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Nuclear Protein Phosphokinases in Normal and Neoplastic Tissues¹

Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232

Protein phosphokinases were isolated from the nuclei of normal and fetal liver and neoplastic tissues. Chromatography on phosphocellulose columns resolved the normal and fetal liver kinases into five reproducible fractions. Each of the fractions differed in optimal divalent cation and substrate requirements. Hepatic proliferation was accompanied by quantitative changes in the kinase activity profiles (with endogenous phosphoprotein as natural substrate). An additional phosphoprotein kinase activity stimulated by Mn²⁺ was found in the nuclei of malignant cells. This tumor-specific kinase could not be detected either in tumor cytoplasm or in fetal or regenerating liver nuclei. Mn²⁺-dependent phosphoprotein kinase from Novikoff hepatoma phosphorylated only one major protein band detectable by polyacrylamide gel electrophoresis. This substrate could not be detected in chromatin of normal tissues.

¹ Supported by USPHS Grant CA 18389 and Robert A. Welch Foundation Grant G-138.

² Present address: Department of Biochemistry, J. Hillis Miller Health Center, University of Florida, Gainesville, Fla. 32610.

³ To whom requests for reprints should be addressed.

Received 1/ 3/77. Accepted 6/ 1/77.