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Fission yeast myosin-II isoforms assemble into contractile rings at distinct times during mitosis

M Bezanilla1, J M Wilson, T D Pollard

  • 1Structural Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.

Current Biology : CB
|February 7, 2001
PubMed

Insights

Schizosaccharomyces pombe has two distinct myosin-II proteins, Myo2p and Myp2p, crucial for cell division. Myo2p initiates ring formation early, while Myp2p enhances cytokinesis later in the cell cycle.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Myosin-II is essential for cytokinesis in Schizosaccharomyces pombe.
  • Unlike other organisms, S. pombe possesses two distinct myosin-IIs: Myo2p and Myp2p, with differential requirements.
  • Myo2p disruption is lethal, while Myp2p disruption causes defects under nutrient limitation and cold sensitivity.

Purpose of the Study:

  • To visualize and characterize the three-dimensional structure and dynamics of myosin-II rings during S. pombe cytokinesis.
  • To determine the temporal assembly and roles of Myo2p and Myp2p in the contractile ring formation and function.

Main Methods:

  • Deconvolution microscopy for 3D reconstruction of GFP-myosin-II.
  • Time-lapse microscopy with GFP-tubulin as a cell cycle marker to observe ring dynamics.
  • Analysis of ring assembly and contraction in live fission yeast cells.

Main Results:

  • Detailed 3D images of GFP-myosin-II rings were obtained for the first time.
  • Myo2p ring assembly was observed during metaphase/anaphase A.
  • Myp2p ring assembly occurs significantly later, at the end of anaphase B.

Conclusions:

  • Myo2p plays an initiating role in the formation of the contractile ring.
  • Myp2p contributes to the efficiency of cytokinesis by acting later in the cell cycle.
  • The distinct temporal roles of Myo2p and Myp2p highlight a complex regulation of cytokinesis in S. pombe.

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