NF-kappaB transcription factors are sequestered in the cytosol due to their association with IkappaB. During activation of NF-kappaB, IKK phosphorylates IkappaB, releasing NF-kappaB for importation into the nucleus. NF-kappaB transcription factors, the NFKBIA component of IkappaB, and subunits of the IKK complex can be SUMOylated (reviewed in Kracklauer and Schmidt 2003, Liu et al. 2013). SUMOylations of IkappaB, NFKBIA, and RELA inhibit NF-kappaB signaling; SUMOylation of NFKB2 is required for proteolytic processing.