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Human Mus81-associated endonuclease cleaves Holliday junctions in vitro

X B Chen1, R Melchionna, C M Denis

  • 1Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.

Molecular Cell
|December 14, 2001
PubMed

Insights

Mus81 protein resolves complex DNA structures called Holliday junctions, which form during replication stress. This novel endonuclease activity is crucial for maintaining genome stability when DNA replication is blocked.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • Mus81 protein shares homology with the ERCC1-XPF endonuclease subunit.
  • Mus81 is vital for replicational stress tolerance in yeast.
  • Human Mus81 exhibits endonuclease activity on structure-specific substrates like Holliday junctions.

Purpose of the Study:

  • To investigate the enzymatic activity and function of Mus81.
  • To elucidate the role of Mus81 in resolving DNA replication-associated structures.
  • To characterize the mechanism of Mus81 in resolving Holliday junctions.

Main Methods:

  • Enzyme assays using structure-specific oligonucleotide substrates.
  • Analysis of Mus81 protein abundance under replication-blocking conditions.
  • Biochemical characterization of Mus81 endonuclease activity.

Main Results:

  • Mus81 endonuclease resolves synthetic Holliday junctions into linear duplexes.
  • Cleavage occurs exclusively on strands of like polarity across the Holliday junction.
  • Mus81 protein levels increase upon exposure to replication-blocking agents.
  • Mus81 is evolutionarily distinct from known Holliday junction resolvases.

Conclusions:

  • Mus81 plays a critical role in resolving Holliday junctions that form during replication stress.
  • The enzyme utilizes a novel mechanism for cleaving Holliday junctions.
  • Mus81 is essential for maintaining genome integrity when DNA replication is compromised.

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