Retroviral oncoprotein Tax induces processing of NF-κB2/p100 in T cells: evidence for the involvement of IKKα

IκB kinase (IKK) is a key mediator of NF-κB activation induced by various immunological signals. In T cells and most other cell types, the primary target of IKK is a labile inhibitor of NF-κB, IκBα, which is responsible for the canonical NF-κB activation. Here, we show that in T cells infected with the human T-cell leukemia virus (HTLV), IKKα is targeted to a novel signaling pathway that mediates processing of the nfκb2 precursor protein p100, resulting in active production of the NF-κB subunit, p52. This pathogenic action is mediated by the HTLV-encoded oncoprotein Tax, which appears to act by physically recruiting IKKα to p100, triggering phosphorylation-dependent ubiquitylation and processing of p100. These findings suggest a novel mechanism by which Tax modulates the NF-κB signaling pathway.