IκBα controls the transcriptional activity of nuclear factor (NF)-κB by retaining it in the
cytoplasm; but, when expressed in the nucleus, it can also inhibit the interaction of NF-κB
with DNA and promote the export of NF-κB from the nucleus to the cytoplasm. Here, we
report that IκBα, when not bound to NF-κB, is constitutively transported to the nucleus, and
we confirm that the interaction of IκBα with NF-κB retains IκBα in the cytoplasm. Nuclear
import of IκBα does not result from passive diffusion but from a specific energy-dependent …