Growth-related expression of a double-stranded RNA-dependent protein kinase in 3T3 cells.
Cultured mouse 3T3-F442A and 3T3-C2 fibroblasts exhibit a transient double-stranded RNA (dsRNA)-dependent phosphorylation of a 67,000-dalton protein (67K) without prior treatment with interferon (IFN). This phosphoprotein is similar but not identical to the dsRNA-dependent eukaryotic initiation factor-2 (eIF-2) alpha protein kinase (dsI), which regulates protein synthesis in rabbit reticulocytes. We have studied the relationship between cell growth and phosphorylation of the 67K protein (designated 3T3-dsRNA-dependent eIF-2 alpha kinase). A low level of dsRNA-dependent phosphorylation of 3T3-dsI was detectable in extracts prepared from cells not treated with IFN and grown at a low cell density. The phosphorylation of dsI and the phosphorylation of a 38K protein identified as the alpha-subunit (38K) of 3T3-eIF-2 (eIF-2 alpha) occurred concomitantly; the levels of these phosphorylations confluent and thereafter decreased markedly. Treatment of cells with IFN at all stages of growth resulted in an increase in phosphorylation of dsI. 3T3-F442A and 3T3-C2 fibroblasts were found to produce and secrete IFN at levels sufficient to induce an elevated dsI activity.
D000818:Animals; D002455:Cell Division; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology; D006801:Humans; D007700:Kinetics; D051379:Mice; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D010748:Phosphopeptides / Q000032:analysis; D010750:Phosphoproteins / Q000302:isolation & purification; D011494:Protein Kinases / Q000096:biosynthesis*; D012330:RNA, Double-Stranded / Q000235:genetics*; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D019892:eIF-2 Kinase
D010446:Peptide Fragments; D010748:Phosphopeptides; D010750:Phosphoproteins; D012330:RNA, Double-Stranded; D011494:Protein Kinases; D019892:eIF-2 Kinase