A firm hand on NF B: structures of the I B –NF B complex

The regulation of gene expression, which allows a living cell to express a defined set of genes according to its environmental conditions and stage of development, occurs primarily at the level of transcription. The precise temporal and spatial control of the transcription factor NFκB has become a paradigm for the complexity of transcriptional regulation in eukaryotes. IκB, the inhibitor and central regulator of NFκB, prevents nuclear import of NFκB, disrupts NFκB–DNA complexes in the nucleus and serves as an adapter for nuclear export of NFκB. Two X-ray crystallographic structures of the IκBα–NFκB complex have recently been determined by Huxford et al. at 2.3 Å [1] and by Jacobs and Harrison at 2.7 Å resolution [2]. The structures give the first detailed picture of the interactions between two representatives of the important NFκB and IκB families. They provide insight into how IκB fulfils its multiple functions.