Regulation of gene expression by the NSP1 and NSP3 non-structural proteins of rotavirus.

The role of the rotavirus non-structural proteins NSP1 and NSP3 in regulating cellular and viral mRNA translation has been investigated by examining the effect of added recombinant NSP3 on protein translation in a T7-based in vitro coupled transcription-translation system. Addition of purified NSP3 to assays primed solely with cellular mRNA was found to have no effect on the translation efficiency of the mRNA. However, as expected, the addition of viral mRNA to such assays competitively inhibited the synthesis of cellular protein, and interestingly, this inhibition was enhanced by the addition of NSP3. Treatment of NSP3 with antisera raised against the purified protein abrogated its function, but only when used prior to mixing the protein with viral mRNA. Addition of partially purified NSP1 to the coupled system was able to alleviate the enhancement of the inhibition of cellular mRNA translation caused by NSP3. The role of NSP1 in this process appears to be to modulate the impact of the NSP3-based inhibition of cellular translation by binding to the 5' end of viral mRNAs.