Nuclear factor kappa B (NF-κB) is a ubiquitous transcription factor and an essential mediator of gene expression during activation of immune and inflammatory responses. NF-κB mediates the expression of a great variety of genes in response to extracellular stimuli. NF-κB is associated with IκB proteins in the cell cytoplasm, which inhibit NF-κB activity. IκB is phosphorylated by IκB kinase (IKK) complex that contains IKKα, IKKβ, and IKKγ. A novel molecule in the IKK complex was recently identified and designated IKKε/IKK-i. IKK epsilon is required for the activation of NF-κB by PMA and T cell receptors but not by TNFα and IL-1. IKKε/IKK-i message is expressed in a variety of tissues and is inducible by TNFα, IL-1, and LPS.
