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SRPK1 and Clk/Sty protein kinases show distinct substrate specificities for serine/arginine-rich splicing factors - PubMed

  • ️Mon Jan 01 1996

. 1996 Oct 4;271(40):24569-75.

doi: 10.1074/jbc.271.40.24569.

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Free article

SRPK1 and Clk/Sty protein kinases show distinct substrate specificities for serine/arginine-rich splicing factors

K Colwill et al. J Biol Chem. 1996.

Free article

Abstract

Serine/arginine-rich (SR) proteins are essential for pre-mRNA splicing, and modify the choice of splice site during alternative splicing in a process apparently regulated by protein phosphorylation. Two protein kinases have been cloned that can phosphorylate SR proteins in vitro: SRPK1 and Clk/Sty. Here, we show that these two kinases phosphorylate the same SR proteins in vitro, but that SRPK1 has the higher specific activity toward ASF/SF2. SRPK1, like Clk/Sty, phosphorylates ASF/SF2 in vitro on sites that are also phosphorylated in vivo. Tryptic peptide mapping of ASF/SF2 revealed that three of the phosphopeptides from full-length ASF/SF2 phosphorylated in vitro contain consecutive phosphoserine-arginine residues or phosphoserine-proline residues. In vitro, the Clk/Sty kinase phosphorylated Ser-Arg, Ser-Lys, or Ser-Pro sites, whereas SRPK1 had a strong preference for Ser-Arg sites. These results suggest that SRPK1 and Clk/Sty may play different roles in regulating SR splicing factors, and suggest that Clk/Sty has a broader substrate specificity than SRPK1.

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