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Mutations in tap uncouple RNA export activity from translocation through the nuclear pore complex
Lyne Lévesque1, Yeou-Cherng Bor, Leah H Matzat
1Department of Cell and Developmental Biology, University of Illinois in Urbana-Champaign, Urbana, IL 61801, USA. levesque@uiuc.edu
Molecular Biology of the Cell
|November 30, 2005
Summary
Transportin-1 (Tap) uses its UBA- and NTF2-like domains to export RNA. These domains are crucial for Tap-RNA complex binding to nucleoporins and efficient nuclear export.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Nuclear pore complexes (NPCs) regulate transport between the nucleus and cytoplasm.
- Transport receptors, like Transportin-1 (Tap), mediate the movement of cargo through NPCs.
- Tap is essential for the nuclear export of cellular messenger RNAs (mRNAs).
Purpose of the Study:
- To investigate the molecular mechanisms by which Tap interacts with nucleoporins.
- To determine the roles of Tap's UBA-like and NTF2-like domains in RNA export and NPC translocation.
- To elucidate the contribution of Nxt1 to Tap-nucleoporin interactions.
Main Methods:
- Site-directed mutagenesis of Tap domains (UBA, NTF2-like, NESs).
- Analysis of Tap-nucleoporin binding affinities using biochemical assays.
- Assessment of RNA export efficiency and NPC shuttling in vivo.
- Investigating the role of Nxt1 in mediating Tap-nucleoporin interactions.
Main Results:
- Mutations in the Tap-UBA region abrogated binding to Nup98, p62, and RanBP2.
- The NTF2-like domain mutations showed nucleoporin-dependent effects on binding.
- Single mutations reduced RNA export but did not abolish NPC interaction or shuttling.
- Combined mutations in UBA and NTF2-like domains impaired shuttling activity.
Conclusions:
- Tap requires both UBA- and NTF2-like domains for efficient RNA export.
- Tap can translocate through NPCs independently of these domains when not bound to RNA cargo.
- Nxt1 enhances Tap-nucleoporin interactions, playing a role in nuclear export.