ABSTRACT
The family of NFκB transcription factors includes a collection of proteins, conserved from drosophila to humans and related through a highly conserved DNA-binding and dimerization region, the Rel homology (RH) domain.1 However, the NFκB family can be divided into two groups, based on differences in their structures, functions, and modes of synthesis.2,3 Members of one group (p105, p100, and drosophila Rel) have long C-terminal domains that contain multiple copies of ankyrin repeats, which act to inhibit these molecules. Members of this group give rise to active, shorter proteins that contain the Rel homology domain (p50 from p105, p52 from p100) either by limited proteolysis4-8 or arrested translation.9,10 Members of this group do not function as transcription activators, except when they form dimers with members of the second group, which includes p65 (RelA), Rel (c-Rel), RelB, and the drosophila Rel proteins dorsal and Dif.11 These proteins are not synthesized as precursors, and in addition to the N-terminal Rel homology domain, they possess one or more C-terminal transcriptional activation domains. Members of both groups
of NFκB proteins can form homo-or heterodimers. NFκB was the original name for the p50-p65 heterodimer.
