Nuclear factor-kappa B, also known as NFkappaB,
KBF1, p110 and EBP-1, was identified as a sequence specific transcriptional
activator that binds to the intronic enhancer of kappa light chain
gene in B lymphocytes (1,2). NF-?B is a heterodimer that consists
of a 50 kDa DNA binding subunit (p50) and a 65 kDa transactivation
subunit (p65/Rel A). Both of these subunits exhibit sequence homology
to the protooncogene c-Rel (4). The p50 has an isoform called p49/p52,
and both proteins are derived from the amino-terminal of precursor
protein p105 and p100, respectively. The p50/p65 heterodimer remains
in the cytosol in an inactive form as a complex with its inhibitor,
I?B. Upon stimulation of cells by a wide variety of stimuli such
as lipopolysaccharide (LPS), pro-inflammatory cytokines (interleukin-1,
tumor necrosis factor), and viral infection, I?B is phosphorylated
and degraded by proteosome. The active NF- ?B heterodimer is translocated
into the nucleus and will induce gene expression.
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