RelA/NF-[kappa]B transcription factor associates with alpha -actinin-4

The NF-[kappa]B/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-[kappa]B in the cytoplasm and the transport mechanism to the nucleus. We found that NF-[kappa]B is associated with the actin-binding protein alpha -actinin-4. NF-[kappa]B and alpha - actinin-4 co-localized along actin stress fibers and in membrane lamellae in A431 cells. After a 30-min stimulation with EGF or TNF- alpha , alpha -actinin-4 and p65 were found in the nucleus. Disruption of cytoskeleton by cytochalasin D prior to treatment with TNF- alpha led to increase of p65 nuclear translocation. Antibodies to p65 subunit of NF-[kappa]B co-immunoprecipitated alpha -actinin-4 from A431 cell lysates and nuclear extracts, but alpha -actinin-1 and beta -actin were not found in the precipitates. Affinity chromatography experiments displayed that p65 and p50 subunits of NF-[kappa]B can bind to matrix-bound chicken gizzard alpha -actinin. We suggest that the alpha -actinin-4 is important for the NF-[kappa]B nuclear translocation and its functions inside the nucleus.