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Analysis of mRNA Nuclear Export Kinetics in Mammalian Cells by Microinjection
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Exportin 6: a novel nuclear export receptor that is specific for profilin.actin complexes
Theis Stüven1, Enno Hartmann, Dirk Görlich
1ZMBH, INF 282, D-69120 Heidelberg and Universität Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany.
The EMBO Journal
|November 1, 2003
Summary
Exportin 6 (Exp6) facilitates nuclear export of actin, a process crucial for cell function. Profilin acts as a cofactor, enhancing this export and suppressing nuclear actin polymerization.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Nuclear transport is essential for eukaryotic cell function.
- Importin beta-superfamily proteins mediate most nucleocytoplasmic transport.
- Actin dynamics are critical for cellular processes, but nuclear roles are less understood.
Purpose of the Study:
- To identify novel transport receptors involved in nuclear actin export.
- To elucidate the role of exportin 6 (Exp6) in regulating nuclear actin.
- To investigate the function of profilin in actin nuclear export.
Main Methods:
- Identification of novel transport receptors.
- Biochemical assays to study protein interactions.
- RNA interference (RNAi) in Drosophila to assess Exp6 function.
- Confocal microscopy to observe actin localization.
Main Results:
- Exportin 6 (Exp6) identified as a novel nuclear export receptor.
- Exp6 mediates the export of profilin-actin complexes from the nucleus.
- Profilin enhances Exp6 binding to actin and suppresses nuclear actin polymerization.
- Exp6 function in profilin-actin export is conserved between humans and Drosophila.
- Drosophila Exp6 knockdown leads to nuclear actin accumulation and paracrystal formation.
- CRM1 does not appear to play a major role in mammalian or insect actin export.
Conclusions:
- Exportin 6 is a key regulator of nuclear actin export.
- Profilin acts as both a nucleotide exchange factor and an export cofactor for actin.
- Exp6-mediated export prevents aberrant nuclear actin polymerization.
- This pathway is conserved across higher eukaryotes and is distinct from CRM1-mediated export.
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