells is still unclear. Here, we identify multiple conserved motifs within the BTR complex that interact cooperatively with the single-stranded DNA (ssDNA)-binding protein RPA. Furthermore, we demonstrate that RPA-binding is required for stable BLM recruitment to sites of DNA replication stress and for fork restart, but not for its roles in HR or mitosis. Our findings suggest a model in which the BTR complex contains the intrinsic ability to sense levels of RPA-ssDNA at replication forks, which controls BLM recruitment and activation in response to replication stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs / genetics
  • Bloom Syndrome / genetics*
  • CRISPR-Cas Systems / genetics
  • DNA Damage
  • DNA Replication*
  • DNA Topoisomerases, Type I / metabolism
  • DNA, Single-Stranded / genetics
  • DNA, Single-Stranded / metabolism*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Gene Knockdown Techniques
  • HeLa Cells
  • Humans
  • Mitosis / genetics
  • Mutation
  • Protein Binding / genetics
  • Protein Domains / genetics
  • RecQ Helicases / genetics
  • RecQ Helicases / metabolism*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Recombinational DNA Repair / genetics
  • Replication Protein A / metabolism*


  • DNA, Single-Stranded
  • DNA-Binding Proteins
  • RMI1 protein, human
  • RMI2 protein, human
  • Recombinant Proteins
  • Replication Protein A
  • Bloom syndrome protein
  • RecQ Helicases
  • TOP3A protein, human
  • DNA Topoisomerases, Type I