Heyninck Karen, Kreike Marja M, Beyaert Rudi
Department of Molecular Biomedical Research, Unit of Molecular Signal Transduction in Inflammation, Flanders Interuniversity Institute for Biotechnology, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium.
FEBS Lett. 2003 Feb 11;536(1-3):135-40. doi: 10.1016/s0014-5793(03)00041-3.
Nuclear factor kappa B (NF-kappa B)-dependent gene expression plays an important role in numerous cellular processes including stress responses, inflammation and cell proliferation. Therefore, the activity of this transcription factor needs to be tightly regulated. Among others, the NF-kappa B-dependent zinc finger protein A20 is involved in the negative feedback regulation of NF-kappa B activation in response to tumor necrosis factor (TNF). We previously demonstrated that A20 can interact with A20-binding inhibitors of NF-kappa B activation (ABINs), which have the potential to inhibit TNF-induced activation of NF-kappa B upon overexpression. The ABIN proteins were therefore proposed to mediate the NF-kappa B inhibiting function of A20. Here we demonstrate the presence of a short homologous region in ABINs and I kappa B kinase gamma, the regulatory subunit of the I kappa B kinase complex. Site-specific mutagenesis of this region abolished the NF-kappa B inhibiting function of ABIN-1, without affecting the interaction with A20. Furthermore, coexpression of these ABIN-1 mutants interfered in a dominant negative manner with the NF-kappa B inhibiting function of ABIN-1, whereas the A20-mediated inhibition was unaffected. These results suggest that A20 and ABIN-1 probably act independently of their mutual interaction.
核因子κB（NF-κB）依赖的基因表达在包括应激反应、炎症和细胞增殖在内的众多细胞过程中发挥着重要作用。因此，这种转录因子的活性需要受到严格调控。其中，NF-κB依赖的锌指蛋白A20参与了对肿瘤坏死因子（TNF）应答时NF-κB激活的负反馈调节。我们之前证明A20可与NF-κB激活的A20结合抑制剂（ABINs）相互作用，过表达时ABINs有抑制TNF诱导的NF-κB激活的潜力。因此，ABIN蛋白被认为介导了A20的NF-κB抑制功能。在此我们证明ABINs和IκB激酶复合物的调节亚基IκB激酶γ中存在一个短同源区域。该区域的位点特异性诱变消除了ABIN-1的NF-κB抑制功能，而不影响其与A20的相互作用。此外，这些ABIN-1突变体的共表达以显性负性方式干扰了ABIN-1的NF-κB抑制功能，而A20介导的抑制不受影响。这些结果表明A20和ABIN-1可能独立于它们的相互作用发挥作用。
