| Background |
NFkB is a heterodimer that consists of a 50 kDa DNA binding subunit (p50) and a 65 kDa transactivation subunit (p65/RelA). Both of these subunits exhibit sequence homology to the protooncogene c-Rel. The p50 has an isoform called p49/p52, and both proteins are derived from the amino-terminal of precursor protein p105 and p100. The p50/p65 heterodimer remains in the cytosol in an inactive form as a complex with its inhibitor, IkB. Upon stimulation of cells by a wide variety of stimuli such as lipopolysaccharide (LPS), pro-inflammatory cytokines (IL-1 & TNF, etc.), and viral infection, IkB is phosphorylated and degraded by proteosome. The active NFkB heterodimer is translocated into the nucleus and induces gene expression.
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