FIGURE 4.

The IKKα NBD is not required for noncanonical NF-κB activation. A, the structural domains of wild-type IKKα (IKKα^WT) and IKKα^ΔNBD are shown. KD, kinase domain; LZ, leucine zipper; HLH, helix-loop-helix. IKKα^ΔNBD is a truncation mutant encompassing residues 1–737 that lacks the C-terminal 8 amino acids containing the NBD (13, 14). B, lysates from WT, IKKα^−/− (α^−/−), IKKα^WT (α^WT), and IKKα^ΔNBD (α^ΔNBD) MEFs were immunoblotted using the antibodies indicated (right). C, WT, IKKα^−/−, IKKα^WT, and IKKα^ΔNBD MEFs were either untreated or incubated with LTα1β2 (LT) for the times indicated, and then lysates were immunoblotted using either anti-p100/p52 (top), anti-IKKα, or anti-tubulin (Tub.) as indicated (right).