Mitogen-stimulated phosphorylation of nuclear proteins in Swiss 3T3 cells: evidence for a protein kinase C requirement.
When Swiss 3T3 fibroblasts are treated with a combination of IGF-I2 and bombesin at mitogenic concentrations, in vivo phosphorylation of some nuclear proteins occurs within 45-90 min. Among these proteins, histone H1 and a 0.75 M PCA soluble polypeptide with an apparent Mr of 21,000, as revealed by electrophoretic analysis, are phosphorylated in vitro by protein kinase C in isolated nuclei purified from 3T3 cells treated for 90 min with IGF-I and bombesin. Since these phosphorylative events follow the earlier changes, recently demonstrated, in nuclear polyphosphoinositide metabolism induced by the same mitogen combination, it seems possible that these two phenomena are related to each other and trigger the synthetic machinery responsible for replicating DNA.
Martelli
A M
AM
Istituto di Anatomia Umana Normale, Università di Bologna, Italy.
Gilmour
R S
RS
Falcieri
E
E
Manzoli
F A
FA
Cocco
L
L
D000818:Animals; D001839:Bombesin / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D004338:Drug Combinations; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D051379:Mice; D008815:Mice, Inbred Strains; D008854:Microscopy, Electron; D008934:Mitogens / Q000494:pharmacology*; D009687:Nuclear Proteins / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology*
D004338:Drug Combinations; D008934:Mitogens; D009687:Nuclear Proteins; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D007334:Insulin-Like Growth Factor I; D011493:Protein Kinase C; D001839:Bombesin