This domain is a region of 70 residues conserved in proteins from plants to humans and contains a serine/arginine rich motif. In rats the full protein is a casein kinase substrate, and this region contains phosphorylation sites for both cAMP-dependent protein kinase and casein kinase II [1].

1: Molecular cloning and characterization of a novel casein kinase II substrate, HASPP28, from rat brain. Shen L, Huang KP, Chen HC, Huang FL; Arch Biochem Biophys. 1996;327:131-141. PMID:8615683