A20 inhibits NF-kappa B activation independently of binding to 14-3-3 proteins

The A20 protein, which belongs to a class of Cys(2)/Cys(2) zinc finger proteins, has been characterized as an inhibitor of NF-kappa B activation. In order to clarify its molecular mechanism of action, the yeast two-hybrid system was used to screen for interacting proteins. We report that different isoforms of 14-3-3 proteins, viz. eta and zeta, are able to bind A20, involving the 14-3-3-binding motif RSKSDP located between zinc fingers 3 and 4. However, A20 mutants that no longer associated with 14-3-3 proteins could still fully inhibit NF-kappa B activation induced by tumor necrosis factor, interleukin-1 beta or phorbol 12-myristate 13-acetate, thus excluding a crucial role for 14-3-3 interaction in this A20 function. (C) 1997 Academic Press.