INDUCTION BY INTERFERON IN HELA-CELLS OF A PROTEIN-KINASE ACTIVATED BY DOUBLE-STRANDED-RNA

Treatment of HeLa cells with human fibroblast interferon results in increased levels of latent protein kinase activity that can be activated by double‐stranded RNA (dsRNA). The protein kinase activity in extracts of interferon‐treated cells is assayed by two methods: (a) inhibition of protein synthesis in rabbit reticulocyte lysates and (b) phosphorylation of two polypeptides of Mr 72000 (PI) and 38000 (the eIF‐2α subunit of initiation factor 2). When extracts of interferon‐treated cells are fractionated by centrifugation at 150000 xg, the protein kinase activity is found in the pellet fraction. The kinase is maximally activated by 0.1 μg/ml poly(I) poly(C). An increase in protein kinase activity is detected after 8 h of treatment with 100 units interferon/ml or after a 17‐h treatment with 12.5 units/ml or greater interferon concentrations. Therefore, the kinase activity increases as a function of both 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 three days when interferon‐treated cells are subsequently grown in the absence of interferon. Copyright © 1979, Wiley Blackwell. All rights reserved