Figure 1. Signaling pathway for NF-B activation. Extracellular inducers including reactive oxygen species (ROS), cytokines, viral and bacterial products, ionizing radiation, and cancer chemotherapy drugs activate cytoplasmic kinases (IKK) and lead to the phosphorylation of IB. The phosphorylated complex is recognized by ubiquitin ligase leading to the attachment of ubiquitin chains. The ubiquinated (Ub) IB is degraded by the 26S proteosome which permits NF-B to enter the nucleus (after Makarov, 2000).