Identification and characterization of protein products of the cot oncogene with serine kinase activity

The products of the cot gene, a novel oncogene isolated by DNA transfection assay using the hamster cell line SHOK, were identified as 46 kDa and 52 kDa proteins by using anti-peptide antibodies. The 46 kDa and 52 kDa proteins both showed autophosphorylation activity at serine residues. The two forms of the Cot protein were suggested to differ in their amino-terminal structures as a result of alternative initiation of translation. Subcellular fractionation revealed that the 46 kDa and 52 kDa proteins are both predominantly localized in the cytosol. These Cot proteins are the fourth oncogene products with serine kinase activity identified.