Interferon-induced inhibition of protein synthesis in L-cell extracts: an ATP-dependent step in the activation of an inhibitor by double-stranded RNA.

Abstract

The translation of encephalomyocarditis virion RNA in extracts from interferon-treated [mouse fibroblast] L-cells is inhibited by addition of double-stranded RNA (dsRNA) at 400 ng/ml. A similar inhibition in response to dsRNA is seen in control cell extracts supplemented with small amounts of a postribosomal supernatant fraction from interferon-treated cells (interferon cell sap). Neither interferon cell sap nor dsRNA alone is inhibitory in control systems. The inhibition is much reduced if translation is carried out at low ATP concentrations. Conversely, the inhibitory capacity of the interferon cell sap is increased 100-fold if it is preincubated with dsRNA and ATP prior to addition to the protein-synthesizing system. After this preincubation all detectable dsRNA can be removed with no diminution of the inhibitory activity of the cell sap. These results are compatible with a 2-step model for the inhibition in which a pre-inhibitor is activated by dsRNA, the activated inhibitor than interacting with the protein synthesis system to inhibit translation.