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Processive DNA helicase activity of the minichromosome maintenance proteins 4, 6, and 7 complex requires forked DNA

J K Lee1, J Hurwitz

  • 1Graduate Program in Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.

Proceedings of the National Academy of Sciences of the United States of America
|January 3, 2001
PubMed

Insights

The minichromosome maintenance (Mcm) complex requires specific DNA structures for processive helicase activity. This finding supports the Mcm4/6/7 complex

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Cell Biology

Background:

  • Minichromosome maintenance (Mcm) proteins 2-7 are crucial for DNA replication initiation and elongation.
  • The Mcm 4, 6, and 7 complex exhibits limited-processivity 3' to 5' DNA helicase activity.

Purpose of the Study:

  • To investigate the requirements for processive helicase activity of the Mcm complex.
  • To elucidate the role of DNA substrate structure in Mcm complex function.

Main Methods:

  • DNA helicase assays using substrates with single-stranded tails.
  • Analysis of Mcm complex formation on DNA substrates.
  • Characterization of unwinding activity in the presence of single-strand DNA binding protein.

Main Results:

  • Processive Mcm helicase activity requires both 5' and 3' single-stranded DNA tails on the substrate.
  • The presence of both tails promotes the formation of double heterohexameric Mcm4/6/7 complexes.
  • These double complexes, with single-strand DNA binding protein, unwind approximately 600 bp of duplex DNA.

Conclusions:

  • The Mcm4/6/7 complex's processive helicase activity is dependent on specific substrate configurations.
  • Formation of double heterohexameric complexes is essential for efficient DNA unwinding.
  • These findings support the model of Mcm4/6/7 acting as a DNA replication helicase.

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