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An elevated level of the mRNA exporter Mex67-Mtr2 in nuclear mRNPs impairs nuclear mRNA export

Nataliia Stefanyshena1, Katja Sträßer1,2

  • 1Institute of Biochemistry, FB08, Justus Liebig University Giessen, Heinrich-Buff-Ring 17, 35392 Giessen, Germany.

Nucleic Acids Research
|January 23, 2026
PubMed

Insights

Excessive Mex67 in nuclear messenger ribonucleoprotein particles (mRNPs) hinders mRNA export. Suppressing export defects by overexpressing adaptors Nab2 or Yra1 normalizes Mex67 levels, revealing precise Mex67 regulation is key for efficient gene expression.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Genetics

Background:

  • Nuclear mRNA export is vital for gene expression in eukaryotes.
  • The Mex67-Mtr2 complex (NXF1-NXT1 in humans) mediates this export.
  • Adaptor proteins like Hpr1, Nab2, Yra1, and Npl3 are involved but their roles are not fully understood.

Purpose of the Study:

  • To investigate the role of adaptor proteins in mRNA export.
  • To determine the effect of Mex67 levels within nuclear mRNPs on export efficiency.
  • To elucidate the relationship between Hpr1 function and Mex67 regulation.

Main Methods:

  • Analysis of nuclear messenger ribonucleoprotein particles (mRNPs) in Saccharomyces cerevisiae.
  • Genetic manipulation including gene deletion (Δhpr1) and overexpression of adaptor proteins (Nab2, Yra1).
  • Quantification of Mex67 levels within nuclear mRNPs.

Main Results:

  • Cells lacking Hpr1 exhibit impaired nuclear mRNA export with elevated levels of Nab2, Yra1, and Mex67 in nuclear mRNPs.
  • Overexpression of Nab2 or Yra1 in Δhpr1 cells rescues the export defect and reduces Mex67 levels in nuclear mRNPs.
  • Elevated Mex67 in nuclear mRNPs precedes and likely causes the export defect, not the other way around.

Conclusions:

  • Precise regulation of Mex67-Mtr2 levels within nuclear mRNPs is essential for efficient nuclear mRNA export.
  • Hpr1 plays a critical role in regulating Mex67 levels, indirectly impacting export.
  • Aberrant Mex67 accumulation in mRNPs disrupts the mRNA export pathway.

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