Down-regulates SLC1A2/EAAT2 promoter activity when expressed ectopically. Activates the nuclear factor kappa-B (NF-kappa-B) transcription factor. Promotes anchorage-independent growth of immortalized melanocytes and astrocytes which is a key component in tumor cell expansion. Promotes lung metastasis and also has an effect on bone and brain metastasis, possibly by enhancing the seeding of tumor cells to the target organ endothelium. Induces chemoresistance (By similarity). Interacts with BCCIP, CREBBP/CBP and RELA/p65. In epithelial cells, recruited to tight junctions (TJ) during the maturation of the TJ complexes. A nucleolar staining may be due to nuclear targeting of an isoform lacking the transmembrane domain. TNF-alpha causes translocation from the cytoplasm to the nucleus (By similarity). In the mammary gland, expressed at the apical surface of epithelial cells lining ducts, as well as in the mammary fat pad. Not detected in the spleen, kidney, lung, or skin; minute amounts seen in the liver. Expressed in Purkinje neurons in the early postnatal and adult cerebellum. Overexpressed in mammary tumors (at protein level). Was originally thought to be a type II membrane protein but this is inconsistent with the results of multiple phosphorylation studies because this topology would locate the phosphorylation sites in the lumen or extracellularly rather than in the cytoplasm.