Interplay between SRPK and Clk/Sty kinases in phosphorylation of the splicing factor ASF/SF2 is regulated by a docking motif in ASF/SF2.
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.
Ngo
Jacky Chi Ki
JC
Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
Chakrabarti
Sutapa
S
Ding
Jian-Hua
JH
Velazquez-Dones
Adolfo
A
Nolen
Brad
B
Aubol
Brandon E
BE
Adams
Joseph A
JA
Fu
Xiang-Dong
XD
Ghosh
Gourisankar
G
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
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