Involved in pre-mRNA splicing as component of the spliceosome. Is required in the specific splicing of CDKN1A pre-mRNA; the function probably involves the recruitment of U2AF2 to the mRNA. Is proposed to recruit PPIL1 to the spliceosome. May be involved in cyclin-D1/CCND1 mRNA stability through the SNARP complex which associates with both the 3'end of the CCND1 gene and its mRNA. Involved in transcriptional regulation. Modulates TGF-beta-mediated transcription via association with SMAD proteins, MYOD1-mediated transcription via association with PABPN1, RB1-mediated transcriptional repression, and retinoid-X receptor (RXR)- and vitamin D receptor (VDR)-dependent gene transcription in a cell line-specific manner probably involving coactivators NCOA1 and GRIP1. Is involved in NOTCH1-mediated transcriptional activation. Binds to multimerized forms of Notch intracellular domain (NICD) and is proposed to recruit transcriptional coactivators such as MAML1 to form an intermediate preactivation complex which associates with DNA-bound CBF-1/RBPJ to form a transcriptional activation complex by releasing SNW1 and redundant NOTCH1 NICD. Identified in the spliceosome C complex (By similarity). Associates with U4/U6-U5 tri-small nuclear ribonucleoproteins (U4/U6-U5 tri-snRNPs). Interacts SKI, SMAD2,SMAD3, RBPJ, RB1, PABPN1, MAGEA1, SIRT1, FOXN3, U2AF2, PPIL1, DAXX and ATP1B4. Interacts with VDR and RXRA; preferentially associates with VDR:RXRA heterodimers. Interacts with NCOR2. Interacts with MAML1. Interacts with NOTCH1 NICD; the interaction involves multimerized NOTCH1 NICD. Forms a complex with NOTCH1 NICD and MAML1; the association is dissociated by RBPJ. Associates with positive transcription elongation factor b (P-TEFb). Component of the SNARP complex which consists at least of SNIP1, SNW1, THRAP3, BCLAF1 and PNN (By similarity). Belongs to the SNW family.