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AI InsightThe phosphorylated form of myc oncoprotein is the only biologically active form which transactivates specific genes related to cell proliferation.
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Özet
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.
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.