Translation of RNA by L cell extracts: Effect of interferon

Abstract

in previous studies we have been unable to detect more than a slight effect of interferon treatment of cells in the absence of infection upon the ability of cell-free systems isolated from them to translate a viral RNA [ 11. None the less it would appear that in vaccinia virus-infected L cells pretreated with interferon it is virus protein synthesis which is inhibited: virus messenger RNA (mRNA) is synthesized but is not translated [2, Metz and Esteban, in preparation]. Here, therefore, we report the results of an investigation of the effect of interferon pretreatment on the translation of a viral RNA in cell-free systems from vaccinia vims-infected ceils. Extracts from mouse L cells translated encephalomyocarditis (EMC) virus RNA and mouse globin mRNA to yield EMCspecific polypeptides and mouse globin. Under the conditions employed, infection or pretreatment of the cells with interferon alone had little effect on the translation of EMC RNA in these systems. With extracts from cells subjected to both interferon treatment and infection, however, the translation of EMC RNA was strikingly inhibited. The bulk of the inhibitory effect appeared to be associated with the ribosome fraction. Inhibition was not seen if the cellfree systems were prepared in the conventional manner by preincubation of the extracts at 37”. Thus, both interferon treatment and infection appear to be required before a clear-cut effect on translation can be seen in the cell-free system.