TAILIEUCHUNG - Báo cáo khoa học: The enzymatic activity of SR protein kinases 1 and 1a is negatively affected by interaction with scaffold attachment factors B1 and 2

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 cellu-lar 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. | ễFEBS Journal The enzymatic activity of SR protein kinases 1 and 1a is negatively affected by interaction with scaffold attachment factors B1 and 2 Dora Tsianou1 Eleni Nikolakaki2 Alexandra Tzitzira1 Sofia Bonanou1 Thomas Giannakouros2 and Eleni Georgatsou1 1 Department of Medicine University of Thessaly Mezourlo 41110 Larissa Greece 2 Department of Chemistry The Aristote University of Thessaloniki Greece Keywords kinase activity inhibition nuclear complex formation SAFB SRPK1 SRPK1a Correspondence E. Georgatsou Laboratory of Biochemistry Department of Medicine Schoolof Health Sciences University of Thessaly Mezourlo 41110 Larissa Greece Fax 30 241 068 5545 Tel 30 241 068 5581 E-mail egeorgat@ Website http Received 24 January 2009 accepted 16 July 2009 doi 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 .

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