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The nucleoporin MEL-28 promotes RanGTP-dependent γ-tubulin recruitment and microtubule nucleation in mitotic spindle

Hideki Yokoyama1, Birgit Koch2, Rudolf Walczak2

  • 11] Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany [2] European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.

Nature Communications
|February 11, 2014
PubMed

Insights

MEL-28 protein binds microtubules during mitosis, independent of its nuclear pore role. This RanGTP-regulated interaction is crucial for microtubule nucleation and spindle assembly after nuclear envelope breakdown.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Mitosis Research

Background:

  • Ran GTPase (RanGTP) drives nuclear envelope and nuclear pore complex (NPC) reassembly post-mitosis.
  • Nucleoporin MEL-28/ELYS binds chromatin and initiates NPC assembly in a RanGTP-dependent manner.

Purpose of the Study:

  • To investigate the role of MEL-28 during mitosis, beyond its function in NPC assembly.
  • To elucidate the RanGTP-regulated interactions of MEL-28 during the cell cycle.

Main Methods:

  • Utilized Xenopus egg extracts for experimental analysis.
  • Investigated protein-microtubule and protein-protein interactions using biochemical assays.
  • Observed protein localization during mitotic events.

Main Results:

  • MEL-28 dissociates from chromatin and binds to spindle microtubules and kinetochores during mitosis.
  • MEL-28 directly binds microtubules in a RanGTP-regulated manner via its C-terminal domain.
  • MEL-28 is essential for RanGTP-dependent microtubule nucleation and spindle assembly by recruiting the γ-tubulin ring complex.

Conclusions:

  • MEL-28 functions as a cell-cycle-regulated target of RanGTP, with distinct roles in interphase and mitosis.
  • MEL-28's binding to chromatin or microtubules dictates its function in NPC assembly versus spindle assembly.
  • The study identifies a novel role for MEL-28 in orchestrating spindle assembly post-mitotic nuclear envelope breakdown.

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