title: Phosphorylation-dephosphorylation differentially affects activities of splicing factor ASF/SF2.
abstract: SR proteins are a conserved family of splicing factors that function in both constitutive and activated splicing. We reported previously that phosphorylation of the SR protein ASF/SF2 enhances its interaction with the U1 snRNP-specific 70K protein and is required for the protein to function in splicing, while other studies have provided evidence that subsequent dephosphorylation can also be required for SR protein function, at least in constitutive splicing. We now show that the phosphorylation status of ASF/SF2 can differentially affect several properties of the protein. In keeping with a dynamic cycle of phosphorylation-dephosphorylation during splicing, ASF/SF2 phosphorylation was found to affect interaction with several putative protein targets in different ways: positively, negatively or not at all. Extending these results, we also show that, in contrast to constitutive splicing, dephosphorylation is not required for ASF/SF2 to function as a splicing activator. We discuss these results with respect to the differential protein-protein interactions that must occur during constitutive and activated splicing.
authors.affiliation: Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Xiao
authors.forename: J L
authors.initials: JL
authors.lastname: Manley
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D002457:Cell Extracts; D004268:DNA-Binding Proteins / Q000235:genetics; D004330:Drosophila / Q000378:metabolism; D029721:Drosophila Proteins; D015696:Gene Products, tat / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D019476:Insect Proteins / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D012322:RNA Precursors / Q000235:genetics; D012326:RNA Splicing / Q000235:genetics*; D012367:RNA, Viral / Q000235:genetics; D016601:RNA-Binding Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012261:Ribonucleoproteins / Q000378:metabolism; D000068103:Serine-Arginine Splicing Factors; D000072668:Splicing Factor U2AF
chemical_list: D002457:Cell Extracts; D004268:DNA-Binding Proteins; C070369:DSX protein, Drosophila; D029721:Drosophila Proteins; D015696:Gene Products, tat; D019476:Insect Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012322:RNA Precursors; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins; D000072668:Splicing Factor U2AF; C000607494:U2AF2 protein, human; D000068103:Serine-Arginine Splicing Factors; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate