SF3a120/SAP114 is a 120 kDa subunit of the heterotrimeric splicing factor 3a (SF3A) protein complex. SF3A along with SF3B and a 12S RNA subunit are components of the 17S U2 small nuclear ribonucleoprotein complex (U2 snRNP) involved in pre-mRNA splicing. SF3a120/SAP114 bears two SURP motif repeats and one ubiquitin-like domain. SURP motifs are found among proteins involved in regulated mRNA splicing. The SURP motifs along with the ubiquitin-like domain of SF3a120/SAP114 appear to function in the heterotrimeric formation between the 120, 60 and 66 kDa subunits.