RNA-binding protein that mediates pre-mRNA alternative splicing regulation. Interacts (via C-terminus) with SRSF1. Interacts (via C-terminus) with SRSF2 (By similarity). Colocalizes with splicing factors SRSF1 and SRSF2 in speckles. Mice show early embryonic lethality shortly after implantation. Belongs to the NSRP1 family.