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

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 (S3OINT) with that from untreated cells (S3OC) revealed: (a) an impairment in S3OINT of the methylation of (unmethylated) reovirus mRNAs by the cellular and virus enzymes; (b) a faster degradation of reovirus mRNAs in S3OINT but only in reaction mixtures supplemented with double-stranded RNA and ATP; (c) an increased phosphorylation by ATP of one (or two) proteins in S3OINT but only in reaction mixtures supplemented with double-stranded RNA and (d) a more pronounced inhibition of translation by double-stranded RNA in S3OINT. No such effects were observed in extracts prepared from HeLa cells treated with mouse interferon