SRPKs is a critical enzyme family that regulates splicing activity in the cell. The first serine-arginine (SR) protein kinase identified is SRPK1, which is isolated from mitotic cells, and it is described to phosphorylate SR proteins and to promote their release from nuclear speckles during the G2/M phase of the cell cycle. SRPK1 is the prototype of the SRPK family, which also includes the two homologous SRPK2 and SRPK3 proteins. SRPKs are characterized by a bipartite catalytic domain separated by a unique spacer sequence and are mainly localized in the cytoplasm of mammalian cells.

SRPKs can translocate into the nucleus of cells under several conditions, such as during the G2/M phase of the cell cycle, or after osmotic stress, or as a consequence of activation of the epidermal growth factor (EGF) signal transduction pathway.