A20-binding inhibitor of nuclear factor-κB (NF-κB)-2 (ABIN-2) is an activator of inhibitor of NF-κB (IκB) kinase α (IKKα)-mediated NF-κB transcriptional activity

NF-κB transcription factors are pivotal players in controlling inflammatory and immune responses, as well as cell proliferation and apoptosis. Aberrant regulation of NF-κB and the signaling pathways that regulate its activity have been involved in various pathologies, particularly cancers, as well as inflammatory and autoimmune diseases. NF-κB activation is tightly regulated by the IκB kinase (IKK) complex, which is composed of two catalytic subunits IKKα and IKKβ, and a regulatory subunit IKKγ/NEMO. Although IKKα and IKKβ share structural similarities, IKKα has been shown to have distinct biological functions. However, the molecular mechanisms that modulate IKKα activity have not yet been fully elucidated. To understand better the regulation of IKKα activity, we purified IKKα-associated proteins and identified ABIN-2. Here, we demonstrate that IKKα and IKKβ both interact with ABIN-2 and impair its constitutive degradation by the proteasome. Nonetheless, ABIN-2 enhances IKKα- but not IKKβ-mediated NF-κB activation by specifically inducing IKKα autophosphorylation and kinase activity. Furthermore, we found that ABIN-2 serine 146 is critical for the ABIN-2-dependent IKKα transcriptional up-regulation of specific NF-κB target genes. These results imply that ABIN-2 acts as a positive regulator of NF-κB-dependent transcription by activating IKKα.