The effect of poliovirus infection on the translation in vitro of VSV messenger ribonucleoprotein particles.

Messenger ribonucleoprotein (mRNP) particles were isolated and examined for the presence of factors involved in the inhibition of protein synthesis induced by poliovirus infection. Vesicular stomatitis virus (VSV) mRNPs were used as a model for cellular mRNPs. These mRNPs were translated in HeLa cell extracts with a similar efficiency and optimal conditions to that of purified mRNA, but they were not translated in extracts prepared from poliovirus-infected HeLa cells, which have been shown to be defective in cap-binding protein activity. We conclude that mRNP proteins do not include cap-binding protein activity, since the mRNPs were not able to bypass the restriction on translation of capped mRNAs in polio-infected cell extracts. In addition, VSV mRNPs were isolated from polio-superinfected cells, in which their translation was inhibited. These mRNPs were translated in vitro as well as normal VSV mRNPs. No evidence of a modification or a blocking factor on the mRNPs which prevented their translation following polio infection was observed. Thus, within the limits of the in vitro translation assays used, no factors involved in the discrimination between polioviral and cellular or VSV mRNA could be detected in the mRNP particle.