The molecular function of Ase1p: evidence for a MAP-dependent midzone-specific spindle matrix. Microtubule-associated

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Scott C Schuyler1, Jenny Y Liu, David Pellman

  • 1Department of Pediatric Oncology, The Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.

The Journal of Cell Biology
|February 20, 2003
PubMed

Insights

Budding yeast Ase1p, a microtubule-associated protein (MAP), functions as a cross-bridge in the spindle midzone. Loss of Ase1p causes premature spindle disassembly, while its overexpression promotes spindle elongation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • The mitotic spindle midzone is crucial for maintaining spindle structure and function during cell division.
  • Microtubule (MT) motor proteins are known contributors to midzone function, but the roles of microtubule-associated proteins (MAPs) are less understood.

Purpose of the Study:

  • To investigate the role of Ase1p, a conserved midzone-specific MAP, in budding yeast spindle organization and function.
  • To elucidate the molecular mechanisms by which Ase1p contributes to spindle midzone integrity and dynamics.

Main Methods:

  • Biochemical assays including size exclusion chromatography and velocity sedimentation to characterize Ase1p.
  • In vitro microtubule binding and bundling assays.
  • Live cell microscopy and Fluorescence Recovery After Photobleaching (FRAP) to analyze Ase1p dynamics in vivo.

Main Results:

  • Ase1p exists as a homodimer and binds/bundles microtubules in vitro.
  • Loss of Ase1p leads to premature spindle disassembly during mid-anaphase.
  • Overexpression of Ase1p induces spindle elongation even in S phase-arrested cells.
  • Ase1p exhibits slow turnover and limited lateral diffusion within the spindle midzone.

Conclusions:

  • Ase1p acts as a microtubule cross-bridge, conferring matrix-like properties to the spindle midzone.
  • Networks of midzone MAPs, including Ase1p, may form the basis of a postulated spindle matrix, essential for spindle stability and elongation.

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