A20 is a Cys2/Cys2 zinc finger protein that is induced by a variety of inflammatory stimuli and regulates gene expression. Specifically, A20 is induced by tumor necrosis factor (TNF) and interleukin 1 (IL-1), and acts as a negative regulator of nuclear factor κ B (NFκB) gene expression. By inhibiting NFκB activation, A20 plays a critical role in terminating NFκB responses to various stimuli. Although the C-terminal region of A20 contains seven zinc finger domains, only four of these doma