Signal-induced NIK accumulation and activation is likely an essential step for triggering the downstream signalling events in non-canonical NF-kB pathway. Like other MAP3Ks NIK may also be triggered by its phosphorylation. It has been suggested that threonine (T559) phosphorylation of NIK is required for its activity. T559 phosphorylation of NIK is likely mediated by autophosphorylation, which could be triggered through NIK accumulation (Lin et al. 1998).