Has a role in pre-mRNA splicing. Phosphorylates SF2/ASF (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Identified in the spliceosome C complex. Interacts with Clk1 C-terminus (By similarity). Phosphorylated by Clk1. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family.