Activates pre-mRNA splicing. May inhibit PP1 phosphatase activity. Interacts with PPP1CA, PPP1CB and PPP1CC (By similarity). Interacts via the PGR motif with PQBP1 in the nucleus. Interacts with the WW domains of WBP4. Predominantly located in the nucleus with granular heterogeneous distribution. Excluded from nucleoli in interphase cells, distributed throughout cytoplasm in dividing cells. Colocalized with SC35 and U2B in the nucleus. In the cytoplasm, associates with the intermediate filament protein vimentin. Ubiquitous. Highly expressed in the heart, pancreas, kidney skeletal muscle, placenta and brain (at protein level). Weakly expressed in liver and lung. The disease is caused by variants affecting the gene represented in this entry.