Involved in pre-mRNA splicing as a component of the spliceosome (PubMed:9724750, PubMed:19592703, PubMed:28781166). May play a role in cross-intron bridging of U1 and U2 snRNPs in the mammalian A complex (PubMed:9724750). Component of the spliceosome B complex (PubMed:9724750, PubMed:28781166). Associated with U2 snRNPs (PubMed:9724750, PubMed:28781166). Binds splicing factors SNRPB, SNRPC and SF1 (PubMed:9724750). Interacts via the WW domains with the Pro-rich domains of KHDRBS1/SAM68 (By similarity). Interacts via the WW domains with the Pro-rich domains of WBP11 (PubMed:19592703). The WW domain recognizes the proline, glycine and methionine-rich (PGM) motif present in the splicing factors, as well as the Arg/Gly-rich-flanked Pro-rich domains found in several WW domain-binding proteins.