Turkish Journal of Medical Sciences

Abstract: The overall goal of this study was to seek molecular linkages between polyamines, casein kinase II, and the myc oncoprotein by using a cell-free, highly purified enzyme kinetic analysis. Casein kinase II (CKII) was purified from sheep lung tissue by using an original 3-column/3-day set of procedures (DEAE cellulose, Sepharose 6L-4B, and poly-L- lysine agrose affinity chromotographies). CKII was purified approximately 550-fold with a recovery of near 40% and a final specific activity of about 250,000 pmol of phosphorylated protein substrate (casein)/min/mg of enzyme protein. Kinetic evaluations with the purified CKII using Mg-GTP as a phosphate donor, etiher casein or myc oncoprotein as substrate, and various polyamines (polylysine, polyornithine, spermidine, or spermine) as stimulators showed: 1) phosphorylation of casein icreased 2-4 fold with various polyamines; 2) without polyamines, phosphorylation of myc oncoprotein was about 10-20% when compared to casein; 3) phosphorylation of myc oncoprotein increased 10- to 30-fold in the presence of various polyamines. The phosphorylated form of myc oncoprotein is the only biologically active form which transactivates specific genes related to cell proliferation.

Key Words: Casein kinase II, polyamines, myc, cell proliferation abbreviations: CKII-casein kinase II; Pmyc-phosphorylated myc oncoprotein; Pmax-phosphorylated max protein.