Involved in pre-mRNA splicing as a component of the spliceosome (PubMed:19592703, PubMed:28781166, PubMed:9724750). May play a role in cross-intron bridging of U1 and U2 snRNPs in the mammalian A complex (PubMed:9724750). {ECO:0000269|PubMed:19592703, ECO:0000269|PubMed:28781166, ECO:0000269|PubMed:9724750}. This is the function of ENSG00000120688 (WBP4, WW domain binding protein 4).