Plays a role in pre-mRNA splicing by facilitating excision of a subset of introns (PubMed:28062851). Required for the splicing of CDCA5/Sororin, a regulator of sister chromatid cohesion (PubMed:28062851). Involved in the regulation of innate immune response (PubMed:20829348). Acts as a negative regulator of Toll-like receptor, interferon-regulatory factor (IRF) and canonical NF-kappa-B signaling pathways (PubMed:20829348, PubMed:26363554). Contributes to the regulation of transcriptional activation of NF-kappa-B target genes in response to endogenous pro-inflammatory stimuli (PubMed:20829348, PubMed:26363554). {ECO:0000269|PubMed:20829348, ECO:0000269|PubMed:26363554, ECO:0000269|PubMed:28062851}. This is the function of Ensembl gene identifier ENSG00000105298 (CACTIN, cactin, spliceosome C complex subunit).