Simplified NF-κB Pathway. In unstimulated cells inactive dimers of NF-κB are located in the cytoplasm bound to IκB proteins preventing NF-κB from translocating into the nucleus. Activation of the inhibitor κB kinases (IKK) by NF-κB-activating stimuli (1) allows phosphorylation of IκB and NF-κB protein. Phosphorylation of IκB leads to its ubiquitination and degradation and therefore dissociation from the NF-κB dimers (2). The free dimers can then translocate into the nucleus (3) and regulate target gene transcription (4). IκB is a transcriptional target for NF-κB (5 and 6), creating a negative feedback loop.