Inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase epsilon.The transcription factor NF?B is retained in the cytoplasm in an inactive form by the inhibitory protein I?B. Activation of NF?B requires that I?B be phosphorylated on specific serine residues, which results in targeted degra-dation of I?B. I?B kinase a(IKKa), previously designated CHUK, interacts with I?B-aand specifically phosphorylates I?B-aon the sites that trigger its degradation, serines 32 and 36. The functional IKK complex contains three subunits, IKKa, IKK