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CRM1 mediates nuclear-cytoplasmic shuttling of mature microRNAs

Daniela Castanotto1, Robert Lingeman, Arthur D Riggs

  • 1Department of Molecular and Cellular Biology, Beckman Research Institute of the City of Hope, 1450 East Duarte Road, Duarte, CA 91010, USA.

Proceedings of the National Academy of Sciences of the United States of America
|December 4, 2009
PubMed

Insights

MicroRNAs (miRNAs) utilize CRM1 for nuclear export, alongside Exportin 5. Inhibiting CRM1 causes nuclear miRNA accumulation, revealing a shared pathway for small RNAs in chromatin remodeling.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Epigenetics

Background:

  • Drosha-processed microRNAs (miRNAs) are exported from the nucleus to the cytoplasm by Exportin 5 for final maturation.
  • The precise mechanisms governing miRNA nuclear-cytoplasmic shuttling are not fully elucidated.

Purpose of the Study:

  • To investigate the role of CRM1 in the nuclear export of microRNAs.
  • To determine if the nuclear-cytoplasmic transport pathway for small RNAs is shared.

Main Methods:

  • Inhibition of CRM1 using Leptomycin B.
  • Competition assays with synthetic small interfering RNAs (siRNAs).
  • Co-immunoprecipitation assays with CRM1 and associated proteins.

Main Results:

  • CRM1 mediates the nuclear-cytoplasmic shuttling of miRNAs.
  • Leptomycin B treatment leads to the accumulation of miRNA guide sequences in the nucleus.
  • Synthetic siRNAs can compete for this nuclear-to-cytoplasmic transport pathway, indicating it is shared.
  • CRM1 co-immunoprecipitates with Argonautes (Ago-1, Ago-2), Topo2alpha, EzH2, and Mta.

Conclusions:

  • CRM1 is an alternative pathway for miRNA nuclear export.
  • This finding suggests a role for Argonautes and small RNAs in chromatin remodeling through CRM1-mediated transport.

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