Nuclear factor NF-kappa-B p105 subunit, also called EBP-1 is a protein that in humans is encoded by the NFKB1 gene. By fluorescence in situ hybridization, the gene was assigned to human chromosome 4q24. NF-kappa-B is a pleiotropic transcription factor present in almost all cell types and is the endpoint of a series of signal transduction events that are initiated by a vast array of stimuli related to many biological processes such as inflammation, immunity, differentiation, cell growth, tumorigenesis and apoptosis. NFKB1 appears to have dual functions such as cytoplasmic retention of attached NF-kappa-B proteins by p105 and generation of p50 by a cotranslational processing.