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Nucleocytoplasmic shuttling of heterodimeric splicing factor U2AF
M Gama-Carvalho1, M P Carvalho, A Kehlenbach
1Institute of Histology and Embryology, Faculty of Medicine, University of Lisbon, 1649-028 Lisbon, Portugal. m.gamacarvalho@fm.ul.pt
The Journal of Biological Chemistry
|December 29, 2000
Summary
The U2 small nuclear ribonucleoprotein auxiliary factor (U2AF) shuttles between the nucleus and cytoplasm. Its arginine/serine-rich (RS) domains are key for this localization and regulate splicing factor availability.
Area of Science:
- Molecular Biology
- RNA Biology
- Cell Biology
Background:
- U2AF is a heterodimeric splicing factor essential for pre-mRNA splicing.
- U2AF consists of 65-kDa (U2AF(65)) and 35-kDa (U2AF(35)) subunits.
- Both subunits contain arginine/serine-rich (RS) domains involved in splicing regulation.
Purpose of the Study:
- To determine the role of RS domains in the subcellular localization of U2AF.
- To investigate the mechanism of U2AF nucleocytoplasmic shuttling.
- To understand how RS domains influence U2AF's role in spliceosome assembly.
Main Methods:
- Studied the subcellular localization of U2AF(65) and U2AF(35) subunits.
- Investigated the role of RS domains in protein localization.
- Examined the nucleocytoplasmic transport mechanism of U2AF.
Main Results:
- U2AF(65) and U2AF(35) continuously shuttle between the nucleus and cytoplasm.
- The RS domain on either U2AF subunit functions as a nuclear localization signal.
- RS domains are sufficient to target heterologous proteins to nuclear speckles and trigger U2AF complex import.
Conclusions:
- RS domains are critical for U2AF's nucleocytoplasmic shuttling.
- U2AF shuttling may regulate spliceosome assembly by controlling factor availability.
- This shuttling mechanism contributes to the regulation of pre-mRNA splicing.