Epidermal growth factor (EGF) is a potent mitogen which elicits a variety of short and long term changes in its target cells, culminating in the stimulation of cellular proliferation. EGF produces its effects initially by activation of the intrinsic tyrosine kinase activity of the EGF receptor. The specific biological effects of EGF are presumed to be mediated by serial activation of other enzymes, including protein kinases. We have discovered a serine-threonine kinase which is rapidly and tran- siently activated on exposure of A431 cells to EGF. This enzyme phosphorylates the microtubule associated protein MAP2. We propose to investigate whether the activation of the MAP2 kinase is mediated through phosphorylation of the enzyme by the EGF receptor or C-kinase. The activity of the EGF-R kinase is regulated by phosphorylation at serine and threonine residues, thus, we will ascertain if MAP2 kinase mediates these effects. The MAP2 kinase has been purified to near homogeneity. We propose to scale up the purification in order to obtain amino acid sequence data. Amino acid sequence data will permit syn-thesis of oligonucleotides for use in cloning and sequencing the gene. The biological function of the MAP2 kinase will be inves-tigated through creation of protein-specific hypomorphic or null mutants deficient in MAP2 kinase. This will be accomplished by introduction antisense oligonucleotides complementary to MAP2 mRNA into cells. We will determine if deletion of this protein kinase alters the responsiveness of the cells to EGF. The MAP2 kinase phosphorylates a c-Fos related peptide, suggesting that the kinase may meditate the transcriptional activation of EGF-regulated genes. The ability of MAP2 kinase to phosphorylate trans-acting transcriptional regulators will be investigated.