Phosphorylation and proteolytic degradation of nucleolin from 3T3-F442A cells.
The effect of phosphorylation on the proteolysis of nucleolin has been investigated. Nucleolin is readily phosphorylated both in vitro and in vivo. Utilizing phosphorylation assays and immunoblotting with anti-nucleolin serum, we have observed that phosphorylation enhances nucleolin as a substrate for a protease. This protease activity cleaves the protein into a highly phosphorylated 30 kDa peptide and a 72 kDa peptide. The involvement of casein kinase II is suggested since this cleavage is promoted by spermine and inhibited by heparin, which are, respectively, a stimulator and an inhibitor of casein kinase II activity. The molecular identity of the protease and the physiologic significance of the proteolytic cleavage of nucleolin remain to be studied.
Warrener
P
P
Department of Biochemistry and Molecular Biology, State University of New York Health Science Center, Syracuse 13210.
Petryshyn
R
R
D016475:3T3 Cells; D000818:Animals; D047388:Casein Kinases; D010450:Endopeptidases / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology; D015151:Immunoblotting; D007700:Kinetics; D051379:Mice; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism*; D010748:Phosphopeptides / Q000032:analysis; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D011188:Potassium / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism*; D016601:RNA-Binding Proteins; D012964:Sodium / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology; D000097796:Nucleolin
D047388:Casein Kinases; D010450:Endopeptidases; D006493:Heparin; D009687:Nuclear Proteins; D010748:Phosphopeptides; D010750:Phosphoproteins; D011188:Potassium; D011494:Protein Kinases; D016601:RNA-Binding Proteins; D012964:Sodium; D013096:Spermine; D000097796:Nucleolin