Release of SR Proteins from CLK1 by SRPK1: A Symbiotic Kinase System for Phosphorylation Control of Pre-mRNA Splicing.Phosphorylation has been generally thought to activate the SR family of splicing factors for efficient splice-site recognition, but this idea is incompatible with an early observation that overexpression of an SR protein kinase, such as the CDC2-like kinase 1 (CLK1), weakens splice-site selection.  Interestingly, CLK1 overcomes this dilemma through a symbiotic relationship with the serine-arginine protein kinase 1 (SRPK1).  We show that SRPK1 interacts with an RS-like domain in the N terminus of CLK1 to facilitate the release of phosphorylated SR proteins, which then promotes efficient splice-site recognition and subsequent spliceosome assembly. 
SRPK1
Release of SR Proteins from CLK1 by SRPK1: A Symbiotic Kinase System for Phosphorylation Control of Pre-mRNA Splicing.Phosphorylation has been generally thought to activate the SR family of splicing factors for efficient splice-site recognition, but this idea is incompatible with an early observation that overexpression of an SR protein kinase, such as the CDC2-like kinase 1 (CLK1), weakens splice-site selection.  Here, we report that CLK1 binds SR proteins but lacks the mechanism to release phosphorylated SR proteins, thus functionally inactivating the splicing factors.  Interestingly, CLK1 overcomes this dilemma through a symbiotic relationship with the serine-arginine protein kinase 1 (SRPK1).  We show that SRPK1 interacts with an RS-like domain in the N terminus of CLK1 to facilitate the release of phosphorylated SR proteins, which then promotes efficient splice-site recognition and subsequent spliceosome assembly. 
CLK1