Involved in the regulation of innate immune response (PubMed:20829348). Acts as 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). Interacts (via N-terminal domain) with NFKBIL1; the interaction occurs in a pro-inflammatory-independent manner (PubMed:20829348). Does not interact with RELA NF-kappa-B subunit (PubMed:20829348). Identified in the spliceosome C complex (PubMed:11991638). Interacts with isoform 2 of TRIM39 (via domain B box-type) (PubMed:26363554). Nuclear localization with a speckled expression pattern in some cells. Colocalizes with NFKBIL1 in the nucleus. Up-regulated by TNF-alpha/TNFA (at protein level). Antigen recognized by autologous antibody in patients with renal-cell carcinoma. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the CACTIN family. An ORF (C19orf029 OS) has been described in the opposite strand of the C-terminus of this gene. Truncated N-terminus.