Functional redundancy of the zinc fingers of A20 for inhibition of NF-κB activation and protein-protein interactions

The turner necrosis factor (TNF) inducible protein A20 is a potent inhibitor of nuclear factor-kappaB (I kappaB)-mediated gene expression in response to TNF and several other stimuli. The C-terminal domain of A20 is characterized by seven zinc finger structures. Here, we show that a minimum of four zinc fingers is required to inhibit TNF-induced nuclear factor-kappaB (NF-kappaB) activation to a level that is comparable to that obtained with the wild-type A20 protein. However, there was no strict requirement for a particular zinc finger structure, since a mutant A20 protein containing only the first four zinc fingers was as potent as a mutant protein containing only the last four zinc fingers. A similar functional redundancy of the A20 zinc fingers was also observed for binding of A20 to a number of other proteins, including two novel NF-kappaB inhibitory proteins (ABIN-1, ABIN-2), A20 itself, the anti-apoptotic protein TXBP151, and a regulatory component of the I kappaB kinase complex, IKK gamma. R Moreover, me demonstrate that complete loss of binding of any of these proteins correlates with complete loss of A20's ability to inhibit TNF-induced NF-kappaB activation, However, binding of IKK gamma as such is not sufficient for inhibition of NF-kappaB dependent gene expression in response to TNF, (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B,V, All rights reserved.