RelA/NF-κB transcription factor associates with α-actinin-4

The NF-κB/RelA family of transcription factors regulates inducible transcription of a large number of genes in response to diverse stimuli. Little is known, however, about the location of NF-κB in the cytoplasm and the transport mechanism to the nucleus. We found that NF-κB is associated with the actin-binding protein α-actinin-4. NF-κB and α-actinin-4 co-localized along actin stress fibers and in membrane lamellae in A431 cells. After a 30-min stimulation with EGF or TNF-α, α-actinin-4 and p65 were found in the nucleus. Disruption of cytoskeleton by cytochalasin D prior to treatment with TNF-α led to increase of p65 nuclear translocation. Antibodies to p65 subunit of NF-κB co-immunoprecipitated α-actinin-4 from A431 cell lysates and nuclear extracts, but α-actinin-1 and β-actin were not found in the precipitates. Affinity chromatography experiments displayed that p65 and p50 subunits of NF-κB can bind to matrix-bound chicken gizzard α-actinin. We suggest that the α-actinin-4 is important for the NF-κB nuclear translocation and its functions inside the nucleus.