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A bipolar spindle of antiparallel ParM filaments drives bacterial plasmid segregation

P Gayathri1, T Fujii, J Møller-Jensen

  • 1Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK.

Science (New York, N.Y.)
|November 1, 2012
PubMed

Insights

Bacterial plasmids use protein filaments to segregate DNA during cell division. Researchers found these filaments grow at one end, forming bipolar spindles that push plasmids to opposite cell poles.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Cell Biology

Background:

  • Bacterial low-copy-number plasmids require DNA segregating machines for stable inheritance.
  • The ParMRC system in Escherichia coli R1 plasmid utilizes ParM protein filaments to separate sister plasmids.

Purpose of the Study:

  • To elucidate the mechanism of ParM filament assembly and its role in plasmid segregation.
  • To understand how ParM filaments interact with ParRC complexes to form a functional segregating machine.

Main Methods:

  • Structural analysis of the ParMRC system.
  • Total internal reflection fluorescence microscopy to observe ParM filament dynamics.

Main Results:

  • ParRC binding accelerates growth at one end of polar ParM filaments, similar to eukaryotic formins.
  • ParM filaments form antiparallel associations, creating bipolar spindles.
  • Spindle elongation, driven by filament bundles, segregates plasmid clusters to opposite poles.

Conclusions:

  • The ParM filament system acts as a dynamic spindle for bacterial plasmid segregation.
  • The mechanism of directed filament growth and antiparallel assembly is crucial for efficient DNA segregation.

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