Signal required for NF- B activation, thus facilitating termination of the immune response.ubiquitin chains (27). It is thus possible that the K1056 linked ubiquitin chain on HOIP may bind its central NZF domain, resulting in the closed conformation of the carboxyl RBR enzymatic domain, thereby reducing its enzymatic activity (Fig. 7). In fact, while the RBR family ligases have been shown to adopt