Enables RS domain binding activity and transcription coactivator activity. Acts upstream of or within regulation of transcription by RNA polymerase II. Predicted to be located in centriolar satellite and nuclear speck. Predicted to be part of protein-containing complex. Is expressed in several structures, including central nervous system; limb; olfactory epithelium; retina; and thymus. Orthologous to human RBM39 (RNA binding motif protein 39). [provided by Alliance of Genome Resources, Apr 2022]