Required for pre-mRNA splicing as component of the spliceosome (PubMed:29360106). Down-regulates NF-kappa-B signaling by competing with RELA for CREBBP/EP300 binding. Involved in the microRNA (miRNA) biogenesis. 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. Component of activated spliceosome complexes (PubMed:29360106). Binds SMAD4 and CREBBP/EP300. Binds the SMAD1/OAZ1/PSMB4 complex. Interacts with DROSHA and SMARCA4. Component of the SNARP complex which consists at least of SNIP1, SNW1, THRAP3, BCLAF1 and PNN. Ubiquitous, with highest expression in heart and skeletal muscle. Degraded by the proteasome upon binding to the SMAD1/OAZ1/PSMB4 complex. The disease is caused by variants affecting the gene represented in this entry.