Interferon Treatment of Ehrlich Ascites Tumor Cells: Effects on Exogenous mRNA Translation and tRNA Inactivation in the Cell Extract

Abstract

We reported earlier that in cell extracts that were prepared from interferontreated Ehrlich ascites tumor cells and preincubated and passed through Sephadex G-25 (S3OINT), the translation of exogenous mRNA (viral and host) was impaired and the impairment could be overcome to a large extent by adding a crude tRNA preparation from Ehrlich ascites tumor cells but not from Escherichia coli. We find now that the rate of inactivation of some tRNA's (especially those specific for leucine, lysine, and serine) but not those of many others is faster in S30INT than in corresponding extracts from control cells. This increased rate of tRNA inactivation may perhaps account for the need for added RNA to overcome at least partially the impairment of translation in S301NT. The relationship of the increased rate of tRNA inactivation to the antiviral effect of interferon is unclear. So far no significant difference has been detected in the amount of tRNA needed to overcome the impairment of encephalomyocarditis virus RNA translation in S301mr between tRNA from interferon-treated cells and tRNA from control cells. Furthermore, no difference was found in the rate of inactivation in S30INT between leucine-specific tRNA's from interferontreated and from control cells. tRNA's specific for leucine and lysine were not inactivated (unless very slowly) during incubation under our conditions in an extract from interferon-treated (or from control) cells unless the extract had been passed through Sephadex G-25 or dialyzed. The translation of exogenous mRNA was, however, impaired in an extract from interferon-treated cells that had not been passed through Sephadex G-25. overcome by added tRNA.

Translational elongation rate changes in encephalomyocarditis virus-infected and interferon-treated cells

“…Finally, it should be noted that inactivation of specific tRNA species leading to preferential elongation blocks has been suggested as a component of the antiviral mechanism induced by interferon (7,16,34,37,41,42). However, we have been unable to demonstrate any decrease in overall elongation rates which may be ascribed to interferon treatment alone in either mock-infected or EMC virus-infected cells.…”

Antiviral activity of interferons.

“…The basic defect here was traced to an impairment of amino acid acceptor activity of lysyl-, seryl-, and, especially, of leucyl-tRNA's. This was due to a faster rate of inactivation of these tRNA forms in extracts from interferon-treated cells than from control cells (119).…”

“…There were, however, some disturbing findings related to this neat explanation for interferon action (29,119). There was no difference in the amounts of tRNA from interferontreated or control cells required to correct the block in translation in extracts from interferontreated cells.…”

The interferon renaissance: molecular aspects of induction and action.

“…It was found that translation in extracts of interferon-treated cells was more sensitive to inactivation by preincubation than was translation in control cells (69). This inactivation was shown to be a result of inactivation of transfer RNA (45,46,70,71,93,156,206) and could be overcome by the addition of a unique species of transfer RNA (71).…”