IkappaB kinase: beginning, not the end.

Abstract

It is not often that a problem in biology is so well defined and yet so elusive. Just a decade ago, David Baltimore and colleagues reported the identification of a nuclear factor that bound to an enhancer element in the κ light chain gene. They called this factor NF-κB (1). Unlike other transcription factors, NF-κB was found to be ensconced in the cytoplasm in association with an inhibitory protein, IκB. Upon stimulation of the cell with a variety of inducers, such as growth factors, lymphokines, cytokines, UV, pharmacological agents, and stress, the NF-κB proteins translocated to the nucleus (2). It was quickly recognized that nuclear translocation of NF-κB was promoted by phosphorylation of IκB followed by dissociation of the complex (3). In the subsequent years, the seven genes encoding NF-κB proteins have been molecularly cloned and found to form a family, referred to as the Rel family (4). The Rel protein was first identified as a cellular homologue of viral Rel (v-Rel), the transforming component of avian reticuloendotheliosis virus (REV) (5). Thus, early on, there was an indication that NF-κB proteins were possible oncogenes.