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Action of Nucleotide Derivatives on Translation in Encephalomyocarditis Virus-infected Mouse Cells

Luis Carrasco

Translation Laboratory, Imperial Cancer Research Fund, Lincoln's Inn Fields, London WC2A 3PX, U.K.

The infection of animal cells by encephalomycocarditis (EMC) virus lead to a drastic change in membrane permeability towards low mol. wt. compounds. Addition of the nucleotide analogue GppCH₂p to the culture medium resulted in a specific inhibition of protein synthesis in EMC virus-infected 3T6 cells. This inhibition was not observed when GTP or ATP were present nor in control mock-infected 3T6 cells. The induction of membrane leakiness after viral infection was not specific for 3T6 cells, as it was also detected in mouse L cells, hamster BHK-21 cells and monkey CV1 cells. The inhibitory action produced by GppCH₂p in virus-infected cells was fully reversed upon addition of fresh medium. Moreover, analysis of the proteins synthesized after medium replacement showed a preferential synthesis of cellular proteins. The presence of zinc ions resulted in an inhibition of the cleavage of large viral polypeptide precursors to mature viral proteins. Under these conditions, membrane leakiness as measured by GppCH₂p, was not observed. However, this seems to be an effect of zinc ions themselves on the membrane, because inhibition of mature protein formation by other means, such as the presence of amino acid analogues, did not prevent inhibition of translation by GppCH₂p in virus-infected cells.

Addition of the cap analogues 7mGppp and 2'-O'-mGppp, resulted in specific stimulation of viral protein synthesis in EMC virus-infected 3T6 cells. On the other hand, the presence of 7mGp had no effect on translation. We propose that a specific capping of viral mRNA takes place in the presence of these compounds, and leads to increased stability and greater efficiency in the translation of viral mRNA.

Present address: Instituto de Bioquimica de Macromoléculas, Centro de Biología Molecular and Departmento de Microbiologia, Universidad Autónoma, Canto Blanco, Madrid 34, Spain.

Received 1 December 1980; accepted 22 December 1980.