The Cellular Localization of the Murine Serine/Arginine-rich Protein Kinase CLK2 Is Regulated by Serine 141 Autophosphorylation*
- From the Max Planck Institute for ‡Biochemistry and¶Neurobiology, Am Klopferspitz 18A, D-82152 Martinsried, Germany
Abstract
Pre-mRNA splicing is catalyzed by a multitude of proteins including serine/arginine-rich (SR) proteins, which are thought to play a crucial role in the formation of spliceosomes and in the regulation of alternative splicing. SR proteins are highly phosphorylated, and their kinases are believed to regulate the recruitment of SR proteins from nuclear storage compartments known as speckles. Recently, a family of autophosphorylating kinases termed CLK (CDC2/CDC28-like kinases) was shown to phosphorylate SR proteins and to influence alternative splicing in overexpression systems. Here we used endogenous CLK2 protein to demonstrate that it displays different biochemical characteristics compared with its overexpressed protein and that it is differentially phosphorylated in vivo. Furthermore, CLK2 changed its nuclear localization upon treatment with the kinase inhibitor 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole. We have also identified a CLK2 autophosphorylation site, which is highly conserved among all CLK proteins, and we show by site-directed mutagenesis that its phosphorylation influences the subnuclear localization of CLK2. Our data suggest that CLK2 localization and possibly activity are influenced by a balance of CLK2 autophosphorylation and the regulation by CLK2 kinases and phosphatases.
Footnotes
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↵* This work was supported by a grant from the Schweizerischer Nationalfonds (to O. N.), the Max-Planck Society, and Sugen Inc.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵§ To whom correspondence should be addressed. Tel.: 49-89-8578-2523; Fax: 49-89-8578-3777; E-mail: nayler{at}biochem.mpg.de.
- Abbreviations:
- SR
-
serine/arginine-rich
- F-MEL
-
Friend murine erythroleukemic
- DRB
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5,6-dichloro-1-β-ribofuranosylbenzimidazole
- RIPA
-
radioimmune precipitation assay
- GST
-
glutathione S-transferase
- GFP
-
green fluorescent protein.
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- Received August 19, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
