title: Interplay between SRPK and Clk/Sty kinases in phosphorylation of the splicing factor ASF/SF2 is regulated by a docking motif in ASF/SF2.
abstract: The arginine-serine (RS)-rich domain of the SR protein ASF/SF2 is phosphorylated by SR protein kinases (SRPKs) and Clk/Sty kinases. However, the mode of phosphorylation by these kinases and their coordination in the biological regulation of ASF/SF2 is unknown. Here, we report the crystal structure of an active fragment of human SRPK1 bound to a peptide derived from an SR protein. This structure led us to identify a docking motif in ASF/SF2. We find that this docking motif restricts phosphorylation of ASF/SF2 by SRPK1 to the N-terminal part of the RS domain - a property essential for its assembly into nuclear speckles. We further show that Clk/Sty causes release of ASF/SF2 from speckles by phosphorylating the C-terminal part of its RS domain. These results suggest that the docking motif of ASF/SF2 is a key regulatory element for sequential phosphorylation by SRPK1 and Clk/Sty and, thus, is essential for its subcellular localization.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
authors.forename: Jacky Chi Ki
authors.initials: JC
authors.lastname: Ngo
authors.forename: Sutapa
authors.initials: S
authors.lastname: Chakrabarti
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Ding
authors.forename: Adolfo
authors.initials: A
authors.lastname: Velazquez-Dones
authors.forename: Brad
authors.initials: B
authors.lastname: Nolen
authors.forename: Brandon E
authors.initials: BE
authors.lastname: Aubol
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Adams
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Fu
authors.forename: Gourisankar
authors.initials: G
authors.lastname: Ghosh
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D018360:Crystallography, X-Ray / Q000379:methods; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000378:metabolism; D012326:RNA Splicing / Q000502:physiology; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors
chemical_list: D009687:Nuclear Proteins; D010455:Peptides; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors; C066780:Clk dual-specificity kinases; C087728:SRPK1 protein, human; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases