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SR splicing factors serve as adapter proteins for TAP-dependent mRNA export
Yingqun Huang1, Renata Gattoni, James Stévenin
1Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University, New Haven, CT 06536, USA.
Molecular Cell
|April 2, 2003
Summary
Multiple adapter proteins, including serine/arginine-rich (SR) proteins, cooperate with TAP/NXF1 to facilitate efficient mRNA export from the nucleus.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- TAP/NXF1 is the primary receptor for general mRNA export in mammals.
- REF family proteins are the only known mammalian RNA binding adapter proteins that partner with TAP/NXF1.
- The mechanisms by which other adapter proteins might interact with TAP/NXF1 are not fully understood.
Purpose of the Study:
- To investigate the interaction of shuttling SR proteins with TAP/NXF1.
- To determine if SR proteins compete with REF proteins for binding to TAP/NXF1.
- To assess the role of SR proteins in mRNA export mediated by TAP/NXF1.
Main Methods:
- In vitro binding assays using TAP/NXF1 and peptides derived from SR proteins.
- Functional assays in Xenopus oocytes to assess mRNA export.
- Dominant-negative inhibition experiments.
Main Results:
- At least three shuttling SR proteins, including 9G8 and SRp20, interact with the same domain of TAP/NXF1 that binds REFs.
- A peptide from the N-terminus of 9G8 inhibits the binding of both REF and SR proteins to TAP/NXF1 in vitro, suggesting competitive interactions.
- The N-terminus of 9G8 exhibits a dominant-negative effect on mRNA export in Xenopus oocytes, which can be overcome by excess TAP/NXF1.
Conclusions:
- Shuttling SR proteins act as adapter proteins that cooperate with REF proteins to recruit TAP/NXF1 for mRNA export.
- Multiple adapter proteins likely cooperate to recruit multiple copies of TAP/NXF1, ensuring efficient mRNA export.
- SR proteins play a significant role in the general mRNA export pathway.