Evidence for the presence of an NF-kappa B signal transduction system in Dictyostelium discoideum

The Rel/NF-kappa B family of transcription factors and regulators has so fa r only been described in vertebrates and arthropods, where they mediate res ponses to many extracellular signals. No counterparts of genes coding for s uch proteins have been identified in the Caenorhabditis elegans genome and no NF-kappa B activity was found in Saccharomyces cerevisiae. We describe h ere the presence of an NF-kappa B transduction pathway in the lower eukaryo te Dictyostelium discoideum. Using antibodies raised against components of the mammalian NF-kappa B pathway, we demonstrate in Dictyostelium cells ext racts the presence of proteins homologous to Rel/NF-kappa B, I kappa B and IKK components. Using gel-shift experiments in nuclear extracts of developi ng Dictyostelium cells, we demonstrate the presence of proteins binding to kappa B consensus oligonucleotides and to a GC-rich kappa B-like sequence, lying in the promoter of cbpA, a developmentally regulated Dictyostelium ge ne encoding the Ca2+-binding protein CBP1, Using immunofluorescence, we sho w specific nuclear translocation of the p65 and p50 homologues of the NF-ka ppa B transcription factors as vegetatively growing cells develop to the sl ug stage. Taken together, our results strongly indicate the presence of a c omplete NF-kappa B signal transduction system in Dictyostelium discoideum t hat could be involved in the developmental process.