Isolation of two interferon-induced translational inhibitors: a protein kinase and an oligo-isoadenylate synthetase

Large-scale purification of translational inhibitors present in interferon-treated mouse L cells, but not in untreated cells, led to the isolation of two interferon-induced activities. One is a protein kinase system that is activatable by double-stranded RNA and ATP and that phosphorylates a Mr 67,000 protein and the smallest subunit of eukaryotic initiation factor-2. The purified protein kinase is a strong translational inhibitor. The second activity is an enzyme that, with double-stranded RNA, slowly polymerizes ATP into oligoadenylate with a 2'-5' phosphodiester linkage. The oligo-isoadenylate in turn activates a potent inhibitor of mRNA translation.