Role of adapter function in oncoprotein-mediated activation of NF-κB: Human T-cell leukemia virus type I Tax interacts directly with IκB kinase γ

Mechanisms by which the human T-cell leukemia virus type I Tax oncoprotein activates NF-κB remain incompletely understood. Although others have described an interaction between Tax and a holo-IκB kinase (IKK) complex, the exact details of protein-protein contact are not fully defined. Here we show that Tax binds to neither IKK-α nor IKK-β but instead complexes directly with IKK-γ, a newly characterized component of the IKK complex. This direct interaction with IKK-γ correlates with Tax-induced IκB-α phosphorylation and NF-κB activation. Thus, our findings establish IKKγ as a key molecule for adapting an oncoprotein-specific signaling to IKK-α and IKK-β.