The Clk/Sty protein kinase phosphorylates SR splicing factors and regulates their intranuclear distribution.
Mammalian Clk/Sty is the prototype for a family of dual specificity kinases (termed LAMMER kinases) that have been conserved in evolution, but whose physiological substrates are unknown. In a yeast two-hybrid screen, the Clk/Sty kinase specifically interacted with RNA binding proteins, particularly members of the serine/arginine-rich (SR) family of splicing factors. Clk/Sty itself has an serine/arginine-rich non-catalytic N-terminal region which is important for its association with SR splicing factors. In vitro, Clk/Sty efficiently phosphorylated the SR family member ASF/SF2 on serine residues located within its serine/arginine-rich region (the RS domain). Tryptic phosphopeptide mapping demonstrated that the sites on ASF/SF2 phosphorylated in vitro overlap with those phosphorylated in vivo. Immunofluorescence studies showed that a catalytically inactive form of Clk/Sty co-localized with SR proteins in nuclear speckles. Overexpression of the active Clk/Sty kinase caused a redistribution of SR proteins within the nucleus. These results suggest that Clk/Sty kinase directly regulates the activity and compartmentalization of SR splicing factors.
Colwill
K
K
Programme in Molecular Biology adn Cancer, Mount Sinai Hospital, Toronto, Canada.
Pawson
T
T
Andrews
B
B
Prasad
J
J
Manley
J L
JL
Bell
J C
JC
Duncan
P I
PI
D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine; D005075:Biological Evolution; D017173:Caenorhabditis elegans; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D017124:Conserved Sequence; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine; D013379:Substrate Specificity; D014162:Transfection
D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D012694:Serine; D001120:Arginine; C066780:Clk dual-specificity kinases; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases