Induction by Interferon in HeLa Cells of a Protein Kinase Activated by Double-Stranded RNA

Abstract

Treatment of HeLa [human cervical carcinoma] cells with human fibroblast interferon results in increased levels of latent protein kinase activity that can be activated by double-stranded (ds) RNA. The protein kinase activity in extracts of interferon-treated cells is assayed by 2 methods: inhibition of protein synthesis in rabbit reticulocyte lysates and phosphorylation of 2 polypeptides of MW 72,000 (P1) and 38,000 (the eIF-2.alpha. subunit of initiation factor 2). When extracts of interferon-treated cells are fractionated by centrifugation at 150,000 .times. g, the protein kinase activity is found in the pellet fraction. The kinase is maximally activated by 0.1 .mu.g/ml poly(I) .cntdot. poly(C). An increase in protein kinase activity is detected after 8 h of treatment with 100 units of interferon/ml or after a 17 h treatment with 12.5 units/ml or greater interferon concentrations. The kinase activity increases as a function of time of treatment and interferon concentration. Addition of actinomycin D to cells during interferon treatment prevents this increase. The protein kinase activity decreases gradually over 3 days when interferon-treated cells are subsequently grown in the absence of interferon. [These findings have relevance to the mechanism of the anti-viral effect of interferon.].