In Vitro Activation and Nuclear Translocation of NF-κB Catalyzed by Cyclic AMP-Dependent Protein Kinase and Protein Kinase C

We have examined whether a precursor form of NF-kappa B, a DNA-binding protein that plays a role in the transcriptional control of several genes, including kappa immunoglobulin light chain and interleukin-2 receptor alpha subunit, could be activated in vitro by protein kinases. DNA-binding activity of NF-kappa B was induced in the cytosolic fraction of unstimulated 70Z/3 murine pre-B cells by incubation with the catalytic subunit of cyclic AMP-dependent protein kinase (PKA) or protein kinase C (PKC). In contrast, PKA and PKC did not activate NF-kappa B in nuclear extracts from unstimulated cells. Identical results were obtained with the human natural killer-like cell line YT, which can be induced to express the interleukin-2 receptor alpha subunit in response to interleukin-1, cyclic AMP, or phorbol 12-myristate 13-acetate. Furthermore, when nuclei from unstimulated cells were incubated with PKA- or PKC-treated cytosolic fraction for 30 min at 30 degrees C, NF-kappa B was translocated into the nuclei. This translocation did not occur at 4 degrees C and was inhibited by wheat germ agglutinin but not by concanavalin A. Our findings support the conclusion that NF-kappa B exists in the cytoplasm of unstimulated cells in an inactive form that can be converted by exposure to PKA or PKC to an active DNA-binding form that can translocate to the nucleus.