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P446L-importin-beta inhibits nuclear envelope assembly by sequestering nuclear envelope assembly factors to the

László Tirián1, Gyula Timinszky, János Szabad

  • 1The University of Szeged, Faculty of Medicine, Department of Biology, Szeged, Hungary.

European Journal of Cell Biology
|August 20, 2003
PubMed

Insights

The P446L mutant importin-beta inhibits nuclear envelope assembly by binding microtubules, sequestering essential nucleoporins. This mutant protein

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Importin-beta is crucial for nuclear envelope assembly.
  • The P446L mutant importin-beta inhibits nuclear envelope assembly in a dominant-negative manner.
  • Understanding the mechanism of inhibition is key to understanding nuclear envelope formation.

Purpose of the Study:

  • To elucidate the mode of action of the P446L mutant importin-beta in nuclear envelope assembly.
  • To investigate the role of microtubule binding in the inhibitory function of P446L-importin-beta.
  • To identify the specific components sequestered by P446L-importin-beta.

Main Methods:

  • In vitro nuclear envelope assembly assays using Sepharose beads.
  • Analysis of protein-binding interactions with microtubules.
  • Investigation of nucleoporin recruitment during nuclear envelope assembly.

Main Results:

  • P446L-importin-beta inhibits nuclear envelope assembly in extracts.
  • Bead-immobilized P446L-importin-beta efficiently recruits nuclear envelope vesicles, similar to wild-type importin-beta.
  • P446L-importin-beta exhibits increased and RanGTP-resistant microtubule binding.
  • P446L-importin-beta sequesters essential nucleoporins to microtubules, preventing their incorporation into the nuclear envelope.

Conclusions:

  • The inhibitory effect of P446L-importin-beta on nuclear envelope assembly is mediated by its enhanced microtubule binding.
  • Sequestering of nucleoporins to microtubules by P446L-importin-beta disrupts nuclear envelope formation.
  • This study reveals a novel mechanism of dominant-negative inhibition involving microtubule interactions.

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