Picornavirus infection induces a profound inhibition of labelling of newly synthesized
RNA in some cell lines. EMC virus blocks transcription in L929 cells, particularly at early times during
infection. This inhibition is not dependent on virus gene expression, since it occurs with UV-inactivated virus and also in the presence of translation inhibitors. The inhibition can be largely accounted for by the blockade of [3H]
nucleoside transport, as suggested by the transport kinetics and incorporation of labelled
nucleoside from preloaded cells. The inhibition of transport and incorporation into TCA-precipitable material was observed with
pyrimidine (
uridine,
thymidine and
cytosine) and
purine nucleosides (
adenosine and
guanosine), but the blockade by EMC virus was higher with the latter
nucleosides. Preloading of cells with any of these
nucleosides resulted in a decreased effect on
nucleoside incorporation into
nucleic acid after
virus infection. These results suggest that the inhibition of incorporation of labelled
nucleosides into
nucleic acid in EMC virus-infected cells can be explained, at least in part, by the decreased pool size of the phosphorylated
nucleosides. These effects are not specific for L cells, because they are also observed in other cell lines.