Characteristics of extracts from interferon-treated HeLa cells: presence of a protein kinase and endoribonuclease activated by double-stranded RNA and of an inhibitor of mRNA methylation

Abstract

Extracts from mouse interferon-treated mouse cells (Ehrlich ascites tumour and L929) were reported earlier to differ in several characteristics from extracts of untreated cells. We report now that the effect of treatment with human interferon of cells of a human line (HeLa S₃) is similarly manifested in the cell extract. A comparison of extracts from interferon-treated HeLa S₃ cells (S₃O_INT) with that from untreated cells (S₃O_C) revealed: (a) an impairment in S₃O_INT of the methylation of (unmethylated) reovirus mRNAs by the cellular and virus enzymes; (b) a faster degradation of reovirus mRNAs in S₃O_INT but only in reaction mixtures supplemented with double-stranded RNA and ATP; (c) an increased phosphorylation by ATP of one (or two) proteins in S₃O_INT but only in reaction mixtures supplemented with double-stranded RNA and (d) a more pronounced inhibition of translation by double-stranded RNA in S₃O_INT. No such effects were observed in extracts prepared from HeLa cells treated with mouse interferon.