NFKB2 (also known as p100) is a member of the NF-kB family of transcription factors. It is synthesised as large precursor with an N-terminal RHD (Rel homology domain) and a C-terminal series of ankyrin repeats that masks the nuclear localization signal of NFKB2/p100 localising it to the cytosol. In resting cells, p100 is associated with RELB (Transcription factor RelB) in the cytosol. Upon cell stimulation, the IkB-like C terminus of p100 is proteolyzed, resulting in RELB-p52 dimers that translocate to the nucleus (Senftleben et al. 2001, Hayden & Ghosh 2004). IKKA (I kappa-B kinase alpha) does not associate directly with p100 but in the presence of NIK (NF-kB-inducing kinase), IKKA stably binds to p100. Serine residues 866 and 870 of p100 are essential for the recruitment of IKKA to p100 by NIK. This interaction is required for p100 phosphorylation and subsequent processing by IKKA (Xiao et al. 2001, 2004).