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Nuclear-Cytoplasmic Transport

  1. Allison Lange,
  2. Anita H Corbett

Published Online: 15 SEP 2009

DOI: 10.1002/9780470015902.a0001351.pub2



How to Cite

Lange, A. and Corbett, A. H. 2009. Nuclear-Cytoplasmic Transport. eLS. .

Author Information

  1. Emory University School of Medicine, Atlanta, Georgia, USA

Publication History

  1. Published Online: 15 SEP 2009

This is not the most recent version of the article. View current version (16 MAR 2015)


In eukaryotic cells, the genomic deoxyribonucleic acid (DNA) in the nucleus is separated from the translational machinery in the cytoplasm by the nuclear envelope. Transport of macromolecules such as proteins and ribonucleic acid (RNA) across this membrane is essential for cellular function and requires active nuclear–cytoplasmic transport systems. These systems consist of soluble transport receptors, which recognize and bind cargo in one compartment, mediate transport through nuclear pore complexes embedded in the nuclear envelope and deliver cargo in the target compartment. Disruption of this highly regulated process results in abnormal cell function and is linked to human disease etiology. Understanding the contribution of nuclear protein and RNA transport to cellular organization is one of the major challenges in cell biology.

Key Concepts

  • Transport into and out of the nucleus occurs through nuclear pore complexes (NPCs), which are large proteinaceous channels that perforate the nuclear membrane.

  • Proteins destined for import into the nucleus contain a nuclear localization signal (NLS) and proteins destined for export from the nucleus contain a nuclear export signal (NES), each of which targets them for transport.

  • Soluble transport receptors called importins and exportins or karyopherins recognize and bind macromolecular cargos and facilitate transport through the nuclear pore.

  • The asymmetric distribution of RanGDP in the cytoplasm and RanGTP in the nucleus controls the directionality of nuclear transport.

  • Nuclear protein import can be regulated through inter- or intramolecular occlusion of the NLS or NES; posttranslation modification of the targeting signal; compartmental sequestration of the cargo protein or altering properties of the nuclear transport machinery including receptors and nuclear pores.

  • Many classes of RNA are transported via Ran-regulated, karyopherin-dependent pathways.

  • Messenger ribonucleic acid (mRNA) export is highly coupled to mRNA processing and is mediated by distinct receptors.

  • Mutations in nuclear targeting signals and nuclear transport receptors have been linked to several human diseases.


  • nuclear transport;
  • importin;
  • karyopherin;
  • nuclear pore complex;
  • nucleocytoplasmic trafficking