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The DEAD-box protein Dbp5p is required to dissociate Mex67p from exported mRNPs at the nuclear rim

Mette K Lund1, Christine Guthrie

  • 1Department of Biochemistry and Biophysics, Genentech Hall, 600 16th Street, San Francisco, California 94143, USA.

Molecular Cell
|November 26, 2005
PubMed

Insights

The DEAD-box ATPase Dbp5p is crucial for mRNA export, ensuring proper rearrangement of mRNA-protein particles (mRNPs). It displaces the Mex67p export receptor, preventing its aberrant accumulation and facilitating efficient nuclear export.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Eukaryotic mRNA export involves complex mRNA-protein particles (mRNPs) translocating through the nuclear pore complex (NPC).
  • This translocation requires extensive structural rearrangements of mRNPs within the NPC.
  • The precise mechanisms governing mRNP remodeling during nuclear export are not fully understood.

Purpose of the Study:

  • To investigate the role of the DEAD-box ATPase Dbp5p in mRNP structural rearrangements during nuclear export.
  • To determine if Dbp5p is essential for the proper displacement of mRNA export factors from mRNPs.

Main Methods:

  • Analysis of dbp5 mutant yeast strains with altered growth phenotypes.
  • Genetic suppression studies involving mutations in Mex67p.
  • Localization studies of mRNA export factors (Mex67p, Yra1p) in wild-type and mutant cells using microscopy.
  • Investigating the effect of nuclear exosome impairment on mRNP accumulation.

Main Results:

  • Mutations in Dbp5p lead to the accumulation of the mRNA export receptor Mex67p on mRNA.
  • This Mex67p accumulation is suppressed by a mex67 mutation, indicating a functional link.
  • In temperature-sensitive dbp5 mutants, Mex67p-bound mRNA accumulates at the nuclear rim, particularly when nuclear exosome function is compromised.
  • Unlike other mRNP accumulation scenarios, Dbp5p-dependent mRNPs are devoid of the nuclear export factor Yra1p.

Conclusions:

  • Dbp5p plays a specific role in displacing Mex67p from mRNPs during nuclear export.
  • This displacement by Dbp5p is essential for terminating the export process.
  • Dbp5p acts as a key regulator of mRNP remodeling, ensuring efficient mRNA translocation through the NPC.

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