Identification of a new serine kinase that activates NF kappa B by direct phosphorylation

A novel serine kinase, named nuclear factor kappa B (NF kappa B) kinase, has been shown to be associated with the NF kappa B.I kappa B complex in the cytosol of human primary T lymphocytes. It activates the DNA binding activity of NF kappa B by directly phosphorylating its p65 and p50 subunits. There is no evidence that it phosphorylates I kappa B. Experiments with inhibitors and antisera showed that it is distinct from other known serine kinases such as mitogen-activated protein kinase or Mos. It has an apparent molecular size of 43 kDa determined by the substrate binding assay. This kinase might have a central role in mediating various signals to NF kappa B.