Induction of Poly (I): Poly (C)-Binding 50 K Protein and 2', 5'-Oligoadenylate Synthetase in Interferon-Treated Mouse L 929 Cells

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A new protein retained by poly (I): poly (C)-Sepharose was induced together with dsRNA-dependent enzymatic activities, a protein kinase and 2', 5'-oligoadenylate synthetase (2, 5 A synthetase), in interferon-treated mouse L 929 cells; it had an apparent molecular weight of 50, 000 (50 K) and was not phosphorylated by the protein kinase. The kinetics of the induction of the poly (I): poly (C)-binding 50 K protein were similar to those of dsRNA-dependent protein kinase and 2', 5'-oligoadenylate synthetase, and their inductions were all dependent on the interferon dose added, though a relatively higher dose was required for the 50 K protein.
When the interferon preparation was heated to 100°C in the presence of sodium dodecyl sulfate, its effect on cells of inducing the activity of 2', 5'-oligoadenylate synthetase was preserved completely, indicating that the interferon molecule itself is responsible for the induction of the synthetase. Since the induction of the enzymatic activity was inhibited by addition of either actinomycin D or cycloheximide, it may not be an activation of a latent enzyme but a de novo synthesis of the enzyme.