Identification of a plant serine-arginine-rich protein similar to the mammalian splicing factor SF2/ASF.

Abstract
We show that the higher plant Arabidopsis thaliana has a serine-arginine-rich (SR) protein family whose members contain a phosphoepitope shared by the animal SR family of splicing factors, In addition, we report the cloning and characterization of a cDNA encoding a higher-plant SR protein from Arabidopsis, SR1, which has striking sequence and structural homology to the human splicing factor SF2/ASF, Similar to SF2/ASF, the plant SR1 protein promotes splice site switching in mammalian nuclear extracts, A novel feature of the Arabidopsis SR protein is a C-terminal domain containing a high concentration of proline, serine, and lysine residues (PSK domain), a composition reminiscent of histones, This domain includes a putative phosphorylation site for the mitotic kinase cyclin/p34(cdc2).