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Analysis of mRNA Nuclear Export Kinetics in Mammalian Cells by Microinjection
11:32

Analysis of mRNA Nuclear Export Kinetics in Mammalian Cells by Microinjection

Published on: December 4, 2010

A Crm1p-independent nuclear export path for the mRNA-associated protein, Npl3p/Mtr13p

Y Liu1, W Guo, P Y Tartakoff

  • 1Pathology Department and Cell Biology Program, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.

Proceedings of the National Academy of Sciences of the United States of America
|June 9, 1999
PubMed

Insights

The study reveals that the protein Npl3p/Mtr13p utilizes a distinct pathway for mRNA export, separate from the Crm1p pathway, involving specific nuclear export and import factors.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Genetics

Background:

  • mRNA export is crucial for gene expression, involving protein association, nuclear pore complex translocation, and cytoplasmic reimport.
  • Understanding the specific RNA carriers and transport steps affected by yeast mutants is limited.
  • Npl3p/Mtr13p is a nucleocytoplasmic shuttling protein that binds poly(A)+ RNA.

Purpose of the Study:

  • To investigate the specific proteins and pathways involved in the mRNA export mediated by Npl3p/Mtr13p.
  • To determine if Npl3p/Mtr13p export utilizes the Crm1p-dependent pathway or a distinct mechanism.
  • To identify factors required for both Npl3p export and reimport.

Main Methods:

  • Utilized yeast genetics and in vivo assays to study Npl3p/Mtr13p nucleocytoplasmic transport.
  • Investigated the role of proteins with leucine-rich nuclear export signals (e.g., Gle1p, Mex67p) in Npl3p export.
  • Examined the requirement of import factors, such as Srp1p, for Npl3p export.
  • Analyzed the effect of specific mutants (e.g., crm1, importin beta superfamily members) on Npl3p transport.

Main Results:

  • Npl3p/Mtr13p export is independent of the Crm1p pathway, which typically exports proteins with leucine-rich nuclear export signals and mRNAs.
  • Npl3p/Mtr13p export requires Gle1p, Mex67p, and a non-nuclear pool of the importin alpha homologue, Srp1p.
  • Changes in Npl3p methylation status do not correlate with its nucleocytoplasmic distribution.
  • Specific importin beta superfamily mutants inhibit Npl3p reimport from the cytoplasm.

Conclusions:

  • Npl3p/Mtr13p export utilizes a subset of proteins involved in mRNA export, suggesting the existence of multiple mRNA export pathways.
  • Npl3p/Mtr13p export and reimport involve distinct sets of proteins and pathways.
  • The findings provide new insights into the complexity of mRNA export and nucleocytoplasmic transport mechanisms in yeast.

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