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The MRN complex and topoisomerase IIIa-RMI1/2 synchronize DNA resection motor proteins

Michael M Soniat1, Giaochau Nguyen1, Hung-Che Kuo1

  • 1Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, USA; Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas, USA.

The Journal of Biological Chemistry
|December 18, 2022
PubMed

Insights

The MRE11-RAD50-NBS1 (MRN) complex and TOP3A-RMI1/2 protein complex help the Bloom syndrome helicase (BLM) and DNA2 enzymes efficiently process broken DNA ends during homologous recombination repair.

Area of Science:

  • Molecular Biology
  • DNA Repair Mechanisms
  • Chromosomal Stability

Background:

  • Homologous recombination (HR) is a crucial DNA repair pathway for maintaining genomic integrity.
  • DNA resection, the initial step in HR, involves processing broken DNA ends by a multi-protein complex called the resectosome.
  • The precise roles of individual proteins within the resectosome, particularly the MRE11-RAD50-NBS1 (MRN) complex and TOP3A-RMI1/2, in regulating DNA resection remain poorly understood.

Purpose of the Study:

  • To elucidate the functional interplay between the MRN complex, TOP3A-RMI1/2, Bloom syndrome helicase (BLM), and DNA2 during long-range DNA resection.
  • To provide direct, single-molecule insights into the regulation of DNA resection by these key protein factors.

Main Methods:

  • Single-molecule imaging techniques were employed to visualize and analyze the dynamics of DNA resection.
  • Characterization of the roles of the MRN complex and TOP3A-RMI1/2 in conjunction with BLM and DNA2 during DNA end processing.

Main Results:

  • The TOP3A-RMI1/2 complex collaborates with BLM to form the BTRR (BLM-TOP3A-RMI1/2) complex, aiding in DNA unwinding initiation.
  • Both TOP3A-RMI1/2 and the MRN complex stimulate DNA2-mediated resection.
  • The MRN complex enhances BTRR binding to DNA and synchronizes the translocation of BLM and DNA2, preventing BLM pausing and ensuring efficient resection.

Conclusions:

  • The MRN complex and TOP3A-RMI1/2 are essential regulators that harness the BTRR complex for efficient DNA resection.
  • TOP3A-RMI1/2 modulates BLM helicase activity, contributing to effective DNA repair and genomic stability.
Keywords:
BLMDNA curtainsDNA resectionDNA2double-strand breaksingle molecule

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