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The enzymatic activity of SR protein kinases 1 and 1a is negatively affected by interaction with scaffold attachment factors B1 and 2
Author(s) -
Tsianou Dora,
Nikolakaki Eleni,
Tzitzira Alexandra,
Bonanou Sofia,
Giannakouros Thomas,
Georgatsou Eleni
Publication year - 2009
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2009.07217.x
Subject(s) - kinase , phosphorylation , biochemistry , scaffold protein , microbiology and biotechnology , nuclear protein , protein kinase a , chemistry , biology , signal transduction , transcription factor , gene
SR protein kinases (SRPKs) phosphorylate Ser/Arg dipeptide‐containing proteins that play crucial roles in a broad spectrum of basic cellular processes. Phosphorylation by SRPKs constitutes a major way of regulating such cellular mechanisms. In the past, we have shown that SRPK1a interacts with the nuclear matrix protein scaffold attachment factor B1 (SAFB1) via its unique N‐terminal domain, which differentiates it from SRPK1. In this study, we show that SAFB1 inhibits the activity of both SRPK1a and SRPK1 in vitro and that its RE‐rich region is redundant for the observed inhibition. We demonstrate that kinase activity inhibition is caused by direct binding of SAFB1 to SRPK1a and SRPK1, and we also present evidence for the in vitro binding of SAFB2 to the two kinases, albeit with different affinity. Moreover, we show that both SR protein kinases can form complexes with both scaffold attachment factors B in living cells and that this interaction is capable of inhibiting their activity, depending on the tenacity of the complex formed. Finally, we present data demonstrating that SRPK/SAFB complexes are present in the nucleus of HeLa cells and that the enzymatic activity of the nuclear matrix‐localized SRPK1 is repressed. These results suggest a new role for SAFB proteins as regulators of SRPK activity and underline the importance of the assembly of transient intranuclear complexes in cellular regulation. Structured digital abstract• MINT‐7228149 : SRPK1 (uniprotkb: Q96SB4‐2 ) phosphorylates ( MI:0217 ) Nt‐LBR (uniprotkb: Q14739 ) by protein kinase assay ( MI:0424 ) • MINT‐7228207 : SRPK1 (uniprotkb: Q96SB4‐2 ) physically interacts ( MI:0915 ) with SAFB1C (uniprotkb: Q15424 ) by pull down ( MI:0096 ) • MINT‐7228438 : SRPK1a (uniprotkb: Q96SB4‐3 ) physically interacts ( MI:0915 ) with SAFB1C (uniprotkb: Q15424 ) by pull down ( MI:0096 ) • MINT‐7228306 : SRPK1 (uniprotkb: Q14151 ) physically interacts ( MI:0915 ) with SAFB2C (uniprotkb: Q14151 ) by pull down ( MI:0096 ) • MINT‐7228452 : SRPK1a (uniprotkb: Q96SB4‐3 ) physically interacts ( MI:0915 ) with SAFB2C (uniprotkb: Q14151 ) by pull down ( MI:0096 ) • MINT‐7228466 : SRPK1 (uniprotkb: Q96SB4‐2 ) physically interacts ( MI:0915 ) with SAFB1 (uniprotkb: Q15424 ) by anti tag coimmunoprecipitation ( MI:0007 ) • MINT‐7228500 : SRPK1a (uniprotkb: Q96SB4‐3 ) physically interacts ( MI:0915 ) with SAFB1 (uniprotkb: Q15424 ) by anti tag coimmunoprecipitation ( MI:0007 ) • MINT‐7228483 : SRPK1 (uniprotkb: Q14151 ) physically interacts ( MI:0915 ) with SAFB2 (uniprotkb: Q14151 ) by anti tag coimmunoprecipitation ( MI:0007 )